COORDINATION OF METAL-CARBONYL ANIONS TO TRIPHENYLALUMINUM, TRIPHENYL-GALLIUM, AND TRIPHENYL-INDIUM AND THE CRYSTAL-STRUCTURE OF TETRAETHYLAMMONIUM TRIPHENYL((ETA-5-CYCLOPENTADIENYL)DICARBONYLIRON)ALUMINATE(FE-AL)

Complexes of triphenylmetal acceptors, Ph3E, where E is Al, Ga, or In, with metal carbonyl anions, m- = CpFe(CO)2-, CpW(CO)3-, Co(CO)4-, and Mn(CO)5-, where Cp =η5-C5H5, were prepared by combining the donor salt with the acceptor in dichloromethane or, in the case of CpFe(CO)2-, in tetrahydrofuran. The following crystalline complexes were isolated: Et4N+Ph3EFe(CO)2Cp- (E=Al, Ga, and In), ((n-Bu)4N+Ph3E)CpW(CO)3- (E = Al and In), (Ph3P)2N+Ph3lnCo(CO)4-, and (n-Pr)4N+Ph3lnMn(CO)5-. The title compound crystallized in space group P21/c with a = 10.507 (3) Å,b= 15.254 (4) Å, c = 18.892 (4) Å, and β = 92.63 (2)Δ. The complex possesses a direct Fe-Al bond of length 2.510 (2) β between the donor and acceptor moieties. This bond, the first between iron and aluminum in an organometallic complex, appears to have predominantly single bond character. By analysis of infrared spectroscopic data (vc-o) the presence of a metal-metal bond was revealed in all complexes except that of (n-Bu)4N+CpW(CO)3- with Ph3Al in which case the oxygen atom of a carbonyl ligand is the site of Lewis basicity in a WC≡OAl link. Dichloromethane solutions of (n-Bu)4N+Ph3GaCpW(CO)3-contain, in addition to uncomplexed CpW(CO)3-, two isomeric complexes: a metal-metal bonded species analogous to the corresponding Ph3In complex and a C-and O-bonded adduct of the type found in the Ph3Al complex. Complexes of Ph3Ga and, especially, of Ph3Al with Co(CO)4- and Mn(CO)5- were thermally unstable. Approximate formation constants for the complexes were estimated from IR band intensities and the relative magnitudes can be rationalized in terms of the principle of hard and soft acids and bases. © 1979, American Chemical Society. All rights reserved.