Electroanalytical investigation on the stability of tetracoordinate nickel(I) complexes

The stability of tetracoordinate nickel(I) complexes, of the type [Ni(CN)₂P₂]^? (P=substituted phosphine), generated by cathodic reduction of the parent nickel(II) complexes, has been studied by cyclic voltammetry and double potential step techniques. Evidence has been obtained that nickel(I) complexes decay to the dimeric species Ni₂(CN)₂P₄ via a first order chemical reaction the rate determining step being the release of a cyanide ion leading to the radical species [Ni(CN)P₂]. The experimental trend obtained for the first order kinetic constants has been explained on the basis of the different “trans-effect” induced by a cyanide ligand in comparison with that induced by a phosphine group and taking into account the different basic character of the phosphine ligands.     

New tetra- and pentacoordinate nickel(I) complexes

Summary The reduction of nickel(II) halides with NaBH₄ in ethanol has been studied in the presence of various tertiary phosphines and arsines. Complexes of the type XNiL₃ have been isolated in this way when X = Cl, Br, I and L = PPh₃, AsPh₃, no reaction being observed when L = PEt₃, PBu₃ and Ph₂P(CH₂)₂PPh₂.The reaction of XNiL₃ with CO gas at room temperature produces pentacoordinate carbonyl complexes XNi(CO)₂L₂ when L is triphenylphosphine. The lack of stability prevents the isolation of similar complexes when L is trip henylarsine.Structural data obtained by i.r. spectroscopy and susceptibility measurements as well as chemical behaviour of the new complexes are described.     

Monocarbonyl cationic rhodium(I) complexes

Summary The preparations and characterisation of cationic complexes of the type [Rh(CO)(MeCN)(PR₃)₂]ClO₄, [Rh(CO)L(PR₃)₂]ClO₄ (L=py or 2-MeOpy), [Rh(CO)(L-L)(PR₃)₂]ClO₄ (L-L = bipy or phen) and [Rh(CO)(PR₃)₃]ClO₄ with PR₃ = P(p-YC₆H₄)₃ (Y=Cl, F, Me or MeO) are described.     

New nickel(II) chloride-morpholine complexes

The compounds [NiCl₂(Morph)₃(H₂O)₂] and [NiCl₂(Morph)₃] have been prepared by treating NiCl₂·6H₂O with morpholine (Mo     

Some cationic carbonyl complexes of rhodium(I)

A number of cationic rhodium(I) complexes of the type [Rh(CO)₂(NN)]ClO₄, [Rh(CO)₂L₃]ClO₄ and [Rh(CO)(NN)L₂]ClO₄, where (NN) is 2,2^′-bipyridine or 1,10-phenanthroline and L is a tertiary phosphine or arsine, have been isolated and their structures assigned. The configuration of the complexes ion [Rh(CO)₂L₃]⁺ appears to depend critically on the size of the ligand L.     

An electroanalytical investigation of the olefin isomerization reaction promoted by electrogenerated cationic nickel(I) complexes

Summary Evidence for the ability of the electrogenerated cationic nickel(I) complex [Ni(PPh₃)₄]⁺ to promote the isomerization of allylbenzene is reported. However, the corresponding triethylphosphitenickel(I) complex displays no catalytic activity, apparently due to the poor leavinggroup character exhibited by the phosphite. The involvement of a -allylnickel hydride in the isomerization reaction is inferred from a comparison of the results obtained with those for the same reaction promoted by nickel hydride.     

Isolated cationic crown ether complexes of gallium(I) and indium(I)

The recently reported homologous low-valent indium and gallium salts M(+)[Al(OR(F))(4)](-) (M = Ga, In; R(F) = C(CF(3))(3)) were used to extend the coordination chemistry of Ga(I) and In(I) to the isolated [18]crown-6 complexes [M([18]crown-6)(PhF)(2)](+)[Al(OR(F))(4)](-) in fluorobenzene solution (PhF = C(6)H(5)F). In contrast to known ion-paired compounds for M = In, our complexes are undisturbed and in the solid state free of contacts to the anion. A peculiar combination of very weak η(1)- and η(6)-coordination to the PhF-solvent was observed that allows speculation about the presence of a stereochemically active lone pair at M(I). Structure and energetics of these novel salts were rationalized on the basis of DFT calculations.     

New thermally stable cationic eta3-allyl(1,4-diphospha-(1,3)-butadiene)nickel complexes for ethylene polymerization

Nickel ethylene polymerization catalysts 1a,b bearing a P,P-ligand with two sp2-hybridized phosphorus atoms have been synthesized; their structure and polymerization studies have been reported for the first time.     

