Syntheses and structures of [Sn{NR}(2){Sn(mu-NMe2)}(2)]: Model intermediates in the formation of imido group 14 cages and rings [R = 2,6-pr(2)(i)C(6)H(3) (Dipp), 2,4,6-Me3C6H2 (Mes)]

The 1:1 reactions of aliphatic primary amines [RNH2] with [Sn(NMe2)(2)] yield the imido Sn(II) cubanes [SnNR](4); however, for highly sterically crowded amines this reaction is retarded and the model intermediates [Sn{NR}(2){Sn(mu-NMe2)}(2)] [R = 2,6-mu-(PrC6H3)-C-i (Dipp) (1), 2,4,6-Me3C6H2 (Mes) (2)] can be isolated. The latter indicate that the formation of imido cubanes and trimers from the metalation reactions of primary amines with a range of group 14 precursors may occur via a common reaction sequence involving stepwise metalation. The low-temperature X-ray structures of 1 and 2 show them to have similar [Sn3N4] cage arrangements consisting of a planar {Sn(NR)(2)} unit straddling a {Sn(mu-NMe2)}(2) ring, No intermolecular association occurs in the solid-state structure of 1. However, the reduced steric demands of the Mes groups in 2 lead to a complicated three-dimensional network consisting of fused hexameric units linked by Sn ... Sn interactions.