Monocyclooctatetraenyl(dithiolene)uranium compounds

The neutral mononuclear dithiolene compounds [U(cot)(dithiolene)(tppo)(2)] [cot = eta-C8H8; dithiolene = dddt (9), dmio (10), mdt (11)], [U(cot)(dithiolene)(hmpa)(2)] [dithiolene = dddt (12), dmio (13), mdt (14)], [U(cot)(mdt)(bipy)] (15) and [U(cot)(mdt)(terpy)] (16) were obtained by treating the dimeric complexes [JU(cot)(dithiolene))21 [dithiolene = dddt (3), dmio (4), mdt (5)] (dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate; dmio = 1,3-dithiole-2-one-4,5-dithiolate; mdt = 1,3-dithiole-4,5-dithiolate) with the corresponding Lewis base [triphenylphosphine oxide (tppo), hexamethylphosphoramide (hmpa), 2,2'-bipyridine (bipy), or 2,2':6',2"-terpyridine (terpy)]. Complexes 9(.)2THF, 11(.)2THF,12, 13, 14, 15 and 16(.)1.5py have been crystallographically characterized. The crystal structures show a significant interaction between the C=C double bond of the dithiolene ligand and the metal Centre. The H-1 NMR spectra reveal the fluxional behaviour of the compounds in solution in relation to the facile inversion of the dithiolene ring. The variation of the activation energies of the inversion process reflects the steric congestion of the complexes. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.