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The complexes trans-RuH(Cl)(tmen)(R-binap) (1) and (OC-6-43)-RuH(Cl)(tmen)(PPh(3))(2) (2) are prepared by the reaction of the diamine NH(2)CMe(2)CMe(2)NH(2) (tmen) with RuH(Cl)(PPh(3))(R-binap) and RuH(Cl)(PPh(3))(3), respectively. Reaction of KHB(sec)Bu(3) with 1 yields trans-Ru(H)(2)(R-binap)(tmen) (5) while reaction of KHB(sec)Bu(3) or KO(t)Bu with 2 under Ar yields the new hydridoamido complex RuH(PPh(3))(2)(NH(2)CMe(2)CMe(2)NH) (4). Complex 4 has a distorted trigonal bipyramidal geometry with the amido nitrogen in the equatorial plane. Loss of H(2) from 5 results in the related complex RuH(R-binap)(NH(2)CMe(2)CMe(2)NH) (3). Reaction of H(2) with 4 yields the trans-dihydride (OC-6-22)-Ru(H)(2)(PPh(3))(2)(tmen)(6). Calculations support the assignment of the structures. The hydrogenation of acetophenone is catalyzed by 5 or 4 in benzene or 2-propanol without the need for added base. For 5 in benzene at 293 K over the ranges of concentrations [5] = 10(-)(4) to 10(-)(3) M, [ketone] = 0.1 to 0.5 M, and of pressures of H(2) = 8 to 23 atm, the rate law is rate = k[5][H(2)] with k = 3.3 M(-1) s(1), DeltaH++ = 8.5 +/- 0.5 kcal mol(-1), DeltaS++ = -28 +/- 2 cal mol(-1) K(-1). For 4 in benzene at 293 K over the ranges of concentrations [4] = 10(-4) to 10(-3) M, [ketone] 0.1 to 0.7 M, and of pressures of H(2) = 1 to 6 atm, the preliminary rate law is rate = k[4][H(2)] with k = 1.1 x 10(2) M(-1) s(-1), DeltaH++ = 7.6 +/- 0.3 kcal mol(-1), DeltaS++ = -23 +/- 1 cal mol(-1) K(-1). Both theory and experiment suggest that the intramolecular heterolytic splitting of dihydrogen across the polar Ru=N bond of the amido complexes 3 and 4 is the turn-over limiting step. A transition state structure and reaction energy profile is calculated. The transfer of H(delta+)/H(delta-) to the ketone from the RuH and NH groups of 5 in a Noyori metal-ligand bifunctional mechanism is a fast process and it sets the chirality as (R)-1-phenylethanol (62-68% ee) in the hydrogenation of acetophenone. The rate of hydrogenation of acetophenone catalyzed by 5 is slower and the ee of the product is low (14% S) when 2-propanol is used as the solvent, but both the rate and ee (up to 55% R) increase when excess KO(t)Bu is added. The formation of ruthenium alkoxide complexes in 2-propanol might explain these observations. Alkoxide complexes [RuP(2)]H(OR)(tmen), [RuP(2)] = Ru(R-binap) or Ru(PPh(3))(2), R= (i) Pr, CHPhMe, (t)Bu, are observed by reacting the alcohols (i)PrOH, phenylethanol, and (t)BuOH with the dihydrides 5 and 6, respectively, under Ar. In the absence of H(2), the amido complexes 3 and 4 react with acetophenone to give the ketone adducts [RuP(2)]H(O=CPhMe)(NH(2)CMe(2)CMe(2)NH) in equilibrium with the enolate complexes trans- [RuP(2)](H)(OCPh=CH(2))(tmen) and eventually the decomposition products [RuP(2)]H(eta(5)-CH(2)CPhCHCPhO), with the binap complex characterized crystallographically. In general, proton transfer from the weakly acidic molecules dihydrogen, alcohol, or acetophenone to the amido nitrogen of complexes 3 and 4 is favored in two ...