36-Nuclear anionic cobalt(II) and nickel(II) complexes in solid-phase insertion reactions

The reactions of single crystals containing 36-nuclear anionic complexes of cobalt(II), (NBu₄)₈[Co₃₆(H₂O-κO)₁₂(μ₃-OH)₂₀(μ₄-Me₂Mal-κ₂O,O′)₂₄(μ₄-Me₂Mal)₆] · 2.5H₂O ? CH₃OH (I), and nickel(II), (NBu₄)₈[Ni₃₆(H₂O-κO)₁₂(μ₃-OH)₂₀(μ₄-Me₂Mal-κ₂O,O′)₂₄(μ₄-Me₂Mal)₆] · 6H₂O ? 2C₂H₅OH (II) and (NHEt₃)₃[Ni₃₆(NHEt₃)(H₂O-κO)_12.25(μ₃-OH)₂₀(μ₄-HMe₂Mal-κ₂O,O′)₄(μ₄-Me₂Mal-κ₂O,O′)₂₀(μ₄-Me₂Mal)₆] · 39H₂O (III), with solutions of 1,4-dioxane and a 0.1 M solution of Dabco (Dabco is 1,4-diazabicyclo[2.2.2]octane) in EtOH are studied. An ethanol solution of Dabco dissolves the crystals of the complexes, whereas the insertion of the solvent molecules with single crystal retention (for the cobalt compound containing tetrabutylammonium cation, I), cracking (for the nickel analog, II), or dissolution (for the cobalt complex containing triethylammonium, III) occurs in 1,4-dioxane. The X-ray diffraction analyses show the substitution of the uncoordinated water and ethanol molecules in the starting compound by 1,4-dioxane molecules in the structure of compound I to form (NBu₄)₈[Co₃₆(H₂O-κO)₁₂(μ₃-OH)₂₀(μ₄-Me₂Mal-κ₂O,O′)₂₄(μ₄-Me₂Mal)₆] · 7C₄H₈O₂ (IV), which is accompanied by a change in the conformation and the shift of tetrabutylammonium cations, indicating a possibility of the modification of the 36-nuclear d-metal complexes with the malonic acid derivatives in the solid-phase resolvation reactions (CIF files CCDC no. 1557499 (III) and 1557500 (IV)).     

Tetraphosphinitoresorcinarene complexes: cationic silver(I) and copper(I) halide complexes as mercurate(II) anion receptors

The reactions of mercury(II) halides with the tetraphosphinitoresorcinarene complexes [P4M5X5], where M=Cu or Ag, X=Cl, Br, or I, and P4=(PhCH2CH2CHC6H2)4(O2CR)4(OPPh2)4 with R=C6H11, 4-C6H4Me, C4H3S, OCH2CCH, or OCH2Ph, have been studied. The reactions of the complexes with HgX2 when M=Ag and X=Cl or Br occur with elimination of silver(I) halide and formation of [P4Ag2X(HgX3)], but when M=Ag and X=I, the complexes [P4Ag4I5(HgI)] are formed. When M=Cu and X=I, the products were the remarkable capsule complexes [(P4Cu2I)2(Hg2X6)]. When M=Ag and X=I, the reaction with both CuI and HgI2 gave the complexes [P4Cu2I(Hg2I5)]. Many of these complexes are structurally characterized as containing mercurate anions weakly bonded to cationic tetraphosphinitoresorcinarene complexes of copper(I) or silver(I) in an unusual form of host-guest interaction. In contrast, the complex [P4Ag4I5(HgI)] is considered to be derived from an anionic silver cluster with an iodomercury(II) cation. Fluxionality of the complexes in solution is interpreted in terms of easy, reversible making and breaking of secondary bonds between the copper(I) or silver(I) cations and the mercurate anions.     

Asymmetric hydrogenation using ferrocenylphosphine rhodium(I) cationic complexes

High optical yields are obtained in the hydrogenation of α-acetamidocinnamic acid using [(COD)Rh((+)PPFA)]ClO₄ and related complexes as catalysts. (+)PPFA is (S)-α-[(R)-2-diphenylphosphinoferrocenyl] ethyldimethylamine.     

(Fluoroalkyl)phosphine complexes of nickel(0) and cobalt(I)

The synthesis of a series of (fluoroalkyl)phosphine complexes of nickel is reported. Treatment of (cod)₂Ni with dfepe (dfepe=(C₂F₅)₂PCH₂CH₂P(C₂F₅)₂) yields (dfepe)Ni(cod) (1), which has been structurally characterized. Treatment of 1 with CO or bipy results in the formation of (dfepe)Ni(CO)₂ (2) and (dfepe)Ni(bipy) (3), respectively. Addition of excess dfepe to 1 results in incomplete cod displacement to form (dfepe)₂Ni (4). The homoleptic complex 4 may be independently prepared in high yield by reduction of (acac)₂Ni with (ⁱBu)₃Al in the presence of butadiene and excess dfepe. Solvation of (dfepe)Ni(cod) in acetonitrile gives a new complex tentatively identified as (dfepe)Ni(MeCN)₂ (6), whereas dissolution of (dfepe)₂Ni in acetonitrile leads to a mixture of 6 and the partial displacement product (dfepe)(η¹-dfepe)Ni(MeCN) (5). In contrast to (R₃P)₄Ni(0) phosphine and phosphite complexes, which undergo protonation by strong anhydrous acids such as HCl, H₂SO₄ and CF₃CO₂H to give (R₃P)₄Ni(H)⁺ products, Treatment of (dfepe)₂Ni with neat CF₃CO₂H or excess HOTf in dichloromethane gave no spectroscopic evidence for (dfepe)₂Ni(H)⁺. Exposure for extended periods leads to dfepe loss and decomposition to Ni(II) products. The synthesis of the first cobalt complex of dfepe, (dfepe)Co(CO)₂H, is also reported.     

