Coordination compounds insertion reactions

M-C as propagating species, 4, 1008 monomer coordination and insertion reactions, 4, 1010 monomer insertion regio- and stereochemistry, 4, 1015 overview, 4, 1005-1166 regioirregular insertions, 4, 1023 stereocontrol mechanism, 4, 1018 stereocontrol symmetry rules, 4, 1020 stereoregular polymers, 4, 1016 in Ru-Os heterodinuclear compounds, 6, 1046 in Ru-Os mixed-metal clusters, 6, 1064 semiconductor growth, conventional precursors, 12, 2 with silicon, 3, 514... 

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. 

Reactions of the hydrido(hydroxo) complex 2 with several substrates were examined (Scheme 6-14) [6]. The reactions are fairly complicated and several different types of reachons are observed depending on the substrate. Methyl acrylate and small Lewis bases such as CO, P(OMe)3, BuNC coordinate to the five-coordinated complex 2 affording the corresponding six-coordinate complexes. In reactions with the unsaturated bonds in dimethylacetylenedicarboxylate, carbon dioxide, phenylisocyanate indications for the addition across the O-H bond but not across the Os-OH bond were obtained. In reactions with olefins such as methyl vinyl ketone or allyl alcohol, elimination of a water molecule was observed to afford a hydrido metalla-cyclic compound or a hydrido (ethyl) complex. No OH insertion product was obtained. 

More typical of coordination compounds are the following insertion reactions ... 

This reaction is a variation of the hydroformylation reaction. Transmetallation of Rh(I)(acac) with the alkylmercury(I) compound gives ClHg(acac) and an alkylrhodium(I) compound. Oxidative addition of H2 gives a Rh(III) compound, and coordination and insertion of CO gives the acylrhodium(IH) compound. Reductive elimination then gives the product and regenerates Rh(I) — but as a Rh-H, not as Rh(acac). 

The insertion reaction is usually more complicated than equation (1) would indicate. The evidence now available suggests that M-X must be coordinately unsaturated in order to react with Y. Therefore, before the insertion reaction can occur, a preliminary step is often required to form M-Z from a coordinately saturated species. Furthermore, the insertion reaction may not go to completion or may not even go at all, unless there is another ligand molecule present to form a stable, coordinately saturated compound from M-Y-Z as the final product. 

Metal-Carbon Compounds. The existence of the insertion reaction and, in fact, the first convincing example of it, was reported by Coffield and co-workers in 1957. They showed that alkylmanganese pentacarbonyls would absorb carbon monoxide, sometimes reversibly, to form acylmanganese pentacarbonyls (16). They further showed in 1959 (17), by means of C14 labeled CO, that with methyl-manganese pentacarbonyl, a coordinated carbon monoxide inserted rather than the incoming carbon monoxide. 

We discussed this catalysis recently (141st National Meeting of the American Chemical Society, March 1962) in terms of an olefin insertion reaction involving a Pt(II) olefin complex (3). We found that catalysis was only accomplished by platinum compounds capable of coordinating olefins. For example, substitution by tertiary phosphines blocks coordination by olefins and greatly reduces the catalytic activity of Pt(II). The substitution by phosphines does not affect the ability of the complexes to cleave the Si—H bond, however. The hindering of a catalytic reaction by blocking coordination sites is a common occurrence and is, I think, a persuasive... 

Alkoxides of nickel(II) are conveniently prepared according to equation (177) in anhydrous conditions.1487 1488 All of these compounds are insoluble in the common organic solvents. Complexes with primary alkoxides are green and six-coordinated complexes with secondary and tertiary alkoxides are tetrahedral with colours ranging from blue to violet. All of the complexes decompose at about 90-100°C. The complexes with secondary and tertiary alkoxides undergo alcoholysis reactions when dissolved in primary alcohols. An interesting insertion reaction occurs when nickel alkoxide reacts with some isocyanates (equation 178).1489... 

Insertion reactions of calcium atoms into M14—M14 bonds yield symmetrical or unsym-metrical M14—Ca compounds according to Scheme 144 and equation 6989. A trimethylsi-lyl trimethylstannyl calcium was also characterized chemically in the cocondensation of calcium with trimethylsilyl trimethylstannane90. Calcium bis(stannide) (equation 69) crystallizes in the form of colorless cuboids in a centrosymmetric space group PI. The calcium atom lies on the crystallographic center of inversion in the middle of the linear Sn—Ca—Sn chain. The calcium atom is coordinated in a distorted octahedral fashion by two tin atoms... 

Step (1) involves the formation of methyl iodide, which then reacts with the rhodium complex Rh(I)L by oxidative addition in a rate-determining step (2) to form a methylrhodium(III) complex. Carbon monoxide is incorporated into the coordination sphere in step (3) and via an insertion reaction a rhodium acyl complex is formed in step (4). The final step involves hydrolysis of the acyl complex to form acetic acid and regeneration of the original rhodium complex Rh(I)L and HI. Typical rhodium compounds which are active precursors for this reaction include RhCl3, Rh203, RhCl(CO)(PPh3)2, and Rh(CO)2Cl2. 

In contrast to CHEC-II(1996) where only rings which have relatively strong cr-bonds between adjacent atoms were reviewed, syntheses of heterocyclic complexes are also be described in this chapter. The chemistry of such chelates or coordination compounds is very interesting as the carbon-metal bond is labile and subject to various reactions such as insertion, protonation, or substitution. However, even though the synthesis of these intramolecular complexes is described in Section 4.19.9, their physical properties are not reported in this chapter. As the cyclic complex is in equilibrium with its open-chain form, the structural properties of such compounds may not be indicative of the heterocycle ring at all. 

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