Transition-Metal Salts/Precursor Selection Guide: How “Different Salts of the Same Metal” Start from Different Chemical Realities—and How to Reproduce Results (including a Selection Navigator and Product Tables 1–5)

I.Background: Why “Transition-Metal Salts” Are Hard to Avoid in Research and Engineering

Under most experimental and process conditions, metals do not enter a system as “metal chunks/metal powders.” Instead, they enter in chemical forms that are weighable, soluble, and transformable—among which metal salts are one of the most common. When the cation comes from a transition element, we arrive at the topic of this article.

Transition-metal (transition-element) salts appear frequently in research and industry mainly because:

1. Multiple oxidation states and reversible redox behavior: Transition metals can often interconvert among several oxidation states, providing the foundation for catalysis, energy conversion, and electron-transfer processes (a textbook-level consensus).

2. A strong tendency to form coordination/complex systems: Transition-metal ions readily coordinate with solvents, counter-anions, or added ligands, meaning that solutions rarely contain only “one metal ion.”

3. Broad application coverage: From homogeneous/heterogeneous catalysis; materials precursors (oxides/sulfides/coordination polymers, etc.); electrochemical deposition and corrosion; to bioinorganic and analytical chemistry—transition-metal salts are common metal sources.

This also explains a practical frustration: for the same metal element, simply changing the “salt form” (anion, hydration state, coordination shell) can lead to major differences in solubility, reaction rate, selectivity, and the likelihood of precipitation/side reactions. The root cause is often the system’s speciation—i.e., the distribution of chemical species actually present in solution or in the reaction medium.

II.Basic Definitions

2.1 Reading the Terminology Around “Transition-Metal Salts”

Core question / term	Definition / key points (more intuitive)	What it means intuitively for “transition-metal salts”
Salt	A compound composed of cations and anions held together mainly by electrostatic interactions. In solution, it may not fully “separate into free ions”; it can also exist as ion pairs and/or coordination complexes.	A “metal salt” is not simply “metal ion + spectator anion.” The anion may coordinate or bridge, altering solubility/reactivity/redox behavior and thereby changing the true starting point.
Transition element	An element whose atom has an incomplete d subshell, or that can form cations with an incomplete d subshell.	Commonly implies: multiple oxidation states, stronger coordination chemistry, and more complex real solution species (more than one form)—hence “same metal, different salt → very different outcomes.”
Oxidation state	An integer label assigned by a uniform set of electron-accounting rules to track redox changes; it is not the same as the atom’s true charge.	Transition metals often appear as M(II)/M(III)/M(0), etc. Different oxidation states generally imply different electron counts, coordination preferences, stability, and redox windows—affecting whether the system more readily reduces to metal/nanophases or more readily hydrolyzes.
Ligand	A molecule/ion that donates an electron pair to the central metal and forms a coordinate bond (monodentate, polydentate, etc.).	Solvent molecules, anions, and added ligands can all “take the coordination site,” determining solubility, activation rate, selectivity, and side reactions. Many “salt effects” are fundamentally ligand competition.
Coordination entity	A specific structural unit centered on a metal and surrounded by ligands (can be charged).	After a “transition-metal salt” enters a system, what truly exists is often one (or several) coordination entities rather than a “bare metal ion.” This sets the reaction starting line.
Hydrate	A crystalline form containing a stoichiometric amount of crystal water (·xH₂O), where the water is part of the crystal structure.	Direct impacts: molar mass (effective metal amount per weighing), water introduced into the system, dissolution/hydrolysis tendency, and batch consistency—especially critical for water-sensitive systems.
Speciation	Under given conditions (solvent, pH, ligands, concentration, ionic strength, temperature, etc.), which chemical species an element exists as and their relative fractions (typically governed by equilibria and variable with conditions).	Explains “why the same metal but different salts/conditions produce different results”: the true reactant is the dominant and/or most reactive species present at that moment—not merely the “salt name” on the label.

2.2 Two Common Chemical Forms of “Transition-Metal Salts”

Category	Typical notation / writing features	Core takeaway	What commonly happens in solution
Simple inorganic salts (primarily ionic assembly)	Often written as  (M = metal cation, A = anion)	The label formula ≠ the only species in solution: upon dissolution the salt becomes solvated and may undergo coordination, hydrolysis, and anion exchange—leading to a speciation distribution.	Depends on solvent, pH, anions, and ligands: outcomes range from “mostly solvent-coordinated M²⁺” to formation of halide complexes, hydrolysis products, and polymeric species.
Coordination salts / coordination compounds (explicit coordination entities)	Often written as	The difference is more “directly encoded” in the coordination environment: the unit is an explicit coordination entity with more defined ligands and coordination numbers. “Changing the salt” often directly means changing the coordination environment—thus changing reaction/nucleation pathways.	Ligand exchange and partial dissociation may still occur, but the “starting point more closely resembles a specific coordination structure,” making it easier to influence pathways, active-species generation, and materials nucleation/deposition.

Note on  :

Here, M is the metal center; L is the ligand; n is the number of ligands; z is the total charge on the coordination entity  (written z± to indicate it can be positive or negative); X is the counter-ion; and m is the number of counter-ions used to balance charge.

III.Core Mechanism: Why Does the Same Metal Give Different “Starting Points” When the Salt Changes?

1. Very often, a metal salt is not merely “a source of metal ions.” When the metal M is fixed, “changing the salt” means changing its salt form—for example, switching counter-anions/counter-ions (Cl⁻, NO₃⁻, OAc⁻, …), switching whether it is an explicit coordination entity (e.g., MCl₂ vs K₂[MCl₄]), or switching hydration state (·xH₂O).

2. After entering solution/reaction media, transition metals commonly coexist as multiple interconvertible species (coordination entities, ion pairs, hydrated/solvated forms, etc.). IUPAC refers to the distribution of an element among such species as speciation. Therefore, “changing the salt” often effectively means “changing the initial speciation,” which then alters the reaction pathway or phase-formation pathway. To make this clear, focus on three determining factors.

