The established standard ketone hydrogenation (abbreviated HY herein) precatalyst [Ru(Cl)(2)((S)-tolbinap)[(S,S)-dpen]] ((S),(S,S)-1) has turned out also to be a precatalyst for ketone transfer hydrogenation (abbreviated TRHY herein) as tested on the substrate acetophenone (3) in iPrOH under standard conditions (45 degrees C, 45 bar H(2) or Ar at atmospheric pressure). HY works at a substrate catalyst ratio (s:c) of up to 10(6) and TRHY at s:c<10(4). Both produce (R)-1-phenylethan-1-ol ((R)-4), but the ee in HY are much higher (78-83 %) than in TRHY (4-62 %). In both modes, iPrOK is needed to generate the active catalysts, and the more there is (1-4500 equiv), the faster the catalytic reactions. The ee is about constant in HY and diminishes in TRHY as more iPrOK is added. The ketone TRHY precatalyst [Ru(Cl)(2)((S,S)-cyP(2)(NH)(2))] ((S,S)-2), established at s:c=200, has also turned out to be a ketone HY precatalyst at up to s:c=10(6), again as tested on 3 in iPrOH under standard conditions. The enantioselectivity is opposite in the two modes and only high in TRHY: with (S,S)-2, one obtains (R)-4 in up to 98 % ee in TRHY as reported and (S)-4 in 20-25 % ee in HY. iPrOK is again required to generate the active catalysts in both modes, and again, the more there is, the faster the catalytic reactions. The ee in TRHY are only high when 0.5-1 equivalents iPrOK are used and diminish when more is added, while the (low) ee is again about constant in HY as more iPrOK is added (0-4500 equiv). The new [Ru(H)(Cl)((S,S)-cyP(2)(NH)(2))] isomers (S,S)-9 A and (S,S)-9 B (mixture, exact structures unknown) are also precatalysts for the TRHY and HY of 3 under the same conditions, and (R)-4 is again produced in TRHY and (S)-4 in HY, but the lower ee shows that in TRHY (S,S)-9 A/(S,S)-9 B do not lead to the same catalysts as (S,S)-2. In contrast, the ee are in accord with (S,S)-9 A/(S,S)-9 B leading to the same catalysts as (S,S)-2 in HY. The kinetic rate law for the HY of 3 in iPrOH and in benzene using (S,S)-9 A/(S,S)-9 B/iPrOK or (S,S)-9 A/(S,S)-9 B/tBuOK is consistent with a fast, reversible addition of 3 to a five-coordinate amidohydride (S,S)-11 to give an (S,S)-11-substrate complex, in competition with the rate-determining addition of H(2) to (S,S)-11 to give a dihydride [Ru(H)(2)((S,S)-cyP(2)(NH)(2))] (S,S)-10, which in turn reacts rapidly with 3 to generate (S)-4 and (S,S)-11. The established achiral ketone TRHY precatalyst [Ru(Cl)(2)(ethP(2)(NH)(2))] (12) has turned out to be also a powerful precatalyst for the HY of 3 in iPrOH at s:c=10(6) and of some other substrates. Response to the presence of iPrOK is as before, except that 12 already functions well without it at up to s:c=10(6).

The new diphosphinediimine ligand PPh2C6H4CHNCMe2CMe2NCHC6H4PPh2 {tmeP2N2} is prepared by reacting NH2CMe2CMe2NH2 with 2 equiv of PPh2(C6H4-2-CHO). The diamine derivative PPh2C6H4CH2NHCMe2CMe2NHCH2C6H4PPh2 {tmeP2(NH)2} is prepared by reducing tmeP2N2 with LiAlH4. The reaction of RuHCl(PPh3)3 with tmeP2N2 in THF produces the complex trans-RuHCl{tmeP2N2}, while a similar reaction of RuHCl(PPh3)3 with tmeP2(NH)2 gives the complex trans-RuHCl{tmeP2(NH)2}, as a mixture of two isomers. The isomer with two N−H bonds syn to the Ru−H bond is converted on heating to an isomer thought to have one N−H syn to the Ru−H. The reaction of the two isomers with KO t Bu under Ar in toluene produces the novel hydridoamido complex RuH{tmeP2NNH}, where the ligand is deprotonated at one nitrogen. Reaction of this amido complex with H2 gives exclusively the dihydridoamine complex trans-Ru(H)2{tmeP2(NH)2}. The complexes have been characterized by X-ray crystallography, NMR, IR, elemental analysis, and a deuterium exchange study. Complex RuH{tmeP2NNH}, or a combination of RuHCl{tmeP2(NH)2} and KO t Bu, slowly catalyzes the hydrogenation of acetophenone (6 atm H2, 20 °C, benzene or 2-propanol). The catalytic cycle is thought to be similar to that for the ketone hydrogenation precatalyst trans-RuHCl{(S,S)-cyP2(NH)2)}. However in the present work both of the proposed catalysts trans-RuH2{tmeP2(NH)2} and RuH{tmeP2NNH} have been completely characterized. The tmeP2(NH)2 system, with hindering methyl groups, is less active than the cyP2(NH)2 system with a trans-1,2-substituted cyclohexyl backbone. The variable configuration of the amine nitrogens that is observed for the tmeP2(NH)2 complexes might also occur in the cyP2(NH)2 systems and could explain the inconsistent selectivity of such catalysts. The diimine complex RuHCl{tmeP2N2} reacts with KO t Bu under H2 to produce the dihydridodiamine complex trans-Ru(H)2{tmeP2(NH)2}, the catalyst for the hydrogenation of acetophenone.