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The photochemistry and electronic spectra of [lV^f^-CsHshfCO),*] (M = Fe, Ru) are reported. Each complex undergoes efficient M-M bond cleavage subsequent to electronic excitation in CCU solution to yield [IVfl^-CsHsHCO^Cl] as the only M-containing product. The disappearance quantum yields at 366 nm for = Fe and Ru are 0.23 and 0.44, respectively, in CCI4 where the Fe species is fully in the bridged form and the Ru species is a mixture of the bridged and nonbridged form. The quantum yield for disappearance of the Ru species is the same in CH3CN and hydrocarbon solution of 0.1 M CCI4 where the structure in solution is essentially fully bridged (CH3CN) or ~50/50 bridged/nonbridged (hydrocarbon). The results support the conclusion that carbonyl bridged metal-metal bonds can be efficiently cleaved by optical excitation. The quantum yields for both M = Fe and Ru are somewhat wavelength dependent, with higher energy excitation giving modestly increased quantum yields. The electronic spectrum of the Ru species is very solvent and temperature sensitive in accord with known effects on the equilibrium between the bridged and nonbridged form. The • -+ * absorption in the bridged form is at

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Products, stoichiometry, and the stability of the photoelectrode show that the n-type semiconductor Sb-Sn02, as a single crystal, can serve as the photoreceptor in a photoelectrochemical cell to electrolyze H20 to H2 and 02. The 02 is evolved at the irradiated Sb-SnÓ2 electrode, and the H2 is evolved at the Pt electrode of the cell. Substantial photocurrents are obtained when the applied potential (+ lead to Sn02) exceeds ~0.5 V, and light of greater energy than the 3.5 eV band

strain in the fulvalene ligand in FV[RU(CO)~]~ (dihedral angle 28.50)12 than in this tungsten complex (dihedral angle 16.1').We conclude that the linking of cyclopentadienyl rings to form fulvalene-bridged dinuclear metal carbonyls results in substantial alterations in spectral and reactivity patterns. These changes can be explained by the existence of the carbon-carbon bond joining the two five-membered rings and by the deformation of the molecule from ideal geometries as evidenced by the substantial lengthening of the W-W bond and the nonplanarity of the fulvalene ligand. Detailed studies of the photochemical reactivity of this compound are in progress.Note Added in Proof. A rational synthesis of F V [ W ( C O ) , ]~~~ and its photochemical reaction with alkynessb have recently been reported. Supplementary Material Available: Listings of least-squares planesin the fulvalene ligand (Table V), hydrogen atom parameters (Table VI), anisotropic thermal parameters (Table VII), and observed and calculated structure factors (Table VIII) for the title complex (1 3 pages). Ordering information is given on any current masthead page. (50) (a) Vollhardt, K. P. C.; Weidman, T. W. Organometallics 1984, 3, 82-86. (b) Drage, J. S.; Tilset, M.; Vollhardt, P. C.; Weidman, T. W. Ibid. When a mixture of [(~5-C,H5)W(CO),]2 and tetramethylthiuram disulfide in toluene solution is irradiated with visible light, the title complex, (~5-C5H5)(CO)3WSC(S)N(CHg)2, is formed in excellent yield. Infrared spectroscopic studies indicate monodentate coordination of the dimethyldithiocarbamate ligand; this conclusion is confirmed by X-ray crystallography. The molecule crystallizes in space group P1, with unit cell parameters a = 7.616 (7) A, b = 9.962 (1 1) A, c = 9.931 ( 8 ) A, a = 113.38 (6)", p = 94.68 (9)O, y = 95.83 (lo)', and Z = 2. With the use of Mo K a radiation, 3932 unique reflections with 28 5 60' were collected, and the structure was solved by the heavy-atom technique and refined to a final R factor of 3.2%. The structure clearly shows monodentate coordination of the dithiocarbamate, with a nonbonding W-S2 distance of 3.905 (1) A. Carbonyl loss from the title complex can be induced either thermally or photochemically, leading to a carbonyl complex with a bidentate dithiocarbamate ligand. Quantum yields are reported for both the formation and decomposition reactions of the title complex. The title complex reacts with W(CO),(THF) to form a W(CO)5 adduct and with iodine to form oxidized products. (a) de Croon, M. H. J. M.; van Gaal, H. L. M.; van der Ent, A. Znorg. Nucl. Chem. Lett. 1974, IO, 1081-1086. (b) van Gaal, H. L. M.; Diesveld, J. W.; Pijpers, F. W.; van der Linden, J. G. M.

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