Phosphido-borane-supported stannates

Abstract

The reactions between SnCl₂ and three equivalents of the alkali metal phosphido-borane complexes [R₂P(BH₃)]M yield the corresponding tris(phosphido-borane)stannate complexes [L_nM{R₂P(BH₃)}₃Sn] [R₂ = iPr₂, L_nM = (THF)₃Li (2Li), (Et₂O)Na (2Na), (Et₂O)K (2K); R₂ = Ph₂, L_nM = (THF)Li (3Li), (THF)(Et₂O)Na (3Na), (THF)(Et₂O)K (3K); R₂ = iPrPh, L_nM = (THF)₄Li (4Li)]. In each case X-ray crystallography reveals an anion consisting of a trigonal pyramidal tin centre coordinated by the P atoms of the phosphido-borane ligands. These tris(phosphido-borane)stannate anions coordinate to the alkali metal cations via their BH₃ hydrogen atoms in a variety of modes to give monomers, dimers, and polymers, depending on the alkali metal and the substituents at the phosphorus centres. In contrast, reactions between SnCl₂ and three equivalents of [tBu₂P(BH₃)]M (M = Li, Na) gave the known hydride [M{tBu₂P(BH₃)}₂SnH], according to multinuclear NMR spectroscopy.