Osmium Derivatives Research Articles

Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

This article dealt with the ruthenium and osmium derivatives of isomeric 1H-indazole-3-carboxylic acid/2H-indazole-3-carboxylic acid (H2L1) and 1H-benzimidazole-2-carboxylic acid (H2L2) along with the π-acidic bpy (bpy = 2,2'-bipyridine) and pap (pap = 2-phenylazopyridine) co-ligands. It thus extended structurally authenticated monomeric ([(bpy)2RuII(HL1-)]ClO4 [1]ClO4, (pap)2RuII(L12-) 2, (bpy)2OsII(L12-) 3, (pap)2OsII(L12-) 4, (bpy)2RuII(L22-) 5, (bpy)2OsII(L22-) 8, and (pap)2OsII(L22-) 9) and dimeric ([(bpy)2RuII(μ-L22-)RuII(bpy)2](ClO4)2 [6](ClO4)2) complexes. It also described modified L2'2- (L2'2- = 2,2'-bisbenzimidazolate)-bridged [(pap)2RuII(μ-L2'2-)RuII(pap)2](ClO4)2 [7](ClO4)2, where L2'2- was developed selectively with the {Ru(pap)2} metal fragment via in situ intermolecular C-C coupling of the two units of decarboxylated benzimidazolate. Moreover, chemical oxidation (OsII to OsIII) of (bpy)2OsII(L12-) 3 (E0 = 0.11 V versus SCE) and (bpy)2OsII(L22-) 8 (E0 = 0.12 V versus SCE) by AgClO4 yielded unprecedented OsIII-AgI derived polymeric {[(bpy)2OsIII-L12--AgI(CH3CN)](ClO4)2}n {[10](ClO4)2}n and dimeric [(bpy)2OsIII-L22--AgI(CH3CN)](ClO4)2 [11](ClO4)2 complexes as a function of trans and cis orientations of the active N2 donor with special reference to the carboxylate O2 of L2-, respectively. Microscopic (FE-SEM, TEM-EDX, and AFM) and DLS experiments suggested a homogeneously dispersed hollow spherical shaped morphology of {[10](ClO4)2}n with an average particle size of 200-400 nm as well as its non-dissociative feature in the aprotic medium. Experimental (structure, spectroscopy, and electrochemistry) and theoretical (DFT/TD-DFT) explorations revealed a redox non-innocent feature of L2- in the present coordination situations and the selective anion sensing (X = F-, CN-, and OAc-) event of [1]ClO4 involving a free NH group at the backface of HL1-, which proceeded via the NH···X hydrogen bonding interaction.

Crystallographic and Theoretical Study of Osme Bonds in Nitrido-Osmium(VI) Complexes

Osme bonds have been recently defined as the attractive interaction between an element of group 8 acting as an electrophile and any atom or group of atoms acting as a nucleophile. To date, the known examples of osme bonds in X-ray structures involve mostly the highly reactive OsO4 and amines and amine oxides. In this work, evidence supporting the existence of osme bonds in osmium(VI) derivatives is reported. In particular, nitrido-osmium(VI) complexes that present square-pyramidal geometries are well disposed to participate in osme bonds opposite to the Os≡N bond. By using a combination of experimental and theoretical results, the existence and importance of this new class of σ-hole interactions is demonstrated in the solid state of several nitrido-osmium(VI) derivatives.

The quest of the best - A SAR study of trithiolato-bridged dinuclear Ruthenium(II)-Arene compounds presenting antiparasitic properties.

