STRUCTURAL STUDIES OF (ETA-5-C5H5)2NB(SC6H5)2, [(ETA-5-C5H5)2NB(SC6H5)2+], AND [(ETA-5-C5H5)2NB(MU-SC6H5)2MO(CO)4+]
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Three related structures have been determined by X-ray crystallography: Cp2Nb(SPh)2 (1), [Cp2Nb-(SPh)2][PF6] (2), and the heterobimetallic [Cp2Nb(-SPh)2Mo(CO)4][PF6] (4). The cationic species were obtained upon reactions of the neutral compounds Cp2Nb(SPh)2 (1) and Cp2Nb(-SPh)2Mo(CO)4(3) with the one-electron oxidants [NO][PF6] or [Fc][PF6]. For 1 there are two independent molecules in the unit cell that belongs to the orthorhombic space group Pbca with cell parameters a = 13.756 (4) , b = 21.532 (6) , c = 25.601 (6) , and Z = 16. The structure was refined to R = 0.0731 and wR = 0.0931, for 2791 unique observed reflections. Crystals of 2 belong to the monoclinic space group C2/c with cell parameters a = 12.058 (2) , b = 16.954 (4) , c = 11.079 (2) , = 95.14 (1), and Z = 4. The structure was refined to R = 0.0445 and wR = 0.0652 for 1776 uniquely observed reflections. The diamagnetic 4 belongs to the monoclinic space group C2/c with cell parameters a = 33.85 (2) , b = 12.409 (4) , c = 15.708 (8) , = 96.26 (4), and Z = 8. The structure was refined to R = 0.0825 and wR = 0.0930 for 3272 uniquely observed reflections. In all three structures the Nb is in a pseudotetrahedral coordination environment comprised of two Cp rings and the sulfur atoms of the phenylmercapto ligands. The Mo is octahedrally coordinated in 4. The average Nb-S distance varies as follows: for 1, 2.516 (3) ; for 2, 2.417 (1) ; for 4, 2.499 (2) . The S-Nb-S angle averages to 75.5 (1) in the Nb(IV) d1 complex 1 and increases to 101.4 (1) in the Nb(V) d complex 2. Complexation of Cp2Nb(SPh)2+ by Mo(CO)4 hardly changes this angle; in 4 the S-Nb-S is 101.8 (1) and the S-Mo-S is 103.1 (1). The Nb-Mo distance of 3.116 (2) in 4 is less than the sum of the covalent radii for Nb and Mo, consistent with the acute angles of 77.7 (1) for Nb-S(1)-Mo and 77.4 (1) for Nb-S(2)-Mo. Whereas the Ph groups are in a syn arrangement with respect to the NbS2 plane in 1, in 2 and 4 they are anti. In solution however variable-temperature 1H NMR studies of 4 showed a dynamic mixture of syn and anti isomers, with a slight predominance of the anti isomer. Both (CO) IR data and cyclic voltammetric studies suggested the positive charge of 4 to be delocalized over both sides of the heterobimetallic complex. 1989, American Chemical Society. All rights reserved.
