Transition metal carbonyl, synthesis

The chemistry of transition metal carbonyls synthesis and reactivity... 

Azidorhodium complexes are of considerable structural interest, but limited applicability can be expected from the unusual triazole synthesis illustrated in Scheme 125.190 It is also difficult to envisage synthetic utility from reactions in which organic azides are decomposed by transition metal carbonyls. Thus 2-arylbenzotriazoles are formed in such reactions on... 

Hi) Formation of transition metal carbonyl complexes Ashe and Colburn have reported (77JA8099) the synthesis of molybdenum carbonyl complexes of arsenin and antimonin but were unable to prepare bismin complexes because of its lability (Scheme 23). As expected for electron-rich aromatic compounds, both formed six-electron 7r-complexes (113) by a ligand displacement mechanism. Arsenin also forms a two-electron complex (114) analogous to those formed by pyridine, whereas antimonin did not give a similar complex under the conditions of this reaction. 

Cyclopropylcarbene complexes of the type L M=C(XR )R2 (X = O, S R1 = alkyl, aryl R2 = cyclopropyl) having a stabilizing heteroalkyl (XR1) group on the electrophilic carbene ligand (Scheme 3) have found widespread application in organic synthesis. These so-called Fischer carbene complexes are best known via their group 6 transition metal carbonyl complexes (CO)5M=(OR )R2(M = Cr, Mo, W)132. Much less abundant are the Schrock-type cyclopropylcarbene complexes L M=CR R2 where no heteroatom is bound to the carbene carbon atom133. 

Comparisons to methods for transition metal acyl synthesis are instructive. Although many transition metal alkyls can be readily carbonylated to transition metal acyls, the carbonylation of transition metal hydrides to transition metal formyls has not been observed [Eq. (2)] (4, 5). As will be seen, many transition metal formyls are thermodynamically unstable with respect to transition metal hydrides and CO. Thus approach A-i (Scheme 1) is not preparatively useful. (See, however, Addendum, p. 34.)... 

Transition metal carbonyls and their derivatives are remarkably effective and varied in their ability to catalyze reactions between unsaturated molecules (e.g., CO and olefinic compounds) or between certain saturated and unsaturated molecules (e.g., olefins and H2 or H20). The carbonyl derivatives of cobalt are particularly active catalysts for such reactions and have been put to use in the industrial synthesis of higher aliphatic alcohols. In fact, much of the growth in knowledge concerning catalysis by metal carbonyls has been stimulated by the industrial importance of the Fischer-Tropsch synthesis, and by the economically less important, but chemically more tractable, hydroformylation reaction. 

This method has been more widely used for the synthesis of bridged germylene complexes than for their silicon analogs. The reactions of transition-metal carbonyl monoanions with Me2GeCl2 give A-type bridged... 

Carbonylation of the parent acetylene via stoichiometric or catalytic reactions involving transition-metal carbonyl complexes has been extensively studied. Various types of carbonylation reactions of acetylene were discovered. In 1968, Pino et al. [30] reported on the synthesis of hydroquinone via a Ru3(CO)12-cat-alyzed carbonylation of acetylene with H2 or H20. The product formally consisted of two molecules of acetylene and CO, and one molecule of H2 (Eq. 14). To achieve a good yield of hydroquinone, the H2 pressure must be kept under... 

Synthesis and structure of transition metal carbonyl in the zeoli-te medium... 

In a recent comprehensive review Willner and Aubke [48] have set the range of syntheses of transition metal carbonyl cations in superacidic media within the general context of synthesis of these types of cations by all known methods. They have presented the available spectroscopic and crystallographic evidence for the structures of the cations and have discussed the nature of bonding in the carbonyl complexes. 

This section highlights some of the significant features of chromium(O) carbonyls and of the chemistry of this oxidation state. Further information can be found in the articles Carbonyl Complexes of the Transition Metals and Organic Synthesis using Transition Metal Carbonyl Complexes, and in the review literature. ... 

The carbonyl complexes of iridium have perhaps not been as extensively studied as those of some other metals (see Carbonyl Complexes of the Transition Metals Carbonylation Processes by Homogeneous Catalysis, and Organic Synthesis using Transition Metal Carbonyl Complexes). Nevertheless some interesting findings in this area both in terms of stmeture and reactivity have been reported. 

Certain classical coordination complexes (see Coordination Complexes) of iron (e.g. Prussian blue) will be dealt with in other articles (see Iron Inorganic Coordination Chemistry and Cyanide Complexes of the Transition Metals), as will much of the chemistries of iron carbonyls (see Metal Carbonyls) and iron hydrides (see Hydrides) (see Carbonyl Complexes of the Transition Metals Transition Metal Carbonyls Infrared Spectra, and Hydride Complexes of the Transition Metals). The use of organoiron complexes as catalysts (see Catalysis) in organic transformations will be mentioned but will primarily be covered elsewhere (see Asymmetric Synthesis by Homogeneous Catalysis, and Organic Synthesis using Transition Metal Carbonyl Complexes). 

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