A structure activity relationship (SAR) study of a library of 56 compounds (54 ruthenium and 2 osmium derivatives) based on the trithiolato-bridged dinuclear ruthenium(II)-arene scaffold (general formula [(η6-arene)2Ru2(μ2-SR)3]+, symmetric and [(η6-arene)2Ru2(μ2-SR1)2(μ2-SR2)]+, mixed, respectively) is reported. The 56 compounds (of which 34 are newly designed drug candidates) were synthesized by introducing chemical modifications at the level of bridge thiols, and they were grouped into eight families according to their structural features. The selected fittings were guided by previous results and focused on a fine-tuning of the physico-chemical and steric properties. Newly synthesized complexes were characterized by NMR spectroscopy, mass spectrometry and elemental analysis, and four single-crystal X-ray structures were obtained. The invitro biological assessment of the compounds was realized by applying a three-step screening cascade: (i) evaluation of the activity against Toxoplasma gondii RH strain tachyzoites expressing β-galactosidase (T.gondii-β-gal) grown in human foreskin fibroblast monolayers (HFF) and assessment of toxicity in non-infected HFF host cells; (ii) dose-response assays using selected compound, and (iii) studies on the effects in murine splenocytes. A primary screening was performed at 1 and 0.1μM, and resulted in the selection of 39 compounds that inhibited parasite proliferation at 1μM by more than 95% and reduced the viability of HFF by less than 49%. In the secondary screening, dose-response assays showed that the selected compounds exhibited half maximal inhibitory concentration (IC50) values for T.gondii-β-gal between 0.01μM and 0.45μM, with 30 compounds displaying an IC50 lower than 0.1μM. When applied to non-infected HFF monolayers at 2.5μM, 8 compounds caused more than 90% and 31 compounds more than 30% viability impairment. The tertiary screening included 14 compounds that did not cause HFF viability loss higher than 50% at 2.5μM. These derivatives were assessed for potential immunosuppressive activities. First, splenocyte viability was assessed after treatment of cells with concanavalin A (ConA) and lipopolysaccharide (LPS) with compounds applied at 0.1 and 0.5μM. Subsequently, the 5 compounds exhibiting the lowest splenocyte toxicity were further evaluated for their potential to inhibit B and T cell proliferation. Overall, compound 55 [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-o-CF3)2(μ2-SC6H4-p-OH)]Cl exhibited the most favorable features, and will be investigated as a scaffold for further optimization in terms of anti-parasitic efficacy and drug-like properties.

Dioxygen Activation by Internally Aromatic Metallacycle: Crystallographic Structure and Mechanistic Investigations.

SummaryMononuclear metal-peroxo species are invoked as the key intermediates in metalloenzymatic or synthetic catalysis. However, either transience or sluggishness reactivity of synthetic analogs of metal-peroxo species impedes our understanding of oxygen activation mechanism. Herein, we designed and characterized a dioxygen-derived mononuclear osmium-peroxo complex, in which the peroxo ligand is stabilized by internally aromatic metallacycle. We demonstrate that the osmium-peroxo species shows catalytic activity toward promoterless alcohol dehydrogenations. Furthermore, computational studies provide a new mechanism for the osmium-peroxo-mediated alcohol oxidation, starting with the concerted double-hydrogen transfer and followed by the generation of osmium-oxo species. Interestingly, the internally aromatic metallacycle also plays a vital role in catalysis, which mediates the hydrogen transfer from osmium center to the distal oxygen atom of Os–OOH moiety, thus facilitating the Os–OOH→Os=O conversion. We expect that these insights will advance the development of aromatic metallacycle toward aerobic oxidation catalysis.

ChemInform Abstract: C‐H Functionalization: Thoroughly Tuning Ligands at a Metal Ion, a Chemist Can Greatly Enhance Catalyst′s Activity and Selectivity

AbstractReview: 370 refs.

