Hydrido-phosphine complexes

Rhodium(i).—Group VII Donors. Hydrido-phosphine complexes. The trifluorophos-phine complex [RhH(PF3)(PPh3)3], an analogue of the well-known homogeneous catalyst [RhH(CO)(PPh3)3], has been synthesized by the displacement process (27).117 Similarly, white crystalline [RhH(PF3)2(PPh3)2] was obtained using a two-molar 

Photoelectron spectra have been reported for [RhH(PF3)4] and some related tri-fluorophosphine species.120 Comparison with related carbonyl complexes suggests similar 7t-acceptor properties for CO and PF3 ligands. Studies have shown that the activity of the hydrogenation catalyst [RhH(CO)2(PPh3)3], which decreases with time, can be regenerated using weak u.v.-visible irradiation.121 

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Mnltinnclear Re hydrides, in particnlar CO/phosphine complexes, with the hydride bridging two or three metals and componnds with H atoms bridging Re and other metals, for example, obtained from the reactions of Re polyhydrides with metal salts, have been reported. The coordination chemistry of hydrido/phosphine complexes has been extended, in a nnmber of cases, to related phosphite, phosphonite, or arsine complexes. ... 

With ruthenium catalysts the same products are formed as in palladium catalysis, i.e. the Cg-6-lactone and traces of esters (compare Equation 6). Ruthenium(II)-hydrido-phosphine complexes such as RuH(OAc)-(PPh3)3, RuH2(PPh3)4, RuH(OAc)(CO)(PPh3)2 or RuH (C0)(PPh3)3 can be used as catalyst precursors. When triisopropyl phosphine is added as ligand yields up to 7 5l> are obtained. Of course, the yields are rather low, however, this is the first proof that both rhodium and ruthenium are active catalyst metals in diene/C02 chemistry. 

The detailed decomposition (P-H ehminahon) mechanism of the hydrido(alkoxo) complexes, mer-crs-[lr(H)(OR)Cl(PR 3)3] (R = Me, Et, Pr R = Me, Et H trans to Cl) (56, 58, 60), forming the dihydrides mer-cis-[lr H)2Cl PR )2] (57, 59) along with the corresponding aldehyde or ketone was examined (Scheme 6-8). The hydrido(ethoxo) as well as the hydrido(isopropoxo) complexes 60 could also be prepared by oxidative addition of ethanol and isopropanol to the phosphine complexes 39 [44]. In the initial stage of the P-H elimination, a pre-equiUbrium is assumed in which an unsaturated pentacoordinated product is generated by an alcohol-assisted dissociation of the chloride. From this intermediate the transition state is reached, and the rate-determining step is an irreversible scission of the P-C-H bond. This process has a low... 

The iridium phosphine complex [IrC PEt,),] 39b can also activate O-H bonds of carboxylic acids. The stoichiometric reaction with a,(o-alkynoic acids RC=C(CH2)2 CO2H (R = Me, Ph) gave cis-hydrido(carboxylato)iridium(III) complexes 92 (Eq. 6.26), and the molecular structure of 92a was determined crystallographically [59]. 

The reactivities of hydrido(phenoxo) complexes of trons-[MH(OPh)L2] (6 M = Ni 7 M = Pt) (L = phosphine) were examined (Eqs. 6.29, 6.30 Scheme 6-16), and a high nucleophiUdty for the metal-bound phenoxide was suggested [9, 10]. Reaction with methyl iodide produced anisole and trans-[MH(I)L2] for both Ni and Pt complexes. Phenyl isocyanate also provided the insertion products into the metal-phenoxo... 

Recently, Y. Yamamoto reported a palladium-catalyzed hydroalkoxylation of methylene cyclopropanes (Scheme 6-25) [105]. Curiously, the catalysis proceeds under very specific conditions, i.e. only a 1 2 mixture of [Pd(PPh3)4] and P(o-tolyl)3 leads to an active system. Other combinations using Pd(0 or II) precursors with P(o-tolyl)3 or l,3-bis(diphenylphosphino)propane, the use of [Pd(PPh3)4] without P(o-tolyl)3 or with other phosphine ligands were all inefficient for the hydroalkoxylation. The authors assumed a mechanism in which oxidative addition of the alcohol to a Pd(0) center yields a hydrido(alkoxo) complex which is subsequently involved in hydropal-ladation of methylenecyclopropane. 

Along similar lines, Schwartz and Gell later reported that tertiary phosphines would also induce reductive elimination in bis(i7-cyclopenta-dienyl) (cyclohexylmethyl) (hydrido)zirconium resulting in high yields of zirconocene bis(phosphine) complexes (53-55). Carbon monoxide was found to readily react with a benzene solution of Cp2Zr(PMePh2)2... 

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... 

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