3.1 Three Key Variables That Decide What the Initial Species Are

Determining factor	What it fundamentally changes	Common experimental phenomena/signals	Why it changes outcomes (core logic)
Metal center and oxidation state	Electronic structure/electron count, and feasible redox and coordination preferences	Color differences; different sensitivity to air/water; different initiation/induction periods	Oxidation state is an integer label from rule-based electron accounting; it correlates with electron count and redox window, affecting accessible active species and pathways.
Anion/counter-ion and ionic interactions	Stability of ion pairs/outer-sphere interactions; whether the anion is (weakly/strongly) coordinating, bridging, or competitively coordinating	Solubility differences; turbidity/precipitation; fluctuating activity/selectivity under the same conditions	Anions/ion pairing shift coordination equilibria and the fractions of key intermediates, thereby changing active species and selectivity (often not “spectators”).
Medium conditions: solvent / water content / added ligands	Solvation/hydration and ligand-exchange equilibria, shifting the overall speciation landscape	The same salt shows different clarity in different solvents; color drifts over time; flocculent material/precipitation appears	Solvent molecules, anions, and added ligands can all coordinate and compete, reshaping the metal’s coordination environment and the types of coordination entities present.

3.2 When Reading Product Labels, What Information Can “Change Speciation”?

Label/spec information	The chemical variable it points to	Why it deserves priority attention
Oxidation-state notation (e.g., M(II)/M(III))	Electronic state / redox window	Directly determines whether reduction is needed and whether it is easily oxidized by air—so the starting point differs immediately.
Anion type (Cl⁻, NO₃⁻, OAc⁻, OTf⁻, …)	Ionic interactions and degree of coordination interference	Counter-ions can participate and shift selectivity/pathways, especially in systems where charged metal species and ion pairing are prominent.
Hydration state (·xH₂O)	Background water and effective molar amount	Hydrate water is part of the crystal structure, affecting weighing calculations and the system’s water content.
Whether it is a coordination-entity salt (e.g., )	Whether the initial coordination environment is “pre-set”	A coordination entity is built from a central atom and a ligand array; different starting coordination environments lead to different exchange and reaction pathways.

IV.Turning “Changing the Salt Changes Everything” into a Controllable Variable: The Minimal Three-Step Verification

4.1 Three quick verification steps: confirm the starting point is consistent and stable

Verification step	The conclusion you want to lock down	Pass signal	If abnormal, what to check first
Step 1: Appearance consistency at the same concentration, same solvent, within the same time window	Whether the initial set of species is broadly the same (at least no obvious deviation)	Clarity/color/whether there is persistent turbidity or flocculation is reproducible within the target time window	Check first: water content/hydration state, solvent grade and mixing order; then: light exposure/air exposure; then: whether halides/base/strong ligands were introduced that trigger rapid exchange
Step 2: Blank control (keep only metal salt + key ligand/acid–base/supporting electrolyte)	Whether the system itself drives spontaneous changes in metal species (it changes even without a substrate)	The blank remains stable on the experimental timescale (appearance and reproducibility)	If the blank is already unstable: prioritize switching counter-ion/solvent or adjusting ligand equivalents; then consider lowering water content/tightening exposure control
Step 3: One simple readout most relevant to your target	Whether the active form / precursor form you need has been established	Catalysis: reproducible onset time/initial rate; Materials: within the phase-formation window, the same morphology/phase-purity trend; Electrochemistry: stable baseline current/potential window	If the readout drifts: return to the three variables and tighten them one by one (oxidation state → counter-ion → medium/ligands), avoiding changes to multiple parameters at once

4.2 The “minimal reproducibility record” checklist

It is recommended to fix the following fields in your lab notes or Methods section:

1. Salt identity: chemical formula + oxidation state + anion; whether it is a coordination-entity salt

2. Hydration information: anhydrous/hydrated (·xH₂O); drying/pretreatment method (if any)

3. Ligands and equivalents: ligand name(s), equivalents, and order of addition (order itself is a condition)

4. Medium conditions: solvent system; how water content is controlled (molecular sieves/glovebox/moisture metrics, etc.)

5. Key environment: air vs inert atmosphere; light exposure vs protected from light; temperature; stirring and stand-time checkpoints, etc.

V.A Map of Typical Application Scenarios

Typical field	Why transition-metal salts are indispensable	Most sensitive variable(s)	Common salt/precursor examples	Common failure/drift modes
Organic synthesis & homogeneous catalysis (cross-coupling, etc.)	Metal salts/coordination salts are weighable catalyst precursors that determine how active species form and remain stable	Oxidation state + counter-ion/ionic interactions (coupled to ligands/medium)	Common Pd/Ni/Fe salt/precursor families (e.g., Pd(II), Ni(II) types)	Slow initiation/deactivation, selectivity drift, sensitivity to halides/strongly coordinating anions, poor batch-to-batch reproducibility
Electrochemistry × transition-metal catalysis (electrosynthesis/electrocatalysis)	Potential directly participates in “reducing/regenerating” catalytic species; the metal salt is the core entry point	Oxidation state + medium/ligands + supporting electrolyte/counter-ion	Various transition-metal catalytic systems (centered on solution-phase cycling of metal species)	Potential window drift, deposition to metal/inactivation, side reactions triggered by background electrolyte/anions
Materials precursors (sol–gel/oxide thin films/catalyst preparation)	Metal salts often serve as molecularly homogeneous starting precursors	Anion type + medium conditions (water/ligands) determine gelation and phase-formation pathways	Metal nitrates/acetates are common sol–gel precursors	Impure phases, uncontrolled particle size/morphology, shifted gelation window, residual anions causing defects
Li-ion cathode precursors (NMC/NCA co-precipitation routes)	Transition-metal sulfate hydrates are commonly co-precipitated from aqueous solutions to form precursors	Hydration/background water + anion system + medium conditions (pH/complexation)	Ni/Mn/Co hydrated sulfates for precursor synthesis	Component segregation, uncontrolled particle-size distribution, impurity phases/residual anions, poor batch stability
Electroplating/surface engineering (Ni/Cu electrodeposition, etc.)	A plating bath is essentially a “metal-salt electrolyte system”; salt form and additives determine deposit quality	Counter-ion/ionic interactions + medium composition (additives/buffers)	Watts nickel bath: NiSO₄ + NiCl₂ + H₃BO₃; chloride control in acidic copper sulfate baths	Roughness/pinholes, internal stress, fluctuating brightness/ductility, sensitivity to chloride/anionic changes

