consistent with 5-coordinate tin for triorganotin diorganophosphinates, (I); both 4- and 5-coordinate tin for bis(triorganotin) organophosphonates, (II); 5-coordinate tin for poly(diorganotin organophosphonates), (III); and 6-coordinate tin for diorganotin bis(diorganophosphinates), (IV). Structures are proposed on the basis of molecularity, infrared, NMR, and Mössbauer data.