Osmium Atoms Research Articles

Structure of Tetracarbonylethyleneosmium: Ethylene Structure Changes upon Complex Formation

Rotational spectra of seven isotopomers of tetracarbonylethyleneosmium, Os(CO)4(eta2-C2H4), were measured in the 4-12 GHz range using a Flygare-Balle-type pulsed-beam Fourier transform microwave spectrometer system. Olefin-transition metal complexes of this type occur extensively in recent organic syntheses and serve as important models for transition states in the metal-mediated transformations of alkenes. Three osmium ((192)Os, (190)Os, and (188)Os) and three unique 13C isotopomers (13C in ethylene, axial, and equatorial positions) were observed in natural abundance. Additional spectra were measured for a perdeuterated sample, Os(CO)4(eta2-C2D4). The measured rotational constants for the main osmium isotopomer ((192)Os) are A = 929.3256(6), B = 755.1707(3), and C = 752.7446(3) MHz, indicating a near-prolate asymmetric top molecule. The approximately 140 assigned b-type transitions were fit using a Watson S-reduced Hamiltonian including A, B, C, and five centrifugal distortion constants. A near-complete r0 gas-phase structure has been determined from a least-squares structural fit using eight adjustable structural parameters to fit the 21 measured rotational constants. Changes in the structure of ethylene on coordination to Os(CO)4 are large and well-determined. For the complex, the experimental ethylene C-C bond length is 1.432(5) A, which falls between the free ethylene value of 1.3391(13) A and the ethane value of 1.534(2) A. The angle between the plane of the CH2 group and the extended ethylene C-C bond ( angleout-of-plane) is 26.0(3) degrees , indicating that this complex is better described as a metallacyclopropane than as a pi-bonded olefin-metal complex. The Os-C-C-H dihedral angle is 106.7(2) degrees , indicating that the ethylene carbon atoms have near sp3 character in the complex. Kraitchman analysis of the available rotational constants gave principal axis coordinates for the carbon and hydrogen atoms in excellent agreement with the least-squares fit results. The new results on this osmium complex are compared with earlier work on the similar complex, tetracarbonylethyleneiron (Fe(CO)4(eta2-C2H4)). The ethylene structural changes upon coordination to the metal are found to be larger for the ethylene-osmium complex than for the analogous ethylene-iron complex, consistent with the expected greater pi donation for the osmium atom.

Activation of Metal Hydride Complexes by Tri-tert-butylphosphine-Platinum and -Palladium Groups

The compounds HM(CO)4SnPh3, M = Os (10), Ru (11) are activated in the presence of Pt(PBut3)2 and Pd(PBu(t)3)2 toward the insertion of PhC2H into the M-H bond. The compounds PtOs(CO)4(SnPh3)(PBu(t)3)[mu-HCC(H)Ph], 12, and PtOs(CO)4(SnPh3)(PBu(t)3)[mu-H2CCPh], 13, were obtained from the reaction of 10 with PhC2H in the presence of Pt(PBu(t)3)2. Compounds 12 and 13 are isomers containing alkenyl ligands formed by the insertion of the PhC2H molecule into the Os-H bond at both the substituted and unsubstituted carbon atoms of the alkyne. Both compounds contain a Pt(PBu(t)3) group that is bonded to the osmium atom and a bridging alkenyl ligand that is pi-bonded to the osmium atom. The reaction of 11 with PhC2H in the presence of Pt(PBu(t)3)2 yielded the products PtRu(CO)4(SnPh3)(PBu(t)3)[mu-HC2(H)Ph], 14, and PtRu(CO)4(SnPh3)(PBut3)[mu-H2C2Ph], 15, which are also isomers similar to 12 and 13. The reaction of 11 with PhC2H in the presence of Pd(PBu(t)3)2 yielded the product PdRu(CO)4(SnPh3)(PBu(t)3)[mu-H2C2Ph], 16. Compound 16 contains a Pd(PBu(t)3) group bonded to the ruthenium atom and a bridging H2C2Ph ligand that is pi-bonded to the palladium atom. Compound 10 reacted with Pt(PBu(t)3)2 in the absence of PhC2H to yield the compound PtOs(CO)4(SnPh3)(PBu(t)3)(mu-H), 17. Compound 17 is a Pt(PBu(t)3) adduct of 10. It contains a Pt-Os bond with a bridging hydrido ligand. Compound 17 reacted with PhC2H to yield 12. Compound 12 reacted with PhC2H to yield the compound PtOs(CO)3(SnPh3)(PBu(t)3)[mu-HCC(Ph)C(H)C(H)Ph], 18. Compound 18 contains a bridging 2,4-diphenylbutadienyl ligand, HCC(Ph)C(H)C(H)Ph, that is pi-bonded to the osmium atom and sigma-bonded to the platinum atom. Fenkse-Hall molecular orbitals of 17 were calculated. The LUMO of 17 exhibits an empty orbital on the platinum atom that appears to be the most likely site for PhC2H addition prior to its insertion into the Os-H bond.

