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Three 18-Electron Tantalum(I) Compounds, TaCl(CO)2(dppe)2, [TaCl(CO)2(dppe)2]2x, and TaCl(CO)4(dppe) (dppe = 1,2-Bis(diphenylphosphino)ethane), Which Exhibit Low Levels of Paramagnetism

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journal contribution
posted on 20.11.1996, 00:00 authored by Mary Ann D. Koeslag, Brian K. Hunter, Joseph H. MacNeil, Aleksander W. Roszak, Michael C. Baird
Reductive carbonylation of TaCl5 in the presence of 1,2-bis(diphenylphosphino)ethane (dppe) under the appropriate conditions results in the formation of TaCl(CO)2(dppe)2 (1), as the major product, and the possibly cyclic oligomer [TaCl(CO)2(dppe)2]2x (2, 2x ≥ 4) as a minor product. Carbonylation of 1 (1 atm) results in the rapid but reversible formation of TaCl(CO)4(dppe) (3). Solutions of all three compounds exhibit low levels of paramagnetism, possibly attributable to thermal population of low-lying triplet excited states. Crystal data for the toluene solvate of 1, C68H64ClO2P4Ta:  triclinic, P1̄ (No. 2), a = 13.937(12) Å, b = 14.811(7) Å, c = 14.929(9) Å, α = 102.30(5)°, β = 95.60(7)°, γ = 98.41(5)°, Z = 2.