New Hypercoordinating Organostannanes for the Modular Functionalization of Mono‐ and Polystannanes: Synthetic and Computational Studies **

A series of potentially hypercoordinate tin compounds derived from a substitutionally labile tosyl stannane ( 5 ) was produced to gain access to a library of propyloxybiphenyl ( 11 ), propylmethoxy ( 12 , 14 , 18 , 22 ) or propylthioester ( 13 , 15 ,  19 , 23 ) stannanes for structure/property/polymerization investigations. Structural characterizations by single crystal X‐ray diffraction of 12 , 14 , 18 and 19 were also undertaken. The relative energies of hypercoordinate conformers for the propylmethoxystannanes 12 , 14 , 18 , and 22 were determined with DFT methods and the fractional abundance of conformers in the gas and solution (CHCl 3 ) phase were estimated. Relativistic DFT calculations of 119 Sn NMR chemical shifts were carried out for a series of non‐hypercoordinate reference compounds and the conformers, allowing the estimation of Boltzmann‐averaged chemical shifts of the hypercoordinate propylmethoxystannanes. A semi‐crystalline homopolymer ( 25 ) was isolated from the dehydropolymerization of 22 using Wilkinson's catalyst. Conversion of the liable tosylated polystannane ( 24 ) to a new partially substituted polystannane ( 28 ) via nucleophile displacement reactions was achieved.