Electrochemical studies on neutral triple-bridged di-ruthenium compounds.

Voltammetric studies reveal that, like [Ru₂Cl₄(PPh₃)₄(CO)], triply-bridged complexes [Ru₂Cl₄L₅] (L = PClPh₂, PMePh₂, PEt₂Ph) are reversibly oxidized to [Ru₂Cl₄L₅]⁺. The mixed valence complexes [Ru₂Cl₅L₃Y] (L = PPh₃, P(tol)₃; Y = CO, CS) undergo a corresponding reduction to [Ru₂Cl₅L₃Y]^?; whereas [Ru₂Cl₅L₄] (L = PEt₂Ph, As(tol)₃) and [Ru₂Cl₆(AsPh₃)₃] are both reduced $\text{and}$ oxidised in reversible one-electron steps. For the bridging (RuCl₃Ru)^z+ moiety, the redox series z = 1, 2, 3, 4 is established.     

On the structure of tetracoordinated organocobalt complexes of the type [CoR2L2]

A series of square-planar organocobalt complexes of the type [CoR₂L₂] (R = 2,3,4,6-C₆,HCl₄ and 2,3,6-C₆H₂Cl₃, L = PEtPh₂, PEt₂Ph, and PEt₃; R = 2,3,5,6-C₆HCl₄, and 2,6-C₆H₃Cl₂, L = PEt₂Ph, PEt₃, and $\text{1}\text{2}$dpe) have been prepared in which the electronegativities of the ligand R vary progressively. The reaction of o-C₆H₄ClMgBr with [CoCl₂L₂] (L = PEtPh₂ PEt₂Ph, γ-pic or $\text{1}\text{2}$bipy) did not give air stable compounds at room temperature, but the solutions obtained at ?78°C appear to contain square-planar species for L = PEtPh₂, PEt₂Ph, and γ-pic, and tetrahedral for L₂ = bipy. The tendency towards square-planar or tetrahedral structures for the compounds [CoR₂L₂] depends on the following factors in order of importance: (i) when the neutral ligand is a phosphine a square-planar structure is adopted; (ii) when L is an aromatic amine, bulky ortho substituents on R favour a square-planar structure; and (iii) a tetrahedral geometry is favoured by bidentate amine ligands. The electronegativity of the organic group R seems to be less important.     

Preparation and characterization of some mixed ligand complexes of platinum(II)

The mixed ligand complexes PtX₂(ER₃)L and PtXY(ER₃)L (where ER₃ = PR₃ or AsMe₃; L = phosphine, arsine; X = Cl; Y = Cl, H or Me) have been prepared and characterized. Reaction of PtMe₂(ER₃)L with HCl yields PtMeCl(ER₃)L, in exclusively one of three possible isomeric forms. Excess tetramethyltin reacts with Pt₂Cl₂(μ-Cl)₂(PMe₂Ph)₂ giving both cis and trans Pt₂(μ-Cl)₂(PMe₂Ph)₂, as identified from the NMR spectra. Cleavage of Pt₂(μ-Cl)₂Me₂(PMe₂Ph)₂ with donor ligands such as AsPh₃, PMe₂ or pyridine, was useful as a synthetic route to the unsymmetrical methylchloro Pt^II derivatives. The reaction of cis-[PtMe₂(PPh₃)(AsPh₃)] with excess dimethylacetylenedicarboxylate (DMA) yielded only one product, which was of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PPh₃)(AsPh₃)], with the alkenyl groups having the same geometry about the CC bond. The use of diethylacetylene-dicarboxylate (DEA) rather than DMA gave a similar product. However, when cis-[PtMe₂(PEt₃)(AsPh₃)] was allowed to react with DMA, two products of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PEt₃)(AsPh₃)] were obtained, with the stereochemistry of both alkenyl groups being either cis or trans.     

