Halocarbonyl cations

Another related class of gitonic superelectrophiles are the superelectrophilic halocarbonyl dications. The halocarbonyl cations (XCO+, X = F, Cl, Br, I) have been prepared under long-lived stable ion conditions and characterized by 13C NMR spectroscopy.68 Sommer and co-workers studied the bromine-assisted carbonylation of propane in superacids, and... 

Five-membered N-heterocycles of general structure (128), carrying an a-XH grouping, react with a-halocarbonyl compounds to give quaternary salts (129) and (131) which readily undergo cyclodehydration to give (5,5)-fused pyrroles (130) and imidazoles (132). With (128 X = S) and a-halocarbonyl compounds, cationic-fused thiazoles (134) are obtained by treatment of the intermediates (133) with a strong acid (HA). 

CpMo(CO)2(NO) reacts with I2 with loss of both CO ligands to give the dimer complex, [ f -CpMo(NO)l2]2 . Oxidation of ()y -arene)M(CO)3 (M = Mo,W) with I2 gives the [()7 -arene)M(CO)3l cation the Mo complex is unstable in solution. Earlier reviews of halocarbonyl complexes of group VIA metals exist. ... 

There has been little new work in the area of binary halocarbonyl and hydridecarbonyl species. Most of these complexes have been used in the preparation of other carbonyl species which are reported in other sections of this chapter. The development of spectroscopic techniques has afforded the characterization of several new species, some of them too unstable to be isolated, which remained elusive during recent decades. The ds—trans isomerization of [Rhl4(CO)2] was studied by IR spectroscopy. Dimeric rhodium(l) bis(carbonyl) chloride, [Rh(/r-Cl)(CO)2]2, is the starting material for the syntheses of new cationic carbonyl complexes of both rhodium(i) and rhodium(lll) such as [Rh(CO)4][M2Cl7] (M=A1, Ga), [Rh(CO)4][Sb2F ], [Rh(CO)5Cl][Sb2F ]2. The compound [Rh(CO)4][l-Et-CBiiFnl was also isolated and its molecular structure was determined by X-ray diffraction methods. ... 

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