Manganese tricarbonyl, complexes

Other cyclic olefine-manganese tricarbonyl complexes were investigated by Whitesides and Lichteriberger (64), and include (77schd)Mn(CO)3,0 sced)Mn(CO)3, and (i7scet)Mn(CO)3. In all three complexes, the ionizations of the six d-electrons fall at 8 eV, giving rise to a broad band, while 7r orbitals of the cyclic ligands produce two bands, at 8.5 and 10 eV. 

Examples of reductive cluster-opening and oxidative cluster-closing reactions are common in the chemistry of metal-hydrocarbon tt complexes. For example, bases convert nido- (hexa-hapto)arene-manganese tricarbonyl complexes into aracAno(pentahapto)-7T-cyclohexadienyl complexes 129,130, 217) ... 

Figure 4. Molecular structure of 1,3- cyclohexadienyl)manganese tricarbonyl complexed with three units of thiourea.

Biinz et al. have been able to achieve a quadruple coupling with the iron tricarbonyl complex of tetraiodocyclobutadiene [147] and even (Scheme 4-43) a quintuple coupling with the manganese tricarbonyl complex of pentaiodocyclopentadiene [148J ... 

Schdllkopfs chiral glycine enolate equivalents, as in the elegant synthesis of the central diarylether unit of ristocetin [169]. It is remarkable that these limitations were partly lifted by using, instead of the manganese tricarbonyl complex the corresponding iron or ruthenium cyclopentadienyl complexes [170] (Scheme 62). 

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"...

Fig. 15 Cytotoxicity test of CO-RM 24 at 100 iM against HT29 colon cancer cell. (Graph taken from ref. 54 Photoinduced CO release, cellular uptake and cytotoxicity of a tris(pyrazolyl)methane (tpm) manganese tricarbonyl complex, J. Niesel, A. Pinto, H. W. Peindy N Dongo, K. Merz, 1. Ott, R. Gust and U. Schatzschneider, Chem. Commun. 2008, 1798-1800). Copyright The Royal Society of Chemistry 2008.

The molecular structures of the two isomeric manganese tricarbonyl complexes with the empirical formula CisHaoMnO P are illustrated in (7) and (8) In both complexes the metal atom is co-ordinated by a phosphorus... 

Figure 10,3 An indole manganese tricarbonyl complex. Reprinted from Inorganica Chimica Acta, 211, Ryan, W. J. Peterson, P E. et al., "Synthesis and Reactivity of (indole)Mn(CO)3 complexes. Electrophilic Activation of the indole 4 and 7 positions, Inorganica Chimica Acta, 211, I, 1-3. (1993), with permission from Elsevier.

Niesel J, Pinto A, Peindy N Dongo HW, et al. Photoinduced CO release, cellular uptake and cytotoxicity of a tris(pyrazolyl)methane (tpm) manganese tricarbonyl complex. Chem Commun. 2008 1798-1800. 

Articles by Sweigart and coworkers have shown that manganese tricarbonyl complexes of r -hydroquinone deprotonate to give ii -semiquinone and q -quinone complexes. " " Solution NMR analysis and crystal structures of the q -semiquinone complex indicated that this complex was polymeric due to strong intermolecular hydrogen bonding, as shown in scheme 29 Reaction of the q -semiquinone and the q" -quinone complexes allowed the production of one-, two- and three-dimensional polymers. These complexes have also been shown to self-assemble by complexation of the oxygen atoms with transition metal ions. 

Scheme 28. Manganese and rhenium tricarbonyl complexes with sohd phase linkers (68).

To examine the chemical behavior of these new ligands 48-50 in coordination chemistry, tricarbonyl complexes with manganese and rhenium were synthesized from [MnBr(CO)s] and [ReBrCCOls] as described earlier for the other heteroscorpionate ligands (Scheme 28). The purpose of these tricarbonyl complexes was to verify tripodal binding of the solid-bound ligand. The protected OH linker in 50 acts as model for the solid phase bound ligand. 

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 ease of arene ring displacement from (45) makes it an excellent manganese tricarbonyl transfer (MTT) reagent. In particular, many free arenes react readily with (45) to generate new [(arene)Mn(CO)3]+ complexes by a mild and useful synthetic route. In this manner, hydroquinones, centropolyindanes, and even ( -biphenyl)Cr(CO)3 are readily... 

A variety of transition metals, for example, chromium, molybdenum, tungsten, iron, vanadium, manganese, and rhodium can be used to prepare relatively stable j -arene complexes (see Arene Complexes). Reactions of j -arene chromium tricarbonyl complexes have been extensively examined, and numerous reviews are available. Although chromium complexes are by far the most utilized in organic synthesis, complexes of iron and manganese are emerging as potentially useful alternatives. 

Ethylene complexes of transition metals near the beginning of the transition series are now known. A neutral complex was prepared in 1960 by the photochemical displacement of carbon monoxide by ethylene from cyclopentadieny 1-manganese tricarbonyl 156) ... 

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