ORGANOMETALLIC COMPLEXES WITH ELECTRONIC BRIDGES .8. BIPHENYL-BRIDGED, TERPHENYL-BRIDGED, NAPHTHALENE-BRIDGED, AND ANTHRACENE-BRIDGED BIMETALLIC AND TRIMETALLIC COMPLEXES OF IRON AND CHROMIUM

The reactions between 2 equiv of NaFp (where Fp = (eta(5)-C5H5)Fe(CO)2) and each of six bifunctional acid chloride derivatives of biphenyl, terphenyl, naphthalene, or anthracene produce six new bimetallic acyl-bridged complexes of iron (e.g., 4,4'-C12H8(COFp)2, 4,4''-C18H12(COFp)2, 1,4-C10H6(COFp)2, 2,6-C10H6(COFp)2, 2,7-C10H6(COFp)2, and 9,10-C14H8(COFp)2). Attempts to thermally decarbonylate these materials were successful in three cases, producing new bimetallic complexes having polyaromatic bridging groups (e.g., 4,4'-C12H8Fp2, 2,6-C10H6Fp2, and 2,7-C10H6Fp2). The monometallic analogues of these complexes (e.g., 1,4-C6H4PhFp, 1-C10H7Fp, and 2-C10H7Fp) were thermally decarbonylated from their acyls similarly. Three of the acyl complexes were heated in the presence of an excess of Cr(CO)6, producing new heterometallic complexes (e.g., (eta(6)-1,4-C6H4PhFp)Cr(CO)3, (eta(6)-4,4'-C12H8Fp2)Cr(CO)3, and (eta(6)-2,6-C10H6Fp2)Cr(CO)3). Each of these complexes was completely characterized by conventional analytical and spectroscopic means which established that the bifunctional aryl- and acyl-bridged complexes were bonded to the Fp fragments by Fe-C sigma-bonds and that the Cr(CO)3 fragments were pi-bonded to one arene ring in each of the heterometallic complexes. In addition, cyclic voltammetric studies (in CH2Cl2, [n-Bu4N]PF6, Pt bead electrode) were carried out on representative examples. These studies confirm that the complexes display the expected transfer of electron density from Fe to Cr and indicate that the Cr(CO)3 fragment in (eta(6)-1,4-C6H4PhFp)Cr(CO)3 preferentially coordinates to the more electron-rich, but also more sterically crowded, arene ring bearing the Fp substituent.