INTERMEDIATES IN THE CATALYTIC DEHYDROGENATIVE COUPLING OF ARYLGERMANES

The use of a new electron-withdrawing germane, H2Ge[3,5-(CF3)(2)C6H3]( 2) (3), has facilitated the isolation and characterization of three ne w complexes implicated in the dehydrogenative coupling of bisarylgerma nes by Pt-0-phosphane complexes. The intermediates include a digermyl species, trans-[(Et3P)(2)Pt{GeH(Ar)(2)}(2)] (7), a bound digermane sho wing the first stage of Ge-Ge catenation, cis-[(Et3P)(2)Pt(H){Ge(Ar)(2 )GeH(Ar)(2)}] (8), and the Ge-H activated form of this product, [(Et3P )(2)HPtGe(Ar)(2)Ge(Ar)(2)PtH(PEt3)(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 comp lex 6, confirming the cis geometry of the hydrogen and germanium ligan ds; this provides yet another example of the stability of germyl hydri des towards reductive elimination. A similar cis geometry was observed for complex 8. Performing the dehydrogenative coupling reaction under a CO2 atmosphere failed to yield any products containing trapped germ ylene species.