Carbonyl chromium complexes

By a photochemically induced elimination of CO, a chromium carbene complex with a free coordination site is generated. That species can coordinate to an alkyne, to give the alkyne-chromium carbonyl complex 4. The next step is likely to be a cycloaddition reaction leading to a four-membered ring compound 5. A subsequent electrocyclic ring opening and the insertion of CO leads to the vinylketene complex 6 ... 

G.A. Ozin, University of Toronto In our Cr/CO matrix cocondensation experiments (Angew. Chem., Int. Ed. Eng. 1975, 14, 292), we reported evidence for the facile formation of a binuclear chromium carbonyl complex Cr2(CO)i0 or Cr2 (CCOi x which could be described as square pyramidal Cr(CO)5 weakly interacting with either a Cr(CO)5 or Cr(CO)6 moiety in the vacant (sixth) site. As a result, the infrared spectrum of this "weakly-coupled" binuclear species closely resembled that of the mononuclear fragment Cr(CO)5. I would like to ask you, whether or not you have any evidence for the existence of such a binuclear species in your Cr(CO)6 /Xe cryogenic solutions following various photolysis treatments. 

Carbazole will react with 1 or 2 mol of ferrocene in hot decalin in the presence of aluminium-aluminium chloride producing crystalline derivatives in which either one or both" of the benzene rings is linked to iron, 25 and 26, respectively. The sandwich compound 25 was deprotonated to 27 with sodamide in liquid ammonia. A chromium carbonyl complex 28... 

Fig. 12. Polystyrene anchored arene-chromium carbonyl complex...

Chlorophyll, and photosynthenc reaction center. 917-919 Chromium carbonyl complexes, bond lengths in, 427 Circular dichrotsm ICD). 496-499 Claasen, H. H., 70 Clathrate compounds, 304-306 Claihro-chelates, 530 Clays. 750 Clementi, E., 31, 32 Closo structures, 798-800. 807 Clostridium pasieurianttm, 934 Clusters, 738, 807-819 Coenzyme, 919 Coenzymes, vitamin B,-,... 

The deoxygenation of arene oxides have also been achieved by using chromium carbonyl complexes. The aromatic hydrocarbons produced are partially converted to chromium complexes. Formation of 246 in methanol suggests Rh-catalyzed solvolysis, resulting in nucleophilic addition of meth-... 

A photo-induced [6+2] cycloaddition of the chiral acrylate 28 with the chromium carbonyl complex 27 afforded the endo- AAuct 29 in high diastereomeric excess (Equation 3) <1995JOC7392>. 

Layered double hydroxides, intercalation in, 12, 828 LCBs, see Long chain branches LC compounds, see Liquid crystalline silicones LCST, see Lower critical solution temperatures LDHs, see Layered double hydroxides LDPE, see Linear low-density polyethylene Lead complexes in C-C bond formations, 3, 887 chromium carbonyl complexes, 5, 208... 

Aza analogs of cyclopentadienylmanganese tricarbonyl have also been prepared.158 160,162 Application of this sequence to pyrazole, imidazole, and 1,2,4-triazole, however, led not to aza analogs but to coordination polymers.168 A mixed manganese and chromium carbonyl complex of 2-benzylpyrrole has been prepared.163a... 

If the issue of n-complex formation with PMDA-ODA polyimide seems confused, the results of model compound studies have, in places, exacerbated the problem. Several research groups have turned to reactions of formally zerovalent chromium to model the chemistry of PMDA-ODA/Cr (58e, 60. 62) The studies assume that the chemistry of atomic Cr and of certain chromium carbonyl complexes is coextensive. Since atomic chromium has not been available as a benchtop reagent, popular sources of formally zerovalent chromium, disguised as Cr(CO)6 and (CH3CN)3Cr(CO)3, have been used. These compounds readily form (arene)Cr(CO)3 complexes (71). 

The diverse chemistry of chromium carbonyl complexes has its origin in the discovery of Cr(CO)6 in 1926 by Job and Cassal. Early developments in this area included the preparation of the (jj -arene)Cr(CO)3 family of organometallics by Nicholls and Whiting in 1959, the synthesis of the first structurally characterized carbene complex by Fischer and Maasbdl (1965), and a... 

A systematic investigation of ligand dissociation from chromium carbonyl complexes provided evidence regarding electronic effects. The complexes Cr(CO)sT, trans-Cr(CO)4T2, and trans-Cx CO)AlAJ have been investigated for their reaction with carbon monoxide. The order of Cr-T bond stabilities in Cr(CO)sT is ... 

Decomplexation of ArCr CO)3. The chromium carbonyl complexes of arenes are useful for activation of the aryl group to nucleophilic attack (6, 28, 125-126 7, 71-72). Decomplexation has been effected with iodine or by photochemical oxidation with destruction of the expensive Cr(CO)3 unit. A more recent method involves reflux with pyridine to form Py3-Cr(CO)3 in yields of 70-100%. The pyridine complex in the presence of BF3 can be reused for preparation of ArCr(CO)3. Isomerization of 1,3-dienes. Ergosteryl acetate (1) is isomerized by chromium carbonyl to ergosteryl 83 acetate (2) in 81% yield. Under the same conditions ergosteryl 83 acetate (3) is isomerized to ergosteryl 81 acetate (4). 80th reactions involve isomerization of a cisoid diene to a transpid diene. In contrast iron carbonyl isomerizes steroidal transoid 3,5- and 4,6-dienes to 2,4-dienes. ... 

The chromium carbonyl complexes with one monodentate and one bidentate ligand in System 8 show systematic changes in F ,i and F ,2 (but in opposite directions), when the ligands are changed from a P—P to a P—As and an As—As type (for -dpadpe the coordination to Cr is through P ). The first, chemically reversible oxidation is made easier in going from dppe to dpae, while the second, chemically irreversible oxidation becomes increasingly more difficult. The one-electron oxidation products slowly decompose to trons-[Cr(CO)2( -L-L)2]+ - . 

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