Conformations of (.eta.5-C5H5)2Nb(S-p-C6H4X)2n(n=0,1): responsiveness to para substituents on aryl groups and to d-electron count Academic Article uri icon

abstract

  • The balance of factors that determine the S-M-S angle and M-S-R conformational preference have been examined in a systematic study of aryl thiolate derivatives of the bent metallocenes (5-C5H5)2Nb(S-p-C6H4X)2n, where for n = 0, X = OMe (2), Me (3), (1), and Cl (4), and for n = +1, X = H (1+) and Cl (4+). Cyclic voltammographs showed two reversible waves for the Nb(III) Nb(IV) and Nb(IV) Nb(V) redox processes whose positions varied uniformly with the Hammett parameter of the X substituent. X-ray crystal structure determinations are presented for 2, 3, 4 and [4+] [PF6-] and compared with 1 and 1+(OrganometaUics, 1989, 8, 1315). The S-aryls of Nb(V) complexes (the d0derivatives, 1+and 4+) as well as the d1complex 4, (5-C5H5)2Nb(S-p-C6H4Cl)2, adopt an endo arrangement relative to the cyclopentadienyl rings and have wide S-Nb-S angles of 101.4, 102.3, and 98.7, respectively. Complexes 1, 2, and 3 have an exo configuration with aryl groups bent back into the cleft between the Cp rings. The exo isomers have small S-Nb-S angles of 75.4, 79.1, and 77.1, respectively. Complex 2 crystallized in the monoclinic space group C2/c, with a = 22.869 (9) , b = 6.962 (3) , c= 13.951 (4) , = 98.38 (3), V = 2197.6 3, and Z = 4. Complex 3 crystallized in the orthorhombic space group Aba2, with a = 13.536 (4) , b = 22.659 (2) , c = 7.017 (3) , V = 2152 3, and Z = 4. Complex 4 crystallized in the monoclinic space group C2/c, with a = 20.252 (6) , b = 9.847 (2) , c= 12.403 (4) , = 124.00 (2), V= 2050.5 3, and Z = 4. Complex 4+ crystallized in the triclinic space group P1, with a = 10.488 (6) , b = 10.672 (6) , c = 11.226 (8) , = 96.29 (5), = 94.28 (5), =112.57 (4), V = 1143.8 3, and Z = 2. Details of the structures will be presented and placed in context with other bent metallocene analogues. 1990, American Chemical Society. All rights reserved.

published proceedings

  • Journal of the American Chemical Society

author list (cited authors)

  • Darensbourg, M. Y., Bischoff, C. J., Houliston, S. A., Pala, M., & Reibenspies, J.

publication date

  • January 1, 1990 11:11 AM