Carbonyls, metal amine complexes

Macrocyclic coordination compounds formed bv condensation of metal amine complexes with aliphatic carbonyl compounds. N. F. Curtis, Coord. Chem. Rev., 1968, 3, 3-47 (78). 

Most of the template syntheses of nonbenzenoid macrocycles originated with Curtis (39) and involve the condensation of metal-amine complexes with aliphatic carbonyl compounds, e.g., the reaction of acetone with tris(diaminoethane)nickel(II) perchlorate at ambient temperature leads to the isolation of three products, two of which may be represented as cts-XLIX and trans-L and the other is formed by a further interconversion of complex L in solution (39,143). With Cu(II) diaminoperchlorates, a mixture of cis and trans complexes analogous to XLIX and L is formed, but with Co(II) only the trans analog of L has been isolated. When ketones containing bulky groups are used, the reaction is much slower, e.g., there is only a small yield of LI from... 

The direct reductive amination (DRA) is a useful method for the synthesis of amino derivatives from carbonyl compounds, amines, and H2. Precious-metal (Ru [130-132], Rh [133-137], Ir [138-142], Pd [143]) catalyzed reactions are well known to date. The first Fe-catalyzed DRA reaction was reported by Bhanage and coworkers in 2008 (Scheme 42) [144]. Although the reaction conditions are not mild (high temperature, moderate H2 pressure), the hydrogenation of imines and/or enam-ines, which are generated by reaction of organic carbonyl compounds with amines, produces various substituted aryl and/or alkyl amines. A dihydrogen or dihydride iron complex was proposed as a reactive intermediate within the catalytic cycle. 

Ethers, sulfides, amines, carbonyl compounds, and imines are among the frequently encountered Lewis bases in the ylide formation from such metal carbene complex. The metal carbene in the ylide formation can be divided into stable Fisher carbene complex and unstable reactive metal carbene intermediates. The reaction of the former is thus stoichiometric and the latter is usually a transition metal complex-catalyzed reaction of a-diazocarbonyl compounds. The decomposition of a-diazocarbonyl compounds with catalytic transition metal complex has been the most widely used approach to generate reactive metal carbenes. For compressive reviews, see Refs 1,1a. 

Reaction of Co111 amine complexes with glycine esters gives products which are dependent on the solvent used (Scheme 7). In non-aqueous solvents peptide bond formation is observed.78"80 It is concluded that the reaction proceeds via the initial formation of a bidentate glycine ester complex in which the coordinated carbonyl group is activated (by the metal ion) towards nucleophilic attack by a further molecule of the glycine ester. Similar reactions have been observed with other Co111 complexes. 

A great variety of aza macrocycle complexes have been formed by condensation reactions in the presence of a metal ion, often termed template reactions . The majority of such reactions have inline formation as the ring-closing step. Fourteen- and, to a lesser extent, sixteen-membered tetraaza macrocycles predominate, and nickel(II) and copper(II) are the most widely active metal ions. Only a selection of the more general types of reaction can be described here, and some closely related, but non metal-ion-promoted, reactions will be included for convenience. The reactions are classified according to the nature of the carbonyl and amine reactants. 

As mentioned above, reactions of this type have been widely used in the synthesis of macrocyclic ligands. Indeed, some of the earliest examples of templated ligand synthesis involve thiolate alkylations. Many of the most important uses of metal thiolate complexes in these syntheses utilise the reduced nucleophilicity of a co-ordinated thiolate ligand. The lower reactivity results in increased selectivity and more controllable reactions. This is exemplified in the formation of an A -donor ligand by the condensation of biacetyl with the nickel(n) complex of 2-aminoethanethiol (Fig. 5-78). The electrophilic carbonyl reacts specifically with the co-ordinated amine, to give a complex of a new diimine ligand. The beauty of this reaction is that the free ligand cannot be prepared in a metal-free reac-... 

Carbamoyl Complexes by Reaction of Metal Carbonyls with Amines. 

The metal-NH3 and metal-amine reductions of acetophenone and acetyl derivatives of polycyclic aromatics are complex and afford primarily mixtures of Birch reduction products. In some cases a ketonic carbonyl survives the reduction, and in some cases it is reduced to the corresponding alcohol. ... 

In the presence of the radical substitution promoter [Fe2(CO)4()u,-SR)i(PPh3)2], tertiary amines react with transition metal carbonyl clusters under exceptionally mild conditions. Modified allenyl and allylic clusters similar to those described earlier have been isolated from such reactions. Two distinct types of products have been isolated (i) those involving the elimination of an alkyl group and (ii) those involving C-C coupling reactions. The product formation described in Scheme 31 was preceded by amine coordination, C-H activation, C-N cleavage, carbene-amine complex formation, transamination, and C-C coupling (6Ia.h)- Such processes are of interest in the area of hydrodenitrification (6/c). 

In 1970 the transition metal catalyzed formation of alkyl formates from CO2, H2, and alcohols was first described. Phosphine complexes of Group 8 to Group 10 transition metals and carbonyl metallates of Groups 6 and 8 show catalytic activity (TON 6-60) and in most cases a positive effect by addition of amines or other basic additives [26 a, 54-58]. A more effective catalytic system has been found when carrying out the reaction in the supercritical phase (TON 3500) [54 a]. Similarly to the synthesis of formic acid, the synthesis of methyl formate in SCCO2 is successful in the presence of methanol and ruthenium(II) catalyst systems [54 b]. 

Si 3H CP/MAS-NMR was used to probe interactions of transition metal carbonyl clusters (Ru3H(CO)M, Os2FI(CO)ii, Co(CO)4 ) deposited in the mesoporous aluminosilicate material MCM-41.637 A 29Si MAS-NMR study has been made of rhodium-amine complexes on Si02 surfaces.638 31P CP/MAS-NMR spectroscopy was able to characterise Cu6(TePh)6(PPh2Et)5 clusters in the pores of MCM-41.639... 

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. 

Thus the activation volume AV for the rate constant kp of an individual ES reaction pathway can be evaluated if the pressure dependencies of the photoreaction quantum yield, of intersystem crossing and of the ES lifetime can be separately determined. However, such parameterization becomes considerably more complex if several different excited states are involved or if a fraction of the photosubstitution products are formed from states that are not vibrationally relaxed with respect to the medium. Currently, parameterization of pressure effects on photosubstitutions has been attempted for a limited number of metal complexes. These include certain rhodium(III) and chromium(III) amine complexes and some Group VI metal carbonyls, which will be summarized here. 

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... 

---