VI.Product Navigation Table | Transition-Metal Salts: Quickly Locate Tables 1–5 by Research Task

Need / scenario	Which table to check first	Rationale for choosing the table	Representative “salt keywords” in the table
Prepare routine solutions / background salts / ionic-strength controls (prefer readily available, stable, easy-to-reproduce salts)	Table 1: Common transition-metal salts (analysis/AR/pharmacopoeia common)	Table 1 covers the most common hydrated chlorides/nitrates/sulfates/acetates—ideal as a starting point for “general metal-salt sources + anion comparisons”	ZnCl₂, NiCl₂·6H₂O, CuSO₄·5H₂O, Fe(NO₃)₃·9H₂O, Co(OAc)₂·4H₂O
Electrochemistry / electroplating / aqueous inorganic reactions (care about supporting electrolyte background, metal-ion stability, reproducible recipes)	Table 1: Common transition-metal salts	In Table 1, sulfates/chlorides/nitrates are the most common entry points for electrochemistry and aqueous systems; suitable for rapid setup and anion-effect comparisons	NiSO₄·6H₂O, FeSO₄·7H₂O, CuSO₄·5H₂O, CoCl₂·6H₂O, MnCl₂·4H₂O
Materials precursors (sol–gel/thin films/oxides) needing a cleaner, more controllable starting point	Table 2: High-purity/anhydrous halides and key precursor salts	Table 2 concentrates anhydrous halides, PrimorTrace, and high-purity “metals basis”/sublimed precursors—better for materials routes requiring low water/low impurities and controllable hydrolysis/speciation	TiCl₄, ZrCl₄, HfCl₄, NbCl₅, TaCl₅, WCl₆, MoCl₅
Dissect “anion effects / real speciation” (compare Cl⁻/Br⁻/I⁻/NO₃⁻/OAc⁻ effects)	Table 1 + Table 2 (Table 1 first; Table 2 if stricter control is needed)	Table 1 enables routine “same metal, different anion” comparisons; if the system is water/trace-impurity sensitive or you need to eliminate batch-impurity effects, use Table 2’s high-purity/anhydrous salts to tighten variables	CuCl₂ vs Cu(NO₃)₂ vs CuSO₄ vs Cu(OAc)₂; NiCl₂ (anhydrous) / NiBr₂ (anhydrous) / Ni(NO₃)₂·6H₂O
Strong oxidation / redox method development or standard oxidants (analysis, cleaning, mechanistic controls)	Table 3: Oxyanion salts and oxide/zirconyl nitrate precursors	Table 3 includes strong-oxidation systems such as KMnO₄ and broader oxyanion families—suited for experiments centered on “redox strength and oxyanion chemistry”	KMnO₄, permanganate systems
Oxyanion routes (Mo/W/V systems): analytical methods, oxide precursors, solution chemistry	Table 3: Oxyanion salts and oxide/zirconyl nitrate precursors	Table 3 specifically consolidates molybdates/tungstates/metavanadates and related oxyanion sources—more direct than starting from halide routes for solution chemistry and oxide precursors	(NH₄)₂MoO₄·4H₂O, Na₂MoO₄·2H₂O, Na₂WO₄·2H₂O, NH₄VO₃
ZrO₂-related materials / surface acidity sites / ceramic supports (aqueous-leaning precursors or hydrated oxides)	Table 3: Oxyanion salts and oxide/zirconyl nitrate precursors	Zr entries in Table 3 cover hydrated zirconyl nitrate and hydrated zirconia—closer to ZrO₂ sol–gel/precipitation/phase-control routes	Zirconyl nitrate hydrate, zirconium(IV) oxide octahydrate
Cross-coupling / homogeneous catalysis / coordination chemistry (Pd/Pt/Rh/Ir/Ru as core precursors)	Table 4: Transition-metal salts (precious metals/silver): catalytic and coordination precursors	Table 4 centers on commonly used precious-metal precursors (chlorides/acetates/hydrated chlorides, etc.), enabling fast catalytic-system startup and reproducible benchmarking	Pd(OAc)₂, PdCl₂, RhCl₃·xH₂O, IrCl₃·xH₂O, RuCl₃·xH₂O, PtCl₂, PtCl₄
Halide scavenging / activation promotion / weakly coordinating anion systems (aim for more “cationic” metal species or reduced Cl⁻ interference)	Table 5: Weakly coordinating anion salts and complexes (OTf⁻ / β-diketonates)	Table 5 provides weakly coordinating anion salts such as AgOTf and Cu(OTf)₂, often used for “dehalogenation/activation/coordination-shell switching”; also includes soluble metal complexes as organic-phase precursors	AgOTf, Cu(OTf)₂
Organic-phase precursors / soluble metal sources (better solubility and processability, e.g., solution coating/thermal conversion)	Table 5: Weakly coordinating anion salts and complexes (OTf⁻ / β-diketonates)	The β-diketonate metal complexes (acac) in Table 5 are better suited to organic solvents and film-forming/thermal-decomposition routes; commonly used as contrasts to inorganic-salt routes	Iron acetylacetonate, nickel acetylacetonate

Note: 

In this article, “transition-metal salts” is used in a broad, research-oriented sense: it focuses on d-block metal salts/precursors, and also includes precious-metal salts and silver salts that are commonly used alongside them in research. It covers metal halides and coordination-compound precursors often used as metal sources (including Zn salts and TiCl₄ as benchmarks). Classification is organized by metal center + anion/type to facilitate side-by-side selection and comparison.

