W0237

Phosphorus–Nitrogen Triple Bonds in Highly Sterically-Congested, Four-Coordinate Phosphorus(V) Species? Lothar Stahl, Ingo Schranz, Graham R. Lief, Dept. of Chemistry, Univ. of North Dakota, Grand Forks, ND 5820, Richard J. Staples, Dept. of Chemistry and Chemical Biology, Harvard Univ., Cambridge, MA 02138.

Molecular compounds with formal phosphorus–nitrogen triple bonds are rare and generally limited to cationic iminophosphenium salts in which the phosphorus atom is putatively one-coordinate. Depending on the counterion and additional donor molecules present, the P–N bonds in these compounds range from 1.463(5) Å to 1.529(15) Å. In the course of ligand-design studies for late-transition metal polyolefin catalysts we have now isolated and characterized amimo(imino)-P-substituted diazasilaphosphetidines in which the four-coordinate phosphorus(V) atom has one exocyclic P–N bond of only 1.486(3) Å length. Both the bond shortness and the almost linear bond angle at nitrogen suggest sp-hybridization at nitrogen and a P–N triple bond. The shortness of this bond is all the more surprising as both the phosphorus and nitrogen atoms forming this bond are highly sterically congested. Syntheses, structures and bonding of this ligand, related ligands and their complexes will be discussed.