Organometallic compounds with bridging ligands

Bianchi et al. determined the orthorhombie erystal strueture of Co2 CO fi-C0)(/r-C402H2) and found that two C-H... 0 bonds eonneeted the molecules. The presence of a Co-Co BCP indieates for the first time the existence of a metal-metal bond in a system with bridged ligands. The BCP properties of the intramolecular bonds and of the intermolecular interactions show features similar to those found in Mn2COio, eonfirming the authors previously established bonding classification for organometallic and coordination compounds. 

The first organometallic compound of the transition metals to be characterized (1827) was Zeise s salt, K[(C2H4)PtCl3]-H20 (Fig. 18.1). It forms when K2[PtCl4] in aqueous ethanol is exposed to ethylene (ethene) a dimeric Pt—C2H4 complex with Cl bridges is also formed. In both species, the ethylene is bonded sideways to the platinum(II) center so that the two carbon atoms are equidistant from the metal. This is called the dihapto-or T]2 mode. A ligand such as an allyl radical with three adjacent carbons directly bonded to a metal atom would be trihapto- or t 3, and so on. 

Reactions with BucNC lead to new organometallic compounds containing an 72-C,N-bound cyclopentadiene imine, which was structurally characterized as a pyridine adduct (Scheme 118). Reactions with benzonitrile lead to the elimination of 1 equiv. of the corresponding pyridine and formation of the dimeric titanium derivative (ArO)2Ti(/x-PhCN)2Ti(OAr)2 containing two bridging benzonitrile ligands. The compound has been structurally characterized... 

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