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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 5reveals a BH4–anion η2coordinated to ruthenium through two bridging hydrides. A variable-temperature 1H NMR study of 6exhibits interesting fluxional behavior of the BH4–ligand. Similarly, the Ru(II) hydrido borohydride complex 9, in which the BH4–moiety is coordinated in a η1bonding mode, was obtained by reaction of [RuCl2(PPh3)(iPr-PNP)] (iPr-PNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) (8) with two equivalents of NaBH4at room temperature. The hydrido borohydride pincer complexes 5, 6, and 9catalyze 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> 9> 5. With the hydrido borohydride complex 6as 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, 6effectively 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–hydrogenation reactions of alcohols is developed, which is relevant to the current interest in hydrogen storage. [ABSTRACT FROM AUTHOR]

The syntheses, structures, and reactivities of diruthenium complexes having a five-, six-, and seven-membered cyclic diene ligands are discussed in this paper. While the μ-η2:η2-cyclohexadiene complex 3was readily prepared by the reaction of the diruthenium tetrahydrido complex 1with 1,3-cyclohexadiene, 3was alternatively synthesized by the reaction of 1with benzene via partial hydrogenation of benzene on a diruthenium plane. While the μ-η2:η2-cyclohexadiene ligand was liberated as benzene upon mild heating, the treatment of 3with tBuNC and CO caused further migration of hydrido ligand to the C6moiety to yield the μ-η2-cyclohexenyl complex 6and the μ-cyclohexylidene complex 8, respectively. The reactions of 1with cyclopentadiene and cycloheptatriene also afforded the bridging cyclic diene complexes 10and 11. While the thermolysis of the μ-η2:η2-cyclopentadiene complex 10resulted in the degradation of the cluster skeleton forming Cp*RuCp (12), the μ-η2:η2-cycloheptadiene complex 11was stable upon heating. These differences can be attributed to the aromatization of the cyclic diene moiety. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of thiophene-2-methylamine with one or two equivalents of PPh2Cl in the presence of NEt3, proceeds in thf to give thiophene-2-(N-diphenylphosphino)methylamine, 1a and thiophene-2-(N,N-bis(diphenylphosphino))methylamine, 2a respectively, under anaerobic conditions. Oxidations of 1a and 2a with aqueous hydrogen peroxide, elemental sulfur or gray selenium in thf gives the corresponding oxides, sulfides and selenides [Ph2P(E)NHCH2-C4H3S] (E: O 1b, S 1c, Se 1d) and [(Ph2P(E))2NCH2-C4H3S], (E: O 2b, S 2c, Se 2d) respectively, in high yield. Furthermore, two novel Ru(II) complexes with the P–N ligands 1a and 2a were synthesized starting with the complex [Ru(η6-p-cymene)(μ-Cl)Cl]2. The complexes were fully characterized by analytical and spectroscopic methods. 31P–{1H} NMR, DEPT, 1H–13C HETCOR or 1H–1H COSY correlation experiments were used to confirm the spectral assignments. The molecular structure of thiophene-2-(N-diphenylthiophosphino)methylamine was also elucidated by single-crystal X-ray crystallography. Following activation by NaOH, compounds 3 and 4 catalyze the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of iso-PrOH as the hydrogen source. [Ru(Ph2PNHCH2-C4H3S)(η6-p-cymene)Cl2], 3 and [Ru((PPh2)2NCH2-C4H3S)(η6-p-cymene)Cl]Cl, 4 complexes are suitable catalyst precursors for the transfer hydrogenation of acetophenone derivatives in 0.1M iso-PrOH solution. Notably 4 acts as an excellent catalyst giving the corresponding alcohols in excellent conversions up to 99% (TOF⩽744h−1). This transfer hydrogenation is characterized by low reversibility under the experimental conditions. [Copyright &y& Elsevier]

Abstract: The “Ru(P–P)” unit (P–P=diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl2Ru-pz-RuCl2(CO)(dppb)] (pz=pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF6 (N–N=diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF6 were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl2(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and 31P{1H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography. [Copyright &y& Elsevier]

Abstract: The complex [Ru(CO)2(triphos-κ2P)Cl2] (1) underwent decarbonylation in dichloromethane solution under air over a period of about two weeks to afford the chelated monocarbonyl complex [Ru(CO)(triphos-κ3P)Cl2] (2). The Single Crystal X-ray structure of 2 showed a slightly distorted metal centred complex. The catalytic activity of one of the complexes [Ru(CO)(triphos-κ3P)Cl2] (2) was examined in the transfer hydrogenation of aromatic carbonyl compounds and was found to be efficient with conversion up to 100% in the presence of isopropanol/NaOH. [Copyright &y& Elsevier]

