ORGANOMETALLIC OXIDES - PREPARATION AND PROPERTIES OF THE DIAMAGNETIC TRINUCLEAR CLUSTER ([(ETA-C5ME5)NB(MU-CL)(MU-O)]3)+ AND RELATED CHLORIDE OXIDES OF NIOBIUM

Oxidation of (eta-C5Me5)2NbCl2 with O2 in tetrahydrofuran containing traces of water gave [(eta-C5Me5)-NbCl2]2(mu-Cl)(mu-OH)(mu-O) (1) and polymeric [Nb2Cl2O4(thf)3]n. Complex 1 (for which a newly refined structure is reported) existed as two isomers, which are distinguished by the relative orientation of eta-C5Me5 and the bridging ligands. Reduction of 1 with zinc powder gave {[(eta-C5Me5)Nb(mu-Cl)(mu-O)]3}+ (2+), which was isolated in combination with three different anions: {[ZnCl2(mu-Cl)]2}2-, {[ZnCl]4(mu-Cl)6}2-, and ({[ZnCl]6(mu-Cl)8}2-)n. Cluster 2+ contained Nb3(13+), was diamagnetic, and had an equilateral triangle of Nb atoms (average Nb-Nb distance 2.876 (1) angstrom), each edge of which was bridged by Cl and O atoms (average Nb-Cl = 2.542 (1) angstrom, average Nb-O 1.937 (3) angstrom). The geometry and electronic structure of 2+ are compared with those of {[(eta-C5Me5)Re(mu-O)2]3}2+ and {[(eta-C6Me6)Nb(mu-Cl)2]3}n+ (n = 1, 2). The structure of the Zn4Cl10(2-) salt of 2+ was reported previously. The Zn2Cl6(2-) salt was monoclinic, space group A2/m, a = 14.7497 (8) angstrom, b = 16.311 (2) angstrom, c = 16.410 (2) angstrom, beta = 95.67 (1)-degrees, Z = 2 (of {2}2{Zn2Cl6}.C6H14), and R = 0.040. The Zn6Cl14(2-) salt was triclinic, P1BAR, a = 11.141 (4) angstrom, b = 14.793 (7) angstrom, c = 14.792 (5) angstrom, alpha = 74.14 (4)-degrees, beta = 77.40 (3)-degrees, gamma = 77.32 (4)-degrees, Z = 2 (of {2}{Zn3Cl7}), and R = 0.104. Oxidation of the salts of 2+ in CH2Cl2 solution with O2 gave {[(eta-C5Me5)NbCl]3(mu-Cl)(mu-O)2(mu(3)-OH)(mu(3)-O)}+ (3+), isolated as the {[ZnCl2(mu-Cl)]2}2- salt. Cluster 3+ had an isosceles triangle of Nb atoms (Nb-Nb = 3.028 (2) angstrom (x2) and 3.318 (2) angstrom). The long Nb-Nb edge was bridged by Cl. The mu(3)-O ligand had much shorter distances to the two Nb atoms forming the long edge (average 2.046 (8) angstrom) than to the third Nb (2.228 (8) angstrom). The mu(3)-OH ligand had equal distances to all three Nb atoms (average 2.207 (8) angstrom). The salt {3}2{Zn2Cl6} was monoclinic, P2(1)/a, a = 11.377 (1) angstrom, b = 30.630 (2) angstrom, c = 11.442 (1) angstrom, beta = 100.82 (1)-degrees, Z = 4 (of {3}{ZnCl3}), and R = 0.070. The physical and chemical properties of 2+ and 3+ are reported and compared to those of related compounds.