Nb2(η6-mesitylene)2(μ-I)4 (mesitylene ≡ 1,3,5-C6H3(CH3)3 ≡ mes) (2) has been synthesized from the reaction of Nb(η6-mes)2 (1) with iodine in THF and characterized by NMR, IR, UV-vis spectroscopy, and single crystal X-ray diffraction. The mesitylene ligands in 2 show nonplanar boat conformations, indicating localization of π-electron density in a 1,4-diene fashion, which is supported by a molecular orbital calculation. NMR spectra, however, indicate that 2 undergoes rapid interconversion of boat conformations as well as ring rotation in solution even at - 62°C. A cyclic voltammogram of complex 2 exhibits two redox waves. A new intermediate-valent dinuclear complex [Nb2(η6-mes)2(μ-I)4]I (3) was prepared from oxidation of 2 with iodine. The powder EPR spectrum of 3 is discussed, while magnetic studies of 3 exhibit Curie-Weiss paramagnetic behavior at temperatures above 100 K with μeff = 1.77 BM. Crystal data: 2, C18H24I4Nb2, monoclinic, P21/n (No. 14), a = 10.186(2) Å, b = 8.837(2) Å, c = 12.797(3) Å, β = 96.95(2)°, V = 1143.3 Å3, Z = 2, and dcalcd = 2.71 g cm - 3; 3, C18H24I5Nb2, monoclinic, C2/c, a = 8.348(2) Å, b = 15.038(3) Å, c = 20.373(4) Å, β = 97.25(3)°, V = 2537.1(9) Å3, Z = 4, and dcalcd = 2.78 g cm-3.
Bibliographical noteFunding Information:
This research was supported by the Chemical Sciences Division, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract W-7405-Eng-82. We thank J.E. Ostenson for magnetic measurements and C.J. Zhong for assistance in the electrochemical measurements.
- Arene complexes