Solid-State 13C NMR Investigation of Methyltin(IV) Compounds. Correlation of NMR Parameters with Molecular Structure

Article abstract of DOI:10.1021/ja00257a018

Solid-state 13C NMR data are reperted for 52 methyltin(IV) compounds.The dependence of NMR parameters (chemical shift and tin-carbon J coupling, <¹J(119Sn,13C)>) on molecular structure has been investigated with reference to the X-ray structures known for many of the compounds. 13C chemical shifts of the tin-methyls generally increase (are more deshielded) in the series tetra- < penta- < hexa- < heptacoordinated methyltin(IV) and tri- < di- < monomethyltin(IV) compounds, although there is considerable overlap between several of these groups. <¹J(119Sn,13C)> values were determined for 29 compounds whose X-ray structures are known; a linear regression of the data for 28 compounds yields the equation <¹J(119Sn,13C)> = 10.7 (Me-Sn-Me angle) -778 (r = 0.975).A Fermi contact term-tin hybridization model is used to rationalize the general behavior; changes in the effective nuclear charge of tin may be responsible for the several poorly behaved compounds that have been identified.Cases have been found in which more than one <¹J(119Sn,13C)> value exists for the methyls in di- and trimethyltin(IV) compounds.This appears to arise in cases where the tin atom bonds to different methyls with substantially different hybrid orbitals.