Vanadium, molybdenum, and sodium triethanolamine complexes derived from an assembly system containing...

The reaction system composed of triethanolamine (TEA) and tetrathiovanadate in the presence of MeONa (MeOLi) or NaNH2 was studied to afford vanadium and alkali metal TEA complexes. Complexes [M subsetV6O6[N(CH2CH2O)2(CH2CH2OH)]6]2S6 (M = Na (1), Li (2)) contain two cyclic V((IV)) [12]metallacrown-6 cations linked by a polysulfide S6(2-) anion. Also separated from the reaction system is a novel sodium TEA complex [[Na(TEA)]2S6]n (3), in which parallel coordination chains [Na(TEA)+]n are connected by O-H...S hydrogen bonds forming 3-D network structure. Variable-temperature conductance of 3 was determined to display semiconductor feature. The desulfurization of VS4(3-) was observed to form S6(2-) anion and/or S8 molecule in the synthetic reactions of 1-3. A striking contrast was noted that MoS4(2-) did not desulfurize in the similar reaction to that of VS4(3-) with TEA, and a Na/TEA complex containing MoS4(2-), (Et4N)2[Na2(mu-TEA)2(CH3OH)2](MoS4)2 (4), was obtained instead. The S...H-O and O...H-O hydrogen bonds play an important role in forming the one- or three-dimensional structures for all these complexes by the linkages between clusters and chains. The IR spectrum indicates the structural similarity of complexes 1 and 2. For complex 4, the Mo=S stretch vibration at 468 cm(-1) showing widening and slight red-shift and the slight movement of the 1H NMR signals of TEA ligand to downfield are considered to be the influence of the S...H-O hydrogen bonds. Variable temperature magnetic susceptibility data were collected for complex 1. The effect magnetic moment per V6 unit varies gradually from 4.04 muB at 300 K to 6.24 muB at 5 K, exhibiting ferromagnetic interaction. Heisenberg-type vector-coupling model and molecular field approximation were used to treat the interaction between the paramagnetic sites and gave a good fitting result: J = 3.97 cm(-1), J' = 1.99 cm(-1), g = 1.99, F = 3.64 x 10(-3). Density functional calculation was also performed to complex 1 and its Li, K analogues. The lowest total bonding energy of -874.001 eV was obtained for [Na subsetV6(mu3-O)6] complex containing six unpaired electrons, indicating the stability of a V6 system with six independent spins S = 1/2. When the alkali metal ion is inserted into the [V6(mu3-O)6] cavity, the positive values of the bonding interaction (E(b)) indicate that the insertion depresses the total energy and that complexes 1 and 2 together with K+ complex may exist. However, the lowest E(b) value of the K+ complex implies its instability.