Methyl- and phenyl-bis(tertiary phosphine) N-bonded carboxamido complexes of platinum(II)

Methyl- or phenylN-carboxamido-complexes of platinum(II) Pt(NHCOR')RL₂ (L = PEt₃, R = Me, R′ = Me, CH = CH₂; L = PEt₃, R = Ph, R′ = Me; L = PMe₂Ph, R = Ph, R′ = Me, Ph; L = PMePh₂, R = Ph, R′ =₃, R = Ph, R′ = Me) have been prepared by the reaction of KOH with cationic nitrile complexes [PtR(NCR′)L₂]BF₄. Thermally unstable hydrido-N-carboxamido-complexes could be detected spectroscopically. IR and NMR (¹H, ³¹P) spectra of some of the complexes indicate the existence of a solvent- and temperature-dependent equilibrium between syn-and anti-isomers arising from restricted rotation about the NC bond of the carboxamido-group. The anti-isomer is favoured by nonpolar solvents and by increasing bulk of L. In the complex [PtH(NCCH CH₂)(PEt₃)₂]BF₄, IR and NMR spectra show acrlonitrile to be bound through nitrogen, not through the olefinic CC bond.     

Substitution reactions of metal-metal quadruply-bonded tetrachlorotetrakis(phosphine)dimolybdenum compounds

Summary The substitutions of dimolybdenum compounds of the type [Mo₂Cl₄L₄] (where L=PEt₃, PEt₂Ph or PEtPh₂), together with the preparation and characterization of the metal-metal quadruply bonded [Mo₂Cl₄(triphos)₂] obtained from K₄Mo₂Cl₈] are described.     

Syntheses and characterization of [Ru(η5-C5H5) (AsPh3)(L)X] and [Ru(η5-C5H5)(AsPh3)(L)(MeCN)]+mY− (L = PPh3 or AsPh3; X = F,Cl, Br,I, CN,H or SnCl3; Y = HgCl3, Zn2Cl6 or BPh4; m = 1 or 2)

The syntheses of the complexes [(η⁵-C₅H₅)Ru(AsPh₃)(L)X] (L = PPh₃ or AsPh₃; X = Cl, F, Br, I, H, CN or SnCl₃) and [(η⁵-C₅H₅)Ru(AsPh₃)(L)(MeCN)]⁺Y⁻ (Y = HgCl₃, BPh₄ or Zn₂Cl₆) are described. They were characterized by elemental analyses, IR, UV and visible, PMR spectroscopy, X-ray powder diffraction, and mass spectral studies.     

Studies on the reactions of bis(acetylacetonato)platinum(II) with lewis bases : IV. Preparations and characterization of novel acetylacetonato complexes [Pt(C5H6O2)L2]

Novel complexes [Pt(C₅H₆O₂)L₂] (IVa, L = PPh₃; IVb, L = PMePh₂, IVc, L = PMe₂Ph) were prepared by the reactions of [Pt(acac)₂] with tertiary phosphines either at elevated temperature (when L = PPh₃) or at room temperature (L = PMePh₂ and PMe₂Ph), whereas AsPh₃ yielded [Pt(acac)(γ-acac)AsPh₃] (Id) by the reaction with [Pt(acac)₂] even under rigorous conditions. Complexes IV were characterized on the basis of their IR and NMR spectra, elemental analyses and chemical reactions, and a structure which possesses a chelate type “acetylacetonato” ligand involving π-oxoallyl bonding is proposed.     

