Chromium carbonyl derivatives

The most abundant dissociation product of the mono-, bi- and trimetallic chromium carbonyl derivatives, 175-177, and base peak in their mass spectra, is the metal-free arsaadamantane ligand ion, C(CH2AsO)j (Scheme 2). ... 

The complex [Cr(CO)5GeNR2 ] is obtained in 38% yield when bis(2,2,6,6-tetra-methylpiperidinato)germanium is combined with a chromium carbonyl derivative. Similarly, Ge[N(SiMe3)2] promotes the elimination of CO2 from a platinum precursor under thermal conditions in 64% yield ll... 

Complexes of types (8.264a-c) are afforded by chromium carbonyl derivatives of phosphoben-zene, which represent the latter in stabilised form. Two of these can be prepared by reaction (8.265). 

Norton has thoroughly investigated half-sandwich chromium carbonyl derivatives, inspired by literature reports of a radical pathway for the hydrogenation of certain unsaturated substrates by low-valent hydride complexes (Figure 28), that is, anthracene/HCo (CO)4, a-methylstyrene/HMt L (Mf L = Mn (CO)s, or CpM (CO)3 with M = Mo or W ), and styrene/HCo (CO)4. Note that the initial equilibrium corresponds to the p-H atom transfer process in CCT and that all above-mentioned substrates lead to highly stabilized radicals. 

In equation 1, the Grignard reagent, C H MgBr, plays a dual role as reducing agent and the source of the arene compound (see Grignard reaction). The Cr(CO)g is recovered from an apparent phenyl chromium intermediate by the addition of water (19,20). Other routes to chromium hexacarbonyl are possible, and an excellent summary of chromium carbonyl and derivatives can be found in reference 2. The only access to the less stable Cr(—II) and Cr(—I) oxidation states is by reduction of Cr(CO)g. 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

Stirring chromium trioxide (added in small portions) with the unheated solvent leads to the formation of a complex useful for oxidising alcohols to carbonyl derivatives. The trioxide must not be crushed before being added to the solvent, because violent decomposition may then occur. 

An interesting example is the stereoselective reduction of a cyclopentadienone derivative with a chromium carbonyl itself without hydrogen (equation 13)32. 

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... 

A number of new methods for the preparation of cyclopropanols from carbonyl derivatives via 1,3-bond formation between the carbonyl and carbons have been developed. 7>ons-2-alkylcyclopropanols are stereoselectively produced from 2- or 3-substituted acrolein upon exposure to chromium(II) chloride in the presence of a catalytic amount of nickel chloride in DMF (equation 56)73. 2,3-Disubstituted acroleins are, in contrast, inert to the chromium reagent. Treatment of / -stannyl carbonyls with titanium(IV) chloride affords cyclopropanols in good yields when the substrates are ketones not bearing j -alkyl... 

Studies on various derivatives of ferrocene, cymantrene, benzene-chromium tricarbonyl, and butadieneiron tricarbonyl were recently reported (174, 176). Carbonyl derivatives containing the COR group lose CO to give an ion probably containing the R group attached to the metal, e.g. 

In 1980 we published a survey (1) of our major results in this area as of late 1979. These results include extensive work on binuclear CF N PF complexes of cobalt (2,3,4,5) and nickel (6). This paper summarizes our more recent results in this area with particular emphasis on binuclear complexes of chromium, molybdenum, and tungsten as well as some new results on iron carbonyl derivatives. 

The mass spectra of binuclear cyclopentadienylmetal carbonyl derivatives of chromium and molybdenum provide useful indications of the relative strengths of the metal-metal bonds in various compound types. The mass spectrum of [C5H5Cr(CO)3]2 (S. M = Cr) exhibits no bimetallic ions but only monometallic ions such as CsHsC CO) (n = 3,... 

Electrocatalytic ETC substitution initiated by oxidation has been reported with chromium triad carbonyl derivatives.113 Several of the reactions studied, and ones that give little or no product when uncatalyzed, are shown in Eqs. (24)—(26). The mechanism described earlier for the reactions of [(MeCp)Mn(CO)2(MeCN)] applies to these reactions. The... 

Surprise products sometimes appear in reactions with metal carbonyl derivatives. For instance in the reaction of 5 with bis(norbomadiene) chromium tetracarbonyl, the product isolated 8, is one in which the silylene has become incorporated into the bicyclic ring structure. 

The derivatives of chromium hexacarbonyl, Cr(CO)e (L)j , make up the single largest class of organochromium compounds, and a substantial number of these are Cr compounds as well. The most common synthetic route involves direct reaction of Cr(CO)6 and x L, but displacement of a weakly bound hgand from a carbonyl derivative is also frequently employed. Carbonyl dissociation is usually promoted with heating or UV irradiation. 

Certain aromatic compounds containing alkyl groups have been converted to carbonyl derivatives by liquid-phase oxidation of these groups with air in the presence of chromium oxide catalysts. 

A compound with the same stoichiometry, (Bu Sb=SbBu )[Cr(CO)5]3), has been obtained from Bu SbCl2 and the analogous chromium decacarbonyl anion in which the Sb—Sb distance is also short (2.720 A) , and there is a third example in the iron carbonyl derivative 97, where the separation is 2.774 279.280... 

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