Hydrido-carbonyl and -phosphine complexes

Hydrido-carbonyl and -phosphine complexes. Several new hydrido-diphenyl-phosphine complexes have been prepared from the recently described cis- or trans- [RuCl2(HPPh2)4] (Scheme 3). 

Hydrido-carbonyl and -phosphine complexes. A series of hydride complexes [IrHCl(PPh3)2(RCOO)] (R = Me, Et, Pr, H, Ph, CF3, MeCHCl, or P-NO2-CgH4) (44) have been prepared via the protonation of [Ir(N2)Cl(PPh3)2] w ith... 

A few representative examples of simple organometallic compounds of nickel(II) including carbonyl and hydrido compounds are reported here. A more complete listing of such types of compound is given in Comprehensive Organometallic Chemistry (vol. 6, p. 37) and references therein. Selected structural data for organometallic nickel(II) complexes with monodentate phosphines are reported in Table 61. 

The products of oxidative addition of acyl chlorides and alkyl halides to various tertiary phosphine complexes of rhodium(I) and iridium(I) are discussed. Features of interest include (1) an equilibrium between a five-coordinate acetylrhodium(III) cation and its six-coordinate methyl(carbonyl) isomer which is established at an intermediate rate on the NMR time scale at room temperature, and (2) a solvent-dependent secondary- to normal-alkyl-group isomerization in octahedral al-kyliridium(III) complexes. The chemistry of monomeric, tertiary phosphine-stabilized hydroxoplatinum(II) complexes is reviewed, with emphasis on their conversion into hydrido -alkyl or -aryl complexes. Evidence for an electronic cis-PtP bond-weakening influence is presented. 

The pale yellow [Ni(PEt3)4] is also tetrahedral but with some distortion. In sharp contrast to nickel, palladium forms no simple carbonyl, Pt(CO)4 is prepared only by matrix isolation at very low temperatures and reports of K4[M(CN)4] (M = Pd, Pt) may well refer to hydrido complexes in any event they are very unstable. The chemistry of these two metals in the zero oxidation state is in fact essentially that of their phosphine and arsine complexes and was initiated by L. Malatesta and his school in the 1950s. Compounds of the type [M(PR3)4], of which [Pt(PPh3)4] has been most thoroughly studied, are in general yellow, air-stable solids or liquids obtained by reducing complexes in H2O or H20/EtOH solutions with hydrazine or sodium borohydride. They are tetrahedral molecules whose most important property is their readiness to dissociate in solution to form... 

There are only limited pKj, scales for transition metal hydride complexes compared to the extensive scales for organic and inorganic acids, despite the fact that hydrides often mediate organometallic reactions these were reviewed in 1991 [42]. Most of these complexes contain carbonyl and/or phosphine ligands and are usually insoluble in water. The for about 20 neutral hydrido-carbonyl... 

Cobalt, nickel, iron, ruthenium, and rhodium carbonyls as well as palladium complexes are catalysts for hydrocarboxylation reactions and therefore reactions of olefins and acetylenes with CO and water, and also other carbonylation reactions. Analogously to hydroformylation reactions, better catalytic properties are shown by metal hydrido carbonyls having strong acidic properties. As in hydroformylation reactions, phosphine-carbonyl complexes of these metals are particularly active. Solvents for such reactions are alcohols, ketones, esters, pyridine, and acidic aqueous solutions. Stoichiometric carbonylation reaction by means of [Ni(CO)4] proceeds at atmospheric pressure at 308-353 K. In the presence of catalytic amounts of nickel carbonyl, this reaction is carried out at 390-490 K and 3 MPa. In the case of carbonylation which utilizes catalytic amounts of cobalt carbonyl, higher temperatures (up to 530 K) and higher pressures (3-90 MPa) are applied. Alkoxylcarbonylation reactions generally proceed under more drastic conditions than corresponding hydrocarboxylation reactions. 

---