Lithium Bis(triisopropylsilyl)phosphanide and its Pentacarbonyltungsten Adduct: Synthesis and Crystal Structures of the Dimer [(thf)Li-P(SiiPr₃)₂]₂ and the Solvent-Separated Ion Pair [(thf)₄Li]+ [(OC)₅W-P(SiiPr₃)₂]^–

Abstract

The lithiation of bis(triisopropylsilyl)phosphane with n-butyllithium in THF gave quantitatively dimeric (thf)LiP(SiiPr 3 ) 2 (1) with three-coordinate lithium atoms. The molecular structure of 1 shows Li-P bond lengths of 253.3(6) pm. In order to obtain the pentacarbonyltungsten complex of the sterically demanding phosphanide, (thf)W(CO)5 was reacted with (thf)LiP(SiiPr 3 ) 2 in THF. The resulting solvent-separated complex [(thf) 4 Li] + [(OC) 5 WP(SiiPr 3 ) 2 ] − (2) was structurally characterized and shows a very large W-P distance of 266.65(7) pm.