Synthesis and properties of trifluoromethylated stannanes. The formation and NMR spectra of the difluoromethylstannanes (CF3)n(CF2H)mSn(CH3)4-n-m

Article abstract of DOI:10.1016/0022-328X(94)87049-7

Difluoromethylstannanes have been obtained by hydrogenation of (CF3)4Sn with the hydrides (CH3)3MH (M=Sn, Ge).The reaction is shown to proceed via attack of the hydride on the tin atom; transfer of fluoride from the CF3 group to the MMe3 group along with elimination of CF2 yields the unstable (CF3)3SnH.Difluorocarbene is inserted quantitatively into Sn-H bonds, thus forming both Me3SnCF2H and (CF3)3SnCF2H.The latter is subject to further formal replacements of CF3 by CF2H groups, finally yielding Sn(CF2H)4.For M=Sn, further methyl/trifluoromethyl exchanges lead to a variety of methyl-containing species, (CF3)n(CF2H)mSnMe4-n-m.For M=Ge, insertion of CF2 into the Ge-H bond is not observed; the lower reactivity of GeMe3H towards CF2 is demonstrated independently by its reaction with such CF2 sources as CF3SiF3 and CF2Br2/C2(NMe2)4; trimethylgermyltin derivatives, (CF3)n(CF2H)mSnGeMe3, are formed, with evolution of CF2H2.The compounds have been identified by their characteristic NMR spectra.Owing to Lewis acid/base interactions NMR chemical shifts and coupling constants are very sensitive to the choice of solvent.Linear correlations between the ²J(SnF) couplings of CF3 and CF2H groups and between ¹J(SnC) and ²J(SnF) are found. Key words: Tin; Difluoromethyl; Group 14; Fluorine