Richard E. DeSimone

Complexes of niobium pentachloride with cyclic polythiaethers

Abstract A number of NbCl5 adducts with cyclic polythiaethers are described and characterized. Complexes are simple Lewis acid-base adducts with the ligands functioning as bridges between NbCl5 units. The ligands display no reducing tendencies toward NbCl5 and all complexes are diamagnetic. IR and NMR spectra support coordination through sulfur. NMR studies indicate that in solution, NbCl5 undergoes rapid exchange among available sulfur coordination sites.

THE CRYSTAL AND MOLECULAR STRUCTURE OF DECACHLORO -μ-1, 4, 8, 11-TETRATHIACYCLOTETRADEC-ANEDINIOBIUM(V). AN ADDUCT OF NbCl5 WITH AN “INSIDE-OUT” BRIDGING MACROCYCLIC LIGAND

Abstract The crystal and molecular structure of decachloro-μ-1,4,8,11-tetrathiacyclotetradecanediniobium(V) is reported. This is the first example of a complex in which such a macrocycle adopts an inside-out or exo configuration. (NbCl5)2-(S4-e-pr[14]) crystallizes in space group P21/n with two complex molecules and two solvent benzene molecules per unit cell of dimensions a = 7.925(6) A, b = 19.516(11) A, c = 10.212(5) A, and β = 88.62° (5). Full matrix least squares refinement gave final discrepancy factors of R1 = 0.109 and R2 = 0.127 for 1061 data having F2 < 3[sgrave](F2). The molecular structure consists of two NbCl5 units bridged through sulfur by the macrocycle with two of the four sulfur atoms uncoordinated. The macrocyclic ring is substantially disordered. The implications of this structure for bonding in macrocyclic complexes is discussed and the possible significance to kinetic studies of macrocyclic complexes is explored.

STRUCTURAL CHEMISTRY OF MOLYBDENUM COMPLEXES OF CYCLIC POLYTHIAETHERS: THE CRYSTAL AND MOLECULAR STRUCTURE OF ETHOXIDO-OXO-BIS(1,5,9,13-TETRATHIACYCLOHEXADECANE)-μ-OXODIMOLYB-DENUM(IV) TRIFLUOROMETHANESULFONATE HYDRATE

Abstract The crystal and molecular structures of ethoxido-oxo-bis(1,5,9,13-tetrathiacyclohexadecane)-μ-oxodimolybdenum- (IV)trifluoromethanesulfonate hydrate are reported. The complex crystallizes in the orthohombic space group Pn21 a with four molecules per unit cell of dimensions a=16.149(2)A, b=20.477(4)A, c=15.217(2)A and V=5381(2)A3. Full matrix least squares refinement gave final discrepancy factors of R1=.076 and R2=.094 for 3147 data having F2 > 2.5σ(F2). The molecular structure is highlighted by a linear O-Mo=O[sbnd]Mo=O unit. The two macrocycles coordinate each Mo atom in a “planar” tetradentate mode, and are staggered ∼ 43° relative to one another.