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1493carbon distance is >3.5 A from all of the published X-ray structural data on I-VI. The trial correlations involving the isotropic shieldings (ah), the tensor components and dZ2, and the asymmetry parameters ( q ) , are not good, but excellent correlations are obtained between bj3 and A6 with R (Figures 1 and The reaction of carbon dioxide with the bis(dinitrogen) complex cis-Mo(N2),(PMe,),, in coordinating solvents, gives the carbonyl-arbonate complexes [MO(~~~-~~,~~-CO~)(CO)(PM~~)~], (2) and Mo(CO,)(CO)(PMe,), (3) derived from the metal-induced reductive disproportionation of COP The use of EtzO or THF as the reaction solvent leads to the preferential formation of binuclear 2 whereas in acetone monomeric 3 is the preferred product. Compounds 2 and 3 interconvert readily by association or dissociation of PMe,, and their solution stabilities have been found to be strongly solvent dependent. Interaction of 3 with the chelating phosphines dmpe or dmpm (dmpe = Me2PCH2CH,PMe2; dmpm = Me,PCH2PMe2), under appropriate conditions, affords the related complexes Mo(CO$OO)(P-P!(PM~,)~ (P-P = dmpe, 4; P-P = dmpm, 5) and Mo(CO,)(CO)(dmpe), (6). Compounds 2 and 3 react with H20 with formation of an unusual tetrametallic, mixed-valence Mo(I1)-Mo(V) complex M04(fi4-CO,)-(C0)2(0)2(~2-0)2(~2-OH)4(PMe,)6 (7) that contains a unique carbonate ligand engaged in a novel type of bonding. The structure of 7 has been determined by X-ray crystallography. Crystals of 7 are orthorhombic, Pbcn, with unit cell constants a = 26.866 (9) A, b = 12.934 (4) A, c = 11.965 (2) A, and D(calcd) = 1.74 g for Z = 4. [MO(~~-T$,~~-CO~)(CO)(PM~~)~]~ (2) or the monomeric, dark-Alvarez et al. (a) Inoue, S.; Yamazaki, N. Organic and Bio-organic Chemistry of Carbon Dioxide; Halsted Press: Tokyo, Japan, 1982. (b) Palmer, D. A.; Van Eldik, R. Chem. Rev. 1983,83, 651. Chatt, J.; Kubota, M.; Leigh, G. J.; March, T. C.; Mason, R.; Yarrow, D. J. J. Chem. Soc., Chem. Commun. 1974, 1033. (a) Carmona, E.; Palma, P.; Paneque, M.; Poveda, M. L.; Gutierrez-Puebla. E.; Monge, A. J. Am. Chem. Soc. 1986,108,6424. (b) Carmona, E.; Gutibrrez-Puebla, E.; Marin, J. M.; Monge, A.; Paneque, M.; Poveda, M. L.; Ruiz, C. J . Am. Chem. Soc. 1989, 1 1 1 , 2883. (c) Carmona, E.; M a r k J. M.; Palma, P.; Paneque, M.; Poveda, M. L. Inorg. Chem. 1989, 28, 1895. Reinking. M. K.; Ni, J.; Fanwick, P. E.; Kubiak, C. P. J. Am. Chem. Soc. 1989, 111, 6454. For mononuclear, structurally characterized M X O , complexes see: (a) Alvarez, R.; Carmona, E.; Marin, J. M.; Poveda, M. L.; GutiQrez-Pucbla. E.; Mongc, A. J. Am. Chem. Soc. 1986,108,2286. (b) Aresta, M.; Nobile, C. F.; Albano, V. G.; Forni, E.; Manassero, M. J. Chem. Soc., Chem. Commun. 1975.36. (c) Bristow, G. S.; Hitchcock, P. 9.; Lappert, M. F. For a preliminary communication-of this work, see: Carmona, E.; GonzBlez, F.; Poveda. M. L.; Marin, J. M. J. Am. Chem. SOC. 1983, 105, 3365.

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