Carbon-13 fourier transform NMR studies of organotin compounds : III. Carbon-13 chemical shifts and tin-119—carbon-13 spin—spin coupling constants in acyclic, monocyclic and bicyclic organostannanes

Abstract

Carbon-13 NMR parameters for 33 organotin compounds with a variety of structurul features were investigated in order to obtain information about the relationship between their structure and 13C NMR parameters. It was found that the substitution of a proton by a trialkyltin group generally produces an upfield shift for the directly bonded carbon. The γ-nuclei usually resonate at lower fields except where there is appreciable steric strain while the β-carbons undergo relatively constant shifts of approximately 3.5 to 4.5 ppm to lower fields. The magnitude of direct bond coupling Jz-sfnc; 1 J( 119Sn 13C)z-sfnc; is influenced by the hybridization of the tin and the directly attached carbon atoms. In rigid organitins, the vicinal coupling constants show a Karplus type variation. In aliphatic organotins, the values of the vicinal 119Sn 13C coupling indicates a flexible molecular framework with a clear cut preference for certain conformations.