Insertion reactions transition metals

The subjects of structure and bonding in metal isocyanide complexes have been discussed before 90, 156) and will not be treated extensively here. A brief discussion of this subject is presented in Section II of course, special emphasis is given to the more recent information which has appeared. Several areas of current study in the field of transition metal-isocyanide complexes have become particularly important and are discussed in this review in Section III. These include the additions of protonic compounds to coordinated isocyanides, probably the subject most actively being studied at this time insertion reactions into metal-carbon bonded species nucleophilic reactions with metal isocyanide complexes and the metal-catalyzed a-addition reactions. Concurrent with these new developments, there has been a general expansion of descriptive chemistry of isocyanide-metal complexes, and further study of the physical properties of selected species. These developments are summarized in Section IV. 

These reactions involve metallate rearrangements , migratory insertion and transition metal-catalysed vinylic substitution reactions. They also perform well in applications in natural product synthesis . Many useful synthetic possibilities arise from application of ring-closing olefin metathesis (RCM) to unsaturated homoaldol products and their derivatives by means of the Grubbs catalyst 3942 4-286 Equation 105 presents some examples. ... 

Metal-Carbon Compounds. Clear examples of olefin insertions into transition metal-carbon groups are rare. The obvious reaction of olefins with alkyl- or acyl-cobalt tetracarbonyls are slow, complicated, and incomplete under the usual laboratory conditions. Under high pressure at elevated temperatures, in the... 

Hydrogenation Reactions Catalyzed by Transition Metal Complexes, 17, 319 Infrared Intensities of Metal Carbonyl Stretching Vibrations, 10, 199 Infrared and Raman Studies of ir-Complexes, 1, 239 Insertion Reactions of Compounds of Metals and Metalloids, S, 225 Insertion Reactions ofTransition Metal-Carbon Bonded Compounds. I. Carbon Monoxide Insertion, II, 87... 

The study of stoichiometric CO insertions into transition metal complexes is of great importance because this reaction is the first step m the catalytic conversion of carbon dioxide. Hence, these investigations can lead to the possibility of introducing carbon dioxide into transition metal-catalyzed synthetic processes. Analogies with carbon monoxide chemistry may be drawn, for instance. from the CO insertion into metal alkyl bonds leading to such important industrial processes as hydroformylation and carbonylalion. 

Although relatively few systematic studies of alkyne insertions into transition metal hydride bonds have been reported, representative reactions of all the transition groups are now known. 

Insertions into transition metal-phosphine bonds have been observed, as shown in reactions (s) °, (t) and (u). ... 

Olefin insertions into transition metal-carbon and transition metal-hydrogen bonds are fundamental reactions in homogeneous catalysis. With unsymmetrically substituted olefins, a remarkable regioselectivity is frequently observed, whereby the orientation of the olefin depends on the metal, the ligands, and the olefin itself. Empirical rules of regioselectivity are given, and interpreted on the base of the electronic structure of the reaction partners. 

Because various important industrial organic processes utilize olefins, convenient methods to convert olefins into various products are vital. Transition metal catalysts with proper ligands have proved most useful in controlling the course of these reactions. Transition metal complexes catalyze skeletal isomerization, double bond isomerization, polymerization, and other processes. Insertion of a terminal olefin into a transition metal hydride bond by 1,2-inserfion or... 

Li can be inserted into transition-metal oxides at room temperature in an inert atmosphere by a reaction between the oxide and n-butyl-Li. A low but non-negligible mobility of Li" ions has been observed in lithiated spinels (Goodenough et al, 1984), which indicates that lithiated ferrites can be used as electrodes in ionic batteries. Lithiation in a-Fc203 (Thackeray, David Goodenough, 1984), Fe304 (Fontcuberta et al, 1986) and y-Fe203 (Pernet et al, 1989) has already been reported. 

These reactions involve metallate rearrangements [231], migratory insertion and transition metal-catalyzed vinylic substitution reactions. They also perform well in applications in natural product synthesis [204,205,209,233]. 

These and other results are best explained, at least when the reaction is carried out in liquid SOj, by the mechanism shown in Figure 12.2. Initial 5 2 attack by the electrophilic sulfur of SOj inverts the configuration at carbon and forms an ion pair. Collapse of the ion pair to form an 0-bound sulfinate occurs reversibly, and the more stable S-bound sulfinate is eventually formed. The cation [CpM(L)(L )] is slow to invert, leading to retention of stereochemistry at the metal. Sulfur electrophiles that are similar to SOj, such as N-sulfinyl-sulfonamides (RS02)NS0 and sulfur bis(sulfonylimide)s (RSOjN)jS, also insert into transition metal-carbon a-bonds with inversion of stereochemistry at carbon, - probably by a mechanism analogous to that shown in Figure 12.2. 

Pd-cataly2ed reactions of butadiene are different from those catalyzed by other transition metal complexes. Unlike Ni(0) catalysts, neither the well known cyclodimerization nor cyclotrimerization to form COD or CDT[1,2] takes place with Pd(0) catalysts. Pd(0) complexes catalyze two important reactions of conjugated dienes[3,4]. The first type is linear dimerization. The most characteristic and useful reaction of butadiene catalyzed by Pd(0) is dimerization with incorporation of nucleophiles. The bis-rr-allylpalladium complex 3 is believed to be an intermediate of 1,3,7-octatriene (7j and telomers 5 and 6[5,6]. The complex 3 is the resonance form of 2,5-divinylpalladacyclopentane (1) and pallada-3,7-cyclononadiene (2) formed by the oxidative cyclization of butadiene. The second reaction characteristic of Pd is the co-cyclization of butadiene with C = 0 bonds of aldehydes[7-9] and CO jlO] and C = N bonds of Schiff bases[ll] and isocyanate[12] to form the six-membered heterocyclic compounds 9 with two vinyl groups. The cyclization is explained by the insertion of these unsaturated bonds into the complex 1 to generate 8 and its reductive elimination to give 9. 

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