Phosphido-borane-supported stannates.

The reactions between SnCl 2 and three equivalents of the alkali metal phosphido-borane complexes [R 2 P(BH 3 )]M yield the corresponding tris(phosphido-borane)stannate complexes [L n M{R 2 P(BH 3 )} 3 Sn] [R 2 = iPr 2 , L n M = (THF) 3 Li (2Li), (Et 2 O)Na (2Na), (Et 2 O)K (2K); R 2 = Ph 2 , L n M = (THF)Li (3Li), (THF)(Et 2 O)Na (3Na), (THF)(Et 2 O)K (3K); R 2 = iPrPh, L n M = (THF) 4 Li (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 BH 3 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 SnCl 2 and three equivalents of [ t Bu 2 P(BH 3 )]M (M = Li, Na) gave the known hydride [M{ t Bu 2 P(BH 3 )} 2 SnH], according to multinuclear NMR spectroscopy.