Synthesis and structure of the [OsThio 6]Br3 · H2O complex

A complex of the composition [OsThio 6]Br3 · H2O is synthesized by the reaction of H2OsBr6 with thiourea in a 0.5 M HBr solution. The [OsThio 6]Br3 · H2O complex is characterized using electronic absorption and infrared spectroscopy. The structure of the complex is determined by X-ray diffraction analysis. The crystals are orthorhombic with the unit cell parameters a = 20.510(4) A, b = 11.186(2) A, c = 11.892(2) A, space group Pccn, and Z = 4. The thiourea molecules are coordinated to the osmium atom through the sulfur atom. The osmium atom has an octahedral coordination. The Os-S distances fall in the range 2.39–2.40 A. The outersphere H2O molecules and Br− anions are involved in hydrogen bonds with the NH2 groups of the thiourea molecules.

Crystal structure and properties of [OsO2(NH3)4]SO4 · H2O

The structure of a single crystal of tetraammindioxoosmium(VI) sulfate [OsO2(NH3)4]SO4 · H2O, which is synthesized by the reaction of K2[OsO2(OH)4] with (NH4)2SO4 in an aqueous solution, is investigated using X-ray diffraction analysis. The compound crystallizes in the monoclinic crystal system, space group P21/c, a = 13.102(2) A, b = 6.158(3) A, c = 11.866(2) A, β = 98.13(2)°, and Z = 4. The [OsO2(NH3)4]SO4 · H2O compound has an island structure. Two crystallographically independent osmium atoms are situated at the centers of symmetry, and their octahedral coordination includes two oxygen atoms and four nitrogen atoms of the ammonia molecules. In both octahedra, the osmyl group is linear. The Os-O distances in the octahedra are identical within the standard deviations [Os(1)-O, 1.762(2) A; Os(2)-O, 1.769(2) A]. The Os-N bond lengths vary from 2.082(3) to 2.101(3) A. The cationic complexes, SO4 groups, and water molecules are linked via the system of hydrogen bonds. The assignment of the absorption bands in the IR spectrum of the compound synthesized is performed, and its thermal behavior in air is studied.

Preparation and Characterization of Novel Os−Diolefin Dimers: New Entry to Os−Cyclooctadiene Complexes

