Hydride complexes molybdenum

The key step involves C-H bond activation, and produces a molybdenum complex with hydride and ketone ligands from the alkoxide ligand. Subsequent... 

Stable zirconium, platinum, molybdenum, and tungsten complexes of cyclooctyne, a zirconium complex of cydoocta-5-enyne, and a bimetallic molybdenum complex of cyclocta-3,7-dienyne have been discussed in earlier reviews.28 More recently, two stable zirconocene complexes of cycloocta-trienyne (275 and 276) have been prepared101 by /3-hydride elimination from 274 in the presence of PMe2R [Eq. (45)]. 

Although bis(phosphite) carbyne complex Cp[P(OMe)3]2Mo=C(c-Pr) is incapable of undergoing carbonyl insertion reactions, it adds 1 equivalent of HCl in ether forming the ring-opened f/ -butadiene complex Cp[P(OMe)3](Cl)Mo( / -butadiene) in 15% yield, and P(OMe)3 in equal amounts (equation 108) . Careful analysis of the reaction using two equivalents of HCl reveals the presence of the metal hydride complex Cp[P(OMe)3]2Cl2MoH as the main products (70%), and free butadiene. It was furthermore shown that the two molybdenum complexes are not interconvertible under the reaction conditions and both the yields and products ratio are invariant with temperature in the range of -40 °C to room temperature and the amount of added HCl (1 or 2 equivalents). 

Cyclohexadiene-Mo(CO)iCp complexes. The molybdenum complex 1 is prepared from 3-bromo-1-cyclohexene by reaction with molybdenum carbonyl and lithium cyclo-pentadienide followed by hydride abstraction. It undergoes a highly regio- and stereoselective reaction with a Grignard reagent to gi c an adduct (2) with an axial substituent... 

Although Able et al. (2, 8) had originally set out to prepare 7r-cyclo-heptatrienyl complexes of metals, the cycloheptatriene complexes they actually obtained served as key intermediates in forming the former complexes. In 1958 Dauben and Honnen (61) reported that cycloheptatriene-molybdenum tricarbonyl reacted with triphenylmethyl tetrafluoroborate in methylene chloride solution with abstraction of hydride ion from the molybdenum complex. The reaction products, obtained in nearly quantitative yields, were triphenylmethane and the 7r-cycloheptatrienyl complex [(7r-C7H7)Mo(CO)3]+BF4 . 

Zero-valent ruthenium complexes (arene)Ru(PRg)2 (PR3 = tertiary phosphine), isoelectronic with the molybdenum complexes (CgHg)Mo-(PR3)3 182), have not yet been reported. However, the hydride cation (XXVII), isoelectronic with the molybdenum hydride cations [(CgHg)-Mo(PR3)3H] 182), has been obtained from the dissociation of [RuH-(PPh3)JPFg in dichloromethane solution 364). 

Addition of hydride to [i7 -C5H5Mo(CO)(NO)-i7 -C3H5]PF6 provides the propene molybdenum analog (6) however, Faller and Rosan (57, 60) have found that hydride addition via cyanoborohydride is stereospecific and produces only one of the pairs of diastereoisomers. The asymmetry in charge induced by the difference in electronic demands of CO and NO appear to provide the driving force for this asymmetric induction. This is a particularly important observation because it represents an electronic control of induction, whereas the usual approach has been to utilize steric effects to promote asymmetric induction (88). The importance of the electronic asymmetry is dramatically demonstrated by perturbations of the endo-exo equilibrium in the molybdenum complexes (60). In this instance there are clearly disparate trans effects of the NO and CO. 

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