Electron alkyne

Four-Electron Alkyne Ligands in Molybdenum(ll) and Tungsten(ll) Complexes... 

For comparative purposes the syntheses and properties of formally seven-coordinate d4 biscyclopentadienyl alkyne complexes will be presented. The absence of a vacant dir orbital places these d4 complexes unambiguously in the two-electron alkyne category, i.e., N = 2 applies where N is defined as the formal electron donor number for the alkyne ligand. As in the porphyrin case a reductive ligation route provided access to these molecules. Sodium amalgam reduction of Cp2MoQ2 in the presence of alkyne yields Cp2Mo(RC=CR) [Eq. (28)] (82). Note that, in... 

The structure of W(CO)(HC=CH)(S2CNEt2)2 reported in 1978 solidified the utility of the four-electron alkyne donor concept (Fig. 7) (57). 

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