The reactivity of the ruthenium−amido bond in RuH(NH2CMe2CMe2NH)(PPh3)2 (1) toward weak acids HX and the influence of the X group on the catalytic activity of the resulting complex are explored here. Complex 1 reacts with the weak acids HX (X = OPh, 4-SC6H4OMe, OPPh2, OP(OEt)2, CCPh, NCCHCN, CH(COOMe)2) to form complexes of the type RuHX(tmen)(PPh3)2 (tmen = 2,3-diamino-2,3-dimethylbutane). The complexes with X = PhOH···OPh, 4-SC6H4OMe, OP(OEt)2, CCPh, CH(COOMe)2 have been characterized by X-ray crystallography. The X group is situated trans to the hydride in all cases and is bonded to ruthenium via the donor atoms O, S, P, C, and O, respectively. The phenol in the phenoxide adduct RuH(PhOH···OPh)(tmen)(PPh3)2 bridges via hydrogen bonds between the alkoxide oxygen and an amino hydrogen to form a six-membered RuO···HO···HN ring. One carbonyl oxygen of the malonate bonds to the Ru, while the other accepts a hydrogen bond from an amino hydrogen. The analogous complexes RuHX(dach)(PPh3)2 (dach = (R,R)-1,2-diaminocyclohexane) were synthesized by the reaction of RuHCl(dach)(PPh3)2 (2) with an equimolar amount of potassium tert-butoxide and HX. For all of the complexes the Ru−H vibrational frequency and the 1H NMR chemical shift of Ru−H correlate with the electronegativity of the trans atom X. The amido complex 1 and the complexes with X = CH(COOMe)2 and OPh are active catalysts for the Michael addition of dimethyl malonate to 2-cyclohexen-1-one. RuH(NCCHCN)(tmen)(PPh3)2 reacts with the Michael acceptor 2-cyclohexen-1-one to give RuH(NCC(C6H9O)CN)(tmen)(PPh3)2, a trapped Michael adduct that has been characterized by X-ray crystallography. On the basis of these observations a catalytic cycle for the Michael addition reactions is proposed that involves the addition of the C−H bond of the Michael donor to the Ru−N bond followed by attack on the Michael acceptor and elimination of the Michael adduct, possibly by a 1,3-proton migration as observed for the malononitrile adduct. Only the complexes with X = H, CCPh are catalysts or precatalysts for the hydrogenation of neat acetophenone to 1-phenylethanol in the absence of added base under 10 atm of H2 at 20 °C. Evidence is provided that the phenylacetylide complexes are precatalysts that are converted to the active trans-dihydride catalysts (X = H).

The new amido complex OsH(NHCMe 2 CMe 2 -NH 2 )(PPh 3 ) 2 (2) reacts with weak acids HX to give complexes OsHX(tmen)(PPh 3 ) 2 (1; X ) Cl, 3; X ) NCCHCN; and X ) H; tmen ) NH 2 CMe 2 CMe 2 NH 2 ) and is an active ketone hydrogenation catalyst. HX is completely transferred from Os to Ru in the reactions of the amido complex RuH(NHCMe 2 CMe 2 NH 2 )(PPh 3 ) 2 with complexes 1 and 3.Ruthenium amido hydrido complexes have been identified as active catalysts for the H 2 hydrogenation and asymmetric hydrogenation of ketones and imines. 1-3 In this paper we make an initial comparison of the properties of the title osmium amido hydrido complex 2 with those 4 of the reported ruthenium analogue RuH-(NHCMe 2 CMe 2 NH 2 )(PPh 3 ) 2 (4) 1 as both a ketone hydrogenation catalyst and as a compound reactive toward weak acids. The reactivity of other late-transition-metal amido complexes toward weak acids has been studied 5-9 and is important in catalytic conjugate addition reactions. 10 We also report a novel HX transfer reaction that promises to allow us to rank the reactivity of amido groups on different metals.The complex 2 is generated in two steps from OsHCl-(PPh 3 ) 3 11 by first reacting it with 2,3-diamino-2,3-dimethylbutane to give OsHCl(tmen)(PPh 3 ) 2 (1; tmen ) NH 2 CMe 2 CMe 2 NH 2 ). The X-ray crystal structure (Scheme 1) has a distorted-octahedral geometry with trans hydride and chloride, cis phosphines, and cis amine ligands. The smaller Cl-Os-N angles of 80.78-(12) and 82.95(12)°and the larger Cl-Os-P angles of 96.00(5) and 106.65(5)°indicate that the chloride ligand is moved away from the bulky triphenylphosphine ligands and toward the less bulky diamine ligand. The triplet at -20.9 ppm in the hydride region of the 1 H NMR spectrum and the singlet observed at 17.9 ppm in the 31 P{ 1 H} NMR spectrum suggest that this structure is maintained in solution. The dehydrohalogenation of 1 by reaction with potassium tert-butoxide produces the amido hydrido complex OsH(NHCMe 2 CMe 2 NH 2 )-(PPh 3 ) 2 (Scheme 1). A broad peak at -23.7 ppm in the 1 H NMR and two broad peaks at 29.8 and 27.1 ppm in the 31 P{ 1 H} NMR indicate that the complex is fluxional at room temperature with magnetically inequivalent phosphorus nuclei. The X-ray crystal structure of 2 (Scheme 1) is almost the same as the structure of the previously reported ruthenium analogue 4: e.g. Os1d N2 ) 1.958(3) Å, Os1-N1 ) 2.181(2) Å, and P2-Os1-N1 ) 165.97(8)°vs RudN ) 1.967(2) Å, Ru-N ) 2.176(1) Å, and P-Ru-N ) 164.98(5)°. 1 The geometry around osmium in 2 is best viewed as distorted trigonal bipyramidal with axial atoms N1 and P2 and equatorial atoms N2, P1, and H1Os. The amido nitrogen N2 is trigonal planar and positioned for optimum dative pπ-(N)fdπ(Os) bonding. This π bonding distorts the equatorial geometry from trigonal to Y-shaped with a small H1Os-Os1-P1 angle (80.3°). 12 As expected, the osmium-amido bond is significantly shorter than the osmium-amine bond.Like the ruthenium analogue 4, the new osmium amido complex 2 is an active ketone hydrogenatio...