Spectroscopic and structural assignment of the absolute stereochemistry in a series of 1,2-difluorovinyl organometalloids. The first crystallographic characterization and structural series of group 14 fluorovinyl compounds

The group 14 trifluorovinyl compounds Ph3ECF=CF2 (E = Ge, Sn, Pb) have been prepared in high yield by the low-temperature reaction of the triphenylelement halide with trifluorovinyllithium, generated from tetrafluoroethane (CF3CH2F, HFC-134a) and 2 equiv of n-butyllithium. The X-ray crystal structures of these materials have been obtained, so affording the first structural series for such species. Subsequent reaction of Ph3GeCF=CF2 with LiAlH4 and a range of organolithium reagents has led to preparation of the 1,2-difluorovinylgermanes Ph3GeCF= CFR (R = H, Me, n-Bu, t-Bu, Ph). Multinuclear NMR spectroscopic and X-ray crystallographic studies of these compounds have been undertaken and have shown unequivocally the exclusive trans-geometry of the 1,2-difluorovinyl moiety.