Metal-metal bonds.

The introduction includes a comprehensive review of the reaction of metal-metal bonded compounds. The reaction of d8 cyclopentadienyl-cobalt (I), -rhodium (I) and -iridium(I) complexes with mercuric chloride and bromide produce A series of 1:1 adducts, which are shown to be isostructural with Cp(CO)2Co.HgCl2 containing donor-acceptor type metal-mercury bonds. The reactions of square planar d8 cycloocta- 1:5 -diene rhodium (I) complexes with mercuric chloride and bromide are reported. The halogen and acetate bridged rhodium complexes form adducts containing a 1:1 rhodium to mercury ratio. The infra-red spectra are discussed and possible structures for the adducts formulated. The square planar complexes RhC.O.D.C1L (where L -PPh3, AsPh3, SbPh3, ptoluidine and piperidine) react with mercuric chloride according to one of the following equations:- (i) 2RhC.0.D.C1L + 4HgCl2 '(RhC.O.D.Cl)2.2HgCl2 + L2Hg2Cl4 or (ii) RhC.O.D.ClL + 2HgCl2 ' RhC.O.D.C1L.2HgCl2. The course of the reaction appears to depend on the molubility of L2Hg2Cl4 in the reaction solvent. Preliminary reactions with similar lridium (I) complexes are reported. The reactions of tri-nuclear systems of the type (where R = CrCp(CO)3, MoCp(CO)3, FeCp(CO)2, co(CO)4 and Mn(CO)5) with mercuric chloride produce 1:1 adducts and possible structuren for the adducts based on infra-red evidence are described. Raman and infra-red studies of the tri-nuclear systems HgR2 are reoorted and metal- metal stretching vibrations assigned. Metal-donor systems are discussed and solution data on some mercury-iron and mercury-ruthenium bonded complexes are studied.