Metal complex with carbon monoxide

The lobes of electron density outside the C-O vector thus offer cr-donor lone-pair character. Surprisingly, carbon monoxide does not form particularly stable complexes with BF3 or with main group metals such as potassium or magnesium. Yet transition-metal complexes with carbon monoxide are known by the thousand. In all cases, the CO ligands are bound to the metal through the carbon atom and the complexes are called carbonyls. Furthermore, the metals occur most usually in low formal oxidation states. Dewar, Chatt and Duncanson have described a bonding scheme for the metal - CO interaction that successfully accounts for the formation and properties of these transition-metal carbonyls. 

A very important reaction of alkyl transition-metal complexes with carbon monoxide results in formation of an acyl derivative, as can be seen for H... 

My last comment concerns the reaction of palladium olefin complexes with carbon monoxide discovered by Tsuji. I agree that this is most likely to proceed by an insertion rather than an ionic mechanism. Chloride attack on coordinated olefin is rare however. Chloride ion is an inhibitor, for example in the palladous chloride catalyzed hydration of ethylene (0). I, therefore, wondered whether carbon monoxide was affecting the ease with which chloride attacks olefin. One can postulate that carbon monoxide participates in this insertion either as a gas phase reactant or by first forming a carbonyl olefin complex. Such complexes of the noble metals were unknown, but examining the reaction between carbon monoxide and the halogen bridged olefin complexes of platinum revealed that they are formed very readily... 

Carbonylation of 2,3-homo-l//-azepines has been effected by means of their metal and carbonyl complexes and provides a useful route to a variety of isomeric azabicyclo-nonadienones. For example, the tricarbonyliron complex with carbon monoxide at 80 °C and 160 atm yields the 9-oxo-2-azabicyclo[3.3.l]nona-3,7-diene (167) (57%) or the 9-oxo-2-azabicyclo[3.2.2]nona-3,6-diene (168) (60%) depending on the exo or endo configuration of the tricarbonyliron complex. A third isomer, namely ethyl 7-oxo-9-azabicyclo[4.2.1]nona-2,4-diene-9-carboxylate (169), is formed on heating (125 °C) the azepine with carbon monoxide under pressure in the presence of the rhodium carbonyl complex [Rh(CO)Cl2] (78CB3927). 

W-(2-Aminoethyl)-l,2-diaminoethane (dien) yields complexes [PdX(dien)]X (X = Cl or I) 204,20s a range of solvated complexes may be obtained by reaction of [Pdl(dien)] with AgC104 in the appropriate solvent. As for the platinum analogue, the aqua complex [Pd(dien)(H20)](C104)2 reacts with tetraphenylborate to yield [PdPh(dien)](BPh4). Reaction of the hydroxo complex with carbon monoxide yields C02 and palladium metal is deposited.206... 

The reaction of 16-electron carbonyl complexes of Pd and Pt with alcohols and amines may presumably proceed without metal-alkoxy or metal-amide bond formatiom (cf. Scheme 8.5). The reaction of alkoxymetal complexes with carbon monoxide offers an interesting mechanistic diversity (Scheme 8.13). 

The reaction of nitrite complexes with carbon monoxide to yield the metal nitrosyl complex and carbon dioxide has been known for a consider-... 

Carbonyl halides of the platinum group metals, however, are often prepared by reacting the metal halide with carbon monoxide. [Ru(CO)3Cl,], and [Rh(CO),Cl], are mentioned above (p. 167). Platinum forms Pt(CO),X, and [Pt(CO)X,],. The latter were the first carbonyl complexes of any element to be described. They were reported by the French chemist, P. Schutzenberger, in 1870. 

Compounds with at least one hond between carbon and metal are known as organometaUic compounds [2], Very stricdy speaking, the carbon in organometaUic compounds should he organic. Metal carbonyls are the transition metal complexes of carbon monoxide, containing a metal-carbon bond. These metal-carbon bonded complexes are such important players of organometaUic chemistry that it cannot afford to keep the metal carbonyls out of the team just because of the definition. The metal carbonyls offer a very facile route to the synthesis of many other organometaUic compounds. 

