Transition metal-germanium double bond

C. Synthesis of Transition Metal Germanium Double Bond Germylene... 

F. Chemistry of the Transition Metal Germanium Double Bond,... 

Acetic acid treatment of the transition metal Ge(IV) hydride salt Kb/5-C5H5Mn(CO)2GeH3] yields a red product, b/5-C5H5Mn (CO)2]2Ge, which contains a linear Mn-Ge-Mn system in which the germanium atom occupies a special position with equal Ge-Mn distances of 2.204 A. Solution infrared spectra show four v(CO) stretching absorptions instead of the two expected from the cen-trosymmetric structure in the solid state, implying free rotation about the Ge-Mn bonds. Simple application of the rare-gas rule would favor a double-bonded formulation containing Ge(IV), but a molecular-orbital... 

The yellow germanium (m.p. 18() C) and brick-red tin complexes (m.p. 1 36 C) are thermally stable but air-sensitive solids which can be sublimed in vacuo, but the purple lead analogue is rather heat and photosensitive. They are monomeric in the vapour and in their solutions in benzene. X-ray diffraction of the tin compound shows that it dimerizes in the solid state. The monomer has both a lone pair and vacant p orbital. It acts as a Lewis base towards transition metal complexes and as a Lewis acid towards pyridine. Dimerization may therefore occur through mutual acid-base interaction to form a bent tin—tin double bond. 

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