Group 14 elements, carbene analogues

M. F. Lappert, R S. Rowe, The Role of Group 14 Elements Carbene Analogues in Transition Metal Chemistry", Coord Chem. Rev. 1990,100,267. 

The tetrasulfides R R MS4 with M=Si, Ge, Sn, or Pb bearing bulky substituents on the group 14 element were synthesized by the reaction of the corresponding divalent species R R M, which are heavier analogues of the carbenes, with elemental sulfur (see Scheme 1) [11-20]. The divalent species... 

Compounds with multiple bonds between a transition metal and group-14 elements as the heavier analogues of carbenes — transition metal complexes of the type (CO)sCr-EH2 (E = C to Sn) — have been calculated at the DFT level by Jacobsen and Ziegler117. The authors report the equilibrium geometries and the transition metal-E bond dissociation... 

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