Multiple bonding versus cage formation in organophosphorus compounds: the gas-phase structures of tricyclo-P3(CBu(t))2Cl and P≡C-Bu(t) determined by electron diffraction and computational methods.

The gas-phase structures of tricyclo-P(3)(CBu(t))(2)Cl and P≡C-Bu(t) have been determined by electron diffraction and associated quantum chemical calculations. Efforts to obtain detailed solid-state data for tricyclo-P(3)(CBu(t))(2)Cl have been thwarted by inability to prepare suitable crystalline material. Additional calculations for another tricyclic isomer of P(3)(CBu(t))(2)Cl and for two phosphorus-containing cyclopentadiene derivatives with pseudo-planar five-membered rings show that the experimentally observed isomer is more stable by at least 52 kJ mol(-1). Calculations for the equivalent structures with P atoms replaced by CH fragments have demonstrated that a ring structure is more favourable by over 200 kJ mol(-1) compared to each of two cage structures.