Decomposition reactions of square-planar bis-aryl-cobalt(II) complexes

The organocobalt complexes [CoR₂L₂], with (a) L = PEtPh₂ and R = 2,3,5,6- C₆HCl₄, 2,4,6-C₆H₂Cl₃ and 2,6-C₆H₃Cl₂; and (b) R = 2,4,6-C₆H₂Cl₃ and L = PEt₃, PEt₂Ph, $\text{1}\text{2}$ dpe, 3,5-lut and $\text{1}\text{2}$ bipy, have been obtained by reaction of RMgX with [CoCl₂L₂] or by ligand exchange from [CoR₂(PEtPh₂)₂]. The decompositions in benzene and carbon tetrachloride, and under oxidative conditions have been studied. In benzene solutions, the stability decreases with decrease in the number of chlorine atoms in R. A mixture of RH and RR is obtained in a ratio which depends on the nature of L, the configuration of the complex, and the presence of oxidants. The thermal decomposition takes place through a tricoordinate intermediate “CoR₂L”, when L = phosphine, or directly from [CoR₂L₂] when L = amine. The oxidatively induced decomposition takes place through a cobalt(III) intermediate, which gives RR when L = phosphine or RX (X = H, Br) when L = amine. The process is intramolecular in all cases.     

Zweikernige Palladium(II)‐, Platin(II)‐ und Iridium(III)‐Komplexe von Bis[imidazol‐4‐yl]alkanen

Dinuclear Palladium(II), Platinum(II), and Iridium(III) Complexes of Bis[imidazol‐4‐yl]alkanes The reaction of bis(1,1′‐triphenylmethyl‐imidazol‐4‐yl) alkanes ((CH₂)_n bridged imidazoles L(CH₂)_nL, n = 3–6) with chloro bridged complexes [R₃P(Cl)M(μ‐Cl)M(Cl)PR₃] (M = Pd, Pt; R = Et, Pr, Bu) affords the dinuclear compounds [Cl₂(R₃P)M–L(CH₂)_nL–M(PR₃)Cl₂] 1 – 17 . The structures of [Cl₂(Et₃P)Pd–L(CH₂)₃L–Pd(PEt₃)Cl₂] ( 1 ), [Cl₂(Bu₃P)Pd–L(CH₂)₄L–Pd(PBu₃)Cl₂] ( 10 ), [Cl₂(Et₃P)Pd–L(CH₂)₅L–Pd(PEt₃)Cl₂] ( 3 ), [Cl₂(Et₃P)Pt–L(CH₂)₃L–Pt(PEt₃)Cl₂] ( 13 ) with trans Cl–M–Cl groups were determined by X‐ray diffraction. Similarly the complexes [Cl₂(Cp*)Ir–L(CH₂)_nL–Ir(Cp*)Cl₂] (n = 4–6) are obtained from [Cp*(Cl)Ir(μ‐Cl)₂Ir(Cl)Cp*] and the methylene bridged bis(imidazoles).     

Cationic pentafluorophenyl complexes of platinum(II)

The complex [O₃ClOPt(C₆F₅)(PEt₃)₂] which we have prepared for the first time, is used as a precursor of a series of cationic complexes [LPt(C₆F₅)(PEt₃)₂]ClO₄ (L = PEt₃, AsPh₃, H₂O, CO, OPPh₃, SPPh₃, HNPr₂, py), which are easily obtained by adding L to the perchlorato complex.     

The chemistry and catalytic properties of ruthenium and osmium complexes. Part 5. Synthesis of new compounds containing arsine ligands and catalytic activity in the homogeneous hydrogenation of aldehydes

Summary The complexes MHCl(CO)(AsPh₃)₃ (1: M=Ru and2: M=Os) readily react with Ph₂PCH₂CH₂AsPh₂ (Arphos) to yield MHCl(CO) (AsPh₃) (Arphos) (3: M=Ru and4: M=Os) and with acetic acid to produce MCl(CO) (OCOMe) (AsPh₃)₂ (5: M=Ru and6: M=Os); the new compounds were characterized by elemental analysis, i.r. and¹H n.m.r. spectroscopy. Complexes (1–6) are efficient catalyst precursors for the homogeneous hydrogenation of the C=O bond of propionaldehyde under moderate reaction conditions; some relations between structures and catalytic activities are described, as well as comparisons with analogous systems containing phosphine ligands.     