Cationic Dihydride Boryl and Dihydride Silyl Osmium(IV) NHC Complexes: A Marked Diagonal Relationship

The complex [OsCl(η6-p-cymene)(IPr)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene, OTf = trifluoromethanesulfonate) reacts with pinacolborane (HBpin) and catecholborane (HBcat) to give the dihydride boryl osmium(IV) derivatives [OsH2(Bpin)(η6-p-cymene)(IPr)]OTf (2) and [OsH2(Bcat)(η6-p-cymene)(IPr)]OTf (3), which undergo hydrolysis to afford the trihydride [OsH3(η6-p-cymene)(IPr)]OTf (4). In agreement with the boron–silicon diagonal relationship, complex 1 also reacts with silanes, HSiR3. The reactions lead to the dihydride silyl species [OsH2(SiR3)(η6-p-cymene)(IPr)]OTf (SiR3 = SiPh3 (5), SiEt3 (6), SiHPh2 (7)), which also undergo hydrolysis to yield 4. Complexes 2 and 5 have been characterized by X-ray diffraction analysis. Their four-legged piano-stool geometries with transoid hydride ligands are similar. In solution, the arene rotates over the remaining four ligands. The activation barrier of the process depends upon the size of the boryl or silyl groups. The nature of the Os–B and Os–Si...

C–H functionalization: thoroughly tuning ligands at a metal ion, a chemist can greatly enhance catalyst's activity and selectivity

This brief essay consists of a few "exciting stories" devoted to relations within a metal-complex catalyst between a metal ion and a coordinated ligand. When, as in the case of a human couple, the rapport of the partners is cordial and a love cements these relations, a chemist finds an ideal married couple, in other words he obtains a catalyst of choice which allows him to functionalize C-H bonds very efficiently and selectively. Examples of such lucky marriages in the catalytic world of ions and ligands are discussed here. Activity of the catalyst is characterized by turnover number (TON) or turnover frequency (TOF) as well as by yield of a target product. Introducing a chelating N,N- or N,O-ligand to the catalyst molecule (this can be an iron or manganese derivative) sharply enhances its activity. However, the activity of vanadium derivatives (with additionally added to the solution pyrazinecarboxylic acid, PCA) as well as of various osmium complexes does not dramatically depend on the nature of ligands surrounding metal ions. Complexes of these metals are very efficient catalysts in oxidations with H2O2. Osmium derivatives are record-holders exhibiting extremely high TONs whereas vanadium complexes are on the second position. Finally, elegant examples of alkane functionalization on the ions of non-transition metals (aluminium, gallium etc.) are described when one ligand within the metal complex (namely, hydroperoxyl ligand HOO(-)) helps other ligand of this complex (H2O2 molecule coordinated to the metal) to disintegrate into two species, generating very reactive hydroxyl radical. Hydrogen peroxide molecule, even ligated to the metal ion, is perfectly stable without the assistance of the neighboring HOO(-) ligand. This ligand can be easily oxidized donating an electron to its partner ligand (H2O2). In an analogous case, when the central ion in the catalyst is a transition metal, this ion changing its oxidation state can donate an electron to the coordinated H2O2 fragment. This provokes the O-O bond rupture in the hydrogen peroxide molecule as is assumed for the role of Fe(2+) ions in the Fenton system.

Preparation and reactivity of half-sandwich hydrazine complexes of ruthenium and osmium

Hydrazine complexes [MCl(η 6- p-cymene)(RNHNH 2)L]BPh 4 ( 1– 6) [M = Ru, Os; R = H, Me, Ph; L = P(OEt) 3, PPh(OEt) 2, PPh 2OEt] were prepared by allowing dichloro complexes MCl 2(η 6- p-cymene)L to react with hydrazines RNHNH 2 in the presence of NaBPh 4. Treatment of ruthenium complexes [RuCl(η 6- p-cymene)(RNHNH 2)L]BPh 4 with Pb(OAc) 4 led to acetate complex [Ru(κ 2–O 2CCH 3)(η 6- p-cymene)L]BPh 4 ( 7). Instead, the reaction of osmium derivatives [OsCl(η 6- p-cymene)(CH 3NHNH 2)L]BPh 4 with Pb(OAc) 4 afforded the methyldiazenido complex [Os(CH 3N 2)(η 6- p-cymene)L}]BPh 4 ( 8). Treatment with HCl of this diazenido complex 8 led to the methyldiazene cation [OsCl(CH 3N NH)(η 6- p-cymene)L}] + ( 9 +). The complexes were characterised spectroscopically and by X-ray crystal structure determination of [OsCl(η 6- p-cymene)(PhNHNH 2){PPh(OEt) 2}]BPh 4 ( 6b) and [Ru(κ 2–O 2CCH 3)(η 6- p-cymene){PPh(OEt) 2}]BPh 4 ( 7b).

