Osmium Hydride Research Articles

ChemInform Abstract: Ruthenium‐ and Osmium—Hydride Compounds Containing Triisopropylphosphine as Precursors for Carbon—Carbon and Carbon—Heteroatom Coupling Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Hydride Transfer from (η5-C5Me5)(CO)2MH (M = Fe, Ru, Os) to Trityl Cation: Different Products from Different Metals and the Kinetics of Hydride Transfer

Reactions of the metal hydride complexes Cp*(CO)2MH (M = Fe, Ru, Os) with Ph3C+BF4- in CH2Cl2 were studied. Hydride transfer from Cp*(CO)2FeH to Ph3C+BF4- gives Cp*(CO)2FeFBF3. Hydride transfer from the ruthenium hydride Cp*(CO)2RuH to Ph3C+BF4- produces the bridging hydride complex {[Cp*(CO)2Ru]2(μ-H)}+BF4-, indicating that Cp*(CO)2RuH exhibits significant nucleophilicity in addition to hydridic reactivity of the Ru−H bond. The osmium hydride Cp*(CO)2OsH reacts with Ph3C+BF4- in CH2Cl2 to give a mixture of Cp*(CO)2OsFBF3 and [Cp*(CO)2Os(ClCH2Cl)]+BF4-. The kinetics of these hydride transfer reactions were monitored by stopped-flow methods, leading to the second-order rate law −d[Ph3C+BF4-]/dt = k[Ph3C+BF4-][MH]. The temperature dependence of the rate constants was determined for the iron hydride, the osmium hydride, and the osmium deuteride Cp*(CO)2OsD. Activation parameters for hydride transfer from Cp*(CO)2FeH are ΔH⧧ = 2.6 ± 0.1 kcal mol-1 and ΔS⧧ = −22.1 ± 0.4 cal K-1 mol-1; for Cp*(CO)2OsH the activ...

Alkylidene and Vinylidene “Pincer” Complexes from Reactions of Alkynes with Ruthenium and Osmium Hydrides

Reactions of 1-pentyne and tert-butylacetylene with RuHCl[1,3-(CH2PBut2)2C6H4] and OsH2Cl(PCP) (PCP = [2,6-(CH2PBut2)2C6H3]-) afforded the square-pyramidal 16-electron alkylidene and vinylidene complexes RuCl(C(Me)Pr)(PCP) (1), RuCl(CCHBut)[1-(CCHBut)-2,6-(CH2PBut2)2C6H3] (2), OsCl(CCHPr)(PCP) (3), and OsCl(CCHBut)(PCP) (4). These reactions were studied in solution by NMR spectroscopy. The structures of 1−4 were determined by X-ray crystallography.

New alkali metal osmium- and ruthenium hydrides

Previously unknown ternary metal hydrides A x OsH z and A x RuH z (A=alkali metal) were synthesized by the reaction of alkali metal hydrides with osmium or ruthenium under a hydrogen pressure up to 6000 bar. The crystal structures of the hydrides were determined using a combination of X-ray and neutron diffraction experiments with deuterated compounds on powdered samples. Na 3OsH 7 and Na 3RuH 7 crystallize at room temperature in a tetragonal structure type (space group: P4 2/ mnm), which is characterized by isolated [OsH 7]- or [RuH 7] anions. The coordination polyhedron formed by the seven hydrogen (deuterium) ligands can be described as a distorted pentagonal bipyramide. Magnetic susceptibility measurements on Na 3OsH 7 in the temperature range between 3.5 K and room temperature revealed a weak temperature independent paramagnetism. Quantum mechanical calculations confirm these facts and show in detail that the large value of the spin–orbit coupling constant is responsible for the magnetic behaviour of these compounds with the oxidation state +4 for the transition metal atoms. With the heavier alkali metals transition metal(IV) hydrides A 3− δ OsH 7− δ and A 3− δ RuH 7− δ could be synthesized. They crystallize with isotypic atomic arrangements related to the cryolite structure type. Highest hydrogen pressure during the reaction leads to the osmium(VI) hydrides Cs 3OsH 9 and Rb 3OsH 9. The atomic arrangement is characterized by [OsH 8] polyhedra intercalated in a cubic HA 3 framework which corresponds to the ReO 3 structure type. Within these polyhedra the hydrogen ligands occupy two 24-fold positions with a statistical distribution.

Isomerization of CH3C⋮CPh to Phenylallene Promoted by an Osmium Hydride Complex

Treatment of OsH3Cl(PPh3)3 in benzene with excess CH3C⋮CPh produced cis-CH3CHCHPh and the novel complex OsCl(C(CH3)CHPh)(CH2CCHPh)(PPh3)2, which contains a β-agostic vinyl ligand and a phenylallene ligand. The structure of the latter unusual complex has been confirmed by a single-crystal X-ray diffraction study.

