Ruthenium aromatic amine complexes

A number of bis(arylamido)- and bis(diarylamido)ruthenium(IV) porphyrin complexes have been reported. In general, these complexes can be prepared by the reduction of [Ru(0)2(por)] with corresponding aromatic amines or by the oxidative deprotonation of [Ru (por)(ArNH2)2], as shown in Scheme 18. 

A recent development31 is the preparation of metal polymer complexes directly on the electrode via the electrochemically induced polymerization of the metal complex. Ruthenium(II) and osmium(II) complexes with ligands containing aromatic amines, e.g. 3- or 4-aminopyridine or 5-amino-1,10-phenanthroline, are electrochemically polymerized to yield a film of the metal polymer on the electrode surface. The polymerization involves free radicals, which are formed via the initial oxidation of the metal complex to a radical cation and subsequent reaction of the radical cation with a base to yield the free radical. 

Three types of product can be obtained from the reaction of amines with carbon monoxide, depending on the catalyst. (1) Both primary and secondary amines react with CO in the presence of various catalysts [e.g., Cu(CN)2, Me3N-H2Se, rhodium or ruthenium complexes] to give V-substituted and V,A-disubstituted formamides, respectively. Primary aromatic amines react with ammonium formate to give the formamide. Tertiary amines react with CO and a palladium catalyst to give an amide. (2) Symmetrically substituted ureas can be prepared by treatment of a primary amine (or ammonia) with CO " in the presence of selenium or... 

Divalent ruthenium complexes are efficient catalysts for A -alkylation of amines by a primary alcohol. RuCl2(PPh3)3 or RuCl3-3H20/P(0Bu)3 effectively catalyze the A -alkylation of aromatic amines (eq (38)) [133-134]. On the other hand, yV-alkylation of aliphatic amines with a primary alcohol is carried out in high yield by the use of RuH2(PPh3>4as catalyst [135]. 

Some highly efficient catalytic systems enabling A-alkylation reactions to work under mild conditions even at room temperature have also been developed. In 2014, Enyong and co-workers [85] described ruthenium complex-catalyzed A-alkylation of primary and secondary amines with simple alcohols under mild conditions (Eq. 12). The authors found that when the substrate alcohol was used as the solvent, the reactions could be achieved at 40-60 °C and even at room temperature whereas when using stoichiometric amounts of alcohol, higher temperatures, mostly 110 °C, were required. In 2015, Taddei and co-workers [86] reported a rather mild [Ru(cod)Cl2]n/PTA/t-BuOK-catalyzed iV-alkylation of aromatic amines with primary alcohols at 55 °C (Eq. 13). This may be the mildest A-alkylation reaction catalyzed by ruthenium complexes described so far. 

The oxidation of both aliphatic and aromatic amines to nitriles by O2 or air in the presence of the Ru2Cl4(az-tpy)2 complex indicates that the conversion is strongly influenced by the alkyl chain length. The amines with shorter chain had lower conversions than those with longer chains. Further, the ruthenium terpyridine complex functionalized with azulenyl moiety at the 4-position of the central pyridine core provided a much higher catalytic reactivity compared with a series of ruthenium terpyridine complexes. The use of deuterated benzylamine demonstrated the importance of RuOH in the mechanism of the reaction." ... 

Nomura, K. Ishino, M. Hazama, M. (1993) Selective reduction of aromatic nitrocompounds affording aromatic-amines under CO/H2O conditions catalyzed by phosphine-added rhodium and ruthenium carbonyl-complexes, J. Mol Catal,1, 273-82. 

Direct hydrogenation of CO2 to methanol was recently reported by Klankermayer and Leimer using a non-pincer catalytic system, comprised of a ruthenium(Il)-complex [(triphos)Ru-(TMM)] 26 (TMM = trimethylenemethane), and an acid, achieving turnover numbers up to 221 [95]. Catalytic N-methylation of secondary and primary aromatic amines using CO2 as Cl source and molecular... 

Allyl methylcarbonate reacts with norbornene following a ruthenium-catalyzed carbonylative cyclization under carbon monoxide pressure to give cyclopentenone derivatives 12 (Scheme 4).32 Catalyst loading, amine and CO pressure have been optimized to give the cyclopentenone compound in 80% yield and a total control of the stereoselectivity (exo 100%). Aromatic or bidentate amines inhibit the reaction certainly by a too strong interaction with ruthenium. A plausible mechanism is proposed. Stereoselective CM-carboruthenation of norbornene with allyl-ruthenium complex 13 followed by carbon monoxide insertion generates an acylruthenium intermediate 15. Intramolecular carboruthenation and /3-hydride elimination of 16 afford the -olefin 17. Isomerization of the double bond under experimental conditions allows formation of the cyclopentenone derivative 12. 

Like ruthenium, amines coordinated to osmium in higher oxidation states such as Os(IV) are readily deprotonated, as in [Os(en) (NHCH2CH2NH2)]2+ [111614-75-6]. This complex is subject to oxidative dehydrogenation to form an imine complex (105). An unusual Os(IV) hydride, [OsH2(en)J2+ [57345-94-5] has been isolated and characterized. The complexes of aromatic heterocyclic amines such as pyridine, bipyridine, phenanthroline, and terpyridine are similar to those of ruthenium. Examples include [Os(bipy )3 ]2+ [23648-06-8], [Os(bipy)2acac] [47691-08-7],... 

Os forms many complexes with nitnte. oxalate, carbon monoxide, amines, and thio ureas. The latter arc important analytically Osmium forms the interesting aromatic sandwich" compound, osmocene. A metallocene is described under Ruthenium. See also Chemical Elements and Platinum and Platinum Group. 

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