Phosphanimin‐Derivate des Osmium(IV): Kristallstrukturen von trans‐[OsCl4(HNPEt3)2] und (H2NPPh3)2[OsCl6]·2CH3CN

AbstractPhosphoraneimine Derivatives of Osmium(IV): Crystal Structures of trans‐[OsCl4(HNPEt3)2] and (H2NPPh3)2[OsCl6]·2CH3CNtrans‐[OsCl4(HNPEt3)2] (1) was prepared by reaction of osmium pentachloride with the silylated phosphoraneimine Me3SiNPEt3 in dichloromethane solution forming yellow moisture sensitive single crystals. The hexachloroosmate(IV) (H2NPPh3)2[OsCl6]·2CH3CN (2) was obtained as yellow single crystals from osmium pentachloride and N‐chlorotriphenylphosphoraneimine, ClNPPh3, in acetonitrile solution. 1 and 2 are characterized by IR spectroscopy and single crystal X‐ray structure determinations.1: Space group P21/c, Z = 2, lattice dimensions at 193 K: a = 830.9(1), b = 1031.1(1), c = 1307.7(1) pm, β = 106.15(1)°, R1 = 0.0248. 1 forms centrosymmetric molecules with distances Os–N of 202.9(4) pm and Os–Cl of 234.7 pm on average.2: Space group ${\rm P}{\bar 1}$, Z = 2, lattice dimensions at 193 K: a = 1030.7(1), b = 1432.6(1), c = 1448.8(1) pm, α = 90.98(1)°, β = 92.40(1)°, γ = 92.98(1)°, R1= 0.0545. 2 forms an ionic structure with (H2NPPh3)+ cations and two different site positions of the centrosymmetric [OsCl6]2− anions. The cations are connected with one of the anions by N‐H···Cl bridges as well as with the solvate molecules CH3CN by N–H···N bridges.

Syntheses, structures and redox properties of some complexes containing the Os(dppe)Cp* fragment, including [{Os(dppe)Cp*}2(µ-CCCC)

The sequential conversion of [OsBr(cod)Cp*] (9) to [OsBr(dppe)Cp*] (10), [Os([=C=CH2)(dppe)Cp*]PF6 ([11]PF6), [Os(C triple bond CH)(dppe)Cp*] (12), [{Os(dppe)Cp*}2{mu-(=C=CH-CH=C=)}][PF6]2 ([13](PF6)2) and finally [{Os(dppe)Cp*}(2)(mu-C triple bond CC triple bond C)] (14) has been used to make the third member of the triad [{M(dppe)Cp*}2(mu-C triple bond CC triple bond C)] (M = Fe, Ru, Os). The molecular structures of []PF6, 12 and 14, together with those of the related osmium complexes [Os(NCMe)(dppe)Cp*]PF6 ([15]PF6) and [Os(C triple bond CPh)(dppe)Cp*] (16), have been determined by single-crystal X-ray diffraction studies. Comparison of the redox properties of 14 with those of its iron and ruthenium congeners shows that the first oxidation potential E1 varies as: Fe approximately Os < Ru. Whereas the Fe complex has been shown to undergo three sequential 1-electron oxidation processes within conventional electrochemical solvent windows, the Ru and Os compounds undergo no fewer than four sequential oxidation events giving rise to a five-membered series of redox related complexes [{M(dppe)Cp*}2(mu-C4)]n+ (n = 0, 1, 2, 3 and 4), the osmium derivatives being obtained at considerably lower potentials than the ruthenium analogues. These results are complimented by DFT and DT DFT calculations.

