SYNTHESIS, STRUCTURE, AND PROPERTIES OF THE [E(7)M(CO)(3)](3-) COMPLEXES WHERE E=P, AS, SB AND M=CR, MO, W

Ethylenediamine (en) solutions of K(3)E(7)(E = P, As, Sb) react with t oluene solutions of LM(CO)(3) (M = Cr, W; L = mesitylene; M = Mo; L = cycloheptatriene) in the presence of 3 equiv of 2,2,2-crypt to give [K (2,2,2-crypt)](3)[E(7)M(CO)(3)] complexes. Nine [E(7)M(CO)(3)](3-) com pounds, 2EM (E = P, As, Sb and M = Cr, Mo, W), have been prepared and characterized by various physical and spectroscopic techniques. The co mpounds comprise distorted norbornadiene-like eta(4)-E(7)(3-) groups b ound to C-3 upsilon M(CO)3 centers. The bonding is described as E(7) p i-type interactions with the metal center. C-13 and P-31 NMR studies a nd ligand exchange reactions show E(7)-M(CO)3 dissociation does not oc cur in the absence of external oxidants. Simulations of the second-ord er AA'A''A''MM'X P-13 NMR spectra show large (1)J(P-P) coupling consta nts (478 Hz, av) associated with the ''olefinic'' P-P groups of the 2P M compounds. The upsilon(CO) bands appear at 1845-1708 cm(-1) in the I R spectra. The:electronic spectra show intense charge-transfer. bands for the 2EM compounds with lower energy pi(3) --> pi(4) transitions ob served for the 2PM series. The reactivity of these compounds to form [ HE(7)M(CO)(3)](2-) and [(L(2))M'(CO)(3)E(7)M(CO)(3)](3-) compounds is discussed. Crystal data for [K(2,2,2-crypt)](3)[P7Cr(CO)(3)].en at 296 K: a 14.236(5) Angstrom, b = 14.523(4) Angstrom, c = 20.895(7) Angstr om, alpha = 80.67(3)degrees, beta = 88.93(3)degrees, gamma = 78.39(3)d egrees, Z = 2, and space group P (1) over bar. Crystal data for [K(2,2 ,2-crypt)](3)[Sb7Cr(CO)(3)] at 243 K:a = 50.300(9) Angstrom, b = 13.89 7(3) Angstrom, c 28.433(5) Angstrom, beta = 108.43(1)degrees, Z = 8, a nd space group C2/c.