Germylenes chromium complexes

In a third class of 7t-cyclopentadienyl complexes, compounds of type LVIII are bound to a transition metal via the lone pair at the germanium atom. The first compounds in this series, the pentacarbonyl-[chloro(pentamethylcyclopentadienyl)germylene]chromium(0) (LIXa) and -tungsten(O) (LIXb) were synthesized by alkylation of the ylide complexes (CO)5M—GeCl2 THF according to Eq. (22) (201). Nucleophilic substitution reactions of LIXb lead to the alkyl- and amino-substituted complexes LIXc-e [Eq. (23)] (202). 

Diethyl-1,3,2-dithiagermolane (336) reacts with the chromium pentacarbonyl complex of dichlorogermylene (in the form of solvate with THF) to give a cyclic germylene complex (337) which can be further stabilized with an additional nitrone ligand <87JOM(33i)ii>. 

Data on the redox potentials of germylenes, stannylenes, plumbylenes and their complexes are scarce. In fact, only the electrochemistry of dihalogermylenes, dihalostan-nylenes and their complexes with Lewis bases338 as well as with chromium, molybdenum and tungsten pentacarbonyles339 has been studied. 

In 1981 we reported for the first time that the 6w(amino)stannylene 2 can replace CO ligands in hexacarbonyl complexes of chromium or molybdenum. It has since been found that this type of reaction can be expanded to either the Z M(amino)-germylene 1 or to W(CO)6 as summarized in Eq, (1). 

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