Similarities and Contrasts Between Silyl and Stannyl Derivatives of Ruthenium and Osmium

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Similarities and Contrasts between Silyl and Stannyl Derivatives of Ruthenium and Osmium

Silyl and stannyl complexes of ruthenium and osmium bearing halogen substituents on the silicon and tin atoms undergo many interesting reactions. While there are formal similarities, there are also marked differences between these silyl and stannyl derivatives. This review first surveys the synthetic approaches we have developed to the silyl and stannyl complexes that involve oxidative addition of halogenated silanes coupled with reductive elimination for the preparation of the silyl complexes LnM(SiRnX3-n) (M = Ru, Os) and reaction between LnMH and the vinylstannane R3SnCHCH2 to give first the triorganostannyl complexes LnM(SnR3) (M = Ru, Os), which are then functionalized by redistribution reactions to give LnM(SnRnX3-n) (M = Ru, Os). Among the unusual compounds derived from these halogenated silyl and stannyl complexes are derivatives with the following novel ligands: Si(OH)3, Sn(OH)3, silatranyl, stannatranyl, SnH3, and SnMe2SnPh3. A contrast between the osmasilanol LnOs(SiMe2OH) and the osmastannol LnOs(SnMe2OH) is that the former deprotonates to a silanolate anion, [LnOs(SiMe2O)]-, while the latter, when treated with base, ortho-stannylates a triphenylphosphine ligand. Another contrast is provided by the ease with which osmium trimethylstannyl complexes undergo α-methyl migration reactions.

Oxidation of alcohols with hydrogen peroxide catalyzed by soluble iron and osmium derivatives

Osmium chloride OsCl3 efficiently catalyzes (yields of products up to 90%, turnover numbers (TON) up to 1500) the oxidation of 2-cyanoethanol with hydrogen peroxide to produce the corresponding aldehyde and acid. Oxidation of isopropanol over OsCl3 gave acetone in 58% yield. The reactions were carried out either in acetonitrile or without any solvent. The analogous iron compound FeCl3 was found to be less efficient in the oxidation of 2-cyanoethanol (yields of products up to 67%, TON up to 135). Oxidation of isopropanol in this case gave acetone (yield 53%) and acetic acid (yield 11%). Some other soluble derivatives of iron or osmium exhibited noticeably lower catalytic activity in the alcohol oxidation with H2O2.

Crystallization and preliminary crystallographic analysis of the circadian clock protein KaiB from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1.

KaiB is a component of the circadian clock oscillator in cyanobacteria, which are the simplest organisms that exhibit circadian rhythms. KaiB consists of 108 amino-acid residues and has a molecular weight of 12 025 Da. KaiB and Cys-substituted KaiB mutants from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 were expressed as GST-fusion proteins in Escherichia coli, purified and crystallized. The crystals of wild-type KaiB belong to the monoclinic space group P2(1), with unit-cell parameters a = 89.6, b = 71.2, c = 106.8 A, beta = 100.1 degrees. While the native crystals diffract to 3.7 A, osmium derivatives, which show an approximately 4 A shrinkage in the b axis, diffract to 2.6 A. The crystals of the singly Cys-substituted mutant T64C with Hg, which show different morphology, diffract to 2.5 A and belong to the monoclinic space group P2, with unit-cell parameters a = 63.7, b = 33.4, c = 93.7 A, beta = 100.1 degrees. Anomalous difference Patterson maps of the Os- and Hg-derivative crystals had significant peaks in their Harker sections, suggesting that both derivatives are suitable for structure determination.