Carbon monoxide also reacts with olefins such as ethylene to produce high molecular weight polymers. The reaction of CO with ethylene can be initiated by an x-ray irradiator (62) or transition-metal cataly2ed reactions (63). The copolymeri2ation of ethylene with carbon monoxide is cataly2ed by cationic Pd (II) complexes such as Pd[P(CgH )2] (CH CN) (BF 2 where n = 1-3. With this catalyst, copolymeri2ation can be carried out at 25°C and pressures as low as 2.1 MPa. 

Palladium(II) complexes possessing bidentate ligands are known to efficiently catalyze the copolymerization of olefins with carbon monoxide to form polyketones.594-596 Sulfur dioxide is an attractive monomer for catalytic copolymerizations with olefins since S02, like CO, is known to undergo facile insertion reactions into a variety of transition metal-alkyl bonds. Indeed, Drent has patented alternating copolymerization of ethylene with S02 using various palladium(II) complexes.597 In 1998, Sen and coworkers also reported that [(dppp)PdMe(NCMe)]BF4 was an effective catalyst for the copolymerization of S02 with ethylene, propylene, and cyclopentene.598 There is a report of the insertion reactions of S02 into PdII-methyl bonds and the attempted spectroscopic detection of the copolymerization of ethylene and S02.599... 

The phase-transfer catalysed reaction of nickel tetracarbonyl with sodium hydroxide under carbon monoxide produces the nickel carbonyl dianions, Ni,(CO) 2- and Ni6(CO)162, which convert allyl chloride into a mixture of but-3-enoic and but-2-enoic acids [18]. However, in view of the high toxicity of the volatile nickel tetracarbonyl, the use of the nickel cyanide as a precursor for the carbonyl complexes is preferred. Pretreatment of the cyanide with carbon monoxide under basic conditions is thought to produce the tricarbonylnickel cyanide anion [19], as the active metal catalyst. Reaction with allyl halides, in a manner analogous to that outlined for the preparation of the arylacetic acids, produces the butenoic acids (Table 8.7). 

Catalytic processes based on the use of electrogenerated nickel(O) bipyridine complexes have been a prominent theme in the laboratories of Nedelec, Perichon, and Troupel some of the more recent work has involved the following (1) cross-coupling of aryl halides with ethyl chloroacetate [143], with activated olefins [144], and with activated alkyl halides [145], (2) coupling of organic halides with carbon monoxide to form ketones [146], (3) coupling of a-chloroketones with aryl halides to give O -arylated ketones [147], and (4) formation of ketones via reduction of a mixture of a benzyl or alkyl halide with a metal carbonyl [148]. 

Clearly the molecular events with iron were complex even at 80 K and low NO pressure, and in order to unravel details we chose to study NO adsorption on copper (42), a metal known to be considerably less reactive in chemisorption than iron. It was anticipated, by analogy with carbon monoxide, that nitric oxide would be molecularly adsorbed on copper at 80 K. This, however, was shown to be incorrect (43), and by contrast it was established that the molecule not only dissociated at 80 K, but NjO was generated catalytically within the adlayer. On warming the adlayer formed at 80 K to 295 K, the surface consisted entirely of chemisorbed oxygen with no evidence for nitrogen adatoms. It was the absence of nitrogen adatoms [with their characteristic N(ls) value] at both 80 and 295 K that misled us (43) initially to suggest that adsorption was entirely molecular at 80 K. 

An intramolecular allenylidene-alkynyl coupling was also observed in the reaction of the mixed alkynyl-allenylidene rhodium(I) complex 73 with carbon monoxide (Scheme 25). In this case, the initially formed thermally unstable allenyl derivative 74 evolved into the metallated cyclobutenone 75 when an excess of CO was present [276]. 

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