Table 1 | Common Transition-Metal Salts (Halides / Nitrates / Sulfates / Acetates)

Category	CAS No.	Aladdin Cat. No.	Name	Spec / Purity	Product features & applications
Transition-metal salts | Zinc salts (Zn²⁺) | Halides | Chlorides	7646-85-7	Z112526	Zinc chloride	Premium grade reagent, ≥98%	A common Zn²⁺ source and a classic Lewis acid: used in organic synthesis/catalysis (carbonyl activation, promoting halogenation/condensation, etc.), coordination chemistry and organometallic systems; also used as a materials precursor (ZnO/doped systems) and as a salt source in electrolyte/galvanizing-related research.
Transition-metal salts | Nickel salts (Ni²⁺) | Halides | Chlorides (hydrate)	7791-20-0	N112126	Nickel(II) chloride hexahydrate	Premium grade reagent, ≥98%	A commonly used Ni²⁺ precursor: for electroplating/electrochemistry, coordination chemistry, and preparation of catalytic precursors (Ni complexes, reduction to Ni(0) active species, etc.); the hydrated form facilitates solution preparation and ionic-strength/salt-effect controls.
Transition-metal salts | Cobalt salts (Co²⁺) | Halides | Chlorides (hydrate)	7791-13-1	C116457	Cobalt(II) chloride hexahydrate	Premium grade reagent	A common Co²⁺ salt source: used in coordination chemistry; catalytic/electrochemical precursors (e.g., Co oxides/hydroxides, electrocatalyst materials); and studies of solution coordination/hydration behavior. For systems sensitive to ligand exchange and chloride ions, the hydrated chloride requires blank controls.
Transition-metal salts | Copper salts (Cu²⁺) | Halides | Chlorides (hydrate)	10125-13-0	C111678	Copper(II) chloride dihydrate	Premium grade reagent	Source of Cu²⁺ and Cl⁻: widely used in organic synthesis/catalysis (halogenation, oxidative coupling, Lewis-acid-promoted reactions, etc.), etching systems, and coordination chemistry. Because Cl⁻ is a strongly influencing anion, its interference with the coordination shell and side reactions should be evaluated in catalysis/electrochemistry.
Transition-metal salts | Copper salts (Cu²⁺) | Nitrates (hydrate)	10031-43-3	C298895	Copper(II) nitrate trihydrate	Premium grade reagent	Source of Cu²⁺ and nitrate: a common copper source in oxidative/nitrate systems for catalysis and materials precursors (CuO/Cu₂O, MOFs/coordination polymers), corrosion/etching, and solution-chemistry controls. Nitrate can introduce oxidation/coordination effects—important for mechanistic controls.
Transition-metal salts | Cobalt salts (Co²⁺) | Nitrates (hydrate)	10026-22-9	C431137	Cobalt(II) nitrate hexahydrate	Suitable for analysis, premium grade	A common Co²⁺ nitrate precursor: used to prepare Co oxides/hydroxides and electrocatalyst materials, as well as in coordination chemistry and solution-system studies. Nitrate may affect reduction/complexation pathways, making it a useful cobalt source for nitrate-system controls.
Transition-metal salts | Chromium salts (Cr³⁺) | Nitrates (hydrate)	7789-02-8	C434117	Chromium(III) nitrate nonahydrate	Suitable for analysis, premium grade	Cr³⁺ salt source and an analytical-grade precursor: for coordination chemistry, pigments/chromium oxide precursors, and solution-chemistry studies. Nitrate brings oxidizing character, ionic-strength effects, and coordination competition—useful for “anion/medium” controls.
Transition-metal salts | Chromium salts (Cr³⁺) | Halides | Chlorides (hydrate)	10060-12-5	C100293	Chromium(III) chloride hexahydrate	AR, ≥98%	A common Cr³⁺ source: for coordination chemistry, Cr₂O₃/chromium-based materials precursors, and studies of solution hydrolysis/complexation. Cr³⁺ undergoes slow ligand exchange and its speciation is highly sensitive to ligands and acidity—useful as a “real-species vs reproducibility” control system.
Transition-metal salts | Nickel salts (Ni²⁺) | Sulfates (hydrate)	10101-97-0	N431238	Nickel(II) sulfate hexahydrate	Suitable for analysis, ACS, premium grade	A typical Ni²⁺ salt for electrochemistry/electroplating: used for nickel plating, electrolyte ionic-strength controls, and coordination/precipitation/phase-control studies. Sulfate often serves as a “background anion,” but compatibility still needs verification for precipitation/complexation-sensitive systems.
Transition-metal salts | Manganese salts (Mn²⁺) | Halides | Chlorides (hydrate)	13446-34-9	M431934	Manganese(II) chloride tetrahydrate	Suitable for analysis, ACS, premium grade	A common Mn²⁺ source: used in inorganic/coordination chemistry, catalytic and electrochemical materials precursors (MnOₓ, etc.), and ionic-strength/salt-effect controls. Cl⁻ can affect coordination and corrosion/side reactions—useful for “halide sensitivity” testing.
