Chromium dicarbonyl

The carbonyls are disposed trans to each other, which is deduced from the single carbonyl in the infrared spectrum. A similar cation may be formed by mild oxidation of the chromium dicarbonyl phosphine, Cr(CO)2QP [QP = tris(o-diphcnylphosphinophenyl)phosphine]. 

CrOjPjCjHj, Chromium, dicarbonyl(ii -cyclopentadienylXtl -cyclotriphos-phido)-, 29 247... 

NCrFeO,P2C45H3, Chromate(l-), hydrido-nonacarbonyliron-, j-nitrido-bis(tri-phenylphosphorus)(l+), 26 338 NCr03C,Hj, Chromium, dicarbonyl(T] -cyclopentadienyl)nitrosyl-, 28 196 NCr03C H, Chromium, tricarbonylit] -lV, -dimethylbenzenamine)-,... 

As mentioned above, ICR spectrometers have been used as research tools for the investigation of gas phase ion-molecule reactions. An example of the sort of ion-molecule study which can be carried out by FT-ICR techniques but which would be beyond the capability of any other technique is the study of the ion-molecule condensation chemistry of the three organometallic compounds, ijS.cydopentadienyl manganesetricarbonyl (CpMn(C0)3), j, 176-cyclopentadienyl chromium-dicarbonyl nitrosyl (CpCr(C0)2N0), 2, and- j5 cyclopentadienyl chromiumdicarbonylthionitrosyl (Cprr(C0)2NS),. Compounds and form an isoelectronic pair 2 and 3 are a congener pair. 

NCrFe09P2C45H3i, Chromate(l—), hydri-dononacarbonyliron-, -nitrido-bis(triphenylphosphorus)(l +), 26 338 NCr03C7H, Chromium, dicarbonyl(r/ -cyclopentadienyl)nitro8yl-, 28 196 NCrOjCjiH, Chromium, tricarbonyl(i -NJV-dimethylbenzenamineK 28 139 NCr09C,oH9, Chromium, (tert-butyl isocyanide)pentacarbonyl-, 28 143 NCrOsCigH,3, Chromium, (benzoyl isocyanide)dicarbonyl(>t -methyl benzoate)-, 26 32... 

C2 7H2 sCrOg, Tr icarbonyl (5,1 O-t - (4- (2-methoxy-1 -propenyl) -2-phenyl-1 -naphthol))chromium ether, 44B, 778 C28H22MO2O6, Azulenetricarbonylmethylmolybdenum dimer, 33B, 382 C2 8H2 aCrOijP, (TT-Methylbenzoate) (triphenylphosphine)chromium dicarbonyl, 4IB, 916... 

Structural studies of large molecules may be illustrated by cyclopentadienyl chromium dicarbonyl nitrosyl ( ) —C5 H5)Cr(CO)2NO, a simple piano-stool-type configuration. Interest in these metal-nitrosyl compounds arises since NO is a neurotransmitter. A study of various iso-tomers gives the overall molecular configuration and structure of Fig. 15. 

The major developments of catalytic enantioselective cycloaddition reactions of carbonyl compounds with conjugated dienes have been presented. A variety of chiral catalysts is available for the different types of carbonyl compound. For unactivated aldehydes chiral catalysts such as BINOL-aluminum(III), BINOL-tita-nium(IV), acyloxylborane(III), and tridentate Schiff base chromium(III) complexes can catalyze highly diastereo- and enantioselective cycloaddition reactions. The mechanism of these reactions can be a stepwise pathway via a Mukaiyama aldol intermediate or a concerted mechanism. For a-dicarbonyl compounds, which can coordinate to the chiral catalyst in a bidentate fashion, the chiral BOX-copper(II)... 

Uemura and coworkers utilized an arene-chromium complex ligand to form the C—N bond on a pyridine ring [146]. In the presence of 3 mol% of the monophosphine(dicarbonyl)chromium... 

The intermediate cyclooctene complex appears to be more reactive with respect to CS coordination and more sensitive to oxidation when the arene ring bears electron-withdrawing groups (e.g., C02CH3). Dicarbonyl(methyl rj6-benzoate)-thiocarbonyl)chromium is air stable in the solid state and reasonably stable in solution.9 The infrared spectrum exhibits metal carbonyl absorptions at 1980 and 1935 cm"1 and a metal thiocarbonyl stretch at 1215 cm"1 (Nujol) (these occur at 1978, 1932, and 1912 cm"1 in CH2C12 solution).10 Irradiation of the compound in the presence of phosphite or phosphine leads to slow substitution of CO by these ligands, whereas the CS ligand remains inert to substitution. The crystal structure has been published."... 

