Carbamoyl complexes amines

Nesmeyanov has provided interesting examples of apparent intramolecular nucleophilic attack by amine on carbonyl ligands (37). Angelici (38,39) has demonstrated that amine attack on cationic metal carbonyl complexes is a general reaction resulting in the formation of carbamoyl complexes ... 

Reaction 21 for a tricarbonyl species could correspondingly be written instead of Reaction 17. The formation of carbamoyl complexes (M—CONRo) by the reaction of amines with metal carbonyls, especially cationic ones, has been reviewed by Angelici (24). Further studies are in progress. 

It was originally proposed that under the reaction conditions CO reduces the nitrobenzene 38a to nitrosobenzene 32. However, no free nitrosobenzene could be detected by trapping experiments. Instead, the carbamoyl complex 39 was isolated and crystallized (Figure 3.10) [135]. Although complex 39 showed decreased catalytic activity in the allylic amination as compared with [Cp Fe(CO)2]2... 

As early as 1965, Angelici (108) was concerned with the reaction of Mn(CO)5Cl with primary and secondary aliphatic amines. He initially considered the product with MeNH2, namely, Mn(CO)5(NH2Me)(NHMe), to be a complex of heptacoordinated manganese. A subsequent X-ray structure analysis showed, however, that it is in fact a hexacoordinated carbamoyl complex, Mn(CO)4(NH2Me)CONHMe (109). In continuation of these studies, the reaction of cationic CO complexes of various tran-... 

Carbamoyl Complexes by Reaction of Metal Carbonyls with Amines. 

Rarely a carbamoyl complex can be isolated from an amine and a neutral (uncharged) metal carbonyl e.g., the reaction between Mn2(CO)jo and MeNH is ... 

The reaction of an amine with a carboalkoxy-metal complex can be used to prepare a carbamoyl complex ... 

Carbamoyl complexes are not obtained using aryl amines ". Cationic complexes with hydrazine give carbazoyl complexes (having a CONHNHj ligand), but these species decompose to form metal isocyanate complexes ... 

It is well known that the oxidative carbonylation of aniline and the reductive carbonylation of nitrocompounds to give DPU or MPC occur according to the stoichiometry of reactions (1-2) and (4-5). Alkoxycarbonyl complexes (M-COOR 1) and carbamoyl complexes (M-CONHR 2) which then evolve into the final products, are believed to be key intermediates for these reactions. The two accepted different mechanisms for the formation of 1 and 2 along with their catalytic cycles are illustrated in the schemes 1 and 2 for the oxidative carbonylation of amines catalyzed by noble metals. Both the cycles involve a two electron redox process. 

Carbamoyl complexes from metal carbonyls and amines 5.8.2.12.4 Carbanions reactions with alkene complexes 5.8.2.3,4 metal carbonyls 5.8.2.S.5 Carbene complexes by alkene metathesis 5.8.2.3.11 formation 5.8.2.8.5 Carbides alkali metal formation 5.10.2.1 bonding 5.10.2 formation 5.10.2 industrial uses 5.10.2 interstitial formation 5.10.2 Carbometallacycle formation 5.S.2.2.2 Carbometallacycles from n-allyl complexes 5.S.2.3.9 Carbon reaction with alkali metals 5.10.2.1 Carbon dioxide complexes formation 5.8.2.14.1 Carbon monoxide displacement by alkenes 5.8.2.3.1 Carbonyl complexes by ligand exchange 5.8.2.12.2 from carbon monoxide 5.8.2.12.1, 5.8.2.12.2... 

As mentioned above, a variety of nucleophiles can form a bond with the carbon of the carbonyl ligand. One feature common to most of the reactions of various nucleophiles is that the bond formation between carbonyl carbon and nucleophile is more or less a reversible process. Alkoxycarbonyl or carbamoyl complexes formed from carbonyl complexes and alcohol or amine readily undergo the reversed course, namely C(0)-0R or C(0)-NR2 bond cleavage, either spontaneously or upon treatment with an acid (see e.g. Scheme 8.5). It is also noted that metallocarboxylic acids, M-COOH (typically M = PtR(PR3)2 R = Cl, Ph) tend to dissociate OH ion, rather than H+ in solution [12,13]. 

Two isomers are formed upon reaction of aromatic amines with Ru(dppe)(C0)2[C(0)0CH3]2. The structures, 5 and 5, correspond to the substitution of the two different methoxy groups. Although aryl amines do not substitute for both methoxy groups, more nucleophilic, alkyl amines such as isopropylamine rapidly form the bis(carbamoyl) complex, 6. The latter complex has been structurally characterized and clear evidence of the hydrogen-bonding was found.(17) This section will summarize the results of the kinetic studies of the formation and subsequent reaction of 5 and 5 and studies of the thermolysis of 6. 

The last possible mechanism for removal of the organic product shown in Scheme 2 is referred to as a cycloreversion. Regardless of whether this is proposed to occur from 5 or 5 or even a bis(carbamoyl) complex, 9, direct experimental evidence rules out this mechanism. Cycloreversion from 5 or 5 would lead directly to carbamate, the wrong product, and cycloreversion from 9 would require second order kinetics with respect to the concentration of aryl amine. 

Alkoxides and amines also attack coordinated carbon monoxide to give alkoxycarbonyl and aminocarbonyl complexes, respectively (Equations 11.5 and 11.6). Stable complexes of both types have been isolated and thoroughly characterized. Less stable alkoxycarbonyl and carbamoyl complexes are intermediates in a number of synthetically important carbo-nylation processes discussed in Chapters 17 and 19. 

The reactions between ReBr(CO)5 or Re(CH2SiMe3)(CO)5 and amines RNH2 (R = Et, allyl, Pr ) affords the carbamoyl complexes Re(CONHR)(NH2R)(CO)4. These react with EtCOCl to form the cationic amine complexes [Re(CO)5(NH2R)]. The chelated iminoacyl Mn C(=NTol)C(CH2C6H4Cl)Nrol (CO)4 reacts with phosphines and phosphites to give substitution products rather than an pendant iminoacyl complex. ... 

PdCUI (L2 = 2 PPha or several N-N or P-N chelating ligands) reacts with alcohols or amines in the presence of CO and a base to yield bis-alcoxycarbonyl or carbamoyl complexes respectively (eqs. 15, 16) ... 

Carbonyl complex 9, which can be generated by the direct replacement of triflate by carbon monoxide, is, in the presence of diethylamine, in equilibrium with carbamoyl complex 10 (Equation (3)). In the presence of excess amine, in solution, 10 can be formed free from 9 however, solvent removal always results in partial reversion to 9. 

Sacco and coworkers found that the basicity of the nucleophile was strong enough to displace the equilibrium of the reaction completely to products when the pK of the amine was higher than 4. Thus, when using the much less basic p-nitroanUine (H2NC6H4-4-NO2), pJ = 1, the carbamoyl complex was formed in good yield only in... 

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