The complex [H(EtOH)2][{OsCl(eta4-COD)}2(mu-H)(mu-Cl)2] (1) has been prepared in high yield by treatment of OsCl3.3H2O (54% Os) with 1,5-cyclooctadiene in ethanol under reflux. Under air, it is unstable and undergoes oxidation by action of O2 to afford the neutral derivative {OsCl(eta4-COD)}2(mu-H)(mu-Cl)2 (2). The terminal chlorine ligands of the anion of 1 are activated toward nucleophilic substitution. Thus, reaction of the salt [NBu4][{OsCl(eta4-COD)}2(mu-H)(mu-Cl)2] (1a) with NaCp in toluene gives [NBu4][{Os(mu1-C5H5)(eta4-COD)}(mu-H)(mu-Cl)2{OsCl(eta4-COD)}] (3) as a result of the replacement of one of the terminal chlorine atoms by the cyclopentadienyl ligand. The CH2 group of the latter can be deprotonated by the bridging methoxy ligand of the iridium dimer [Ir(mu-OMe)(eta4-COD)]2. The reaction leads to the trinuclear derivative [NBu4][{(eta4-COD)Ir(mu5-C5H4-mu1)Os(eta4-COD)}(mu-H)(mu-Cl)2{OsCl(eta4-COD)}] (4) containing a bridging C5H4 ligand that is eta1-coordinated to an osmium atom of the dimeric unit and mu5-coordinated to the Ir(eta4-COD) moiety. Salt 1a also reacts with LiC[triple bond]CPh. In this case, the reaction produces the substitution of both terminal chlorine ligands to afford the bis(alkynyl) derivative [NBu4][{Os(C[triple bond]CPh)(eta4-COD)}2(mu-H)(mu-Cl)2] (5). Complexes 1, 2, 3, and 4 have been characterized by X-ray diffraction analysis. Although the separations between the osmium atoms are short, between 2.6696(4) and 2.8633(5) A, theoretical calculations indicate that only in 2 is there direct metal-metal interaction, as the bond order is 0.5.

Synthesis, Crystal Structure and Magnetic Properties of Na3OsO5

AbstractNa3OsO5 has been synthesized by solid state reaction of Na2O2 and osmium powder under a flow of oxygen. Na3OsO5 crystallizes trigonal in space group P3121 with a = 5.5529(2) Å, c = 13.4726(8) Å, V = 359.77(3) Å3, Z = 3, 958 independent reflections, R1 = 1,97 %, wR2 = 4.27 %. The crystal structure consists of OsO5 trigonal bipyramids separated by sodium cations, and is isostructural to Na3ReO5. The osmium atoms adopt a packing analogous to ccp, where Na occupies the octahedral and tetrahedral vacancies, so the cation structure is derived from the Li3Bi structure type. Features of the synthesis of Na3OsO5 and related osmates are discussed. Na3OsO5 shows paramagnetic behaviour down to 25 K where it orders antiferromagnetically. Below 7 K a weak ferromagnetic contribution is detected. The paramagnetic region of the 5d1 system has been successfully described in the temperature range 50 – 330 K accounting for strong spin‐orbit coupling, ligand‐field potential of D3h symmetry (corresponding to the trigonal bipyramidal $\rm OsO^{3-}_{5}$ unit), and cooperative magnetic effects (molecular field parameter λMF).

Platinum Promoted Insertion of an Alkyne into a Metal−Hydrogen Bond

HOs(CO)4SnPh3, 1 reacts with PhC2H in the presence to Pt(PBut3)2 to yield the alkyne insertion product PtOs(CO)4(SnPh3)(PBut3)[mu-HC2(H)Ph], 2 containing a Pt(PBut3)(CO) group coordinated to the osmium atom and the alkenyl ligand. In the absence of PhC2H, 1 reacts with Pt(PBut3)2 to form a Pt(PBut3) adduct, PtOs(CO)4(SnPh3)(PBut3)(mu-H), 3 at the Os-H bond. This adduct is readily transformed to 2 upon reaction with PhC2H. In the absence of the Pt(PBut3) promoter, PhC2H does not react with 1.

Syntheses, Structures, and Electrochemical Properties of Os3(CO)9-n(CNCH2Ph)n(μ3-η2:η2:η2-C60) (n = 2−4)

