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
摘要:
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.