Molecular Phosphide Complexes of Zirconium.

Molecular Zr phosphides are extremely rare, with no examples containing a one-coordinated and terminal triple-bonded phosphorus atom. We report here an isolable and relatively stable Zr phosphide complex, [(PN)Zr≡P{μ-Na(OEt)}] (), stemming from a cyclometalated Zr-hydride, [(PN)(PN')Zr(H)] (), and NaPH. Complex is prepared from two- or one-electron reductions of precursors [(PN)ZrCl] () or metastable Zr[(PN)ZrCl], respectively. Oxidation of with ClCPh (2 equiv) or I (1 equiv) resulted in re-formation of the PN ligand and isolation of the Zr complexes [(PN)ZrX] (X = Cl, ; X = I, ), whereas addition of a weak acid to allowed us to intercept the hydrido-halide intermediate [(PN)Zr(I)(H)] (X = Cl, I) spectroscopically before conversion to or . Complex exchanged with D (1 atm) to fully deuterate the methylene all -methyl groups of the PN and PN' ligands and the hydride. Discrete salts of can be readily prepared from Na encapsulation with the crown ether 1,4,7,10,13,16-hexaoxacyclooctadecane (18-C-6) or cryptand 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (222-Kryptofix) to form [Na(18-C-6)(THF)][(PN)Zr≡P] () and [Na(222-Kryptofix)][(PN)Zr≡P] (), respectively, which were structurally and spectroscopically characterized. Compounds - demonstrate exceptionally short Zr≡P bonds (, 2.3270(18) Å; , 2.291(3) Å; , 2.2989(17) Å) and highly downfield P NMR spectral resonances (, 819 ppm; and , 927 and 955 ppm) in accord with a terminal phosphide ligand. The Zr≡P motif in - can be stabilized via coordination to a softer Tl ion to form a nonsolvated phosphide [(PN)Zr≡P{μ-Tl}] (), exhibiting a phosphide resonance at ∼711 ppm.