A series of mono- and dihydrido- as well as mono- and dimethylosmium(II) complexes containing [(mes)Os(CNR)] as a building block

The dihydridoosmium(II) complexes [(mes)OsH 2(CNR)] ( 7– 10) were prepared in excellent yield from the dichloroosmium(II) precursors [(mes)OsCl 2(CNR)] upon treatment with 10% magnesium amalgam in THF in the presence of ethanol. Under similar conditions, the methylisocyanide derivative [(mes)OsH 2(CNMe)] ( 6) as well as the monohydrido compounds [(mes)OsH(X)(CNMe)] ( 11, 13) were obtained. The same methodology using [(mes)OsCl(C 6H 5)(CNR)] as the starting material was applied for the preparation of the hydrido(phenyl)osmium(II) complexes [(mes)OsH(C 6H 5)(CNR)] ( 19– 23) which were also isolated in almost quantitative yield. Treatment of these complexes with HCl in CH 2Cl 2 at −78°C led to the cleavage of the osmiumphenyl but not the osmiumhydride bond. Reactions of [(mes)OsCl 2(CNR)] with MeLi/LiCl gave exclusively the dimethylosmium(II) compounds [(mes)Os(CH 3) 2(CNR)] ( 29– 32) while the corresponding reactions with MeLi/LiI afforded a mixture of 29– 32 and the monomethyl derivatives [(mes)OsI(Me)(CNR)] ( 26, 33– 35). A cyclic carbeneosmium(II) complex 37 was obtained from [(mes)OsCl 2(CNPh)] and MeLi/LiI followed by treatment with deactivated Al 2O 3. The etheneosmium(0) compound [(mes)Os(C 2H 4)(CNMe)] ( 38) was prepared from the dimethylosmium(II) precursor 29 and briefly investigated as starting material for photochemical CH activation reactions.

C−H Bond Activation in the Formation of an Osmium(IV) Metallacycle

The osmium methylimido complex [(η5-C5H5)Os(NCH3)(CH2SiMe3)2][SO3CF3], 1, reacts with PPh3 to give both the methyleneamido complex (η5-C5H5)Os(NCH2)(CH2SiMe3)2, 2, and the unique osmium(IV) hydride [(η5-C5H5)Os(H)(PPh3){CHSiMe3PPh2(C6H4)}][SO3CF3], 4. A single-crystal X-ray diffraction study of 4 shows that this molecule has a distorted square pyramidal structure with the center of the cyclopentadienyl ring at the apex. This molecule results from a series of reactions that includes two C−H activation steps: α-hydrogen elimination and orthometalation.

The mechanism of displacement of dihydrogen and dinitrogen from iron, ruthenium and osmium hydrides and implications for models of nitrogenase action

The substitution of dihydrogen in complexes [FeH(H2)(phosphine)x]+ [phosphine = R2PCH2CH2PR2 (R = Et or Me) or P(CH2CH2PR′2)3 (R′ = Me or Ph)] by ligands L (MeCN, PhCN, or Cl–) has been shown to be first order in the concentration of complex and zero order in the concentration of L, in both acetone and thf. Activation parameters have been determined, and the mechanism of substitution is proposed to involve rate-determining loss of H2 from the parent complexes and subsequent rapid co-ordination of L. This mechanism differs from that recently proposed for an analogous complex of Ph2PCH2CH2PPh2, and the reasons for this are discussed. Less thorough studies of some related dinitrogen complexes, and of some homologous complexes of Ru and Os, are consistent with a similar loss of dinitrogen or dihydrogen being rate determining.

Hydride Is Not a Spectator Ligand in the Formation of Hydrido Vinylidene from Terminal Alkyne and Ruthenium and Osmium Hydrides: Mechanistic Differences

RuHX(H2)L2 (L = PtBu2Me; X = Cl, I) and OsH3ClL2 (L = PiPr3) react (time of mixing) with terminal alkynes in a 1:2 stoichiometry to give MHX(CCHR)L2 and RCHCH2. The reactions of RuHX(H2)L2 with PhC⋮CD lead to RuDX(CCHPh)L2 as the only isotopomers. This result is understood in terms of an insertion of the alkyne in the Ru−H bond to make a vinyl, followed by an α-hydrogen migration, giving the hydrido/vinylidene. This reaction path has been studied by ab initio (B3LYP) calculations with location of the minima and transition states. In agreement with isotopic labeling experiments, it is shown that the path starting with insertion into the Ru−H bond is more favorable than a 1,2-migration within the coordinated alkyne ligand. The favored reaction is calculated to be exothermic from the starting compounds to intermediates and to products with the energies of all transition states well below that of the separated reactants. The mechanism involves the formation of a 14-electron η1-vinyl intermediate which, after ...