Transition-metal salts | Manganese salts (Mn²⁺) | Sulfates (hydrate)	10034-96-5	M431158	Manganese(II) sulfate monohydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade, spray-dried	A common Mn²⁺ sulfate: used in analysis/method development, culture/formulation, and inorganic precursors (MnOₓ, doped systems). Sulfate is relatively “background-type,” suitable for ionic-strength/salt-effect and precipitation-window comparisons.
Transition-metal salts | Iron salts (Fe²⁺) | Sulfates (hydrate)	7782-63-0	I434044	Iron(II) sulfate heptahydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	A common reducing Fe²⁺ source: for redox systems, Fenton/Fenton-like mechanistic studies, coordination chemistry, and precipitation/hydrolysis behavior. Fe²⁺ is readily oxidized—reproducibility depends on dissolved oxygen, acidity, and storage conditions.
Transition-metal salts | Iron salts (Fe³⁺) | Nitrates (hydrate)	7782-61-8	I434042	Iron(III) nitrate nonahydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	A common source of Fe³⁺ and nitrate: for coagulation/hydrolysis precipitation, coordination chemistry, oxidative systems, and iron oxide precursors (Fe₂O₃/FeOOH, etc.). Nitrate and acidity windows influence true speciation and precipitation phases.
Transition-metal salts | Copper salts (Cu²⁺) | Sulfates (hydrate)	7758-99-8	C433966	Copper(II) sulfate pentahydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	A classic general-purpose Cu²⁺ salt: for analysis/titration and coordination chemistry, crystal growth and electrochemistry, and materials precursors such as CuO/Cu(OH)₂. Sulfate is often used as a “background anion” control, but precipitation with bases/chelators must still be considered.
Transition-metal salts | Zinc salts (Zn²⁺) | Sulfates (hydrate)	7446-20-0	Z433480	Zinc sulfate heptahydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	A common Zn²⁺ background salt and zinc source: for formulation/method development, solution ionic-strength controls, and precursors for ZnO/Zn(OH)₂, etc. In sulfate systems, coexistence with carbonates/phosphates may require evaluating precipitation and complexation windows.
Transition-metal salts | Copper salts (Cu²⁺) | Carboxylates/Acetates (hydrate)	6046-93-1	C433064	Copper(II) acetate monohydrate	Suitable for analysis, ACS, premium grade	A common Cu²⁺ organic-acid salt: used in organic synthesis/catalysis (oxidation, coupling, etc.), coordination chemistry, and as a precursor for MOFs/coordination polymers. Acetate is a relatively “mildly coordinating” anion and is often used to compare anion effects versus chloride/nitrate systems.
Transition-metal salts | Zinc salts (Zn²⁺) | Carboxylates/Acetates (hydrate)	5970-45-6	Z433041	Zinc acetate dihydrate	Suitable for analysis, ACS, premium grade	A common Zn²⁺ source: for coordination chemistry, MOFs (e.g., Zn–BDC-type systems), and ZnO/doped-material precursors. In solution, acetates more readily form controllable complexes—useful as sol–gel/thin-film precursor comparisons.
Transition-metal salts | Cobalt salts (Co²⁺) | Carboxylates/Acetates (hydrate)	6147-53-1	C433114	Cobalt(II) acetate tetrahydrate	Suitable for analysis, ACS, premium grade	A common Co²⁺ acetate: convenient precursor for Co-based materials (CoOₓ, Co(OH)₂, etc.) and coordination chemistry. Acetate can coordinate/buffer, often used to compare real-species differences versus CoCl₂/Co(NO₃)₂ and other anions.
Transition-metal salts | Nickel salts (Ni²⁺) | Carboxylates/Acetates (hydrate)	6018-89-9	N112914	Nickel(II) acetate tetrahydrate	AR, ≥99%	A commonly used mild Ni²⁺ source: for coordination chemistry, NiO/Ni(OH)₂ precursors, and catalyst-material preparation. Acetate is relatively weakly coordinating/controllable—useful for anion-effect comparisons versus halide/nitrate systems.
Transition-metal salts | Copper salts (Cu²⁺) | Halides | Bromides	7789-45-9	C105401	Copper(II) bromide	AR, ≥99%	Source of Cu²⁺ and Br⁻: for coordination chemistry, copper-based materials precursors, and halide-effect studies. In organic synthesis it is also used as a bromination/oxidation-related salt-form control, suitable for comparison with CuCl₂/Cu(NO₃)₂ systems.
Transition-metal salts | Manganese salts (Mn²⁺) | Nitrates (hydrate)	20694-39-7	M191978	Manganese(II) nitrate tetrahydrate	≥98%	A common Mn²⁺ nitrate: for MnOₓ materials and electrochemical precursors, solution chemistry, and analytical controls. Nitrates are oxidizing; when used in reducing/organic systems, pay attention to side reactions and safety/compliance requirements.
Transition-metal salts | Iron salts (Fe³⁺) | Sulfates (standardized by metal content)	10028-22-5	F684177	Ferric sulfate	Fe: 21.0–23.0%	A general iron source and a common salt in analysis/water treatment: for redox/hydrolysis precipitation studies, iron-oxide precursors, and ionic-strength controls. The “Fe content” specification facilitates dosing by metal content and recipe reproducibility.

