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.