Terminal Parent Phosphanide and Phosphinidene Complexes of Zirconium(IV)

The reaction of [Zr(Tren DMBS )(Cl)] [ Zr1 ; Tren DMBS =N(CH 2 CH 2 NSiMe 2 Bu t ) 3 ] with NaPH 2 gave the terminal parent phosphanide complex [Zr(Tren DMBS )(PH 2 )] [ Zr2 ; Zr−P=2.690(2) Å]. Treatment of Zr2 with one equivalent of KCH 2 C 6 H 5 and two equivalents of benzo‐15‐crown‐5 ether (B15C5) afforded an unprecedented example (outside of matrix isolation) of a structurally authenticated transition‐metal terminal parent phosphinidene complex [Zr(Tren DMBS )(PH)][K(B15C5) 2 ] [ Zr3 ; Zr=P=2.472(2) Å]. DFT calculations reveal a polarized‐covalent Zr=P double bond, with a Mayer bond order of 1.48, and together with IR spectroscopic data also suggest an agostic‐type Zr⋅⋅⋅HP interaction [∡ ZrPH =66.7°] which is unexpectedly similar to that found in cryogenic, spectroscopically observed phosphinidene species. Surprisingly, computational data suggest that the Zr=P linkage is similarly polarized, and thus as covalent, as essentially isostructural U=P and Th=P analogues.