Chromium penta carbonyl

Their strong reducing nature is a special characteristic of the penta-carbonyl metalates(-II) and decacaibonyl dimetalates(—I) of chromium, molybdenum, and tungsten that distinguishes them from the other carbonyl metalate anions of the 3d metals, e.g., [Co(CO)J. The oxidation of the mononuclear species with water... 

In organic chemistry one surely thinks at once of the construction of cyclopropane derivatives from olefins and carbenes. Indeed, it has been shown that this also is possible with our complexes and with C=C double bonds that are electron-poor and arc either polarized or easily polarizable (77-81). As an example of this, I would like to cite the reaction of penta-carbonyl[methoxy (phenyl) carbene]chromium (0), -molybdenum (0), or -tungsten(0) with ethyl vinyl ether (79). One obtains the corresponding cyclopropane derivatives in this case, however, only when one removes... 

Ofele and Herberhold explored the coordination chemistry of NHC with chromium tetra-carbonyl- and penta-carbonyl-chromium complexes more than 40 years ago [5,73]. Since then, several complexes of the general formula (NHC)Cr(CO)5 or (NHC)2Cr(CO)4 have been structurally characterized [74-78]. A variety of monodentate Cr-NHC adducts (with various oxidation states for the chromium center) have also been synthesized and characterized. For instance, the reactivity of NHCs with chromium (II) metallocene complexes has been studied. The reaction of chromocene with imidazolium chloride was reported to afford 14-electron Cr (II) complexes of the type CpCr(NHC)Cl 50 via a CpH elimination reaction (Scheme 14.26), isolated as highly air sensitive species [79,80]. Oxidation of the latter with PbCl2 (when NHC = PPr) or with CHCI3 (when NHC = IMes) produced the corresponding Cr (III) NHC dichloro... 

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