C. DICARBONYL(METHYL r/6-m-METHYLBENZOATE)(THIO-CARBONYL)CHROMIUM(O)... 

Certain other 1,3-dicarbonyl chelates were brominated with difficulty or not at all. For example, the trifluoro- and hexafluoroacetylacetonates (VI, R = CF3, R = CH3, and R = R = CF3) were not brominated under a variety of vigorous conditions. However, in the case of the chromium chelates of 1-phenyl-1,3-butanedione and dibenzoylmethane (VI, R = C( Hr), R = CH5, and R = R = C(iHr)), reaction with N-bromosuccinimide (NBS) was successful. That the electron density at the central carbon of the chelate ring is an important factor in the success or failure of these electrophilic substitutions is evident from the fact that the bis-(ethylenediamine)-2,4-pentanedionocobalt(III) cation cannot be brominated even under vigorous conditions. 

A. (BENZOYL ISOCYANIDE)DICARBONYL(ii6-METHYL BENZOATE)CHROMIUM (0)... 

CrNOsCmHij, Chromium, (benzoyl-isocyanide)dicarbonyl(Tf-methyl-benzoate)-, 26 32... 

A selection of cases in which 2 has been found to be particularly efficacious is given in the Table. Additional examples are cited in references 1 and 5. Particularly noteworthy examples include the oxidation of acid- and base-sensitive systems, systems containing sulfur and selenium, and 1,3-diols to 1,3-dicarbonyl compounds. Use of chromium reagents in these latter cases often leads to fragmentation products. 

Bromopentacarbonylmanganese, 49 tom -Bromotetracarbonyl(methyl-methylidyne)chromium, 50 frmethylidyne)tungsten, 49 Carbonylhydridotris(triphenylphosphine)-rhodium(I), 329 Chromium carbonyl, 51 Decacarbonyldimanganese, 49 Dicarbonylcyclopentadienylcobalt, 96 Dicarbonyl(cyclopentadienyl)[(dimethyl-sulfonium)methyl]iron(II) tetrafluoroborate, 98... 

The chromium trioxide-pyridine complex affords fair yields of dicarbonyl compounds by oxidation of suitably protected precursors 2,3 4,5-di-<3-isopropylidene-(2/f/e/n f/o-/l-D-(2ra/)/rtrt-hcxos-2-ulose-2,6-pyranose was thus prepared in 53% yield from 2,3 4,5-di-0-isopropylidene-/f-D-fructo-... 

It is, however, impossible to use this route to obtain cyanocarbonyl metalates having more than three CN ligands. The /e/racyanodicarbonyl metalates(O) of chromium, molybdenum, and tungsten (126) are readily accessible from the dicarbonyl complexes M(CO)2bipy2 (M = Cr, Mo, W), Cr(CO)2[(Ph2P)2CH J2, or Cr(CO)1I(Ph,P) C2H4]2 (125) with KCN in liquid NH3 at 120°C. 

Upon UV irradiation in hydrocarbon solution, the hexacarbonyls of chromium, molybdenum, and tungsten react differently with conjugated dienes like 1,3-butadiene (la), ( )-l,3-pentadiene (lb), 2-methyl-1,3-butadiene (lc), ( , )-2,4-hexadiene (Id), ( )-2-methyl-l,3-pentadiene (le), 2-ethyl-1,3-butadiene (If), or 1,3-cyclohexadiene (Ig). Chromium hexacarbonyl (2) yields, with the acyclic dienes la-lf, tetracarbonyl-r/2-dienechromium(0) complexes (3a-3f) in a smooth reaction (8-10). With 1,3-cyclohexadiene, in addition to 3g, dicarbonylbis(>/4-l,3-cyclohexadiene)chromium(0) (4g) is obtained [Eqs. (7) and (8)j. During chromatography on silica gel, the 1,3-cyclohexadiene complex 3g dismutates readily to [Cr(CO)6] and 4g [Eq. (9)]. Under the same conditions with 2 1,3-cyclopentadiene (lh) yields, in a hydrogen-transfer reaction, the stable dicarbonyl- / 5-cyclopentadienyl-r/ 3-cyclopent-enylchromium (5) (11-13) [Eq. (10)]. 

Fig. 2. Molecular structure of dicarbonyl- j4-( , )-2,4-hexadienebis(trimethylphosphine)-chromium(O) (24d) (25). Reprinted with permission from Z. Naturforsch. 39B, 1553 (1984). Copyright by Verlag der Zeitschrift fur Naturforschung.

Photoreactions of [Cr(CO)3( /6-C7H8)] (41) with 6-mono- and 6,6-disub-stituted pentafulvenes (59a-59f) preferentially yield dicarbonyl complexes with substituted tj3 5-2-cyloheptadienylene-2-cyclopentadienylidenemethane chelate ligands (82,83). In the course of the reaction, C-6 of the fulvene forms a C—C bond to C-l of the 1,3,5-cycloheptatriene ligand, and one CO ligand is displaced. This reaction is of the same type as the formation of the f/3 5-[ 1 -(3-butene-1,2-diyl)-7-isopropylidenecycloheptadienyl] complexes 47c, 47e and 47t. The fulvene unit is transformed into a monosubstituted cyclo-pentadienyl entity, / -coordinated to the chromium, with the 1,3,5-cyclo-... 

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