New Alkyne Complexes of Niobium(I)

Article abstract of DOI:10.1039/DT9920002003

The reaction between the seven-co-ordinated niobium(I) complexes (dppe = Ph2PCH2CH2PPh2, X = Br or I) or (X = Cl, Br or I) and alkynes leads to the d⁴ niobium alkyne complexes 2-RCCR)(dppe)> (R = Ph) and 2-RCCR)(PEt3)2> (R = H, Me, Et or Ph).These complexes have been characterized by 1H, 13C, 31P and 93Nb NMR and IR spectroscopies.Low-field acetylenic proton and carbon resonances confirm the description of the alkyne as a four-electron donor.The 93Nb NMR resonance exhibit the expected dependence of shielding on the nature of the halide ligand, i.e.Cl < Br < I.The crystal and molecular structures of have been determined: triclinic, space group P1<*>, a = 9.000(1), b = 16.906(2), c= 17.952(3) Angstroem, α = 80.07(1), β = 78.59(1), γ = 75.50(1) deg.The molecule has a slightly distorted octahedral geometry with the carbonyl and the phosphine ligands in trans positions.Average distances are: Nb-CO 2.11(5), Nb-C(alkyne) 2.09(9) and Nb-I 2.91(2) Angstroem.

Full text of DOI:10.1039/DT9920002003

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