Chemistry of mixed ligand complexes of platinum: crystal and molecular structure of trans-[PtCl(CH3)(PEt3)(AsPh3)]

The dimethyl platinum(II) complex containing mixed ligands, cis-[Pt(CH₃)₂(PEt₃)(AsPh₃)] reacted with one equivalent of hydrogen chloride yielding trans-[PtCl(CH₃)(PEt₃)(AsPh₃)]. The X-ray crystal structure of the molecule shows the trans orientation of the PEt₃ and AsPh₃ ligands.     

Chemical Research Faculties: An International Directory : Edited by G.L. Pollock. The American Chemical Society, Washington, 1984, xxxv + ca. 530 pages. US $129.95 (U.S.A. and Canada); US $155.95 (elsewhere). ISBN 0-8412-0817-4.

Heterobinuclear complexes of formula [LMCl₂(pz)M′(tfb)] (M = Ru, L = p-cymene, M′ = Rh; M = Ir, L = C₅Me₅, M′ = Rh; M = Rh, L = C₅Me₅, M′ = Ir) and [(C₅Me₅)IrCl(pz)₂Rh(tfb)] (tfb = tetrafluorobenzo[5.6]bicyclo[2.2.2]octan-2,5,7-triene) have been prepared. The molecular structure of [(p-cymene)Ru(μ-Cl)2(μ-pz)Rh(tfb)] has been determined by X-ray diffraction. It consists of two moieties, (p-cymene)Ru and (tfb)Rh, triply-bridged by a pyrazolate group and two chlorine atoms.     

Zur kenntnis der chemie der metallcarbonyle und der cyanokomplexe in flüssigem ammoniak : XXXIII. Über die darstellung neuer carbamoylcarbonyl-komplexe aus bekannten und neuen kationischen carbonylverbindungen des mangans und rheniums

The covalent carbamoyl carbonyl compounds Re(CO)₅COHN₂, cis-M(CO)₄(L)CONH₂, M(CO)₃(L)₂CONH₂ and M(CO)₃(D)CONH₂ (M = Mn, Re; L = PPh₃, PEt₃; D = bipy, phen) are formed by reactions of the cationic complexes [Re(CO)₆]⁺, [M(CO)₅L]⁺, [M(CO)₄L₂]⁺ and [M(CO)₄D]⁺ (M = Mn, Re; L = PPh₃, PEt₃; D = bipy, phen) with liquid NH₃ with concomitant deprotonation: [M(CO)_6?nL_n]⁺ + 2 NH₃ → M(CO)_5?nL_nCONH₂ + NH₄⁺ (n = 0, 1, 2) and [M(CO)₄D]⁺ + 2 NH₃ → M(CO)₃(D)CONH₂ + NH₄⁺ The stability of the above-mentioned carbamoyl carbonyl complexes increases from the penta- to the tetra- to the tri-carbonyl derivatives. In all cases the rhenium compounds are much more stable than the corresponding manganese complexes. Whereas the carbamoyl compound Re(CO)₄(PEt₃)CONH₂ can be isolated by reaction of [Re(CO)₅PEt₃]⁺ with NH₃, the corresponding manganese complex undergoes Hofmann degradation of amides even at ?70°C to form HMn(CO)₄PEt₃ and NH₄NCO. The IR and some mass and ¹H NMR spectra of the new hexacoordinated carbamoyl carbonyl complexes are discussed and the reactions of these compounds with liquid NH₃, HCl and CH₃OH are described.     

Bridging alkyls in d-transition metal chemistry: reaction of (cod)2 RH2 (μ-R)2 with Lewis bases to give (cod)Rh(R)(L) and their reaction with aromatic hydrocarbons

