“…The chemistry of catenated organotin compounds began as early as A particularly active area of investigation is that concerned with the nature of "divalent" tin species, R2Sn, It has now been well established that these compounds are in many cases polymers of the R2Sn structure, and do not, in fact, contain tin species in the divalent stateo Some diorganotin compounds, particularly those prepared from organolithium or organomagnesium reagents and stannous chloride, have been shown (52,53,(56)(57)(58) to correspond to RgSn compounds only in gross composition, and to contain tin polymers with chain branching, so that RgSn-and RSn= moieties are present in the compounds, A review (53) of the nature of these compounds and the problems involved in their study has recently appeared, so that the present writing will in the main treat only those compounds which have been shown to be reasonably discrete species.…”