Benzyl isocyanide-substituted C60-triosmium complexes, Os3(CO)9-n(CNCH2Ph)n(μ3-η2:η2:η2-C60) (n = 2 (3), 3 (4), and 4 (5)), have been prepared by reactions of either Os3(CO)9(μ3-η2:η2:η2-C60) (1) or its lesser isocyanide-substituted complexes with appropriate amounts of (triphenylphosphino)benzylimine (PhCH2NPPh3). Compounds 3−5 have been characterized by spectroscopic (IR, MS, 1H and 13C NMR) methods, cyclic voltammetry, and X-ray diffraction studies. Single-crystal X-ray diffraction studies reveal that isomer 3a has two inequivalent equatorial isocyanide ligands as a cis,trans-1,2-isomer and isomer 4a has three equivalent equatorial isocyanide ligands as a 1,2,3-isomer with C3 symmetry. In compound 5, one benzyl isocyanide is axially coordinated to an osmium atom, whereas the other three benzyl isocyanide ligands are equatorially coordinated to each osmium atom. 1H and 13C NMR data, however, indicate that compound 3 exists as a mixture of 1,2- (3a) and 1,1-isomers (3b) in a ratio of 7:1, compound 4 as a mixture of 1,2,3- (4a) and 1,1,2-isomers (4b) in a ratio of 1:1, and compound 5, interestingly, as a single species of a 1,1,2,3-isomer in solution. The cyclic voltammetric studies reveal that all the CVs of 3−5 and related Os3(CO)8(CNCH2Ph)(μ3-η2:η2:η2-C60) (2) show four reversible redox waves that correspond to a one-electron process each with the third and fourth waves overlapped within the chlorobenzene solvent potential window. As more isocyanide ligands are coordinated in 2−5, all the corresponding half-wave potentials are gradually shifted to more negative potentials, reflecting the electron-donor property of the isocyanide ligand. Furthermore, C60-mediated electron delocalization from C60 to the triosmium center takes place in the trianionic species of 2−5. The two isomers of 3 and 4 apparently undergo an equivalent electrochemical process, respectively.

Cluster Fragmentation and Facile Cleavage of Phenyl Groups from the SnPh3Ligand in Reactions of Os3(CO)11(SnPh3)(μ-H) with CO and HSnPh3

Two new cluster complexes, Os3(CO)12(Ph)(μ3-SnPh), 8 (35% yield), and Os4(CO)16(μ4-Sn), 9 (10% yield), were formed when the complex Os3(CO)11(SnPh3)(μ-H), 6, was heated to reflux in toluene solvent under a CO atmosphere. Compound 8 was transformed to 9 in 28% yield when a solution in octane solvent was heated to reflux under a CO atmosphere. Biphenyl was a coproduct in this reaction. Compound 8 contains three osmium atoms with a triply bridging SnPh group. The triosmium cluster has opened and there is only one Os−Os bond between the three osmium atoms. Compound 9 contains two Os2(CO)8 groups held together by a central quadruply bridging tin atom, giving an overall bow-tie structure for the five metal atoms. Two other new compounds, Os2(CO)6(μ-SnPh2)2(SnPh3)2, 10, and HOs(CO)4(SnPh3), 11, were formed in 51% and 20% yields, respectively, from the reaction of 6 with HSnPh3. Compound 10 contains only two osmium atoms linked by an Os−Os bond and two bridging SnPh2 ligands. Each osmium atom also contains one te...

Syntheses and Electronic Behaviors of Osmium‐Organic Moiety Hybrid Materials

Several alternating osmium‐organic moiety hybrid materials were prepared by reacting osmium chloride with organic diols and dithiols. Osmium‐organic moiety units over 60% were thought to be involved in the materials. ESR and XPS spectral analyses indicated that an electron transfer from an organic phenylene moiety to the osmium atom with a partial reduction of the osmium atom took place.

A New Tris(diphenylstannylene)triosmium Carbonyl Cluster Complex and Its Reactions with Pt(PBut3)2and Pt(PPh3)4