Abstract: Two families of arene ruthenium oxinato complexes of the types [(η6-arene)Ru(η2-N,O-L)Cl] and [(η6-arene)Ru(η2-N,O-L)(OH2)]+ have been synthesized from the dinuclear precursors [(η6-arene)RuCl2]2 (arene= para-cymeme or hexamethylbenzene) and the corresponding oxine LH (LH=8-hydroxyquinoline, 5-chloro-8-hydroxyquinoline, 5,7-dichloro-8-hydroxyquinoline, 5-nitro-8-hydroxyquinoline, 5,7-dimethyl-8-hydroxyquinoline, 5,7-dichloro-2-methyl-8-hydroxyquinoline). The molecular structures of the neutral chloro complexes [(η6-C6Me6)Ru(η2-N,O-L)Cl] (LH=8-hydroxyquinoline, 5,7-dichloro-2-methyl-8-hydroxyquinoline) and [(η6-MeC6H4Pr i )Ru(η2-N,O-L)Cl] (LH=5,7-dichloro-2-methyl-8-hydroxyquinoline) as well as those of the cationic aqua derivatives [(η6-MeC6H4Pr i )Ru(η2-N,O-L)(OH2)]+ (LH=8-hydroxyquinoline, 5,7-dimethyl-8-hydroxyquinoline), isolated as the tetrafluoroborate salts, show in all cases a piano-stool arrangement with the arene ligand, the chelating oxinato ligand and the chloro or the aqua ligand surrounding the ruthenium center in a pseudo-tetrahedral fashion. The analogous reaction of [(η6-MeC6H4Pr i )RuCl2]2 with other N,O-chelating ligands such as 2-pyridinemethanol or tetrahydrofurfurylamine did not give the expected analogs but resulted in the formation of the complexes [(η6-MeC6H4Pr i )Ru(η2-NC5H4CH2OH)Cl]+ and [(η6-MeC6H4Pr i )Ru(η1-NHCH2C4H3O)Cl2]. The neutral and cationic complexes of the types [(η6-arene)Ru(η2-N,O-L)Cl] and [(η6-arene)Ru(η2-N,O-L)(OH2)]+ have been found to catalyze the hydrogenation of carbon dioxide to give formate in alkaline aqueous solution with catalytic turnovers up to 400. [Copyright &y& Elsevier]

Abstract: The stoichiometric reaction of phenylene-1,4-diaminotetra(phosphonite), p-C6H4[N{P(OC6H4OMe-o)2}2]2 (P2NФNP2) (1) with [RuCl2(p-cymene)]2 in acetonitrile produces cis,cis-[{RuCl2(CH3CN)2}2(P2NФNP2)] (2), whereas the similar reaction of 1 with [RuCl2(p-cymene)]2 in THF medium affords a tri-chloro-bridged tetrametallic complex, [{(η 6-p-cymene)Ru2(μ 2-Cl)3Cl}2(P2NФNP2)] (3) irrespective of the stoichiometry and reaction conditions. The formation and structure of complexes 2 and 3 are assigned through various spectroscopic and micro analysis data. The molecular structure of 2 is confirmed by single crystal X-ray diffraction study. The catalytic activities of complexes 2 and 3 have been investigated in transfer hydrogenation reactions. [Copyright &y& Elsevier]

Abstract: The cationic complexes [(η 6-arene)Ru(N,O-amino amide)X]Y (arene=p-cymene or indane; N,O-amino amide=(l)-proline amide or (l)-phenylalanine amide; X=Cl or I; Y=Cl, I or PF6) have been synthesised and fully characterized by spectroscopic and analytical methods. In several cases (1a, 3a, 4a, 4b, 5) the metal configuration has been definitively established by X-ray analysis on single crystal. The lability of the metal center in solution has been studied by 1H NMR and CD techniques. The highest configurational stability has been found in the complexes of the type [(η 6-indane)Ru(N,O-proline amide)Cl]Y (4a,b). The complexes 1b, 2a–b, 3b, 4b and 5 are good precatalysts for the transfer hydrogenation of acetophenone in basic i-PrOH, with ee up to 76% at 30°C. An ESI(+)-MS study of pre-catalytic solutions has provided useful information on the catalytic mechanism. [Copyright &y& Elsevier]