Table 2 | High-Purity / Anhydrous Halides and Key Precursor Salts (PrimorTrace / metals basis / sublimed grade)

Category	CAS No.	Aladdin Cat. No.	Name	Spec / Purity	Product features & applications
Transition-metal salts | Niobium salts (Nb⁵⁺) | Halides | Chlorides (anhydrous)	10026-12-7	N431134	Niobium(V) chloride	Anhydrous grade, ≥99.995% metals basis	High-purity Nb(V) precursor: for niobium oxides/niobium-based catalytic and optoelectronic materials (Nb₂O₅, etc.), Lewis-acid/halide-chemistry reactions, and coordination chemistry. Anhydrous high purity is better for water-sensitive systems where controlled speciation is needed.
Transition-metal salts | Copper salts (Cu⁺) | Halides | Iodides (anhydrous)	7681-65-4	C433811	Copper(I) iodide	Anhydrous grade, ≥99.995% metals basis	A typical Cu(I) catalytic precursor: used in coupling/halogenation and many Cu(I)-catalyzed systems (ligand-assisted reactions, click/alkyne-related systems, etc.), and in Cu coordination compounds/materials. Anhydrous high purity helps control Cu(I)/Cu(II) balance and side reactions.
Transition-metal salts | Nickel salts (Ni²⁺) | Halides | Bromides (anhydrous)	13462-88-9	N431942	Nickel(II) bromide	Anhydrous grade, ≥99.9% metals basis, powder	An anhydrous Ni²⁺ source: used as a Ni precursor in cross-coupling/reducing systems, coordination chemistry, and materials precursors. Halide anions strongly affect dissolution/coordination and active-species distribution—useful for “anion-effect” comparisons.
Transition-metal salts | Hafnium salts (Hf⁴⁺) | Halides | Chlorides (anhydrous / sublimed grade)	13499-05-3	H431978	Hafnium tetrachloride	Sublimed grade, ≥99.9% metals basis	High-purity Hf precursor: for HfO₂/high-k dielectrics, thin-film deposition (precursor routes), inorganic synthesis, and coordination chemistry. Sublimed grade emphasizes low impurities, suitable for systems extremely sensitive to trace metals/hydrolysis.
Transition-metal salts | Nickel salts (Ni²⁺) | Halides | Chlorides (anhydrous, high purity)	7718-54-9	N433839	Nickel(II) chloride	PrimorTrace™, anhydrous grade, ≥99.99% metals basis, powder	Ultra-high-purity anhydrous Ni²⁺ source: for impurity-sensitive electrochemistry/catalysis/coordination systems and “anion-effect” studies. Anhydrous halides better control speciation differences from hydration/hydrolysis, serving as a highly reproducible Ni starting point.
Transition-metal salts | Tantalum salts (Ta⁵⁺) | Halides | Chlorides (sublimed grade, high purity)	7721-01-9	T283511	Tantalum(V) chloride	PrimorTrace™, sublimed grade, ≥99.99% metals basis	High-purity Ta(V) precursor: widely used for tantalum oxides/tantalum-based thin films and ceramic-material precursors, Lewis-acid organic synthesis, and coordination chemistry. Sublimed grade stresses low impurities, suitable for material routes sensitive to metal impurities and hydrolysis side reactions.
Transition-metal salts | Copper salts (Cu⁺) | Halides | Chlorides (high purity)	7758-89-6	C112392	Copper(I) chloride	PrimorTrace™, ≥99.999% metals basis	A typical Cu(I) source: for Cu(I) complex synthesis and diverse Cu-catalysis/coupling precursors. Ultra-high purity is preferable for mechanistic controls sensitive to trace metals/impurities (e.g., Cu(I)/Cu(II) balance and side reactions).
Transition-metal salts | Nickel salts (Ni²⁺) | Nitrates (hydrate, high purity)	13478-00-7	N108888	Nickel(II) nitrate hexahydrate (explosive precursor label)	PrimorTrace™, ≥99.999% metals basis	High-purity Ni²⁺ nitrate: commonly used in sol–gel/solution-precursor preparation of NiO/Ni-based materials and analytical controls. Nitrates are oxidizing and may have compliance requirements (as noted on the label); in reducing/organic systems, pay close attention to side reactions and blanks.
Transition-metal salts | Cobalt salts (Co²⁺) | Halides | Bromides (high purity)	7789-43-7	C486143	Cobalt(II) bromide	PrimorTrace™, ≥99.99% metals basis, beads, >10 mesh	High-purity Co²⁺ halide: for coordination chemistry/catalytic precursors and halide-effect studies. Bromide may differ from chloride in solubility and coordination competition—useful as a “halogen control” cobalt source. Bead form facilitates weighing and transfer.
Transition-metal salts | Manganese salts (Mn²⁺) | Carboxylates/Acetates (high purity, hydrate)	6156-78-1	M110795	Manganese(II) acetate tetrahydrate	PrimorTrace™, ≥99.99% metals basis	High-purity Mn²⁺ precursor: for MnOₓ materials, electrochemistry, and coordination chemistry. Acetate is relatively mild and can participate in complexation/buffering, suitable for comparing “anion mildness/coordination controllability.”
Transition-metal salts | Molybdenum salts (Mo⁵⁺) | Halides | Chlorides (high purity)	10241-05-1	M401642	Molybdenum pentachloride	PrimorTrace™, ≥99.99% metals basis	A high-valent Mo(V) halide precursor: for Mo coordination compounds and Mo-based catalytic/material precursors (upstream salt for conversion to Mo oxides/sulfides, etc.). Extremely moisture-sensitive—well suited to emphasize “anhydrous/hydrolysis control” and true-species documentation.
Transition-metal salts | Titanium salts (Ti⁴⁺) | Halides | Chlorides (high purity)	7550-45-0	T118447	Titanium tetrachloride	PrimorTrace™, ≥99.99% metals basis	A classic Ti(IV) precursor: widely used for TiO₂/titanium-based thin films and sol–gel routes, and Ti Lewis-acid/catalysis studies. Highly moisture-sensitive (readily hydrolyzes/fumes); ultra-high purity suits device-grade films and impurity-sensitive material systems.
Transition-metal salts | Copper salts (Cu⁺) | Halides | Bromides (high purity)	7787-70-4	C104701	Copper(I) bromide	PrimorTrace™, ≥99.99% metals basis	A common Cu(I) bromide: for Cu(I) complexes and many organic-synthesis catalytic systems (e.g., coupling, radical/polymerization-related catalysis). Comparing with CuCl helps separate halide/solubility/coordination effects on active species and side reactions.
Transition-metal salts | Zinc salts (Zn²⁺) | Nitrates (hydrate, high purity)	10196-18-6	Z111706	Zinc nitrate hexahydrate (explosive precursor label)	PrimorTrace™, ≥99.99% metals basis	High-purity Zn²⁺ nitrate: for ZnO/doped oxides and solution-precursor routes, MOFs/coordination polymers, and analytical controls. Nitrates are oxidizing and may require compliance management; in organic/reducing systems, check compatibility and run blanks.
Transition-metal salts | Cobalt salts (Co²⁺) | Sulfates (hydrate, high purity)	10026-24-1	C1455809	Cobalt sulfate heptahydrate	Ultra pure, Co ≥ 20.5%	High-purity Co²⁺ source: for electrochemistry/electroplating, coordination chemistry, and Co-based materials precursors (CoOₓ/Co(OH)₂, etc.). Sulfate is relatively “background-type,” suitable for ionic-strength/salt-effect work and impurity-sensitive comparisons.
Transition-metal salts | Tungsten salts (W⁶⁺) | Halides | Chlorides (anhydrous, high purity)	13283-01-7	T431895	Tungsten(VI) chloride	≥99.99% metals basis, powder; purity excludes molybdenum	High-purity W(VI) precursor: for WO₃/tungsten oxides and tungsten functional materials, coordination chemistry, and catalysis. Moisture-sensitive; high purity and Mo-exclusion are valuable for “dopant/impurity highly sensitive” material comparisons.
Transition-metal salts | Zirconium salts (Zr⁴⁺) | Halides | Chlorides (anhydrous, high purity)	10026-11-6	Z109460	Zirconium chloride	≥99.9% metals basis	A common Zr(IV) precursor: for ZrO₂, Zr Lewis-acid catalysis, and Zr complexes/materials (including some Zr-MOF routes). Anhydrous halides are moisture-sensitive—suited to emphasize solvent/water-content control and reproducibility records.
Transition-metal salts | Iron salts (Fe²⁺) | Halides | Chlorides (anhydrous)	7758-94-3	I106504	Iron(II) chloride, anhydrous	≥99.5%, powder	A typical Fe(II) precursor: for inorganic/coordination and organometallic systems, reducing iron-source controls, and iron-based materials precursors. Fe²⁺ is readily oxidized by air; for reproducibility, monitor dissolved oxygen, acidity, and storage/weighing exposure time.
Transition-metal salts | Vanadium salts (V³⁺) | Halides | Chlorides	7718-98-1	V498277	Vanadium(III) chloride	≥96%	A V(III) precursor: for vanadium coordination/organometallic chemistry, reducing vanadium sources, and upstream salts for vanadium catalysis/material routes. Air/moisture sensitive—useful for control studies on how “oxidation state–ligand–medium” shapes speciation.

