Publisher Summary This chapter discusses metal–isocyanide chemistry. In the interim, reviews have appeared on specific aspects of isocyanide chemistry. The generally accepted valence bond and molecular orbital (MO) approach to the bonding of metal isocyanides has been well described in Treichel's review, and has been used to rationalize variations in infrared (IR) stretching frequencies between bonded and nonbonded isocyanides and the better π-acceptor qualities of aryl versus alkyl isocyanide groups. A number of new synthetic routes to isocyanide complexes of chromium, molybdenum, and tungsten have been investigated. A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. A number of routes have been employed for the synthesis of metal–isocyanide complexes by generating the isocyanide ligand on the metal atom. A number of monomeric complexes have been prepared, which may be considered as substitution products of the [Co(CNR) 5 ] + and [M(CNR) 4 ] + cations. Electrochemical investigations have been reported on a range of homoleptic and mixed carbonyl–isocyanide complexes, in attempts to rationalize substituent effects on the isocyanide with the electronic structure of the metal. Insertion reactions of isonitriles into metal–alkyl or metal–aryl bonds are now well established, occurring with metal–alkyl or –aryl groups from group IVA to IB and, recently, with uranium and thorium carbon bonds.

Metal Isocyanide Complexes

Organopalladium complexes containing palladiumpalladium bonds

The chemistry of binuclear palladium(II) and platinum(II) complexes

Publisher Summary Organometallic chemistry encountered rapid expansion experienced by the synthesis, spectroscopy, structural chemistry, theory, and reactivity of compounds characterized by terminal carbene (methylene, A) and carbyne (methylidyne, B) functionalities. The chemistry of μ-methylene complexes did not develop as extensively as that of its mononuclear counterparts, the latter being characterized by terminal carbene ligands. As in the bonding of carbenes with single atoms metal, the methylene group has a filled orbital (a 1 ) that can act as a sigma donor to the system. Symmetrical methylene (alkylidene) bridges represent the predominant geometry. Stability against thermolysis and photolysis is one of the striking properties of dimetallacyclopropanes, especially of those involving carbonyl and cyclopentadienyl ligands on the metals. There is so far not a single exception to the rule that a μ-methylene complex is at least as stable as its μ-carbonyl counterpart. Substitution reactions at the methylene bridge have been observed, albeit the yields were quite low suggesting that major side reactions had occurred. The molecular regimes in discrete di- and polynuclear complexes are mostly coordinatively saturated, whereas metal surfaces, especially if they are relatively flat and close-packed, have no coordinatively saturated surface atoms, even in the presence of chemisorbed species. There is an array of well-established analogues of the μ-methylene complexes in which the heavier congeners of carbon adopt bridging positions.

The Methylene Bridge

Ambidentate ligands, the schizophrenics of coordination chemistry

Organo halide addition to tris(bis(diphenylphosphino)methane)dipalladium. Preparation of novel methylene- and phenylene-bridged complexes by two-center, three-fragment oxidative addition

Chung-Li. Lee

Papers

Organo halide addition to tris(bis(diphenylphosphino)methane)dipalladium. Preparation of novel methylene- and phenylene-bridged complexes by two-center, three-fragment oxidative addition

Novel reactions of metal-metal bonds. Reactions of Pd2{C6H5)2PCH2P(C6H5)2}2Cl2 with acetylenes, olefins, and isothiocyanates

Novel reactions of metal-metal bonds. Reactions of Pd2{C6H5)2PCH2P(C6H5)2}2Cl2 with acetylenes, olefins, and isothiocyanates