Heterocarbenoids of germanium and tin and their polyhedral oxidation products: The case for thermodynamic product control in Group 14 chalcogenides

Abstract

The polycyclic Group 14 amides [P(μ-N t Bu) 2P( t BuN) 2]M, M = Ge ( 4), Sn ( 5) were synthesized from cis-[P(μ-N t Bu) 2P( t BuNLi · THF) 2] and GeCl 2 · dioxane or SnCl 2, respectively. Oxidation of these heterocarbenoids or of the analogous diazastannylene [MeSi(μ- t BuN) 2SiMe( t BuN) 2]Sn with O 2, S 8 and Se n furnished the chalcogenides {[P(μ-N t Bu) 2P( t BuN) 2]GeO} 2 ( 6), {[P(μ-N t Bu) 2P( t BuN) 2]SnE} 2, E = O ( 7), S ( 8), Se ( 9), {[SP(μ-N t Bu) 2P( t BuN) 2]SnS} 2 ( 10), and {[MeSi(μ- t BuN) 2SiMe( t BuN) 2]SnE} 2, E = S ( 11), Se ( 12), respectively. All products ( 6– 12) were shown by single-crystal X-ray methods to consist of dimeric molecules with central (M–E) 2 rings, M = Group 14 element, E = chalcogen. The exclusive formation of dimeric compounds with bridging M–E–M bonds, vs. alternative monomeric structures with terminal M E bonds, is rationalized in terms of the thermodynamic favorability of the dimers. The case is made that most, if not all, currently known Group 14 chalcogenides, even those labeled “kinetically stabilized”, are really thermodynamic products.