Molybdenum complexes single bonds

The extent of alkyne ir donation in Mo(RC=CR)(SBu )2(CNBu% (SO) is not easily quantified as discussed in the structural and molecular orbital sections. Proton shifts for HC=CH and PhC=CH ligands in these complexes are near 10.4 ppm, above the N = 4 median value and approaching an N = 3 chemical shift. The 13C chemical shifts range from 170 to 185 ppm, also above classic four-electron donor alkyne values, presumably reflecting competition with the two adjacent equatorial thiolates for donation to the two vacant metal dir acceptor orbitals. Single bond VCH values of 215 and 211 Hz are typical of terminal alkynes bound to molybdenum(II) (133). 

The structure of cycloheptatriene-molybdenum tricarbonyl (XXX, M = Mo) was subsequently confirmed by x-ray analysis (76). The six olefinic carbon atoms were found to be approximately planar and symmetrically bonded to the metal, with the methylene carbon bent away from the latter. Carbon-carbon ring distances indicated alternate double and single bonds in the planar portion of the molecule, rather than a delocalized TT-electron system, as was originally suggested. The analogous complex (C7H8)W(C0)3 was subsequently described in the literature (62, 164). 

Coordination to the metal is not shown. The enediolate in the intermediate is intended to be below the plane of the paper, (b) Dinuclear complex of Mo and o-arabinose. Single bonds to molybdenum are drawn as broken. On the alkyl shift mechanism the C3 shifts with its bonding pair of electrons from C2 to Cl. 

Various metal-metal single o-bonded complexes have been obtained by the reaction of metal carbonyls with metal-carbon o-bonded porphyrins or by the reaction of metal carbonyl anions and chlorometalloporphyrins (Scheme 14). For example, the reaction of dimanganese carbonyl and methyl indium(III) porphyrin gives manganese pen-tacarbonyl indium porphyrin In(Por)Mn(CO)5. The same compound is isolated when chloroindium porphyrin is allowed to react with the manganese pentacarbonyl monoanion. Various iron, cobalt, tungsten, and molybdenum complexes have been prepared by these two methods. 

Because the Si-Cl bond is sensitive to moisture, compounds containing i-Pr2SiCl are less common. However, with careful manipulation, such confounds were characterized by NMR, MS, elemental analysis, and single-crystal X-ray diffraction analysis. " For exanple, the bis(benzene)molybdenum complex was metalated with 2 equiv f-BuLi to give the diionic intermediate 10, which was subjected to react with i-Pr2SiCl2 to give complex 11 the yield of the latter step is 37% (eq 10). ... 

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