Five coordinate complexes of 2,2-Dibutyl-1,3,2-dioxastannolans

Abstract

2,2-Dibutyl-1,3,2-dioxastannolans, Bu 2Sn(OCR 2) 2, unlike the dioxastannanans, Bu 2Sn(OCR 2) 2,CR 2, or the acyclic dialkoxides, Bu 2Sn(OR) 2, react with ligands L, drofuran to form a series of solid complexes, Bu 2Sn(OCR 2) 2,L. Under reduced pressure, the ligands, L, are lost, and the dioxastannolans are regenerated. Measurements of IR, 1H and 119Sn NMR, and Mössbauer spectra, and of molecular weights in solution, imply that the complexes have a trigonal bipyramidal configuration, with equatorial butyl groups, apical ligand L, and the dioxastannolan ring bridging apical and equatorial positions. It is suggested that the relative stability of these complexes results from minimisation of angle strain in the 5-membered ring.