Functionalized tetrastannacyclobutanes, Part I

The reaction of ditbutyldichlorostannane with 5 equivalents of magnesium leads to 1,1,2,2,3,3,4-hepta-tbutyl-4-(chloromagnesio)-tetrastannacyclobutane 1. A mechanism of this reaction is proposed. 1 is structurally characterized by 1D and 2D 119Sn NMR experiments. New monofunctionalised four membered cyclostannanes could be obtained by derivatisation of 1. X-Ray analysis of 1,1,2,2,3,3,4-hepta-tbutyl-4-methyl-tetrastannacyclobutane 2 and 1,1,2,2,3,3,4-hepta-tbutyl-4-chlorpropyl-tetrastannacyclobutane 5 show bent ring systems with folding angles about 157°.