Synthesis and characterization of heterobimetallic mixed-ligand complexes containing Zr(μ-OPri)2Al bridging units

Interesting varieties of heterobimetallic mixed-ligand complexes [Zr{M(OPrⁱ) _n }₂ (L)] (where M = Al, n = 4, L = OC₆H₄CH = NCH₂CH₂O (1); M = Nb, n = 6, L = OC₆H₄CH = NCH₂CH₂O (2); M = Al, n = 4, L = OC₁₀H₆CH = NCH₂CH₂O (3); M = Nb, n = 6, L = OC₁₀H₆CH = NCH₂CH₂O (4)), [Zr{Al(OPrⁱ)₄}₂Cl(OAr)] (where Ar = C₆H₃Me₂-2,5 (5); Ar = C₆H₂Me-4-Bu₂-2,6 (6), [Zr{Al(OPrⁱ)₄}₂(OAr)₂] (where Ar = C₆H₃Me₂-2,5 (7); Ar = C₆H₂Me-4-Bu₂-2,6 (8), [Zr{Al(OPrⁱ)₄}₃(OAr)] (where Ar = C₆H₃Me₂-2,5 (9); Ar = C₆H₃Me₂-2,6 (10), [ZrAl(OPrⁱ)_7-n (ON=CMe₂) _n ] (where n = 4 (11); n = 7 (12), [ZrAl₂(OPrⁱ)_10-n (ON=CMe₂) _n ] (where n = 4 (13); n = 6 (14); n = 10 (15) and [Zr{Al(OPrⁱ)₄}₂{ON=CMe(R)} _n Cl_2–n] [where n = 1, R = Me (16); n = 2, R = Me (17); n = 1, R = Et (18); n = 2, R = Et (19)] have been prepared either by the salt elimination method or by alkoxide-ligand exchange. All of these heterobimetallic complexes have been characterized by elemental analyses, molecular weight measurements, and spectroscopic (I.r., ¹H-, and ²⁷Al- n.m.r.) studies.     

Syntheses and characterization of a new class of zirconia precursors of oxime-modified zirconium(IV) isopropoxide

Some oxime modified complexes of the type [Zr{OPrⁱ}_4?n{L}_n] {where, n = 1–4 and LH=(CH₃)₂C=NOH (1–4) and C₉H₁₆C=NOH (5–8)} have been synthesized by the reaction of [Zr(OPrⁱ)₄·PrⁱOH] with oximes, in anhydrous refluxing benzene. These synthesized complexes were characterized by elemental analyses, molecular weight measurements, ESI-mass, FT-IR and NMR (¹H and ¹³C{¹H}) spectral studies. The ESI-mass spectral studies indicate dimeric nature for [Zr{OPrⁱ}₂{ONC(CH₃)₂}₂] (2), [Zr{OPrⁱ}₃{ONC₁₀H₁₆}] (5) and [Zr{OPrⁱ}{ONC₁₀H₁₆}₃] (7) and monomeric nature for [Zr{ONC₁₀H₁₆}₄] (8). Oximato ligands appear to bind the zirconium in side on manner in all the complexes. Thermogravimetric curves of (2) and (8) exhibit multi-step decomposition with the formation of ZrO₂, under nitrogen atmosphere. Sol–gel transformations of precursors (5), (6), (7) and (8) in organic medium, yielded nano-sized tetragonal phase of zirconia samples (a), (b), (c) and (d), respectively, on sintering at ~600 °C. All these samples were characterized by Powder XRD patterns and EDX analyses. Surface morphologies of these samples were investigated by SEM images.     

Glycol modified cis -diisopropoxy- bis ( N -phenylsalicylideneiminato)zirconium(IV): syntheses,characterization and low temperature transformation to nanocrystalline zirconia

Zr(OPrⁱ)₄·PrⁱOH reacts with N-phenylsalicylideneimine in anhydrous benzene in 1 : 2 molar ratio to afford [Zr{O(C₆H₄)CH=NPh}₂{OPrⁱ}₂] (1). Further reactions of 1 with various glycols yield heteroleptic complexes of the type [Zr{O(C₆H₄)CH=NPh}₂{O–G–O}] [where–G–= (CH₂)₂ (2), (CH₂CHCH₃) (3), (CH₃CHCHCH₃) (4), (CH₂CHC₂H₅) (5), (CH₂)₃ (6), (CH₂CH₂CHCH₃) (7), and (CH₂)₆ (8)]. All new derivatives have been characterized by elemental analyses, FTIR and NMR (¹H and ¹³C{¹H}) studies. FAB mass spectra of 1 and 7 revealed the monomeric nature of these complexes. Complete hydrolyses and low temperature transformations of 1 and 7 using Sol-Gel technique formed tetragonal phase of ZrO₂ at 700°C, whereas transformation of tetragonal to monoclinic phase occurred at 900°C. SEM observations of these samples indicate formation of agglomerates of nanocrystalline zirconia (Scherer analysis).     

