Germylenes complexes with transition metals —

Stable mononuclear transition-metal germylene complexes with a formal triple bond between the Ge and metal atoms (Cr, Mo, W, 56-62) have been synthesized by a combination of salt-elimination and decarbonylation reaction (equation 44)150,151. The decarbonylation process for the Cr and W intermediates 61 and 62 can involve either a thermal or a photochemical reaction the molybdenum germylyne complexes 56 and 57 were obtained directly, even at low temperatures. 

Over the past decade, several more transition metal germylene complexes with ix coordination have been synthesized and characterized by X-ray crystallography for... 

Like silylenes and carbenes germylenes are isolobal with phosphines and may function as ligands to transition metal complexes. (Adapted from Bazlnet et ah, 2001)... 

TABLE 4. Transition metal complexes with bridging germylene ligands... 

This method has been more widely used for the synthesis of bridged germylene complexes than for their silicon analogs. The reactions of transition-metal carbonyl monoanions with Me2GeCl2 give A-type bridged... 

As mentioned above, cationic phosphenium is isoelectronic with carbene, silylene, germylene, stannylene, and plumbylene, because the central element has lone pair electrons and a vacant p orbital as well as two substituents. Therefore, their transition metal complexes have attracted considerable attention. It might be of special interest to compare cationic phosphenium complexes with silylene complexes because phosphorus and silicon are both situated in the third row of the periodic table. 

Treatment of Mo(II) , W(II) and Au(I) complexes with one equivalent of GeCl2 dioxane, in CH2CI2 at —78°C and subsequent wanning to room temperature, resulted in rapid and clean insertion of germylenes into the metal-hydrogen or metal-chlorine bond . This is a convenient route to synthesize functionalized transition-metal germanium compounds The reaction is exemphfied in equations 18 and 19. 

TABLE 8. X-ray structural data of transition metal germanium complexes with bridging germylene ... 

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