General Organometallics

These derivatives have not only provided new synthetic pathways but have shown improved thermal stability (as in the case of arsenic ylides) and a modified pattern of chemical reactivity. The donor properties of ylides 55, 24), and most of their synthetic applications 103), have been covered in other reviews and articles 3, 26) and are not duplicated here. The general organometallic chemistry of arsenic, antimony, and bismuth is the subject of the invaluable monograph by Doak and Freedman 11). The broad scope of phosphorus ylide and pentaorganophosphorane chemistry was covered in the leading multivolume series on organophosphorus chemistry edited by Kosolapoff and Maier 3, 21). Finally, the recent... 

Organo-element chemistry, i.e. reviews wherein the general organometallic chemistry of a specific element or group of elements is described... 

In this review, primarily the developments in thallium coordination chemistry since the early 1980s will be surveyed. CCC (1987) is an excellent reference source for work prior to that time. In general, organometallic compounds are outside the scope of this article. There are several useful review and reference articles that describe thallium chemistry, including organothallium work. " " " Thallium is an important element in the field of high-temperature superconducting materials." ... 

Earlier reviews on the subject of mechanisms have been presented in such standard works as the Kharasch and Reinmuth textbook [12], which appeared in 1954, as well as in the chapters on organomagnesium chemistry in such general organometallic textbooks as the ones by Joffe and Nesmeyanov [16] and by Niitzel [17]. Later reviews in this area are much more characteristic of accounts of investigations by the different specialists in this (and related) field(s) [18-25]. 

In this chapter, for general organometallics we give an overview, with most of the examples for particular heterocyclic rings in the main chapters (with further discussions) however, for the transition metals, because of the regularity of reactivity across the whole range of heterocycles, most of the examples are given in this chapter. 

In general, organometallic vitamin B12 derivatives, such as coenzyme B12 (2) and methylcobalamin (3), are surprisingly resistant against proteolytic removal of the organometallic functionality. Indeed, the nucleotide can be decoordinated reversibly by protonation (p2ira(2-H+) = 3.7 p2ifa(3-H+) = 2.9 Fig. 5) (13). Under... 

In general, organometallic zinc species are too unreactive to undergo crosscoupling reactions with carbon electrophiles. Several useful exceptions to this rule are, however, worthy of mention. 

There are two large classes of molecular clusters in which the ligands are all of the same nature The halide cluster class and the carbonyl or, in general, organometallic cluster class. According to the formal oxidation numbers acquired by metal atoms in these two classes of clusters, they are often classified as high and low-valence clusters respectively. 

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