Formation of Imine−Vinylidene−Osmium(II) Derivatives by Hydrogen Transfer from Alkenyl Ligands to Azavinylidene Groups in Alkenyl−Azavinylidene−Osmium(IV) Complexes

Treatment at room temperature of the hydride−azavinylidene complexes OsHCl2(NCR2)(PiPr3)2 [CR2 = CMe2 (1), (2)] with Ag[CF3SO3] and the subsequent addition at −25 °C of phenylacetylene to the resulting solutions affords the alkenyl−azavinylidene derivatives [Os{(E)-CHCHPh}Cl(NCR2)(PiPr3)2][CF3SO3] [CR2 = CMe2 (3), (4)], where the Hβ atoms of the alkenyl ligands interact with the osmium atoms to form agostic bonds. The addition at −30 °C of NaCl to tetrahydrofuran solutions of 3 and 4 produces the split of the agostic interactions and the formation of the neutral six-coordinate alkenyl−azavinylidene compounds Os{(E)-CHCHPh}Cl2(NCR2)(PiPr3)2 [CR2 = CMe2 (5), (6)]. In dichloromethane at room temperature complexes 5 and 6 evolve into the imine−vinylidene derivatives OsCl2(CCHPh)(NHCR2)(PiPr3)2 [CR2 = CMe2 (7), (8)], as a result of the hydrogen transfer from the styryl ligands to the azavinylidene groups. The structure of 7 in the solid state has been determined by an X-ray diffraction study. The geometry arou...

Syntheses and structural studies of five- and six-coordinate o-halophenyl derivatives of ruthenium(II) and osmium(II)

Reaction between MHCl(CO)(PPh 3) 3 (M=Ru, Os) and the o-halophenyl mercury compounds, Hg(C 6H 4X-2) 2 (X=Cl, Br, I) gives the five co-ordinate complexes, M(C 6H 4X-2)Cl(CO)(PPh 3) 2 ( 1a M=Ru, X=Cl; 1b M=Ru, X=Br; 2a M=Os, X=Cl; 2b M=Os, X=Br; 2c M=Os, X=I). In these complexes there is a significant bonding interaction between the coordinatively unsaturated metal centre and the o-halo-substituent on the σ-bound phenyl group as revealed by crystal structure determinations of 2a, 2b, and 2c. Each of the five-coordinate complexes readily adds CO forming the corresponding six-coordinate dicarbonyl complexes, M(C 6H 4X-2)Cl(CO) 2(PPh 3) 2 ( 5a M=Ru, X=Cl; 5b M=Ru, X=Br; 6a M=Os, X=Cl; 6b M=Os, X=Br; 6c M=Os, X=I). Crystal structure determination of 6a confirms regular octahedral geometry for these six-coordinate complexes with no interaction between the metal centre and the o-halo-substituent on the σ-bound phenyl group. The complexes 1a, b, 2a– c, 5a, b, 6a– c, are potentially precursors of benzyne complexes through reduction (removal of ClX) but all attempts at reduction were unsuccessful. The related thiocarbonyl complexes, Os(C 6H 4X-2)Cl(CS)(PPh 3) 2 ( 7a X=Cl; 7b X=Br) and Os(C 6H 4X-2)Cl(CO)(CS)(PPh 3) 2 ( 8a X=Cl; 8b X=Br), have been prepared similarly beginning with OsHCl(CS)(PPh 3) 3. The crystal structure of 8a has been determined. Both 8a and 8b undergo a slow migratory-insertion reaction upon heating to yield the corresponding η 2-thioacyl complexes, Os(η 2-C[S]C 6H 4X-2)Cl(CO)(PPh 3) 2 ( 9a X=Cl; 9b X=Br), the crystal structures of both of which have been determined. Once the o-halophenyl group is no longer directly bonded to the metal, as in 9a and 9b, normal reactivity returns to the o-halo substituent and 9b undergoes lithium–bromine exchange when treated with n-butyllithium and the resulting lithiated material, when treated with Sn n Bu 3Cl, gives Os(η 2-C[S]C 6H 4Sn n Bu 3-2)Cl(CO)(PPh 3) 2 ( 10).