Heterotri- and -tetrametallic alkoxides of chromium(III) containing aluminium(III), gallium(III) and niobium(V)

CrCl₃ · 3THF reacts with two equivalents of potassium alkoxometallates K{M(OPr ⁱ ) _x } [M = Al(A), Ga(B), x = 4; M = Nb(C), x = 6] to give heterobimetallic chloride isopropoxides [Cr{M(OPr ⁱ ) _x }₂Cl(THF)] [M = Al(A – 1), Ga(B – 1), and Nb(C – 1)], in which the replacement of the chloride with an appropriate alkoxometallate (tetraisopropoxoaluminate, tetraisopropoxogallate, or hexaisopropoxoniobate) results in the formation of novel heterotrimetallic derivatives. The 'single pot synthesis of an heterotetrametallic isopropoxide [Cr{Nb(OPr ⁱ )₆}{Al(OPr ⁱ )₄}{Ga(OPr ⁱ )₄}] (7) has been carried out by the sequential addition of (A), (B), and (C) to a benzene suspension of CrCl₃ · 3THF. Alcoholysis of [Cr{Al(OPr ⁱ )₄}₂{Nb(OPr ⁱ )₆}] (1) and [Cr{Al(OPr ⁱ )₄}₂{Ga(OPr ⁱ )₄}] (5) with t-BuOH has also been studied and the derivatives characterized by elemental analyses, molecular weight determinations, spectroscopic [Electronic, i.r., ²⁷Al-n.m.r.] and magnetic susceptibility studies.     

Homometallic glycolates containing hydroxyl functionality for anchoring another metal: synthesis and characterization of heterometallic alkoxide–glycolates of Ti and Zr incorporating Al and Nb

Reaction of Ti(OPrⁱ)₄ with 2-methyl-2,4-pentanediol [HOGOH, where G = CMe₂CH₂CH(Me)] in 1?:?3 M ratio under reflux afforded the monomeric [Ti(OGO)(OGOH)₂] (1), which on further reactions with [Al(OPrⁱ)₃] or [Nb(OPrⁱ)₅] in 1?:?1 and 1?:?2 M ratios afforded heterometallic derivatives, [Ti(OGO)₃{M(OPrⁱ)_n?2}] and [Ti(OGO)₃{M(OPrⁱ)_n?1}₂] [where M = Al (n = 3), Nb (n = 5)], respectively. Similar reactions of Zr(OPrⁱ)₄?PrⁱOH with a number of glycols [HOGOH, where G = CH(Me)CH(Me), CMe₂CMe₂, CMe₂CH₂CH(Me)] yielded dimeric [Zr₂(OGO)₂(OGOH)₄]. [Zr₂(OGO)₆{M(OPrⁱ)_n?2}₂] and [Zr₂(OGO)₄(OGOH)₂M(OPrⁱ)_n?2] [M = Al (n = 3), Ti (n = 4), Nb (n = 5)] were prepared by 1?:?2 and 1?:?1 reactions, respectively, of [Zr₂(OGO)₂(OGOH)₄] with Al(OPrⁱ)₃, Ti(OPrⁱ)₄, or Nb(OPrⁱ)₅. Surprisingly, a 1?:?2 reaction of [VO(OPrⁱ)₃] with 2,2-diethyl-1,3-propanediol in benzene followed a different reaction and produced a neutral tetranuclear derivative [V₄(O)₄(μ-OCH₂CEt₂CH₂O)₂(OCH₂CEt₂CH₂O)₄] (18). All of these derivatives were characterized by elemental analysis, molecular weight measurements, FT-IR, and ¹H NMR (and wherever possible, by ²⁷Al or ⁵¹V NMR) spectroscopic studies. The derivatives [Zr₂(OCMe₂CH₂CH(Me)O)₂(OCMe₂CH₂CH(Me)OH)₄] (9 and 18) were additionally characterized by single-crystal X-ray structure analysis.     

