Chromium complex binuclear

There are many examples today of polynuclear metal complexes yielding a parent ion in the mass spectra, but initially their observation for high molecular weight compounds, such as di[bis(pentafluorophenyl)-phosphidoirontricarbonyl] (I), having a molecular ion of mje 1010 (90) was considered unusual, as were the binuclear chromium complexes (II)... 

Preston and Reed (196,196a) have studied some binuclear complexes of chromium, iron, and nickel (VI). With chromium complexes, formation of CrCpJ was observed from many ions, e.g., where X=Z = SMe,... 

Metal chloride complexes (59) with structures analogous to that of the samarium complex (50) have been obtained by the reaction of (57) with titanium or zirconium tetrachlorides via elimination of LiCl. Equimolar reaction of (57) and CrCl2(thf)2 has been shown to yield binuclear chromium complex (60), whilst reaction with a twofold excess of CrCl2(thf)2 affords a partially substituted tetranuclear complex (61). ... 

Since the expression is second order in chromium, a binuclear chrome complex was postulated. Furthermore, the reaction would be expected to be second order in polymer. The higher order which was observed was explained in terms of a fraction of intramolecular cross-links which did not contribute to the storage modulus. This fraction Increases with polymer dilution. Thus, equations (iii) becomes... 

Binuclear difluoro-bridged chromium complexes are rare and the only well-characterized previous example is the multidentate Cr(in) derivative [A, A"-(2-0-3, 5- Bu2-C6H2-CH2)2-1,2-NHCH2CH2NH]Cr(p,-F) 2 [25]. The terphenyl stabilized chromium fluoride 4-CF3-Ar Cr(p,-F) 2 (11) was obtained by decomposition during the reduction of 4-CF3-Ar Cr(p,-Cl) 2 with KCg in THF. Unlike the generally blue color observed for the chlorides, 11 has a pale purple color. 

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. 

Exchange coupling, Heisenberg, 43 265-270 Exchange energy, 38 438-439 Exchange reactions, see also specific elements binuclear complexes, formation of, 10 183-188, see also Binuclear complexes one-equivalent, 10 154-178, 188-212 of actinide ions, 10 177, 178 of cerium, 10 176, 177, 206, 207, 211 of chromium, 10 163-168, 174, 175, 188-198, 206, 208... 

Red or blue, variously hydrated chromium(II) complexes of thiocarboxylic acids, e.g. S[(CH2)2SCH2C02H]2, have been isolated, and the red complexes are antiferromagnetic.205 Some antiferromagnetic complexes of adenine may have binuclear structures (Table 16). 

Mononuclear and binuclear chromium(III) complexes containing bispicen and related tetradentate ligands have been prepared. The isomers cis-a- (118) and -/3- (119) [CrCl2(bispicen)]+ are obtained by the methods outlined in Scheme 58495-496 but complexes with the trans geometry are unknown. 

Implicit in the foregoing is the assumption that the oxidation states can be assigned with certainty in the binuclear intermediate, and this issue will now be considered explicitly. In the present case, a strong item of evidence is that the n <- %d absorption, characteristic of the Ru11—heterocycle, is observed in the successor complex an Rum-heterocycle shows no absorption in the same region of the spectrum. The d—d absorption characteristic of Crm in an oxygen environment is also observed. Finally, the rate of aquation at the chromium center is characteristic of the Crm state. 

The complex of tartaric acid and antimony (emetic) was described three centuries ago. Nevertheless, the structure of this compound has been elucidated these last fifteen years by X-ray diffraction ( 1 ). In fact, emetic presents a binuclear cyclic structure. Many authors mentioned similar complex with transition metals (vanadium (2), chromium (3)) or metalloids (arsenic (4), bismuth (5)). Emetic with phosphorus was not mentioned. Nevertheless, tartaric acid or alkyl tartrates has been utilized in phosphorus chemistry tartaric acid reacts with trialkyl phosphites giving heterocyclic phosphites (6). Starting from alkyl tartrates, we prepared spirophosphoranes with a P-H bond and sixco-ordinated compounds (7). With unprotected tartaric acid, many possibilities appear condensation as a diol, as a di(oc-hydro-xyacid), or even as a 8-hydroxyacid. 

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 complexes [Cr(H20)jCH2X]2+ (X = Cl, Br, or OCH3) were found to react with mercuric nitrate [Eq. (8)] (38,65). This reaction is believed to involve a binuclear displacement of Cr by attack of Hg on the carbon atom. In contrast, the reaction of [Cr(H20)JCH2I]2+ with Hg2+ involves an abstraction of I- by Hg2+ [Eq. (9)]. The reaction of [Cr(H20)5CH2I]2+ with Cr2+ as shown in Eq. (10) has also been reported (66). This reaction is believed to proceed via a carbon-bridged dinuclear chromium intermediate. 

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