Low temperatùre (−70°C) reaction of (cod)₂Rh₂2 (μ-Cl)₂ with two molar equivalents of RLi in diethyl ether gives (cod)₂Rh₂ (μ-R)₂ where R = Me, Me₃SiCH₂. Even though the bridging alkyls are air and moisture sensitive, they may be stored for prolonged periods at −30°C. The bridging alkyls are fluxional at + 20°C and the NMR spectra are consistent with a dimer of idealized D_2h symmetry. Low temperature NMR spectroscopic studies suggest that the dimers have idealized C_2v symmetry as found by X-ray studies described earlier. The bridging alkyls readily react with Lewis bases to give monomeric (cod)Rh(R)(L) where R = Me and L = PMe₃, PEt₃, P(NMe₂)₃, P(OMe)₃, py and R = Me₃SiCH₂, L = P(OMe)₃. The five coordinate, fluxional complex, (cod)RhMe(PMe₃)₂ also may be isolated. The four coordinate (cod)RhMe(PEt₃), slowly reacts with toluene to give (cod)Rh(m-tolyl)(PEt₃), (cod)Rh(p-tolyl)(PEt₃), and methane and (cod)RhMe(PMe₃) slowly reacts with benzene to give (cod)Rh(Ph)(PMe₃) and methane.     

The preparation of cis- and trans-[PtH(C6Cl5)(PEt3)2 and a study of the “hydride-donor capacity” of the complexes trans- [PtH(C6X5(PEt3)2] (X = F and Cl)

The preparations of cis- and trans-[PtH(C₆Cl₅)(PEt₃)₂] by thermal decomposition of cis- and trans-[Pt(OCHO)(C₆Cl₅)(PEt₃)₂], respectively, are reported. Also described are cis- and trans-[Pt(SnCl₃)(C₆Cl₅)(PEt₃)₂], obtained by treating SnCl₂ with cis- and trans-[PtCl(C₆,Cl₅)(PEt₃)₂], respectively. It is shown that while trans- [PtH(C₆Cl₅)(PEt₃)₂] does not form hydride-bridged complexes in the presence of trans-(PtH(MeOH)(PEt₃)₂]⁺, the corresponding complex trans-[PtH(C₆)(PEt₃)₂] reacts with the same solvento complex, in methanol, giving labile [(PEt₃)₂HPt(-μH)Pt(C₆F₅)(PEt₃)₂]⁺.     

Acid–base equilibria of the aqua adducts of Ru(II) arene complexes with functionalised pyridines

Acid?Cbase equilibria of the aqua adducts of Ru(II) arene complexes, general formulae [(??⁶-p-cymene)Ru (L^1?3)Cl₂] where L¹?=?3-acetylpyridine (1), L²?=?4-acetylpyridine (2) and L³?=?2-amino-5-chloropyridine (3), then [(??⁶-p-cymene)Ru(HL⁴)Cl₂] with HL⁴?=?isonicotinic acid (4); [(??⁶-p-cymene)Ru(HL^5?8)Cl] where H₂L⁵?=?2,3-pyridine dicarboxylic acid (5), H₂L⁶?=?2,4-pyridine dicarboxylic acid (6), H₂L⁷?=?2,5-pyridine dicarboxylic acid (7) and H₂L⁸?=?2,6-pyridine dicarboxylic acid (8) have been studied. pK _a values were determined by potentiometry at 25?°C and constant ionic strength of 0.1?M NaNO₃. The assumed equilibria were confirmed by UV and ¹H-NMR spectroscopy.     

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.     

Ring opening of 3,3,4,4-tetracyano-2,2-bis(triphenylarsine)-1-oxa-3-platinacyclobutane promoted by various phosphines

In the presence of added ligand, (PMe₂Ph, PEt₃, PMePh₂ and PEt₂Ph) the title compound undergoes ligand exchange and ring opening to give compounds of the type {L₂Pt(CN)[OC(CN)C(CN)₂]} having a trans configuration. A spectrophotometric kinetic study was carried out in CH₂Cl₂ and C₂H₅OH and the rate found to be proportional to the concentration of added phosphine. A linear relation between the second order rate constants and the cone angles of entering ligands points to the dominance of steric effects.     

A Binuclear Ruthenium(III)-Dioxygen Complex

Abstract

A binuclear μ-peroxo ruthenium(III) complex of the composition [Cl₂(AsPh₃)₃RuO₂Ru(AsPh₃)₃Cl₂]Cl₂ is reported.