A Sr(II)-Zr(IV)-Cd(II) Alkoxide Cluster: Synthesis and X-Ray Structure of [{Cd(OPri)3}Sr{Zr2(OPri)9}]2

New heterotrimetallic alkoxide [{Cd(OPrⁱ)₃}Sr{Zr₂(OPrⁱ)₉}]₂ (1) is obtained quantitatively in an anion-exchange reaction involving well-characterised iodide heterobimetallic alkoxide ICd{Zr₂(OPrⁱ)₉} and the alkali metal reagent KSr(OPrⁱ)₃. The formation of 1 is accompanied with an exchange of metals (Cd(II) and Sr(II)) between the constituting fragments (‘Cd{Zr₂(OPrⁱ)₉}⁺’ and ‘Sr(OPrⁱ)₃ ^?’) and the chelating Zr₂(OPrⁱ)₉ ^? anion, in 1, coordinates to Sr²⁺ in contrast to the precursor ICdZr₂(OPrⁱ)₉ where it is bound to Cd²⁺. The heterotrimetallic nature of 1 is unambiguously established by multinuclear (¹H, ¹³C and ¹¹³Cd) NMR spectral data and a single crystal X-ray diffraction analysis.     

Homo- and hetero-dinuclear derivatives of aluminium containing Schiff-base ligands: synthesis,characterization and antibacterial activity of mononuclear derivative of aluminium

Reactions of Al(OPrⁱ)₃ with LH₂ =?[R′C(NYOH)CHC(R)OH] R=R′=CH₃, Y =?(CH₂)₂ (L¹H₂); R =?CH₃, R′ =?C₆H₅, Y =?(CH₂)₂ (L²H₂); R =?R′ =?CH₃, Y =?(CH₂)₃ (L³H₂); R =?CH₃, R′ =?C₆H₅, Y =?(CH₂)₃ (L⁴H₂), in 1 : 2 molar ratio give mononuclear derivatives of aluminium AlLLH (1a–1d). Equimolar reactions of AlLLH with M(OPrⁱ)₃ (M =?Al and B) yield homo- and hetero-dinuclear derivatives AlLLM(OPrⁱ)₂ (M=Al=2a–2d M=B=3a–3d). Reaction of 2a with L¹H₂ affords AlL¹L¹AlL¹ (4). All these derivatives have been characterized by elemental analysis, molecular weight measurements and plausible structures have been suggested on the basis of IR, NMR [¹H, ¹³C, ²⁷Al and ¹¹B] spectral data and FAB-mass studies of 2b and 3b. Schiff base L¹H₂ and its mononuclear derivative with aluminium (AlL¹L¹H) have been screened for their antibacterial activity against Escherischia coli and Bacillus subtilis.     

Heterobimetallic diethanolaminate complexes of titanium and zirconium with alkaline earth metals

Ti(OPr ⁱ )₄ or Zr(OPr ⁱ )₄ · Pr ⁱ OH react with hydrocarbon-insoluble complexes M{(OCH₂CH₂)NH(CH₂CH₂OH)}₂ (M = Mg, Ca, Sr, Ba) in a 2:1 molar ratio to yield hydrocarbon-soluble heterobimetallic diethanolaminate isopropoxide complexes [M{(OCH₂CH₂)₂NH}₂{M(OPr ⁱ )₃}₂] (M = Mg, Ca, Sr, Ba; M = Ti, Zr), which have been characterized by elemental analyses, molecular weight measurements and spectroscopic [i.r., n.m.r. (¹H and ¹³C)] studies.     

Synthesis and structure of [Cp2Zr(OPr)(HOPr)] and its activity in the polymerisation of propene oxide

The reaction of Cp₂Zr(OPrⁱ)₂ with [H(OEt₂)₂][H₂N{B(C₆F₅)₃}₂] in dichloromethane at room temperature gives [Cp₂Zr(OPrⁱ)(HOPrⁱ)]⁺[H₂N{B(C₆F₅)₃}₂]⁻ · Et₂O in high yield. The crystal structure is reported. The complex contains a short Zr-alkoxide and a longer Zr-alcohol bond; the OH group of the coordinated isopropanol is hydrogen-bonded to a diethyl ether molecule. The complex initiates the polymerisation of propylene oxide, most probably via a cationic mechanism.     

