Manganese complexes with olefins

The first metal-olefin complex was reported in 1827 by Zeise, but, until a few years ago, only palladium(II), platinum(Il), copper(I), silver(I), and mercury(II) were known to form such complexes (67, 188) and the nature of the bonding was not satisfactorily explained until 1951. However, recent work has shown that complexes of unsaturated hydrocarbons with metals of the vanadium, chromium, manganese, iron, and cobalt subgroups can be prepared when the metals are stabilized in a low-valent state by ligands such as carbon monoxide and the cyclopentadienyl anion. The wide variety of hydrocarbons which form complexes includes olefins, conjugated and nonconjugated polyolefins, cyclic polyolefins, and acetylenes. 

The ease with which olefins form complexes with metals naturally led to investigation of acetylenes as ligands but until recent years only a few ill-defined, unstable acetylene complexes of copper and silver were known. Now complexes of acetylenes with metals of the chromium, manganese, iron, cobalt, nickel, and copper subgroups are known. These complexes fall naturally into two classes—those in which the structure of the acetylene is essentially retained and those in which the acetylene is changed into another ligand during complex formation. Complexes of the first class are discussed here and the second class is discussed in Section VI. 

Catalytic, asymmetric epoxidations are one of the most important asymmetric processes. In 1980 Katsuki and Sharpless reported a stoichiometric asymmetric epoxidation of allylic alcohols, a method that was later improved to become a catalytic process.9 Moreover, catalytic asymmetric epoxidations of unfunctionalized olefins using salen-manganese complexes have been reported independently by several groups.10-12 In striking contrast to these successful achievements, an efficient catalytic asymmetric epoxidation of enones with broad generality has not been developed.13-22... 

The manganese complex, Ph3SiMn(CO)5 has been used to promote hydrosilylation of olefins both thermally and photochemically. With HD4 and pentene, and 0.1 mol% of Ph3SiMn(CO)5, thermal activation gave a 20% yield of D4-D4 but none from photochemical activation.109 A few complexes of iron, Fe(CO)5,110a Fe(CO)2 P(OPh)3]2H(SiMe2Ph),110b and Fe(dppe)2(CH2=CH2)ul have been reported to couple tertiary silanes but few details are available. 

The reactions of Me3MMn(CO)5 (M = Si, Ge) with fluoro-olefins and fluoroacetylenes give a range of bonded alkyl- and alkenyl-manganese complexes for which the parameters shown in [23] to [27] are reported. 

A. Murphy, G. Dubois, T. D. P. Stack, Efficient epoxidation of electron-deficient olefins with a cationic manganese complex, J. Am. Chem. Soc. 125 (2003) 5250. 

G. Yin, A. M. Danby, D. Kitko, J. D. Carter, W. M. Scheper, D. H. Busch, Olefin epoxidation by alkyl hydroperoxide with a novel cross-bridged cyclam manganese complex Demonstration of oxygenation by two distinct reactive intermediates. [Erratum to document cited in CA146 316400], Inorg. Chem. 46 (2007) 2173. 

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