The reaction of Os3(CO)12 with Ph3SnH yielded the bimetallic Os−Sn cluster complexes Os3(CO)11(SnPh3)(μ-H) (16) and Os3(CO)9(μ-SnPh2)3 (17) in 20 and 21% yields, respectively. Compound 16 consists of an Os3 triangle with a terminal SnPh3 group on one of the Os atoms and a bridging hydrido ligand across one of the Os−Os bonds. Compound 17 consists of a central Os3 triangle with SnPh2 groups bridging each of the three Os−Os bonds. Pt(PBut3)2 reacts with compound 17 to afford Os3(CO)9[Pt(PBut3)](μ-SnPh2)3 (18), a Pt(PBut3) adduct of 17, in 29% yield by adding a Pt(PBut3) group across one of the Os−Sn bonds. The osmium and tin atoms lie in a plane, while the Pt(PBut3) group is displaced slightly out of that plane. Pt(PPh3)4 reacts with 17 to give the cluster complex Os3(CO)9[Pt(Ph)(PPh3)2](μ-SnPh2)2(μ3-SnPh) (19) in 21% yield by insertion of a Pt(PPh3)2 into one of the Sn−C bonds to one of the phenyl groups. The osmium and tin atoms are coplanar, and there is a Pt(Ph)(PPh3)2 group terminally bonded to one of ...

Synthesis, characterization, and X-ray crystal structure of the octabromodiosmate(III) salt [(C 5Me 4H) 2OsBr] 2[Os 2Br 8] and its conversion to [(C 5Me 4H) 2OsBr][Os 2HBr 4(cod) 2

Treatment of hexabromoosmic acid, H 2OsBr 6, with 4 equiv. of tetramethylcyclopentadiene (C 5Me 4H 2) in tert-butanol at reflux for 8 h affords the unusual salt [(C 5Me 4H) 2OsBr] 2[Os 2Br 8], 1, which is the bis(tetramethylcyclopentadienyl)bromoosmocinium(IV) salt of the octabromodiosmate(III) dianion. The brown color of the salt suggests that the anion adopts an eclipsed conformation ( D 4 h symmetry) and this conclusion has been confirmed by a single-crystal X-ray diffraction experiment. The X-ray crystal structure indicates that the osmium atoms in the [ Os 2 Br 8 2 - ] anion are disordered over two sites. The bromine atoms show no evidence of disorder and are disposed in a quasi-cubic arrangement; the two Os–Os vectors are almost exactly orthogonal to each other and each vector points toward a different pair of opposite square faces of the Br 8 cube. The Os–Os bond distances are 2.219(5) and 2.229(1) Å; the average Os–Br distance in the anion is 2.417(2) Å. Treatment of [(C 5Me 4H) 2OsBr] 2[Os 2Br 8] with excess 1,5-cyclooctadiene in ethanol at gentle reflux for 3 h affords [(C 5Me 4H) 2OsBr][Os 2HBr 4(cod) 2], 2. An X-ray crystallographic study was carried out on a sample in which the cation was a mixture of [(C 5Me 4H) 2OsBr +] and [(C 5Me 4H) 2OsH +]. The results demonstrate that the anion adopts a confacial bioctahedral structure in which the hydride ligand and two bromides bridge between the two osmium centers. The C C bonds of the cod ligands are trans to the bridging bromide groups. The Os–Os bond distance in the anion is 2.874(1) Å. The average Os–Br distance is 2.596(2) Å for the bridging bromides and 2.565(2) Å for the terminal bromides. Compound 2 is the first example of an anionic diosmium complex containing a bridging hydride. The reaction of 1 with cod also results in the formation of bis(tetramethylcyclopentadienyl)osmocene, (C 5Me 4H) 2Os, 3, which has been isolated and characterized. Treatment of (C 5Me 4H) 2Os with 1.0 equiv. of HBF 4 · Et 2O affords the osmocinium salt [(C 5Me 4H) 2OsH][BF 4].