Synthesis,characterization, volatilization,alcoholysis and hydrolytic studies of nonaalkoxodititanatocopper(II) complexes

Heterobimetallic alkoxides of Cu(II) of the types [Cu{η⁴-Ti₂(OEt)₉}Cl] (1) and [Cu{η³-Ti₂(OR)₉}₂] [R = Prⁱ (2), R = Et(3)] have been prepared for the first time by the reactions of CuCl₂ · xROH with KTi₂(OR)₉ in 1:1 and 1:2 molar ratios, respectively, in benzene medium. The chloro(nonaalkoxo dititanato)copper(II) complexes undergo chloride replacement reactions by a variety of monodentate alkoxo (⁻OPrⁱ, ⁻OEt) and chelating [Al(OPrⁱ) ₄ ⁻ , Al(OEt) ₄ ⁻ , Nb(OPrⁱ) ₆ ⁻ , Zr₂(OPrⁱ) ₉ ⁻ , Sn₂(OPrⁱ) ₉ ⁻ , and Sn₂(OEt) ₉ ⁻ ] ligands to form interesting hetero(bi-and tri-)metallic complexes. Alcoholysis (with methyl alcohol and tert-butyl alcohol) and hydrolytic [with Ba(OH)₂ · 8H₂O powder] reactions of a few typical compounds have also been investigated. All of these have been characterized by elemental analyses, molecular weight determinations, spectral (i.r. and visible) and magnetic studies. On attempted volatilization under reduced pressure these complexes liberated titanium alkoxides as a volatile component leaving nonvolatile residues.     

Synthesis and characterization of a new type of heterometallic derivative of zirconium

ZrCl₄ reacts with the potassium salt of the bifunctional tridentate Schiff base HOC₆H₄C(H)=NCH₂CH(Me)OH (LH₂) in a 1:1 molar ratio in benzene to give a new complex Zr(L)Cl₂ which, on reaction with different potassium isopropoxymetallates [e.g., KAl(OPr ⁱ )₄, KTi(OPr ⁱ )₅, and KNb(OPr ⁱ )₆], yield novel heterobimetallic derivatives. These new homo and heteronuclear coordination compounds have been characterized by elemental (N, Cl, Al, Ti, and Nb) analyses, molecular weight (ebullioscopic) measurements and spectral [i.r., n.m.r. (¹H, ¹³C and ²⁷Al)] studies and probable structures for them have been suggested.     

Incorporation of Titanium(IV) into Sterically Hindered Schiff Bases of Heterocyclic β -Diketones Involving Ketooximes and Glycol as Coligands: Preparation and Structural Considerations

Titanium(IV) complexes of the general formula TiL(OPr ⁱ )₂ [where LH₂ = R CH₃ where R = ─C₆H₅, ─C₆H₄Cl(p)] were prepared by the interaction of titanium isopropoxide with sterically hindered Schiff bases derived from heterocyclic β -diketones in 1:1 molar ratio in dry benzene. The complexes TiL(OPr ⁱ )₂ were used as versatile precursors for the synthesis of other titanium(IV) complexes. Titanium(IV) complexes of the type TiLL'(OPr ⁱ ) (where L'H═R¹R²C═NOH, R¹ = R² = ─CH₃; R¹ = ─CH₃,R² = ─C₆H₅; R¹ = ─COC₆H₅, R² = ─C₆H₅) were synthesized by the reaction of TiL(OPr ⁱ )₂ with ketooximes (L'H) in equimolar ratio in dry benzene. Another type of titanium(IV) complexes having the general formula TiLGH(OPr ⁱ ) (where GH₂═HO─G─OH, G = ─CH₂─CH₂─) have been prepared by the reaction of TiL(OPr ⁱ )₂ with glycol in 1:1 molar ratio in dry benzene. Plausible structures of these new titanium(IV) complexes have been proposed on the basis of analytical data, molecular weight measurements, and spectral studies.     

Synthesis and Spectroscopic [Electronic,IR, NMR (1H, 13C, 89Y)] Characterization of Hexaisopropoxoniobates and ‐Tantalates of Yttrium(III) and Lanthanides(III)

