Syntheses of phosphinine-based tripodal ligands

The syntheses of several tripodal phosphinine-based Ligands are presented, 1,3,2-Diazaphosphinine (1) undergoes Diels-Alder reactions with tris-(propy nyl)phenylsilane to yield tris-(1,2-azaphosphinine)phenylsilane 6, This int ermediate serves as precursor for the preparation of two tripodal Ligand. F irst, tris(phosphinine)phenylsilane (7) is obtained from the reaction with trimethylsilylacetylene. Under more drastic conditions, compound 6 reacts w ith 8-octyne to yield the tripodal ligand 8 containing six n-propyl groups. Reaction of 8 with [W(CO)(5)(THF)] affords the corresponding W(CO)(3) comp lex 9 whose structure was confirmed by an X-ray crystallographic study. The synthesis of two extended tripodal ligands 12 and 13 containing three phos phinine units each connected to the same CH linker by dimethylsilyl groups was also studied. As a prerequisite, the precursor tris(propynyldimethylsil yl)methane (10) was synthesized by reaction of three equivalents of propyny llithium with tris(bromodimethylsilyl)methane. Reaction of excess 1 with 10 yielded the corresponding tris (dimethylsilyl-1,2-azaphosphinine)methane ( 11) as an intermediate. The formation of ligands 12 and 13 was achieved by reacting 11 with trimethylsilylacetylene or 4-octyne, respectively, in exce ss. The reaction of ligand 13 with [W(CO)(5)(THF)] in toluene yielded the c orresponding W(CO)(3) complex 14 which was structurally characterized.