Synthesis of [{Os 3(CO) 10(μ 2-H)} 2{μ 2,μ 2-NC 6H 4C 6H 4N}] and [{Os 3(CO) 9(μ 2-H)PPh 3} 2{μ 2,μ 2-NC 6H 4C 6H 4N}]: Carbon–carbon bond formation promoted by organorhodium species

Synthesis and characterization of linked cluster [{Os 3(CO) 10(μ 2-H)} 2{μ 2,μ 2-NC 6H 4C 6H 4N}] ( 1) from the reaction of [Os 3Rh(μ-H) 3(CO) 12] with aniline in the presence of an excess amount of 4-vinyl phenol in refluxing heptane is reported. A similar reaction with [Os 3(CO) 10(NCMe) 2] as starting material gave a known compound, [Os 3(CO) 10(μ 2-H)(μ 2-HNC 6H 5)] ( 2). The treatment of complexes 1 and 2 with Wilkinson’s catalyst in refluxing heptane respectively, yielded [{Os 3(CO) 9(μ 2-H)PPh 3} 2{μ 2,μ 2-NC 6H 4C 6H 4N}] ( 3). An interesting and unexpected C–C coupling of phenyl-amido ligands was observed in complexes 1 and 3, which is believed to be catalysed by the organometallic rhodium species. The newly synthesized compounds 1 and 3 were fully characterized by IR, 1H NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray crystallography. Both structures 1 and 3 comprise two triangles of osmium atoms. The two triangular osmium metal cores are linked by a bi-amido ligand via the two nitrogen atoms N(1) and N(1)* and N(1) and N(2), at their equatorial sites. The electronic absorption spectra of complexes 1, 2, and 3 display both low energy absorption, dπ (Os) → π* (amido) metal-to-ligand charge-transfer (MLCT) transition, and π → π* intra-ligand electronic transitions of the amido and bi-amido ligands.

Synthesis and characterisation of the carboxylate linked osmium clusters [{Os 3H(CO) 10} 2(CO 2CH 2CO 2)], [{Os 3H(CO) 10} 2(CO 2C 2H 4CO 2)], [{Os 3H(CO) 10} 2(C 4O 4)] and [{Os 3H(CO) 10} 2(C 4O 4){Co 2(CO) 6}

Reactions between the activated cluster [Os 3(CO) 10(NCMe) 2] and malonic acid, succinic acid and dicarboxylic acetylene, respectively, lead to the formation of the linked cluster complexes [{Os 3H(CO) 10} 2(CO 2CH 2CO 2)] ( 1), [{Os 3H(CO) 10} 2(CO 2C 2H 4CO 2)] ( 2), and [{Os 3H(CO) 10} 2(C 4O 4)] ( 3) in good yield. Cluster 3 was subsequently treated with [Co 2(CO) 8] and this results in the addition of a “Co 2(CO) 6” group giving [{Os 3H(CO) 10} 2(C 2O 4){Co 2(CO) 6}] ( 4). The X-ray crystal structures are reported for 2– 4. In each structure the two triangular triosmium units are linked by the carboxylate groups and within each complex the carboxylate groups are chelating and bridge two osmium atoms.

Triosmium and triruthenium clusters containing morpholine ligand: X-ray structure of Os3(CO)10(μ-η2-NC4H6O)(μ-H)

Treatment of the labile cluster Os3(CO)10(CH3CN)2 with morpholine in benzene at 60∘C afforded Os3(CO)10(μ-η2-NC4H6O)(μ-H) (1). Decarbonylation of 1 at 128∘C gave Os3(CO)9(μ3-η2-NC4H6O)(μ-H) (2), which reacts with PPh3 at ambient temperature to give an addition product Os3(CO)9(μ-η2-NC4H6O)(PPh3)(μ-H) (3). Compound 1 reacted with PPh3 at 98∘C to give the substitution product 4 which is an isomer of 3. The reaction of Ru3(CO)12 with morpholine in the presence of Me3NO in refluxing benzene at 80∘C afforded Ru3(CO)9(μ3-η2-NC4H6O)(μ-H) (5). Compounds 1– 5 have been characterized by elemental analysis, infrared, 1H NMR, and mass spectroscopic data. The molecular structure of 1 has been determined by single crystal X-ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group P2/c with a = 29.598(8) A, b = 9.202(2) A, c = 14.496(4) A, β = 93.19(3)∘, Z = 8, and V = 3942(2) A3. Compound 1 consists of an isosceles triangle of osmium atoms with one elongated Os–Os edge, which is bridged by the hydride and the morpholine ligand.