Hexaisopropoxoniobates/tantalates of lathanides of the type [Ln{(μ‐OPrⁱ)₂M(OPrⁱ)₄}₃] (M = Nb, Ln = Y( 1 ), La( 2 ), Nd( 3 ), Er( 4 ), Lu( 5 ); M = Ta, Ln = Y( 6 ), Gd( 7 )) have been prepared by the reactions of LnCl₃.3PrⁱOH with three equivalents of KM(OPrⁱ)₆ in benzene. Reactions in 1:2 molar ratio of LnCl₃.3PrⁱOH with KTa(OPrⁱ)₆ yielded derivatives of the type [{(PrⁱO)₃Ta(μ‐OPrⁱ)₃}Ln{(μ‐OPrⁱ)₂Ta(OPrⁱ)₄}(Cl)] (Ln = Y( 8 ), Gd( 9 )), which on interactions with one equivalent of KOPrⁱ afforded [{(PrⁱO)₃Ta(μ‐OPrⁱ)₃}Ln {(μ‐OPrⁱ)₂Ta(OPrⁱ)₄}(OPrⁱ)] (Ln = Y( 10 ), Gd( 11 )). All these derivatives have been characterized by elemental analyses and molecular weight measurements as well as by their spectroscopic [IR, ¹H and ¹³C NMR (Y, La, Lu), electronic (Nd, Er)] studies. ⁸⁹Y NMR studies have also been carried out on derivatives ( 6 ), ( 8 ), and ( 10 ).     

Synthesis and spectroscopic studies of homo- and heteroleptic N-arylsalicylaldiminates of titanium(IV), zirconium(IV) and chromium(III)

Homo- and heteroleptic N-arylsalicylaldiminate derivatives of Ti^IV and Zr^IV of the type, MX_4–x (OC₆H₄CH=NAr) _x (X = OPrⁱ, x = 2,3; X = Cl, x = 1,2,3,4; Ar = C₆H₃Me₂-2,6, C₆H₃Et₂-2,6) have been prepared by reactions in the desired molar ratios of: (i) Ti(OPrⁱ)₄/Zr(OPrⁱ)₄·PrⁱOH with N-arylsalicylaldimines in benzene, and (ii) MCl₄ (M = Ti, Zr) with Me₃SiOC₆H₄CH=NAr or HOC₆H₄CH=NAr in the presence of Et₃N as a base or the potassium salt of N-arylsalicylaldimines in benzene. The three homoleptic derivatives of Cr^III, Cr(OC₆H₄CH=NAr)₃ (Ar = C₆H₂Me₃-2,4,6, C₆H₃Et₂-2,6, C₆H₃Prⁱ ₂-2,6) have also been prepared by salt-elimination. All of these new derivatives have been characterized by elemental analyses, spectroscopic [i.r., ¹H and ¹³C-n.m.r. (Ti and Zr complexes), and electronic (for Cr complexes)] studies, as well as molecular weight measurements.     

Four novel classes of heterobimetallic isopropoxides of chromium(III)

Four novel classes of hydrocarbon-soluble isopropoxometallates of chromium(III): [Cr{²-Zr(OPr ⁱ )₅}₃], [Cr- {²-M₂(OPr ⁱ )₉}₃] [M = Zr^IV, Sn^IV], [Cr{²-M(OPr ⁱ ) _x Cl}₃] (M = Al, x = 3; M = Nb, x = 5), and [Cr{⁴-Zr₂-(OPr ⁱ )₈Cl}Cl₂]/[Cr{³-Zr₂(OPr ⁱ )₈Cl}{²-Zr₂(OPr ⁱ )₈Cl}Cl] [ ⁿ represents the number of connectivity sites (n = 2, 3, 4) involved in binding Cr^III] have been prepared for the first time and characterized by the elemental analyses, spectroscopic (i.r., electronic) and magnetic susceptibility studies as well as molecular weight measurements. The [Cr{²-Ga(OPr ⁱ )₄}₃] derivative has also been prepared and its magnetic and electronic properties compared with the above four novel types of Cr^III complexes.     

Highly fluorous zirconocene(IV) complexes and their catalytic applications in the polymerization of ethylene

The catalytic activities of the highly fluorous systems formed by the zirconocene(IV) complexes [Zr{η⁵-C₅H₄SiMe₂C₂H₄R_F}₂Cl₂] (R_F = C₆F₁₃ (4a), C₁₀F₂₁ (4b)) or [Zr-{η⁵-C₅H₃(SiMe₂C₂H₄C₆F₁₃)₂}₂Cl₂] (5a) and MMAO in toluene have been studied and compared with analogous nonfluorous systems generated from [Zr{η⁵-C₅H₄SiMe₃}₂Cl₂] and [Zr{η⁵-C₅H₅}₂Cl₂]. Although less active than the reference systems, the fluorous catalysts are stable over prolonged polymerization times, giving rise to polymers with similar molecular weights to those obtained with [Zr{η⁵-C₅H₄SiMe₃}₂Cl₂].     