Solvent effects on the aquation of cationic,anionic and nonionic chlorocobalt(III) complexes

The kinetics of aquation of - and - cis[Co(edda)Cl2]–, - cis[Co(edda)(H2O)Cl] and - cis[Co(trien)Cl2]+ were investigated in aqueous mixtures of t-BuOH, MeOH, DMSO, ethylene carbonate and urea. The transfer Gibbs energy values for the reactants, evaluated from the solubility of the complexes, confirm the decisive role of the reactant solvation on the aquation rate.     

Paramagnetic complexes of nickel(I) stabilized by norbornadiene

Nickel(I) compounds whose concentration was 10^–4–10^–6 of the total concentration of nickel added to the system were identified by EPR in the reaction of 2,5-norbornadiene with nickel homoligand allyl complexes Niall₂ (all is C₃H₅, 1-CH₃C₃H₄, or 2-CH₃C₃H₄). The Ni(I) complexes were stable at room temperature under oxygen-free conditions. It was shown that the paramagnetic complexes were in equilibrium with diamagnetic forms. The temperature dependence of the concentration of the paramagnetic species was determined. The structure of the paramagnetic nickel(I) complexes and the possible routes of their formation are discussed on the basis of the obtained data.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 490–493, July–August, 1990.     

Iridium(III) soft salts from dinuclear cationic and mononuclear anionic complexes for OLED devices

Two iridium(III) soft salts based on ion-paired dinuclear cationic and mononuclear anionic complexes were designed and investigated as phosphorescent emitters for solution processed OLEDs. New dinuclear cationic complexes were prepared with two different bridging ligands, a carbazole and a phenylene spacer. Best devices were designed with the soft salt bearing a carbazole moiety.     

Carbonyl cationic rhodium(I) and iridium(I) complexes with sulphur donor and triphenylphosphine ligands

Summary The reaction of previously reported Rh^I and Ir^I cationic complexes towards carbon monoxide and triphenylphosphine has been studied. Carbonyl rhodium(I) mixed complexes of the formulae [Rh(CO)L₂(PPh₃)]ClO₄, (L=tetrahydrothiophene(tht), trimethylene sulfide(tms), SMe₂, or SEt₂), [(CO)(PPh₃)Rh{-(L-L)}₂Rh(PPh₃)(CO)](ClO₄)₂ (L-L= 2,2,7,7-tetramethyl-3,6-dithiaoctane (tmdto), (MeS)₂(CH₂)₃ (dth), or 1,4-dithiacyclohexane (dt), [Rh(CO)L(PPh₃)₂]ClO₄ (L= tht, tms, SMe₂, or SEt₂), and carbonyl iridium(I) complexes of the formulae [Ir(CO)₂(COD)(PPh₃)]ClO₄, [Ir(CO)(COD)(PPh₃)₂]ClO₄, [(CO)(COD)(PPh₃) Ir{-(L-L)} Ir(PPh₃)(COD)(CO)](ClO₄)₂ (L-L = tmdto or dt), [(CO)₂ (PPh₃)Ir(-tmdto)Ir(PPh₃)(CO)₂](ClO₄)₂, [(CO)₂(PPh₃) Ir(-dt)₂Ir(PPh₃)(CO)₂](ClO₄)₂, were prepared by different synthetic methods.     

New π-carboxo complexes of nickel(0)

The synthesis of several new zerovalent nickel complexes containing carboxo coordinated organic molecules bearing substituents such as CN, CO₂R, CF₃, F, and F₂CCF demonstrates that a range of electron withdrawing functional groups is capable of effecting the necessary activation of the CO bond to cause π-coordination.     

Preparation and properties of some cationic binuclear platinum(I) complexes

Reaction of [Pt₂Cl₂(μ-dppm)₂] with ligands, L, in the presence of [PF₆^- gave stable cationic diplatinum(I) complexes [Pt₂L₂(μ-dppm)₂][PF₆]₂ where L = PMe₂Ph, PMePh₂, PPh₃, NH₃, C₅H₅N. Reaction of [Pt₂(NH₃)₂(μ-dppm)₂][PF₆]₂ with CO gave [Pt₂(CO)₂(μ-dppm)₂][PF₆]₂ and an unsymmetrical complex [Pt₂(CO)(C₅H₅N)(μ-dppm)₂][PF₆]₂ was also prepared. The compounds were characterized by vibrational and ¹H and ³¹P NMR spectroscopy and the presence of direct platinumplatinum bonds is indicated.