Cyclopentadienylniobium(V) Phosphine Chemistry: Adduct Formation vs Reduction. X-ray Structure of CpNbCl4(PMePh2)

James Fettinger (1) , D. Webster Keogh (1) , Rinaldo Poli (1)

1 University of Maryland [College Park]

The reaction between CpNbCl4 and the phosphine ligands PMexPh3-x (x = 0, 1, 2, 3) has been investigated. While no reaction occurs with PPh3, stable adducts are formed with all the other ligands in the above series. These have been isolated and characterized by elemental analysis, 1H and 31P-NMR spectroscopy, and an X-ray structural determination for the PMePh2 adduct. The three phosphines PMe3, PMe2Ph, and PMePh2, however, also engage in a subsequent reduction process with formation of Cl radicals and Nb(IV) complexes. CpNbCl3- (PMe3)2 has been independently synthesized from CpNbCl4, Na, and PMe3 in a 1: 1 :2 ratio and fully characterized. The relative rate of reduction depends on the nature of the phosphine, increasing in the order PMePh2 < PMe2Ph < PMe3. X-ray data for CpNbCl4(PMePh2): monoclinic, C2/c,a = 23.818(2)Å, b = 12.4719(10) Å, c = 15.8137-(12)Å, β = 106.365(7)°, V = 4507.2(6) Å3, Z = 8, Dx, = 1.609 g.cm-3, μ(,Mo Kα) = 0.603 mm-1, R = 0.0349 for 329 parameters and 3989 data with I > 2σ (l). The structure shows a distorted pseudooctahedral geometry with the Cp and PMePh2 ligands occupying two axial coordination sites and the four equatorial Nb-Cl bonds being bent away from the Cp ring.

Domaines: Chimie de coordination; Cristallographie

James Fettinger, D. Webster Keogh, Rinaldo Poli. Cyclopentadienylniobium(V) Phosphine Chemistry: Adduct Formation vs Reduction. X-ray Structure of CpNbCl4(PMePh2). Inorganic Chemistry, 1995, 34 (9), pp.2343-2347. ⟨10.1021/ic00113a014⟩. ⟨hal-03531736⟩