Table 3 | Oxyanion Salts and Oxides / Zirconyl Nitrate Precursors (Mo/W/V/Mn/Zr)

Category	CAS No.	Aladdin Cat. No.	Name	Spec / Purity	Product features & applications
Transition-metal salts | Mn(VII) oxyanion salt | Permanganate (strong oxidant)	7722-64-7	P485670	Potassium permanganate (explosive precursor / controlled chemical label)	For analysis (max 0.000005% mercury column), premium grade reagent, ACS	A classic strong oxidant and one of the benchmark systems for redox titration: used for redox capacity calibration, oxidation reaction/pollutant oxidation mechanism studies, and surface cleaning/oxidative treatments. Highly sensitive to organics/reductants—must be managed under strict hazardous-chemical protocols and with blank controls.
Transition-metal salts | Tungstates (W(VI)) | Oxyanion salts | Tungstate (sodium salt, hydrate)	10213-10-2	S431261	Sodium tungstate dihydrate	Suitable for preparing protein-free filtrate according to Folin	A commonly used tungsten-containing reagent in methodology: used in Folin-related procedures for preparing protein-free filtrates/protein precipitation steps; also a W source and tungstate-chemistry precursor (e.g., to WO₃) for catalysis/materials and solution-chemistry comparison studies.
Transition-metal salts | Molybdates (Mo(VI)) | Oxyanion salts | Molybdate (ammonium salt, hydrate)	12054-85-2	A431567	Ammonium molybdate tetrahydrate	Ultrapure grade, powder	A common Mo(VI) “molybdenum source” and analytical reagent: for phosphate/silicate-related colorimetric or precipitation methodologies, and as a precursor for MoO₃/Mo-based catalysts and functional materials. Ultrapure powder suits trace-impurity-sensitive catalysis/materials and analytical controls.
Transition-metal salts | Molybdates (Mo(VI)) | Oxyanion salts | Molybdate (sodium salt, hydrate)	10102-40-6	S104867	Sodium molybdate dihydrate	AR, ≥99%	A common Mo(VI) sodium salt: for molybdate solution chemistry, analytical methods (phosphate/silicate-related systems), and MoO₃/molybdenum-based material precursors. The sodium salt is convenient as a control entry point with a fixed “background cation.”
Transition-metal salts | Metavanadates (V(V)) | Oxyanion salts | Metavanadate (ammonium salt)	7803-55-6	A111822	Ammonium metavanadate	AR, ≥99%	A typical V(V) “vanadium source”: for V₂O₅/vanadium oxides and catalytic/electrochemical materials, as well as redox and coordination chemistry. Also commonly used as a precursor salt for vanadium doping/surface modification in mechanistic comparisons.
Transition-metal salts | Zirconium salts (Zr⁴⁺) | Nitrates | Zirconyl nitrate (hydrate)	14985-18-3	Z104396	Zirconyl nitrate hydrate	AR, ≥99.5%	A common Zr precursor: for ZrO₂ sol–gel routes, ceramics/catalyst supports, and surface acidity-site studies. Nitrate systems facilitate aqueous/alcoholic precursor solutions, serving as a reproducible starting point for ZrO₂-related material routes.
Transition-metal salts | Zirconium system (Zr⁴⁺) | Oxides/hydrated oxides | Hydrated zirconium(IV) oxide	13520-92-8	Z431979	Zirconium(IV) oxide octahydrate	Suitable for analysis, premium grade	A hydrated zirconia precursor: commonly used for preparing/benchmarking ZrO₂ (ceramics, catalyst supports, interface/acid–base site studies), sol–gel, and surface chemistry. The hydrated form aids dispersion and precipitation/phase-control experiments.

