Intermediates in the Catalytic Dehydrogenative Coupling of Arylgermanes

Abstract

The use of a new electron-withdrawing germane, H 2 Ge[3,5-(CF 3 ) 2 C6H 3 ] 2 ( 3 ), has facilitated the isolation and characterization of three new complexes implicated in the dehydrogenative coupling of bisarylgermanes by Pt 0 -phos-phane complexes. The intermediates include a digermyl species, trans -[(Et 3 P) 2 Pt{GeH(Ar) 2 } 2 ] ( 7 ), a bound digermane showing the first stage of Ge-Ge catenation, cis -[(Et 3 P) 2 Pt(H){Ge(Ar) 2 -GeH(Ar) 2 }] ( 8 ), and the Ge-H activated form of this product, [(Et 3 P) 2 HPtGe(Ar) 2 -Ge(Ar) 2 PtH(PEt 3 ) 2 ] ( 6 ). Complexes such as 6 and 8 have not previously been isolated as intermediates in dehydrogenative coupling reactions. An X-ray crystal structure was determined for complex 6 , confirming the cis geometry of the hydrogen and germanium ligands; this provides yet another example of the stability of germyl hydrides towards reductive elimination. A similar cis geometry was observed for complex 8 . Performing the dehydrogenative coupling reaction under a CO 2 atmosphere failed to yield any products containing trapped germylene species.