H-2 NMR investigation of the rhodium-catalyzed deuterioformylation of 1,1-diphenylethene: Evidence for the formation of a tertiary alkyl-metal intermediate

Rhodium-catalyzed deuterioformylation of 1,1-diphenylethene at partial substrate conversion (15 and 34%) at 100 degrees C and 100 atm (CO/D-2 = 1:1) gives, in addition to the expected 3,3-diphenylpropanal-1,3-d(2), the monodeuterated olefin. 1,1-diphenylethene-2-d(1) and the labeled normal aldehyde arising from this substrate. The above compounds have been detected by H-2 NMR analysis of the crude reaction mixtures. These findings demonstrate that a tertiary alkyl-rhodium intermediate is formed, under hydroformylation conditions, in a larger amount than the normal isomer, but it undergoes beta-hydride elimination only without formation of the branched aldehyde.