Some Zirconium(IV) Complexes of Sterically Constrained Sulfur-Containing Schiff Bases of Heterocyclic β -Diketones: Synthetic Strategy and Structural Investigation Based Upon Spectroscopic Studies

Zirconium(IV) Schiff base chelates having the general formula ZrL(OPr ⁱ )₂ [where LH ₂ = R CH ₃ , R = –C ₆ H ₅ , –C ₆ H ₄ Cl(p)] were synthesized by the reaction of Zr(OPr ⁱ )₄.Pr ⁱ OH with sterically constrained sulfur-containing Schiff bases of heterocyclic β -diketones in a 1:1 molar ratio in dry refluxing benzene. The complexes ZrL(OPr ⁱ ) ₂ were used as important precursors for the synthesis of the complexes of the type Zr(L) ₂ . The complexes, Zr(L) ₂ , were prepared by the interaction of precursor ZrL(OPr ⁱ ) ₂ with sterically constrained sulfur-containing Schiff bases of heterocyclic β -diketones in a 1:1 molar ratio in dry benzene. The structures of these zirconium(IV) chelates have been discerned with the help of elemental analyses, physicochemical studies, and spectral [IR and NMR ( ¹ H and ¹³ C)] data. A distorted trigonal bipyramidal and a distorted octahedral geometry may be assigned to zirconium(IV) chelates of the types ZrL(OPr ⁱ ) ₂ and Zr(L) ₂ , respectively.     

Mono‐ and heterodi‐nuclear complexes of aluminium: synthesis,characterization and antifungal activity

Some new types of mononuclear derivatives, AlL(1–4)L(1–4)H ( 1a–1d ) of aluminium were synthesized by the reaction of Al(OPrⁱ)₃ and LH₂ [XC(NYOH)CHC(R)OH], X = CH₃, Y = (CH₂)₂, R = CH₃(L1H₂); X = C₆H₅, Y = (CH₂)₂, R = CH₃(L2H₂); X = CH₃, Y = (CH₂)₃, R = CH₃(L3H₂); X = C₆H₅, Y = (CH₂)₃, R = CH₃(L4H₂) in 1:2 molar ratio in refluxing benzene. Reactions of AlL(1–4)L(1–4)H with hexamethyldisilazane in 2:1 molar ratio yielded some new ligand bridged heterodinuclear derivatives AlL(1–4)L(1–4)SiMe₃ ( 2a – 2d ). All these newly synthesized derivatives were characterized by elemental analysis and molecular weight measurements. Tentative structures were proposed on the basis of IR and NMR spectra (¹H, ¹³C, 27 Al and ²⁹Si) and FAB‐mass studies. Schiff base ligands and their mono‐ and heterodi‐nuclear derivatives with aluminium have been screened for fungicidal activities. These compounds showed significant antifungal activity against Aspergillus niger and A. flavus. Copyright © 2007 John Wiley & Sons, Ltd.     

[FeFe] Hydrogenase: 2-Propanethiolato-Bridged {FeFe} Systems as Electrocatalysts for Hydrogen Production in Acetonitrile-Water

Diiron bis(monothiolato)-bridged hydrogenase mimics [Fe₂(μ-SⁱPr)₂(CO)₆] A (ⁱPr=isopropyl) and their phosphine derivatives [Fe₂(μ-SⁱPr)₂(CO)₅( L_1/2 )] and [Fe₂(μ-SⁱPr)₂(CO)₄( L₃ )] {tricyclohexylphosphine ( L₁ , PCy₃) 1 , triphenylphosphine ( L₂ , PPh₃) 2 and cis-1,2-bis(diphenylphosphino)ethylene ( L₃ , dppv) 3 } have been synthesized and investigated for electrocatalytic proton reduction activity in CH₃CN−H₂O. Based on the FTIR data (red-shift), the electron-donating ability of the phosphines followed the order: dppv>PCy₃>PPh₃ (average shift value with respect to complex A was 61 ( 1 ), 51 ( 2 ) and 80 ( 3 ) cm⁻¹). From CV measurements, it was seen that the catalytic reduction potential (acetic acid as proton source) shifted considerably towards positive potentials (anodic shift) on changing the solvent from pure CH₃CN to CH₃CN−H₂O (4 : 1 v/v). An increase in the percentage of water in CH₃CN led to the decomposition of complexes 1 and 3 . Though complexes A and 2 were stable in CH₃CN−H₂O (3 : 2 v/v), no improvement in electrocatalytic currents was observed.