The reaction of a series of cationic and neutral complexes [(η5-Ind)Mo(CO)2L2]0,+ (1, L = NCMe; 2, L = CNMe; 3, L = OPPh3; 4, L = OP(OMe)3; 5, L = PMe3; 6, L2 = (PhSCH2)2; 7, L2 = (O2CCF3)-; 8, L2 = (O2CCH3)-; 9, L2 = (O2CPh)-; 10, L2 = [(NPh)2CH]-; 11, L2 = [(N-p-tolyl)2CH]-; 12, L2 = (S2CNEt2)-; 13, L2 = (S2P(OEt)2)-; 14, L2 = acac-; 15, L2 = MeC(O)CHC(NPh)CMe) with acetonitrile produces the ring-slipped adducts [(η3-Ind)MoL2(NCMe)(CO)2]0,+ only in the cases where L = NCMe, OPPh3, OP(OMe)3 or L2 = (O2CCF3)-, acac-. The adducts are labile and have been characterized by means of the distinctive chemical shift of the central pseudo-allylic proton of the η3-indenyl ligand. In the other cases no ring slippage is observed. In NCMe solvent 6 undergoes substitution to give 1, but the macrocycle trithiacyclononane (ttcn) reacts with 1 to give [(η3-Ind)Mo(CO)2(κ3-ttcn)]+ as the BF4 - salt. PMe3 reacts with 1 to give substitution products in a stepwise fashion. [(η5-Ind)Mo(NCMe)(PMe3)(CO)2]BF4 is formed instantaneously at −70 °C, but 5 forms slowly at room temperature without any detectable ring-slipped intermediate. The crystal structure of the isonitrile cation 2 is presented. 2 adds neither NCMe nor CNMe but undergoes CO substitution with excess CNMe. Extended Hückel and density function calculations predict the most stable conformation of [(η5-Ind)MoL2(CO)2]+ (L = NCR, CNR) to be the one with the ring trans to the carbonyls, while for the [(η3-Ind)MoL2(NCR)(CO)2]+ complexes the ring lies over the carbonyls. According to the dft calculations, acetonitrile addition induces η5 → η3 slipping of the ring in the NCR derivatives but not in the CNR analogues, because the reaction is enthalpically driven in the former and not in the latter. The dft calculations of part of the reaction path indicate that the indenyl ring starts to slip when the incoming ligand is still far from the metal (∼400 pm), thus supporting earlier kinetically based proposals.

The oxidative decarbonylation of the η(3)-allyl dicarbonyl complexes [Mo(η(3)-C(3)H(5))Cl(CO)(2)(L)] (L = 2,2'-bipyridine (bipy) (1), 4,4'-di-tert-butyl-2,2'-bipyridine (di-tBu-bipy) (2)) by reaction with aqueous tert-butylhydroperoxide (TBHP) or H(2)O(2) gave the following compounds in good to excellent yields: the oxo-bridged dimers [MoO(2)Cl(L)](2)O (L = bipy (3), di-tBu-bipy (6)) using TBHP(10 equiv.)/CH(3)CN/r.t.; the molybdenum oxide/bipyridine hybrid material {[MoO(3)(bipy)][MoO(3)(H(2)O)]}(n) (4) and the octanuclear complex [Mo(8)O(24)(di-tBu-bipy)(4)] (7) using TBHP(50 equiv.)/H(2)O/70 °C; the oxodiperoxo complexes MoO(O(2))(2)(L) (L = bipy (5), di-tBu-bipy (8)) using H(2)O(2)(10 equiv.)/CH(3)CN/r.t. The structure of 7·x(solvent) (where solvent = CH(2)Cl(2) and/or diethyl ether) was determined by single crystal X-ray diffraction. Despite possessing the same windmill-type complex as that described previously for 7·10CH(2)Cl(2), the crystal structure of 7·x(solvent) is unique due to differences in the crystal packing. Compounds 1-8 were examined as catalysts or catalyst precursors for the epoxidation of cyclooctene using aqueous TBHP or H(2)O(2) as oxidant at 55 or 70 °C. Reactions were performed without co-solvent or with the addition of water, ethanol or acetonitrile. Cyclooctene oxide was always the only reaction product. Solids recovered after 24 h reaction at 70 °C were identified by FT-IR spectroscopy as the hybrid 4 from (1,3-5)/TBHP, complex 5 from (1,3-5)/H(2)O(2), and complex 8 from (2,6-8)/H(2)O(2). With TBHP as oxidant, the highest epoxide yields (for 24 h reaction at 70 °C) were obtained using excess H(2)O as solvent (28-38% for 1,3-5; 87-98% for 2,6-8), while with H(2)O(2) as oxidant, the highest epoxide yields were obtained using CH(3)CN as solvent (54-81% for 3-8).

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