Neutron diffraction study of the ‘elongated’ molecular dihydrogen complex [(C5Me5)Os(H2)H2(PPh3 )

Protonation of the osmium(IV) hydrides (C 5 Me 5 )OsH 3 (L) with HBF 4 in diethyl ether afforded the cationic dihydrogen complexes [(C 5 Me 5 )Os(H 2 )H 2 (L)][BF 4 ], where L is PPh 3 1 or AsPh 3 2; a single-crystal neutron diffraction study of 1 reveals that the H–H distance is 1.014(11) A.

Reaction of ruthenium(II) and osmium(II) hydrides with anhydrous HF

The reactions of anhydrous HF with the ruthenium(II) and osmium(II) hydride complexes [MH2(CO)x(PPh3)y] (M = Ru or Os; x = y = 2; x = 1, y = 3) have been studied. For [OC-6-13][MH2(CO)2(PPh3)2], elimination of dihydrogen affords the previously described [OC-6-13][MF2(CO)2(PPh3)2]. For [OC-6-13][MH2(CO)(PPh3)3], elimination of dihydrogen is accompanied by loss of one phosphine ligand and aggregation to give the novel, triply fluoride-bridged, dinuclear, [M2(µ-F)3(CO)2(PPh3)4][HF2]; anion exchange with Na[BPh4] afford air-stable products. These complexes have been characterised by mass spectrometry, NMR, IR and metal-edge extended X-ray absorption fine structure spectroscopies which confirm their dinuclear structures.

Reactions of Osmium Hydride Complexes with Terminal Alkynes: Synthesis and Catalytic Activity of OsH(.eta.2-O2CCH3)(C:CHPh)(PiPr3)2

Reactions of Osmium Hydride Complexes with Terminal Alkynes: Synthesis and Catalytic Activity of OsH(.eta.2-O2CCH3)(C:CHPh)(PiPr3)2

ChemInform Abstract: Insertion of 2,3‐Dihydrothiophene into Platinum and Osmium Hydrides: A Model for Reactions Occurring During Thiophene Hydrodesulfurization.

AbstractDihydrothiophene (II) is proposed as an intermediate in the catalytic hydrodesulfurization of thiophene.

Insertion of 2,3-dihydrothiophene into platinum and osmium hydrides: a model for reactions occurring during thiophene hydrodesulfurization

It was of interest to explore the reactivity of 2,3-DHT with metal hydride complexes to see if hydrogen migration to the partly hydrogenated thiophene occurs. The results in this paper demonstrate that insertion of 2,3-DHT into metal hydride bonds occurs readily to give metallathiacyclopropane complexes which upon protonation yield tetrahydrothiophene

Mononuclear η 3-allylosmium hydride complexes and the x-ray crystal structure of the solvento complex [OsH(H 2O)(CO) 2(PPh 3) 2]BF 4 · EtOH

The osmium(II) hydride [OsHCl(CO)(PPh 3) 3] reacts with 2-methylallylmagnesium chloride and allylmagnesium chloride to give the air-stable η 3-allylosmium hydride complexes [OsH(CO)(η 3-CH 2CRCH 2)(PPh 3) 2] (R = Me or H). The orientation of the η 3-allyl ligand in these complexes has been established by NOE difference spectra. Treatment of [OsH(CO)(η 3-CH 2CMeCH 2)(PPh 3) 2] with fluoroboric acid in the presence of a ligand L (L = Ph 3P or CO) affords the cationic hydride complexes [OsH(CO)(OH 2)(L)(PPh 3) 2][BF 4]. The crystal structure of [OsH(CO) 2(OH 2)(PPh 3) 2][BF 4] · EtOH has been determined.

Interaction between dipotassium hexahalogeno-osmates K 2OsX 6 (X = Cl, Br) and olefins: metal hydride formation by allylic hydrogen atom abstraction and catalytic isomerization of olefins

Dipotassium hexahalogeno-osmates, K 2OsX 6 (X = Cl, Br) dissolved in non-aqueous inert organic solvents (benzene, o-dichlorobenzene, bromo-benzene) by addition of dicyclohexyl-18-crown-6 ether (C 20H 36O 6) are catalytic precursors for the multiple double bond shift in olefins. Studies on the interaction between K 2OgX 6 and several olefins (1-heptene, 1-heptene-3d 2, 1-pentene, cis-stilbene, 3,3-dimethyl-l-butene) support an osmium hydride species, probably [OsHX 5] =, as the true catalyst, which affords the olefin isomerization through successive 1,2-addition-elimination steps to the CC double bond. Such an alleged osmium hydride species is formed by allylic hydrogen atom abstraction from the olefin with formation of the corresponding conjugate diolefin.

The observation of1J(187Os–H) coupling in the1H nuclear magnetic resonance spectra of some osmium hydrides

1 J(187Os–H) has been observed for the complexes OsH4(PEt2Ph)3, OsH4(AsEt2Ph)3, and a species believed to be OsH6(AsEt2Ph)2.