Supported ammonia synthesis catalysts based on potassium derivatives of anionic ruthenium, osmium and iron carbonyl clusters. The first catalysts on carbon support exhibiting activity in ammonia synthesis in the absence of a specially added electron promoter

The first catalysts on carbon support exhibiting activity in ammonia synthesis in the absence of a specially added electron promoter have been found. The catalysts were prepared by depositing K 2[Ru 4(CO) 13], K 2[Os 3(CO) 11] and K 2[Fe 2(CO) 8] from THF solutions on the original graphite-like active carbon `Sibunit' followed by drying of the samples obtained at 20°C in vacuum. The highest efficiency is displayed by the K 2[Ru 4(CO) 13] catalyst which is active in ammonia synthesis starting from 250°C (1 atm). On passing from K 2[Ru 4(CO) 13] to K 2[Os 3(CO) 11] and then to K 2[Fe 2(CO) 8] the rate of ammonia synthesis lowers. The replacement of `Sibunit' by usual commercial active carbon SKT results in a sharp decrease in activity and stability of the catalysts. An introduction of metallic potassium into the catalysts on `Sibunit' carbon accelerates strongly the process of ammonia synthesis. A study of the K 2[Ru 4(CO) 13]+K and K 2[Fe 2(CO) 8]+K catalysts has shown that at constant transition metal and carbon contents in the system, the activity of both catalysts passes through a maximum with an increase in potassium quantity, in the case of ruthenium the position of the maximum being reached at considerably less amounts of potassium in the sample than in the case of iron. The K 2[Ru 4(CO) 13]+K catalyst is much less active than the K 2[Fe 2(CO) 8]+K catalyst at 200°C but considerably exceeds it in activity at higher temperatures (250–350°C).

Seven-coordinate dioxygen complexes from dioxygen addition to five-coordinate σ-phenyl, isocyanide-containing derivatives of ruthenium(II) and osmium(II). Crystal structures of OS(η 2-O 2)(η 2-CPh = N p-chlorophenyl)Cl(PPh 3) 2 and Os(η 2-SO 4)(η 2-CPh = N p-chlorophenyl)Cl(PPh 3) 2

Reaction of the hydrido complexes MHCl(CNR)(PPh 3) 3 ( 1a, M = Ru, R = p-tolyl; 1b, M = Os, R = p-tolyl; 1c, M = Os, R = p-chlorophenyl) with HgPh 2 results in formation of the five-coordinate σ-phenyl complexes MPhCl(CNR)(PPh 3) 2 ( 2a, M = Ru, R = p-tolyl; 2b, M = Os; R = p-tolyl; 2c, M = Os, R = p-chlorophenyl). These five-coordinate complexes, upon contact with dioxygen, form seven-coordinate dioxygen complexes M(η 2-O 2)(η 2-CPhNR)Cl(PPh 3) 2 ( 3a, M = Ru, R = p-tolyl; 3b, M = Os, R = p-tolyl; 3c, M = Os, R = p-chlorophenyl) in which the phenyl group has migrated onto the isocyanide ligand to form a dihapto-iminoacyl ligand. The crystal structure of 3c has been determined. The complex 3c reacts with SO 2 to form the sulphate derivative Os(η 2-SO 4)(η 2-CPhN p-chlorophenyl)Cl(PPh 3) 2 ( 4c), the crystal structure of which has also been determined. Sodium acetate reacts with 2a and 2b to form MPh(η 2-O 2CCH 3)(CN p-tolyl)(PPh 3) 2 ( 5a, M = Ru; 5b, M = Os). CO reacts with OsPhCl(CN p-tolyl)(PPh 3) 2 to form OsPhCl(CO)(CN p-tolyl)(PPh 3) 2 ( 6b) and with CN p-tolyl to give OsPhCl(CN p-tolyl) 2(PPh 3) 2 ( 7b). Reaction of 2a with CO, and migration of the phenyl group, results in formation of the dihapto-iminoacyl complex Ru(η 2-CPhN p-tolyl)Cl(CO)(PPh 3) 2 ( 8a). Treatment of 2a with CN p-tolyl, followed by addition of HCl, gives the carbene complex RuCl 2(CPhNH p-tolyl)(CN p-tolyl)(PPh 3) 2 ( 9a). The hydrido complexes 1a–1c, which are the immediate precursors of the five-coordinate σ-phenyl isocyanide complexes, are generated by reaction of the dihydrido complexes MH 2(CNR)(PPh 3) 3 ( 10a, M = Ru, R = p-tolyl; 10b, M = Os, R = p-tolyl; 10c, M = Os, R = p-chlorophenyl) with HCl.

