title: 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.
abstract: Reductive carbonylation of TaCl(5) 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)](2)(x)() (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, C(68)H(64)ClO(2)P(4)Ta: triclinic, P&onemacr; (No. 2), a = 13.937(12) Å, b = 14.811(7) Å, c = 14.929(9) Å, alpha = 102.30(5) degrees, beta = 95.60(7) degrees, gamma = 98.41(5) degrees, Z = 2.
authors.affiliation: Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Mary Ann D.
authors.initials: MA
authors.lastname: Koeslag
authors.forename: Brian K.
authors.initials: BK
authors.lastname: Hunter
authors.forename: Joseph H.
authors.initials: JH
authors.lastname: MacNeil
authors.forename: Aleksander W.
authors.initials: AW
authors.lastname: Roszak
authors.forename: Michael C.
authors.initials: MC
authors.lastname: Baird