Unusual~(31)P Chemical Shielding Tensors in Terminal Phosphide Complexes Containing a Phosphorus-Metal Triple Bond

摘要

Phosphorus-31 NMR data for one-coordinate phosphorus compounds are extremely scarce in the literature. Until recently, the only stable compounds with a terminal phosphorus atom involved in a triple bond were phosphaalkynes, RC=P, and the isoelectroniciminophosphenium cations, [RN+P]~+. The isotropic ~(31)P chemical shift range for these compounds extends from 96 to --207 ppm. In general, phosphaalkynes and iminophosphenium ions are found to have their ~(31)P chemical shifts at lower frequency (moreshielded) compared to phos-phaalkenes and iminophosphines, respectively. This trend is analogous to the relationship between ~(13)C chemical shifts in alkynes and alkenes. Recently, the first terminal phosphide (P~(-3)) complexes containing a phosphorus-metal triple bond were successfully synthesized. Surprisingly, ~(31)P NMR signals in these complexes were found above 1000 ppm. Observation of such unusual ~(31)P chemical shieldings suggests that phosphorus-metal triple-bonding schemes may differ substantially when compared to phosphorus--carbon and phosphorus--nitrogen triple-bonding schemes.