NMR studies of tin hydrides

Abstract

The proton magnetic resonance spectra of various organo tin hydrides have been studied. Spectra were normally run under conditions of high scale expansion (0.2 Hz or 0.4 Hz cm ) and numerous heteronuclear double resonance experiments performed. The values of chemical shifts and coupling constants were compared with previously reported data. Proton spectra of di-cyclohexyl tin hydride and di-benzyl tin hydride have been reported for the first time. Some of the hydrides were deuterated [(CH3)2SnH2, (C6H5)2SnH2, C6H5H3 and (C6H5CH2SnH2] and the effects of deuterium substitution both on shielding and on spin spin coupling constants have been measured. Sn spectra at 22.37 MHz were obtained by the pulse FT method and values for 119 Sn chemical shift and tin-proton and tin-deuterium coupling constants obtained. Isotopic effects were observed both on shifts and coupling constants as a result of deuterium substitution. A linear dependence for Sn shifts on the number of substituents in methyl and phenyl stannanes has been found. The spin-lattice relaxation times (T1) of the naturally abundant magnetic tin satellites in the proton spectra of these hydrides have been measured and were found to be shorter than the relaxation times of the central feature resulting from molecules containing non-magnetic tin. Correlation times were calculated from the dipolar contribution to the total relaxation time. The temperature dependence of C spin-lattice relaxation time in di-methyl tin hydride has also been studied. The dipole dipole contribution was determined by measurement of the proton nuclear Overhauser enhancement of the methyl carbon. A computer program has been used for the iterative curve fitting of the experimental spectra of deuterated di-phenyl tin hydride to determine the quadrupole relaxation time (Tq) of the deuterium nucleus.