CRYSTAL-STRUCTURES OF (ETA-5-C5ME5)(ETA-5-2,4-C7H11)CR AND (ETA-5-C5ME5)-(ETA-5-2,4-C7H11)CRCO - AN EXAMPLE OF S 2,4-DIMETHYLPENTADIENYL LIGAND GEOMETRY

The half-open chromocene complex (eta5-C5Me5)(eta5-2,4-C,71H11)Cr (1) has been characterized by X-ray diffraction. It crystallizes in space group P1BAR with a = 7.592(2), b = 8.665(6), c = 12.452(14) angstrom, alpha = 78.50(8), beta = 79.41(6) and gamma = 86.72(4)-degrees, Z = 2, V = 787(15) angstrom3 and D(calc) = 1.19 g/cm3. The structure of this paramagnetic complex reveals a nomal U-shaped pentadienyl moiety. Complex 1 is carbonylated in hexane solution under 40 psi CO at room temperature to yield the diamagnetic monorarbonyl adduct (eta5-C5Me5)(eta5-2,4-C7H11)CrCO (2). The X-ray structure of 2 has also been determined; the complex crystallizes in space group PI with a = 8.2810(14), b = 8.8096(17), c = 12.0825(24) angstrom, alpha = 97.147(15), beta = 91.712(15) and gamma = 116.128(14)-degrees, Z = 2, V = 781.7(3) angstrom3 and D(calc) = 1.319 g/cm3. The structure of 2 reveals an unusual S-pentadienyl ligand geometry.