@article {42724,
	title = {Efficient hydrogenation of organic carbonates, carbamates, and formates indicates alternative routes to methanol based on CO2 and CO},
	journal = {Nature Chemistry},
	volume = {3},
	year = {2011},
	month = {JUL},
	pages = {609{\textendash}614},
	abstract = {<p>Catalytic hydrogenation of organic carbonates, carbamates and formates is of significant interest both conceptually and practically, because these compounds can be produced from CO2 and CO, and their mild hydrogenation can provide alternative, mild approaches to the indirect hydrogenation of CO2 and CO to methanol, an important fuel and synthetic building block. Here, we report for the first time catalytic hydrogenation of organic carbonates to alcohols, and carbamates to alcohols and amines. Unprecedented homogeneously catalysed hydrogenation of organic formates to methanol has also been accomplished. The reactions are efficiently catalysed by dearomatized PNN Ru(II) pincer complexes derived from pyridine- and bipyridine-based tridentate ligands. These atom-economical reactions proceed under neutral, homogeneous conditions, at mild temperatures and under mild hydrogen pressures, and can operate in the absence of solvent with no generation of waste, representing the ultimate {\textquoteleft}green{\textquoteright} reactions. A possible mechanism involves metal{\textendash}ligand cooperation by aromatization{\textendash}dearomatization of the heteroaromatic pincer core.</p>},
	doi = {10.1038/nchem.1089},
	author = {Balaraman, Ekambaram and Gunanathan, Chidambaram and Zhang, Jing and Shimon, Linda J. W. and Milstein, David}
}
@article {42718,
	title = {Electron-rich PNP- and PNN-type Ru(II) hydrido-borohydride complexes. synthesis, structure and catalytic activity towards dehydrogenation of alcohols and hydrogenation of esters},
	journal = {Organometallics},
	volume = {30},
	year = {2011},
	month = {OCT},
	pages = {5716{\textendash}5724},
	abstract = {<p>Electron-rich PNP- and PNN-type ruthenium(II) hydrido borohydride pincer complexes, [RuH(BH4)(tBu-PNP)] (tBu-PNP = (2,6-bis(di-tert-butylphosphinomethyl)pyridine) (5) and [RuH(BH4)(tBu-PNN)] (tBu-PNN = 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) (6), were prepared from their corresponding N2-bridged dinuclear Ru(II) complexes [(tBu-PNP)RuCl2]2(μ-N2) (3) and [(tBu-PNN)RuCl2]2(μ-N2) (4), respectively. The X-ray structure of 5 reveals a BH4{\textendash} anion η2 coordinated to ruthenium through two bridging hydrides. A variable-temperature 1H NMR study of 6 exhibits interesting fluxional behavior of the BH4{\textendash} ligand. Similarly, the Ru(II) hydrido borohydride complex 9, in which the BH4{\textendash} moiety is coordinated in a η1 bonding mode, was obtained by reaction of [RuCl2(PPh3)(iPr-PNP)] (iPr-PNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) (8) with two equivalents of NaBH4 at room temperature. The hydrido borohydride pincer complexes 5, 6, and 9 catalyze the acceptorless dehydrogenative coupling of primary alcohols to esters and the dehydrogenation of secondary alcohols to the corresponding ketones, accompanied by evolution of hydrogen gas. The reactivity follows the order 6 \&gt; 9 \&gt; 5. With the hydrido borohydride complex 6 as catalyst, high yields (up to 98\%) and high turnover numbers (TON \~{}1000) were obtained in the dehydrogenation of primary alcohols under mild and neutral conditions. In addition, 6 effectively catalyzes the hydrogenation of nonactivated aromatic and aliphatic esters to the corresponding alcohols with TON \~{}200 under a relatively mild pressure of dihydrogen and neutral and homogeneous conditions. Thus, an efficient homogeneous catalytic system for the dehydrogenation{\textendash}hydrogenation reactions of alcohols is developed, which is relevant to the current interest in hydrogen storage.</p>},
	doi = {10.1021/om200595m},
	author = {Zhang, Jing and Balaraman, Ekambaram and Leitus, Gregory and Milstein, David}
}
