Tricarbonyl manganese cations

Cationic arene tricarbonyl manganese complexes, usually isolated as their BF4-or PFg- salts, are yellow solids. They are stable to air in the solid state and can be stored for long periods provided that they are kept out of light. They are best purified by crystallization by slow diffusion of diethylether into acetone- or CH2Cl2-solutions of the complex. Only direct methods of complexation are reported here. For other methods, involving transformations of the arene in the complex, the reader is referred to Chap. 6, to reviews [68], and to the recent literature [69,70]. 

Density functional theory studies arene chromium tricarbonyls, 5, 255 beryllium monocyclopentadienyls, 2, 75 chromium carbonyls, 5, 228 in computational chemistry, 1, 663 Cp-amido titanium complexes, 4, 464—465 diiron carbonyl complexes, 6, 222 manganese carbonyls, 5, 763 molybdenum hexacarbonyl, 5, 392 and multiconfiguration techniques, 1, 649 neutral, cationic, anionic chromium carbonyls, 5, 203-204 nickel rj2-alkene complexes, 8, 134—135 palladium NHC complexes, 8, 234 Deoxygenative coupling, carbonyls to olefins, 11, 40 (+)-4,5-Deoxyneodolabelline, via ring-closing diene metathesis, 11, 219... 

Apart from the di- and oligoolefm iron tricarbonyl complexes, which nowadays are frequently used in organic synthesis [71, 72], the chemistry of the readily accessible cyclohepatriene chromium and molybdenum tricarbonyls 2 and 3 was the focus of intense research efforts as well. Only a few months after the synthesis of 2 and 3 was published [58,59], both Hyp Dauben and Peter Pauson reported that these compounds react with triphenylmethyl tetrafluoro-borate in methylene chloride to give the tropylium complexes 4 and 5 in excellent yield (Scheme 7.1) [73, 74]. Later this method of hydride abstraction was also used for the preparation of the tropylium cation itself and subsequently led to the generation of several cationic rc-complexes of iron, manganese and cobalt [71, 72], The reactions of the cations of 4 and 5 with nucleophilic... 

The arene manganese tricarbonyl cations undergo a reversible reaction with amines giving neutral carboxamido derivatives 14) ... 

The reaction of nucleophiles with chloroarene-Mn(CO)3 and fluoro arene-Cr(CO)3 complexes has been employed for the synthesis of diaryl ethers and has been particularly applied (ref. 55) to the selective arylation of polyfunctional phenols by reaction of the phenoxide formed from NaH in dimethylformamide with the 4-chlorotoluene-manganese tricarbonyl cation (as the hexafluorophosphate) in acetonitrile at ambient temperature over 18 hours. 

In a new and significant development, it was found that chlorocyclohexadienyl manganese tricarbonyl complexes undergo palladium-catalyzed coupling reactions with a variety of carbon nucleophiles to afford products from which hydride may be abstracted with trityl cation, thus generating new [( -arene)Mn(CO)3]+ complexes containing substituents that cannot be introduced in any other manner. This is particularly true of electron-withdrawing substituents. Scheme 16 illustrates the chemistry involved. 

Scheme Cationic arene manganese tricarbonyl complexes prepared from the [Mn(CO)5] fragment. [Mn(CO)5] is generated in situ via Method A Mn(CO)5Br (58)/AlCl3/A Method B Mn2(CO)io/TFA/TFA-anhydride/reflux Method C Complex 58/AgBF4/CH2Cl2/reflux. In all cases the counteranion is either BF4" or PFg"...

The production of supramolecular polymers containing chromium tricarbonyl and manganese tricarbonyl moieties was deseribed."" Sweigart recently reported the self-assembly of r -quinone and r -semiquinone complexes derived from hydroquinone coordinated to cationic manganese tricarbonyl moieties." The metal-mediated deprotonation of these complexes allowed for the pro-duetion of polymers such as 16. 

The requisite tricarbonyl(ii -cyclohexadienylium)iron cation 2 is prepared from 1,3-cyclohexadiene and FefCOlj followed by treatment with triphenylmethyl carbocation tetrafluoroborate as shown. Subsequent oxidative cyclization of iron complex 3 with commercial manganese dioxide affords the iron-complexed dihydrocarbazol-3-one 4. 

Scheme 2.3 summarizes the regioselectivity of nucleophilic addition reactions on the A ring of estradiol derivatives modified by incorporation of a cationic manganese tricarbonyl group [97]. 

Most arene complexes are hexahapto, and ternary complexes usually have 18 valence electrons. The most known and used ones for their applications in arene synthesis are the arene-metal-tricarbonyls (columns of chromium and manganese), in particular the arene-chromium-tricarbonyl and the arene-manganese-tricarbonyl cations... 

Reaction of the anionic Fischer type carbene derivatives [(OC)5M=C(X)CH2Li] (M = Cr, W X = OEt, OMe, NHBu ) with the cationic manganese benzene complex [MnCri -C6H6)(C0)3]+[PF6] afforded358 the dinuclear bridged neutral Ti -cyclohexadienyl manganese tricarbonyl derivatives [(p-C(X)CH2) (ti5-C6H6)Mn(CO)3 M(CO)5 ], (38). 

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