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We report the dehydrogenative synthesis of esters from enol ethers using water as the formal oxidant, catalyzed by a newly developed ruthenium acridine-based PNP(Ph)-type complex. Mechanistic experiments and density functional theory (DFT) studies suggest that an inner-sphere stepwise coupled reaction pathway is operational instead of a more intuitive outer-sphere tandem hydration–dehydrogenation pathway. [ABSTRACT FROM AUTHOR]

Synthesis of a pincer-type linear nitrosyl complex [Rh(PtBu2CNEt2)(NO)]+ (3+) is described. The product and all intermediates involved were fully characterized by FTIR, NMR, cyclic voltammetry and X-ray crystallography. Attempts at obtaining (3+) from its chlorinated precursor Rh(PCN)(NO)Cl (2) revealed that a relative stabilization of this complex ion is introduced by the BArF− counteranion, as other counteranions—PF6−, BF4− and triflate—proved to coordinate to the metal center. Redox reactivity both of (3+) and of that of its five-coordinate derivatives (2) and [Rh(PCN)(NO)(CH3CN)]+ (4+) was found to distinguish itself from analogous PCP complexes due to a relative stabilization of higher oxidation states. Oxidation of these three complexes was studied by FTIR spectroelectrochemistry. Reduction of complex (3+) to yield a short-lived {RhNO}9 species [Rh(PCN)(NO)]˙ (3˙) was also carried out. Complex (3˙) was proved able to activate carbon–halogen bonds in aryl halides, in much a similar way as that of its PCP analogue. Complex (3+) was also seen to establish a linear ↔ bent nitrosyl equilibrium upon addition of CO which could not be fully displaced with excess CO. [ABSTRACT FROM AUTHOR]

We report here the activation of CO2 using two Mn-PNN pincer complexes that can exhibit different modes of metal–ligand cooperation amido/amino mode that involves [1,2]-activation of CO2 and dearomatization/aromatization mode that involves [1,3]-activation of CO2. We also compare their catalytic activity for CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

The first example of oxidative addition of a C–H bond to a square planar d8-Iridium complex, without any external additive, such as an acid, is described. Our mechanistic investigations show that metal–ligand cooperation through aromatization–dearomatization of the lutidine backbone is involved in this process, and that the actual C–H activation step occurs through an Ir(iii) intermediate. [ABSTRACT FROM AUTHOR]

The first example of hydrogenation of amides homogeneously catalyzed by an earth-abundant metal complex is reported. The reaction is catalyzed by iron PNP pincer complexes. A wide range of secondary and tertiary N-substituted 2,2,2-trifluoroacetamides were hydrogenated to form amines and trifluoroethanol. [ABSTRACT FROM AUTHOR]

A novel, one-step synthesis of substituted pyridine- and quinoline-derivatives was achieved by acceptorless dehydrogenative coupling of γ-aminoalcohols with secondary alcohols. The reaction involves consecutive C–N and C–C bond formation, catalyzed by a bipyridyl-based ruthenium pincer complex with a base. [ABSTRACT FROM AUTHOR]

Synthesis of a pincer-type linear nitrosyl complex [Rh(P tBu 2 CN Et 2 )(NO)] + (3 + ) is described. The product and all intermediates involved were fully characterized by FTIR, NMR, cyclic voltammetry and X-ray crystallography. Attempts at obtaining (3 + ) from its chlorinated precursor Rh(PCN)(NO)Cl (2) revealed that a relative stabilization of this complex ion is introduced by the BArF - counteranion, as other counteranions-PF 6 - , BF 4 - and triflate-proved to coordinate to the metal center. Redox reactivity both of (3 + ) and of that of its five-coordinate derivatives (2) and [Rh(PCN)(NO)(CH 3 CN)] + (4 + ) was found to distinguish itself from analogous PCP complexes due to a relative stabilization of higher oxidation states. Oxidation of these three complexes was studied by FTIR spectroelectrochemistry. Reduction of complex (3 + ) to yield a short-lived {RhNO} 9 species [Rh(PCN)(NO)]˙ (3˙) was also carried out. Complex (3˙) was proved able to activate carbon-halogen bonds in aryl halides, in much a similar way as that of its PCP analogue. Complex (3 + ) was also seen to establish a linear ↔ bent nitrosyl equilibrium upon addition of CO which could not be fully displaced with excess CO.

We report here the activation of CO2 using two Mn-PNN pincer complexes that can exhibit different modes of metal-ligand cooperation amido/amino mode that involves [1,2]-activation of CO2 and dearomatization/aromatization mode that involves [1,3]-activation of CO2. We also compare their catalytic activity for CO2 hydrogenation.

A novel, one-step synthesis of substituted pyridine- and quinoline-derivatives was achieved by acceptorless dehydrogenative coupling of γ-aminoalcohols with secondary alcohols. The reaction involves consecutive C-N and C-C bond formation, catalyzed by a bipyridyl-based ruthenium pincer complex with a base.

Imines are selectively formed by coupling of nitriles and amines under mild hydrogen pressure. The reaction is catalyzed by a bipyridine-based PNN Ru(II) pincer complex and proceeds under mild, neutral conditions at 4 bar of H(2).

The cationic, pincer-type complexes [(SNS)Ir(COE)][BF4] (1) and [(SNS)Rh(COE)][BF4] (2) (SNS = 2,6-bis(t-butylthiomethy1)pyridine; COE = cyclooctene) complexes were prepared, and their structure and reactivity were studied. They are fluxional at room temperature as a result of "arm" hemilability, which can be frozen at low temperatures. Reaction of complex 1 with H2 resulted in a dimeric dihydride complex [(SNS)Ir(H2)]2[BF4]2 (3) in which the sulfur atoms bridge between two metal centers. The Rh complex 2 did not react with H2. Both the carbonyl complexes [(SNS)Ir(CO)][BF4] (5) and [(SNS)Rh(CO)][BF4] (6) show differences in the IR stretching frequencies in solution vs. solid states, which are a result of uncommon metal-metal interactions between square planar d8 systems in the solid state. Complexes 1, 3, 5 and 6 were structurally characterized by X-ray crystallography. A network of hydrogen bonds involving the BF4(-) counter anion and hydrogen atoms of complex 5 was observed.