Organometallic chemistry carbon monoxide reactions

The attack on coordinated carbon monoxide by nucleophiles was first extensively developed in synthetic organometallic chemistry by E. 0. Fischer and his students (6) as discussed by others in this volume, this reaction provides one route to the reduction of coordinated CO and to catalysis of the water gas shift reaction. Those carbonyl groups which are susceptible to attack by nucleophiles are electron deficient, as judged by their high CO stretcing frequencies (7). 

In this chapter, the recent advances in amidocarbonylations, cyclohydrocarbonylations, aminocarbonylations, cascade carbonylative cyclizations, carbonylative ring-expansion reactions, thiocarbonylations, and related reactions are reviewed and the scope and mechanisms of these reactions are discussed. It is clear that these carbonylation reactions play important roles in synthetic organic chemistry as well as organometallic chemistry. Some of the reactions have already been used in industrial processes and many others have high potential to become commercial processes in the future. The use of microwave irradiation and substitutes of carbon monoxide has made carbonylation processes suitable for combinatorial chemistry and laboratory syntheses without using carbon monoxide gas. The use of non-conventional reaction media such as SCCO2 and ionic liquids makes product separation and catalyst recovery/reuse easier. Thus, these processes can be operated in an environmentally friendly manner. Judging from the innovative developments in various carbonylations in the last decade, it is easy to anticipate that newer and creative advances will be made in the next decade in carbonylation reactions and processes. 

Carbon monoxide, a common ligand in organometallic chemistry, is known to insert into palladium-carbon bonds readily. This feature of the metal is frequently utilized when palladium catalyzed reactions are run in the presence of CO. The products of such reactions, also known as carbonylative couplings, incorporate a carbonyl group between the coupling partners. 

The organometallic chemistry of halocarbonyl complexes of molybde-num(II) and tungsten(II) has been extensively studied since the early report in 1956 by Piper and Wilkinson1 of the cyclopentadienyl halocarbonyl complexes [MoX(CO)3Cp] (X = Cl, Br, I). More than 700 references of relevance to the review were collected up to June 1995, and hence some selection had to be made. The review is concerned with molybde-num(II) and tungsten(II) complexes containing both carbon monoxide and at least one halide ligand. The review is mainly restricted to the formation of complexes with those ligands as the final products of reactions, and not reactions of this type of complex. 

Although the above catalytic processes involve different metals, different ligands and very different reaction conditions, the cycles which support their catalytic mechanism can be based on a series of few but similar fundamental steps. This supports the view that a unified approach based on (he relevant aspects of organometallic and coordination chemistry can produce a framework for understanding this area of carbon monoxide catalytic chemistry, at least in a qualitative way. In fact, to a first approximation, any particular mechanistic... 

Since 1939 I have come into closer contact with the organometallic chemistry of transition metals than I did during my first attempts to arylate Fe(CN)g , My attention was attracted to the paper by Job and Cassal, who synthesized chromium, molybdenum, and tungsten carbonyls by a simultaneous reaction of the halides with carbon monoxide and Grignard compounds. 

Third, and not least, the mechanistic features of the Fischer-Tropsch hydrocarbon synthesis mirror a plethora of organometallic chemistry. More precisely Molecular models have been invoked that could eventually lead to more product selectivity for eq. (1). Although plausible mechanistic schemes have been considered, there is no way to define precisely the reaction path(s), simply because the catalyst surface reactions escape detection under real process conditions (see Section 3.1.1.4). Nevertheless, the mechanism(s) of reductive hydrocarbon formation from carbon monoxide have strongly driven the organometallic chemistry of species that had previously been unheard of methylene (CH2) [7-9] and formyl (CHO) [10] ligands were discovered as stable metal complexes (Structures 1-3) only in the 1970s [7, 8]. Their chemistry soon explained a number of typical Fischer-Tropsch features [11, 12]. At the same time, it became clear to the catalysis community that molecular models of surface-catalyzed reactions cannot be... 

Carbon monoxide insertion into a metal-alkyl bond [Eq. (33)] is a fundamental reaction in organometallic chemistry as well as an important... 

If we consider the reactions of metalloenzymes, it is not difficult to identify organometallic-type chemistry. Many of these reactions have been known for some time. For example, the well-known deleterious effect that carbon monoxide has on the reactivity of a variety of metalloproteins. The effect is a consequence of carbon monoxide binding to a metal site in the enzyme. 

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