Ligand substitution in the heterometallic cluster Cp*IrOs 3(μ-H) 2(CO) 10

The reactions of the heterometallic cluster Cp*IrOs 3(μ-H) 2(CO) 10 with phosphines, isonitriles and pyridine under TMNO activation afforded the substitution products Cp*IrOs 3(μ-H) 2(CO) 10− n L n ( n = 1, 2; L = PPh 3, P(OMe) 3, t BuNC, CyNC or py) in good yields. For the monosubstituted derivatives, the substitution site was exclusively at an osmium atom in an axial position for L = phosphine or phosphite. Spectroscopic evidence suggested the presence of isomers in solution for the PPh 3 derivative. In contrast, for L = isonitrile, the ligand occupied an equatorial site. In the disubstituted derivatives, the group 15 ligands were coordinated to two different osmium atoms, one each at an axial and an equatorial site. The isomerism and fluxional behaviour of some of these clusters have also been examined.

Reactions of triosmium clusters with indole: X-ray structures of [Os3(CO)10(μ-OH)(μ-OMeCO)] and [Os3(μ-H)(CO)10(μ-1, 2-η2-NC8H6)

Treatment of [Os3(CO)12] with indole in presence of a methanolic solution of Me3NO⋅2H2O at 60∘C afforded the previously reported compounds [(μ-H)Os3(CO)10(μ-OMe)] 2, [(μ-H)Os3(CO)10(μ-OH)] 3 and [Os3(CO)10(μ-OH)(μ-OMeCO)] 4 in 10, 5 and 20% yields, respectively. The reaction of [Os3(CO)10(MeCN)2] with indole at room temperature gave [(μ-H)Os3(CO)10(μ-1,2-η2-NC8H6)] 5 in 40% yield. Compounds 4 and 5 have been characterized by single crystal X-ray diffraction studies. Compound 4 crystallizes in the monoclinic space group P2(1)/c with a = 23.1239(3), b = 9.8087(4), c = 16.9017(6) A, β = 92.6998(14)∘, Z = 8 and V = 3829.3(2) A3 and 5 crystallizes in the monoclinic space group P2(1)/c with a = 9.009(3), b = 9.764(4), c = 24.906(6) A, β = 93.452(14)∘, Z = 4 and V = 2186.9(13) A3. Compound 4 consists of an open cluster of three osmium atoms with the hydroxy and methoxycarbonyl ligands bridging the open Os–Os edge. Compound 5 consists of an isosceles triangle of osmium atoms with one elongated Os–Os edge which is bridged by the hydride and the indolyl ligands.

Synthesis, structures and reactivity of triosmium clusters containing terminal pyrazines, bridging hydroxy and methoxycarbonyl ligands

Four triosmium carbonyl clusters bearing terminal pyrazines, bridging hydroxy and methoxycarbonyl ligands of general formula [Os 3(CO) 9(μ-OH)(μ-OMeCO)L] ( 1, L = pyrazine; 2, L = 2-methylpyrazine; 3, L = 2,3-dimethylpyrazine; 4, L = 2,3,5-trimethylpyrazine) were synthesized by the reactions of [Os 3(CO) 12] with the corresponding pyrazine derivatives and water in the presence of a methanolic solution of Me 3NO in moderate yields. Compounds [Os 3(CO) 9(μ-OH)(μ-OMeCO)L] react with a series of two electron donor ligands, L′ at ambient temperature to give [Os 3(CO) 9(μ-OH)(μ-OMeCO)L′] ( 5, L′ = PPh 3; 6, L′ = P(OMe) 3; 7, L′ = t BuNC; 8, L′ = C 5H 5N) in good yields by the displacement of the pyrazine ligands. This implies that the pyrazine ligands in 1– 4 are relatively labile. Compounds 2, 3, 4, and 8 were characterized by single crystal X-ray diffraction analyses. All the four compounds possess two metal–metal bonds and a non-bonded separation of two osmium atoms defined by Os(1)⋯Os(3), which are simultaneously bridged by OH and MeOCO ligands and a heterocyclic ligand is terminally coordinated to one of the two non-bonded osmium atoms.