Table 4 | Transition-Metal Salts (Precious Metals / Silver): Catalytic and Coordination Precursors (Pd/Pt/Rh/Ir/Ru/Ag)

Category	CAS No.	Aladdin Cat. No.	Name	Spec / Purity	Product features & applications
Transition-metal salts | Precious metal (Pd²⁺) | Carboxylates/Acetates | Palladium(II) acetate	3375-31-3	P432639	Palladium(II) acetate (47% Pd)	Suitable for synthesis	A classic Pd(II) catalytic precursor: widely used in coupling reactions and homogeneous catalysis (forming Pd(0)/ligand-complexed active species). Favorable solubility and ligand exchange make it suitable as a baseline “Pd source” for catalyst screening and reproducibility benchmarking.
Transition-metal salts | Precious metal (Pd²⁺) | Halides | Palladium(II) chloride	7647-10-1	P433731	Palladium(II) chloride	Reagent grade, high purity, ≥99%	An important Pd(II) source: for preparing Pd complexes and catalytic precursors (with ligands/reductants to generate active Pd species). Cl⁻ coordinates strongly; commonly used to contrast “chloropalladium” versus Pd(OAc)₂ systems for mechanistic deconvolution.
Transition-metal salts | Precious metal (Rh³⁺) | Halides | Rhodium(III) chloride (hydrate)	20765-98-4	R109233	Rhodium(III) chloride hydrate	Rh 38.5–42.5%	A typical Rh catalytic precursor: for Rh complex synthesis and homogeneous catalysis (e.g., hydrogenation, isomerization, C–H functionalization pathways as a “Rh source starting point”). The true species of hydrated chlorides are highly sensitive to ligands/solvents/halides—well suited for emphasizing reproducibility records and blank controls.
Transition-metal salts | Precious metal (Pt²⁺) | Halides | Platinum(II) chloride	10025-65-7	P109265	Platinum(II) chloride	Pt basis ≥73%	A common Pt(II) precursor: for Pt complex preparation, homogeneous/electrocatalysis research, and Pt-based materials precursors. Pt(II) favors coordination chemistry and controllable ligand exchange, often used as a starting point for structure–property/mechanistic studies.
Transition-metal salts | Precious metal (Pt⁴⁺) | Halides | Platinum(IV) chloride	13454-96-1	P111013	Platinum(IV) chloride	Pt ≥57%	A Pt(IV) oxidation-state precursor: suitable when higher oxidation state and subsequent reductive conversion are desired (e.g., routes to Pt(II)/Pt(0) or upstream chemistry related to chloroplatinates). Sensitive to solvent and reducing conditions; often used to contrast active-species pathways versus Pt(II) salts.
Transition-metal salts | Precious metal (Ir³⁺) | Halides | Iridium(III) chloride (hydrate)	14996-61-3	I111008	Iridium(III) chloride hydrate	Reagent grade, Ir ≥52%	A common Ir precursor: for homogeneous catalysis, Ir complex synthesis, and electro-/photocatalysis research. Hydrated chlorides show strong dependence of solution speciation on ligands/solvents/halides—suitable for documenting “true species” and reproducible starting points.
Transition-metal salts | Precious metal (Ru³⁺) | Halides | Ruthenium(III) chloride (hydrate)	14898-67-0	R432146	Ruthenium(III) chloride hydrate	Suitable for analysis, premium grade	A common Ru precursor: for homogeneous/electrocatalysis, coordination chemistry, and materials preparation (RuO₂, conductive oxides). Cl⁻ and hydration state define speciation; for reproducible catalysis, record solubility/color and ligand equivalents.
Transition-metal salts | Silver salts (Ag⁺) | Nitrates | Silver nitrate	7761-88-8	S433976	Silver nitrate (explosive precursor label)	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	A typical general-purpose Ag⁺ source: for halide capture/precipitation controls (AgCl/AgBr/AgI), electrochemistry and silver-based materials (Ag/Ag₂O, AgNPs), and analytical/colorimetric methodologies. Light- and reduction-sensitive; manage per hazardous-chemical and light-protection requirements.

Table 5 | Transition-Metal Complexes and Weakly Coordinating Anion Salts (OTf⁻ / β-diketonate ligands)

Category	CAS No.	Aladdin Cat. No.	Name	Spec / Purity	Product features & applications
Transition-metal salts | Silver salts (Ag⁺) | Weakly coordinating anion salts | Silver trifluoromethanesulfonate (OTf⁻)	2923-28-6	S119490	Silver trifluoromethanesulfonate	≥99.98% metals basis	A typical Ag⁺ source with a weakly coordinating anion: commonly used for halide capture/halogen abstraction (forming AgX) and generating more “cationic” metal species (as an additive/activation salt-form control). Compared with AgNO₃, it can reduce oxidation/coordination differences introduced by NO₃⁻.
Transition-metal salts | Copper salts (Cu²⁺) | Weakly coordinating anion salts | Copper(II) trifluoromethanesulfonate (OTf⁻)	34946-82-2	C100681	Copper(II) trifluoromethanesulfonate	≥98%	A Cu(II) triflate: often used as a Lewis acid / “weakly coordinating anion” copper source in copper catalysis to generate more reactive cationic copper species or to reduce halide interference. Suitable for mechanistic comparisons versus CuCl₂/CuBr₂/Cu(OAc)₂ and related systems.
Transition-metal complex | Iron complex | β-diketonate ligand | Iron acetylacetonate	14024-18-1	I106157	Iron acetylacetonate	≥98%	A soluble iron precursor (often used for Fe-based thin films/oxides/nanomaterial precursors and catalysis): β-diketonate ligands improve organic-phase solubility and processability, facilitating comparisons in solution coating/thermal conversion routes.
Transition-metal complex | Nickel complex | β-diketonate ligand | Nickel acetylacetonate	3264-82-2	N105676	Nickel acetylacetonate	≥95%	A soluble Ni precursor: commonly used for Ni-based thin films/oxides/nanomaterial precursors and catalysis. β-diketonate ligands enhance organic-phase solubility and processability, enabling route/speciation comparisons with inorganic salts (NiCl₂, Ni(OAc)₂, etc.).

Note: The above are representative Aladdin products. For additional specifications, please refer to the product list at the end of the article, or search the Aladdin website using “product name / CAS / catalog number.”

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Post-Transition Metals and Their Salts: A Classification Guide from Definitions to Value-Chain Applications (Including Product Lists in Tables 1–4)

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