Structure and Bonding in Organometallic Compounds

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Characteristic of most reactive RM compounds is their existence as two or more R M units closely associated with each other. The nature of these metal alkyl complexes has been extensively studied via X-ray crystal analysis by Rundle and co-workers, who showed that the a-carbon atom of the alkyl groups forms a bridge between metal atoms in different RM units. Thus, the dimer of trimethyialuminum may be viewed as 

Lithium alkyls in ether or benzene show a mean degree of association of from three to seven, whereas phenyl- and benzyllithium are dimeric in ether (17, 135). The lower degree of association in ether may stem from etherate formation. The structure of these auto-complexes may be analogous to that of beryllium and aluminum alkyls, or perhaps a lithium atom acts as a Lewis acid that is, Li [Li(C6H6)2]e. Wittig (135) favors this formulation over a phenyl bridging scheme. 

Recently, the equilibrium postulated by Schlenk to exist between various species in the Grignard reagent  

Another manner in which intramolecular electron donation can help to fill the available orbitals of the metal atom is via a cyclic cr-bond between 

The existence of hexamethyldiplatinum, (CH3)3Pt—Pt(CH3)3 (49) and the possible existence of R—Hg—Hg—R (54) are further instances. (Compare ref. 103 for possible metal-metal bonding in associated alkyls.) 

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Structure and Bonding in Organometallic Compounds Diffraction Methods... 

Structure and Bonding in Organometallic Compounds Diffraction Methods, Pages 573-603, L. Brammer and G. Minguez Espallargas... 

Structure and Bonding in Organometallic Compounds Organometallic Thermochemistry, Pages 605-638, J.A. Martinho Simoes and... 

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