Organorhenium complexes

Complexes within this general class comprise a wide variety of uninegative (X) ligands and neutral two-electron donors and constitute the largest family of organorhenium complexes. ... 

In the previous chapter (07AHC(93)185), complexes of polypyridine ligands with non-transition and early transition metals were considered. Most publications, however, are dedicated to the rhenium(I) and ruthenium(II) complexes, and the number of sources is so high that they deserve separate chapters. Moreover, studies of such complexes become more and more popular due to their unique photochemical and electrochemical properties and ability to form molecular assemblies and nanocrystallites. Herein we consider organomanganese and organorhenium complexes of polypyridine ligands. As always in this series of chapters, emphasis will be on the synthetic and coordination aspects, as well as reactivity. We have attempted to document all the publications on applied aspects, but without analyzing them since this could be the subject of a separate chapter. 

The second chapter is the twelfth in the series on the organic chemistry of heterocyclic ligands in metallic complexes by A.P. Sadimenko of University of Fort Hare (Republic of South Africa). The present contribution deals with the chemistry of polypyridine ligands in organomanganese and organorhenium complexes. Its current importance can be measured by the fact that, of the nearly 700 references, approximately half date from the last 10 years. 

Apart from the wealth of monoalkyl- and monoarylrhenium complexes Re03R (type I), other mono- and dinuclear organorhenium oxides in the oxidation states seven (types II and III) and six (types IV to VII) have been reported (see Scheme 9.6) [119-121]. The first representative of the type II family was Re02(CH2SiMe3)3, which was obtained by Wilkinson s group in 1975, albeit in low yield [123]. Mertis and Wilkinson prepared also the... 

This preparation of 1 has been improved considerably since then [2]. Since 1993, MTO has been commercially available (cf. Section 3.3.13.1.3). In 1997, the synthetic method starting from trimethylstannyl perrhenate has been extended to other perrhenates so that the moisture-sensitive Re207 can be replaced by more conveniently handled starting materials [2]. Nowadays 1 can be synthesized directly from rhenium powder in amounts of several kilograms. This synthetic progress was accompanied by the discovery of a plethora of derivatives and catalytic applications of organorhenium(VII) oxides. The use of these complexes in catalysis, however, is still strongly dominated by 1 itself [2, 3]. 

The simple organorhenium(VII) compound methyltrioxorhenium (Structure 1 in Scheme 1) - called MTO - has developed a plethora of applications in catalytic processes [1], This rapid development occurred in the decade of 1990-2000. The epoxidation of olefins (cf. Section 2.4.3) became attractive to industrial applications. There is sound evidence that MTO represents the most efficient catalyst for this process, being active even for highly dilute solutions of hydrogen peroxide. The latter oxidant is not decomposed by MTO, as opposed to many other metal complexes (cf. Section 3.3.13.1). 

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