Isocyanide complexes, carbonyl-phosphine

Tetrakis(alkyl isocyanide) complexes of nickel(O), Ni(CNR)4, and the mixed isocyanide complexes with phosphines and unsaturated molecules are strictly analogous to the corresponding carbonyl complexes.23,24 They are generally more stable than [Ni(CN)4]4-. Mixed isocyanide complexes have been prepared by the reaction of Ni(cod)2 and CNBu followed by reaction with the appropriate phosphine or unsaturated molecules (alkenes, arylnitroso compounds, azo compounds, etc.) as outlined in equations (7) and (S).25... 

The diphosphine (R,S)-BPPFA [(R,pS)-9] reacts analogously with acetic anhydride to give the corresponding acetate which can be derivatized. Replacement of the acetate by hydroxide leads to a useful ligand BPPFOH 1534, which has been used for the rhodium-catalyzed enantioselective reduction of a-oxo acids to a-hydroxy acids (Section D.2.3.1.). Recently, the chemistry of gold(I) complexes of such chiral phosphines has been developed they catalyze aldol-type cycloadditions of isocyanides to carbonyl compounds to give chiral dihydrooxazoles. which can be hydrolyzed to synthetically important chiral amino alcohols and amino acids 30,39,40. 

An unusual deoxygenation of one carbonyl ligand has been reported to occur in the reaction of [RuIGp(GO)2] with the iminophosphorane-phosphine Ph2P(GH2)3N=PPh3 which yields the isocyanide complex [RuIGp r/ -... 

Several papers have appeared recently comparing various properties of carbonyl metal complexes substituted by various phosphines or phosphite ligands or isocyanides. Angelici and Ingemanson (4) studied the equilibrium... 

The great majority of platinum(I) complexes are binuclear with monofunctional or bifunctional bridging groups. However, there is also a series of unsupported dimers with the general structure shown in (12). These are generally stabilized by phosphine, carbonyl, and isocyanide ligands.17 Dimeric hydride complexes can have terminal or bridging hydrides and these are discussed above in Section 6.5.2.1.4. 

Rhenium(0) compounds are rare and frequently lie in the realm of the organometallic chemistry. A simple example is decacarbonyldirhenium(0) in which two staggered, square-pyramidal Re(CO)5 fragments are held together by a single rhenium-rhenium bond. Substitution of carbonyl ligands is possible by tertiary phosphines and arsines, silanes and isocyanides, and binuclear Re-Re, Mn-Re, and Co-Re complexes have been studied. " Successive replacement of CO ligands can readily be observed by vibrational spectroscopy. This has been demonstrated... 

Lever has successfully predicted Mn"/ potentials of 24 Mn-carbonyl complexes containing halide, pseudohalide, isonitrile, and phosphine co-ligands, with additivity parameters derived from the potentials of Ru "/" couples [39]. An important consideration for heteroleptic complexes is the influence of isomerism on redox thermodynamics. For Mn(CO) (CNR)6- complexes, with n = 2 or 3, the Mn"/ potentials for cis/trans and fac/mer pairs differ by as much as 0.2 V [40]. The effect arises from the different a-donor and 7r-acceptor abilities of carbonyl (CO) and isocyanide and their influence on the energy of the highest energy occupied molecular orbital (HOMO). 

The complex Mn2(/x-H)(/x-PPh2)(CO)8 undergoes carbonyl substitution reactions with phosphite, phosphine, or isocyanide ligands, either thermally or... 

TRI- AND TETRANUCLEAR CARBONYL-RUTHENIUM CLUSTER COMPLEXES CONTAINING ISOCYANIDE, TERTIARY PHOSPHINE, AND PHOSPHITE LIGANDS. RADICAL ION-INITIATED SUBSTITUTION OF METAL CLUSTER CARBONYL COMPLEXES UNDER MILD CONDITIONS... 

In the case of the heterobimetallic systems, the few examples known so far are [ClPt(p-dppm)2(p-C=N-Me)Ni(CNMe)]Cl (64), reported by Kubiak and collaborators, which is obtained via a transmetallation of [(CNMe)]Ni (p,-dppm)2(p,-C = N-Me)Ni(CNMe)] with [Pt(dppm)Cl2].80 The other examples are the mixed M-Pt systems 65—74 (M = W, Fe, Mo, Cr) containing a dis-phosphine backbone (dppm or dppa), as described by Knorr and collaborators81 -84 (Fig. 31). These complexes were obtained via substitution of the bridging carbonyl by an isocyanide ligand. 

---