Ruthenium derivatives of the type [RuCl(arene)(NN)][BPh4] (arene = benzene, p-cymene) have been synthesized with NN = 2-hydroxyphenylbis(pyrazol-1-yl)methane (bpzmArOH) or 2-hydroxyphenylbis(3,5-dimethylpyrazol-1-yl)methane (bpz*mArOH). In the p-cymene derivative containing bpzmArOH, activation of the hydroxy group is observed and a scorpionate complex is obtained with the ligand behaving in a tridentate manner, [Ru(bpzmArO-κ3-N,N,O)(p-cymene)][BPh4]. The structure of this derivative and that of [RuCl(p-cymene)(bpz*mArOH)][BPh4] were determined by X-ray diffraction. The new derivatives, along with other compounds previously described by us that contain similar ligands, were tested in the transfer hydrogenation of benzophenone and other carbonyl compounds under base-free conditions without any other additive to promote the reaction. The precursors were active in this process, and the p-cymene derivatives exhibited a higher activity than the benzene complexes. For the p-cymene complexes the activity was even higher than that found in the presence of base (KOH). The effect of the substituents on the methylene carbon was also studied. Mechanistic and kinetic studies were carried out, and hydride species were observed after a pretreatment of the precatalyst in 2-propanol. Taking into account all of the results, a proposal for the mechanism taking place during the hydrogenation of carbonyl groups under base-free conditions has been made. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of [Ru3(CO)10{(C6F5)2P(CH2)2P(C6F5)2}] (1) with hydrogen in toluene produced four compounds. These compounds were characterized spectroscopically and structurally. Some experiments were carried out to determine the relationship between the different reaction products. The first two compounds (2 and 3) show μ-phosphide groups bridging metal–metal bonds, produced by the rupture of a P–C6F5 bond; 2 also shows a C6F5 ring bonded in a η1 fashion to one of the metal atoms. In both compounds the remaining part of the diphosphine ligand is coordinated in the traditional terminal form. The structure of compounds 4 and 5 show a μ3-phosphinidene group where both aromatic rings bonded to the phosphorus atom have been eliminated. Compound 4 also has a C6F5 ring bonded to a ruthenium atom. [Copyright &y& Elsevier]

The Ru(II) hydride complex (IMes)2Ru(Cl)(H)(CO) (1) {IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene} was synthesized from [Ru(CO)2Cl2]nand free IMes. Complex 1rapidly reacts with CO to produce the cis-dicarbonyl Ru(II) complex (IMes)2Ru(Cl)(H)(CO)2(2). The reaction of 1with NaBAr′4{Ar′ = 3,5-(CF3)C6H3} produces the four-coordinate Ru(II) cationic complex [(IMes)2Ru(H)(CO)][BAr′4] (4), which can be trapped by two equivalents of tert-butylisonitrile to produce [(IMes)2Ru(H)(CO)(CNtBu)2][BAr′4] (5). Experimental and computational studies suggest that complex 4is a diamagnetic system that adopts a sawhorse structure. The hydride ligand of complex 2is readily displaced as dihydrogen upon reaction with HCl to produce (IMes)2Ru(Cl)2(CO)2(3). Both complex 1and 4were found to react with D2(30 psi) at room temperature to produce the isotopomers (IMes)2Ru(Cl)(D)(CO) (1-d1) and [(IMes)2Ru(D)(CO)][BAr′4] (4-d1), respectively, with the rate of formation of 4-d1at least 28 times faster than the conversion of 1/D2to 1-d1. In the presence of excess D2complex 4reversibly incorporates deuterium into the ortho methyl groups of the IMes ligands, whereas complex 1does not show evidence of H/D exchange with the IMes ligands. Both 1and 4were found to catalyze the hydrogenation of olefins, ketones, and aldehydes. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of [Ru3(CO)10(μ-dppm)] (1) with H2S at 66°C affords high yields of the sulfur-capped dihydride [Ru3(CO)7(μ-H)2(μ-dppm)(μ3-S)] (2), formed by oxidative-addition of both hydrogen–sulfur bonds. Hydrogenation of [Ru3(CO)7(μ-dppm)(μ3-CO)(μ3-S)] (3) at 110°C also gives 2 in similar yields, while hydrogenation of [Ru3(CO)7(μ-dppm)(μ3-CO)(μ3-Se)] (4) affords [Ru3(CO)7(μ-H)2(μ-dppm)(μ3-Se)] (5) in 85% yield. The molecular structures of 2 and 5 reveal that the diphosphine and one hydride simultaneously bridge the same ruthenium–ruthenium edge with the second hydride spanning one of the non-bridged edges. Both 2 and 5 are fluxional at room temperature being attributed to hydride migration between the non-bridged edges. Addition of HBF4 to 2 affords the cationic trihydride [Ru3(CO)7(μ-H)3(μ-dppm)(μ3-S)][BF4] (6) in which the hydrides are non-fluxional due to the blocking of the free ruthenium–ruthenium edge. [Copyright &y& Elsevier]

In the title complex, [RuClH(C14H20N2O)(C44H32P2)]·C6H6, the RuII ion is in a slightly distorted coordination environment. One of the amino H atoms is involved in a weak intra­molecular N—H⋯Cl inter­action (H⋯Cl = 2.71 Å), while the other is involved in an intra­molecular N—H⋯π(arene) inter­action (NH⋯ Cg = 2.62 Å, where Cg is the centroid of a benzene ring). [ABSTRACT FROM AUTHOR]