Oxidative Addition of Group 14 Element Hydrido Compounds to OsH(2)(eta(2)-CH(2)=CHEt)(CO)(P(i)Pr(3))(2): Synthesis and Characterization of the First Trihydrido-Silyl, Trihydrido-Germyl, and Trihydrido-Stannyl Derivatives of Osmium(IV).

The dihydrido-olefin complex OsH(2)(eta(2)-CH(2)=CHEt)(CO)(P(i)Pr(3))(2) (2) reacts with H(2)SiPh(2) to give OsH(3)(SiHPh(2))(CO)(P(i)Pr(3))(2) (3). The molecular structure of 3 has been determined by X-ray diffraction (monoclinic, space group P2(1)/c with a = 16.375(2) Å, b = 11.670(1) Å, c =18.806(2) Å, beta = 107.67(1) degrees, and Z = 4) together with ab initio calculations on the model compound OsH(3)(SiH(3))(CO)(PH(3))(2). The coordination geometry around the osmium center can be rationalized as a heavily distorted pentagonal bipyramid with one hydrido ligand and the carbonyl group in the axial positions. The two other hydrido ligands lie in the equatorial plane, one between the phosphine ligands and the other between the SiHPh(2) group and one of the phosphine ligands. Complex 3 can also be prepared by reaction of OsH(eta(2)-H(2)BH(2))(CO)(P(i)Pr(3))(2) (4) with H(2)SiPh(2). Similarly, the treatment of 4 with HSiPh(3) affords OsH(3)(SiPh(3))(CO)(P(i)Pr(3))(2) (5), while the addition of H(3)SiPh to 4 in methanol yields OsH(3){Si(OMe)(2)Ph}(CO)(P(i)Pr(3))(2) (6). Complex 2 also reacts with HGeR(3) and HSnR(3) to give OsH(3)(GeR(3))(CO)(P(i)Pr(3))(2) (GeR(3) = GeHPh(2) (7), GePh(3) (8), GeEt(3) (9)) and OsH(3)(SnR(3))(CO)(P(i)Pr(3))(2) (R = Ph (10), (n)Bu (11)), respectively. In solution, compounds 3 and 5-11 are fluxional and display similar (1)H and (31)P{(1)H} NMR spectra, suggesting that they possess a similar arrangement of ligands around the osmium atom.

Reactions of the Dihydrogen Complex OsCl2(.eta.2-H2)(CO)(PiPr3)2 with Terminal Alkynes: Synthesis of Carbene, Vinylcarbene, and .mu.-Bis-carbene Osmium (II) Derivatives

We thank the D.G.I.C.Y.T. (Project PB 92-0092, Programa de Promocion General del Conocimiento) and E.U. (Project: Selective Processes and Catalysis Involving Small Molecules) for financial support. B.Z. thanks the Ministerio de Educacion y Ciencia de Espana (M.E.C.) and E.O. the Diputacion General de Aragon (D.G.A.) for a grant.