Preparation of tertiary and ditertiary phosphine derivatives of (mu-RSe)(2)Fe-2(CO)(6) via CO substitution. The crystal structure of (mu-PhSe)(2)Fe-2(CO)(4)(Ph(2)PCH=CHPPh(2))

Reaction of (mu-PhSe)(2)Fe-2 (CO)(6) with Ph(3)P and Ph(2)MeP in refluxing benzene afforded mono-substituted derivatives (mu-PhSe)(2)Fe-2(CO)(5)L (1a, L=Ph(3)P; 1b, L = Ph(2)MeP), whereas reaction in re fluxing toluene gave symmetrically bis-substituted derivatives (mu-PhSe)(2)Fe-2(CO)(4)L(2)(2a, L = Ph(3)P; 2b, L = Ph(2)MeP); Reaction of (mu-ArSe)(2)Fq(2)(CO)(6)(Ar = Ph, p-MeC(6)H(4)) with Ph(2)PCH(2)CH(2)PPh(2) in refluxing toluene gave symmetrically substituted ditertiary phosphine-bridged derivatives (mu-ArSe)(2)Fe-2 (CO)(4) (Ph(2)PCH(2)CH(2)PPh(2)) (3a, Ar = Ph; 3b, Ar = p-MeC(6)H(4)), while Ph(2)PCH = CHPPh(2), in benzene yielded non-symmetrically substituted chelated derivatives (mu-ArSe)(2)Fe-2 (CO)(4) (Ph(2)PCH=CHPPh(2)) (4a, Ar = Ph; 4b, Ar = p-MeC(6)H(4)), in which the diphosphine is coordinated to a single iron atom. Structures of the above derivatives have been elucidated by IR and NMR (H-1, C-13 and Se-77) spectroscopy; the molecular structure of 4a was confirmed by X-ray diffraction techniques. It crystallizes in the monoclinic space group P2(1)/c with a = 21.908(3), b = 17.207(2), c = 23.954(2) Angstrom, beta = 114.24(1)degrees, V = 8234 Angstrom(3) X, Z = 4 and Dc = 1.501 g/cm(3); final R = 0.060 for 3941 observed reflections.