Reactions of Unsaturated Quinoline Triosmium Clusters [Os3(CO)9(μ3-η2-C9H5(4-R)N)(μ-H)] (R=Me or H) with Tetramethylthiourea: X-ray Structures of [Os3(CO)8(μ-η2-C9H5(4-Me)N)(η2-SC(NMe2NCH2Me)(μ-H)2] and [Os3(CO)9(μ-η2-C9H6N)(η1-SC(NMe2)2)(μ-H)

Treatment of the electronically unsaturated 4-methylquinoline triosmium cluster \([\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_3\hbox{-}\upeta^{2}\hbox{-}\hbox{C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upmu\hbox{-H})]\) (1) with tetramethylthiourea in refluxing cyclohexane at 81°C gave \([\hbox{Os}_{3}\hbox{(CO)}_{8}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upeta^2\hbox{-SC}(\hbox{NMe}_2\hbox{NCH}_2\hbox{Me})(\upmu \hbox{-H})_2]\) (2) and \([\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N})(\upeta^1\hbox{-SC}(\hbox{NMe}_2)_2)(\upmu\hbox{-H})]\) (3). In contrast, a similar reaction of the corresponding quinoline compound \([\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_{3}\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upmu\hbox{-H})]\) (4) with tetramethylthiourea afforded \([\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upeta^{1}\hbox{-SC(NMe}_{2})_{2})(\upmu\hbox{-H)}]\) (5) as the only product. Compound 2 contains a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and a quinolyl ligand coordinated to the Os3 triangle via the nitrogen lone pair and the C(8) atom of the carbocyclic ring. In 3 and 5, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom, which is also bound to the carbon atom of the quinolyl ligand. Compounds 3 and 5 react with PPh3 at room temperature to give the previously reported phosphine substituted products \([\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N)(PPh}_{3})(\upmu\hbox{-H)}]\) (6) and \([\hbox{Os}_{3}\hbox{(CO}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N)(PPh}_{3})(\upmu\hbox{-H)}]\) (7) by the displacement of the tetramethylthiourea ligand.

Synthesis, characterisation and natural abundance 187Os NMR spectroscopy of hydride bridged triosmium clusters with chiral diphosphine ligands

Treatment of [Os 3(μ-H) 2(CO) 10] with the chiral diphosphines BINAP, tolBINAP [( R)-2,2′-bis(di-4-tolylphosphino)-1,1′-binaphthyl], DIOP [(4 R,5 R)-(−)- O-isopropenylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane] affords [Os 3(μ-H) 2(CO) 8(μ-L)] (L = BINAP ( 1), tolBINAP ( 2), DIOP ( 4)) in high yield. The X-ray structures for 1, 2 and 4 are reported, and structural and spectroscopic comparisons are made between these clusters and [Os 3(μ-H) 2(CO) 8(μ-L)] (L = dppm ( 5), dppe ( 6), dppp ( 7)) which were synthesised similarly. Compounds 5 to 7 were previously synthesised by hydrogenation of 1,2-[Os 3(CO) 10(μ-L)] but the route from [Os 3(μ-H) 2(CO) 10] is preferable. The H-bridged Os⋯Os distances are similar in 1, 2 and 4 indicating that these species are formally unsaturated 46-electron clusters. The P⋯P distances vary from 4.24 to 4.30 Å in 1 and 2, respectively, to 4.53 Å in 4 and there are related changes in the angles associated with the ligand set around the H-bridged osmium atoms. Introduction of the diphosphine ligands completely suppresses the ability to add CO, to insert acetylene to form a μ-η 1,η 2-vinyl compound, and to exchange hydride ligands with styrene-d 8, which are reactions characteristic of [Os 3(μ-H) 2(CO) 10]. Clusters 2 and 5– 7 were also used to examine the potential of natural abundance 187Os NMR spectroscopy through techniques based on inverse detection by HMQC, HSQC and HMBC spectroscopy.