Insertion CO into

Observations that may support this mechanism have been reported specifically, these include the disappearance of IR bands of adsorbed CO during the Fischer-Tropsch reaction (17) and during alkene hydroformy-lation, consistent with CO insertion between metal atoms and alkyl ligands (18). It is important to realize that to insert CO into metal alkyl groups, the alkyl group has to be attached to surface metal sites with empty d-orbitals (19). 

The dilTiculty of inserting CO into the M-H bond can be due to the much stronger M-H bond than M bond. Of particular interest are bimetallic formyl complexes, which may provide some insist into further reduction (2S). The complex (CO)3 (P(OMe)3] MnCHO could be converted into the corresponding methyl complex [104]. 

The alkyl complex reacts with carbon monoxide to apparently insert CO into the cobalt-alkyl bond (insertion reactions will be discussed later in this chapter) to give an acyl complex (containing a —C( = 0)R ligand) ... 

Methylpentacarbonylrhenium(I), ReMe(CO)5, which reportedly is not affected by carbon monoxide under pressure (320 atm) up to 140°C, decomposes to Re2(CO)io, rather than insert CO into Re(COMe)(CO)s. 

Because acetic anhydride is more useful to the chemical industry than acetic acid, there was economic incentive to develop a process that would yield the anhydride directly without first producing the acid as a separate operation. By the early 1980s, Eastman Chemicals, in conjunction with Halcon Chemical Company, developed a procedure that provided acetic anhydride using technology similar to the Monsanto process, and since 1991 a plant run by Eastman has produced anhydride in excess of 500,000 metric tons per year.89 The Eastman-Halcon (E-H) operation amounts formally to inserting CO into the C-0 bond of methyl acetate according to equation 9.36.90... 

Metal complexes are known to insert CO into carbon-sulfur bonds [118], even catalytically [119], Stoichiometric precedents exist for the formation offhioesters from nickel-alkyls, CO, and thiols [120], For example, NiMe2(bipy) reacts with thiols to afford mefhylnickel(ll) fhiolates, which carbonylate to afford acetyl-nickel(ll) fhiolates. These acetylnickel(II) thiolates reductively eliminate fhioester in the presence of CO [121], More biologically relevant is the reactivity of nickel acyls toward fhiolates, which gives fhe thioester concomitant with reduction to Ni(0) (Eq. 12.10) [122]. Thiolates are known to reduce Ni(II) to Ni(0) under an atmosphere of CO [123]. 

Ni(R)N(SiMe2CH2PPh2)2 inserts CO into the Ni-R bond then rearranges... 

To further illustrate these points dealing with orbital symmetry, consider the insertion of CO into H2 along a path which preserves C2v symmetry. As the insertion occurs, the degenerate n bonding orbitals of CO become hi and 62 orbitals. The antibonding n orbitals of CO also become hi and 62. The <5g bonding orbital of H2 becomes ai, and the antibonding H2 orbital becomes 62. The orbitals of the reactant... 

Several stable Group 6 metal-ketene complexes are known [14], and photo-driven insertion of CO into a tungsten-carbyne-carbon triple bond has been demonstrated [15]. In addition, thermal decomposition of the nonheteroatom-stabilized carbene complexes (CO)5M=CPh2 (M=Cr, W) produces diphenylke-tene [16]. Thus, the intermediacy of transient metal-ketene complexes in the photodriven reactions of Group 6 Fischer carbenes seems at least possible. 

Insertion of SO2 into the Fe—C bond in FelPorfCHi was first reported in 1982, giving the sulfinato complexes Fe(Por)S02CH2, which are moderately air stable but can be further oxidized by O2 to give the sulfonato complexes FelPorfSOiCH. " Alkyliron(Ill) porphyrins insert CO to give the acyl complexes Fe(Por)C(0)R. For example, Fe(TPP)C(0)-n-Bu was formed either by this method or by the reaction of I Fe(TPP) r with ClC(0)-/ -Bu, and was characterized by an X-ray crystal structure... 

Some transition metal systems M(CO)R react with a wide range of L, including phosphites, phosphines, arsines, stibines, organic amines, iodide, and CO, to mention a few, yielding the corresponding acyls. Other systems, e.g., CpFe(CO)2R (2S), display a marked selectivity toward various L. Certain unsaturated molecules L [SOj (239), CF2=Cp2 (238), inter alia] insert themselves into the M—R bond instead of effecting the reaction shown in Eq. (8). 

Carbon monoxide insertion is not restricted to transition metal-carbon bonds, although M—C is by far the most common substrate involved. Reactions have also been reported which lead to insertion of CO into M—O (114) and M—N (199) bonds. 1,1-Additions of M—H (27, 114) and M—M (104) linkages to CO have been postulated, too. However, direct replacement of CO, without rupture of the W—H bond, is indicated for the reaction between CpW(CO)3H (or -D) and PPhj (5) ... 

Attempts at the carbonylation of CpCr(NO)2Me in hexane or THF at reflux resulted only in recovery of the nitrosylalkyl (105). A recent report of the reaction between CpCr(CO)3Me and L [L = PPhj, P(p-CjH40Me)3, and PMejPh] to yield trawi-CpCr(CO)2L(COMe) furnishes the first example of insertion of CO into Cr—C bonds (19b). 

Insertion of CO into Ti—C bonds has very recently been reported for reaction of CpiTifCHjPhlj with CO and for oxidative additions of Mel and EtI to Cp2Ti(CO)2. See refs. (89a) and (90a), respectively. 

Insertion of CO into Mo—C bonds has been postulated in the reaction... 

The carbonyl [CpFe(CO)2]2 has been successfully employed as a catalyst for hydroformylation of propylene (229) and for the reaction in Eq. (55) (221). Insertion of CO into Fe—C bonds is thought to occur therein. 

The main aim of this review is to survey the reactions by which the Co—C bond is made, broken, or modified,.and which may be used for preparative purposes or be involved in catalytic reactions. Sufficient evidence is now available to show that there exists a general pattern of reactions by which the Co—C bond can be made or broken and in which the transition state may correspond to Co(III) and a carbanion (R ), Co(II) and a radical (R-), Co(I) and a carbonium ion (R ), or a cobalt hydride (Co—H) and an olefin. Reactions are also known in which the organo ligand (R) may be reversibly or irreversibly modified (to R ) without cleavage of the Co—C bond, or in which insertion occurs into the Co—C bond (to give Co—X—R). These reactions can be shown schematically as follows ... 

No insertion of CO into a Co—C bond has been reported, although possible equilibria and reactions involving CO at a pressure of 1 atm have been examined with DMG 163, 80), salen 44), and eorrinoid complexes... 

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