Spectroscopic studies on silica-supported Os3(CO)12

The formation of the silica-supported cluster HO_s3(CO)₁₀(OSi{ie}) from adsorbed Os₃(CO)₁₂ has been studied in situ by FT-i.r., u.v.-vis reflectance and X-ray photoelectron spectroscopy. The grafted cluster can be formed quantitatively by a slow reaction at 373 K in N2 and no intermediate is involved. Well-resolved u.v,-vis spectra are obtained provided the osmium-to-silica ratio is 1 wt% Os or less. Marked increase in absorption accompanies the anchoring of the cluster to the oxygen the surface. An increase in Os oxidation state is confirmed by XPS. Retention of the Osa cluster framework in the grafted state has been chemically supported by observing displacement in HF solution and stoichiometric formation of HO_s3(CO)₁₀OH, showing at the same time the advantage of surface-mediated preparation of organometallic derivatives.     

Fluorination of [Os3(CO)12] and [Ir4(CO)12

Fluorination of [Os(3)CO(12)] in HF/SbF(5) affords [Os(CO)(4)(FSbF(5))(2)]. According to its crystal structure (orthorhombic, Pna2(1), a = 1590.3(3), b = 1036.6(1), c = 878.2(2) pm, Z = 4), the two SbF(6) units occupy cis positions in the octahedral environment around the Os atom. Fluorination of [Ir(4)(CO)(12)] in HF/SbF(5) produced three different compounds: (1) [Ir(4)(CO)(8)(mu-F)(2)(Sb(2)F(11))(2)] (tetragonal, P4n2, a = 1285.2(2), c = 952.9(1) pm, Z = 2). Here, two of the six edges of the Ir(4) tetrahedron in [Ir(4)CO(12)] are replaced by bridging fluorine atoms. (2) [fac-Ir(CO)(3)(FSbF(5))(2)HF]SbF(6).HF (orthorhombic, Pnma, a = 1250.6(1), b = 1340.7(2), c = 1092.6(2) ppm, Z = 4). The Ir(4) tetrahedron in Ir(4)(CO)(12) is completely broken down, but the facial Ir(CO)(3) configuration is retained. (3) [mer-Ir(CO)(3)F(FSbF(5))(2)] (triclinic, P1, a = 834.9(1), b = 86 4.9(1), c = 1060.0(1) pm, alpha = 69.173(4) degrees, beta = 77.139(4) degrees, gamma = 88.856(4) degrees, Z = 2).     

Chirality and Relativistic Effects in Os3(CO)12

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os₃(CO)₁₂ with D_3h and D₃ symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os₃(CO)₁₂ corresponds to the D₃ symmetry and thus may be characterized either as left-twisted (D_3S) or right-twisted (D_3R). The D_3S↔D_3R transitions occur through the D_3h transition state with an activation barrier of ~10^–14 kJ/mol. Parity violation energy difference (PVED) between D_3S and D_3R states equals to ~5 × 10⁻¹⁰ kJ/mol. An unusual three-center exchange interaction was found inside the {Os₃} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster.     

Di- and tri-nuclear osmium carbonyl chloride complexes: x-ray structures of Os2(CO)8Cl2 and Os3(CO)12Cl2

Summary Os₂(CO)₈Cl₂ (1) is orthorhombic P2₁2₁2₁ witha=9.3599(9),b=9.879(2),c=16.014(3), V=1480³, D_c=3.03 Mgm^–3 for Z=4. Structure solved by Patterson methods. Final R=0.038, R_w=0.038 [w=(²F)] for 1270 observed reflections and 141 parameters. Os₃(CO)₁₂Cl₂ (2) is monoclinic C2/m witha=12.105(3), b=10.612(3),c=8.798(1) , =117.02(2)°, V=1006³, D_c=3.22 Mgm^–3 for Z=2. Structure solved by Patterson methods. Final R=0.036, R_w=0.037 (w=(²F)^–) for 821 observed reflections and 75 parameters.Complex(1) has an osmium-osmium single bond 2.897(1), with the chloride ligands in equatorial positions,(2) has a linear triosmium chain with osmium-osmium single bonds 2.893(1) and the chloride ligands occupy equatorial sites on the terminal osmium atoms. Both(1) and(2) are isostructural with their osmium carbonyl iodide analogues.     

Reactions of triosmium clusters with organic azides; x-ray crystal structures of [Os3(CO)10(NCMe)(N3COPh)], [Os3(μ-H)(CO)10(HN3Ph)], and [Os3(μ-H)2(CO)9(μ3-NPh)]

Organic azides [N₃R] react with [Os₃(CO)₁₁(NCMe)] and with [Os₃(μ-H)₂(CO)₁₀] to form [Os₃(CO)₁₀(NCMe)(N₃COR)] (R  Ph) and [Os₃(μ-H)(CO)₁₀(HN₃R)] (R  Ph, n-Bu, CH₂Ph, cyclo-C₆H₁₁), respectively; the latter may be converted to [Os₃(μ-H)₂(CO)₉(μ₃-NR)] by thermolysis; the molecular structure of the phenyl derivative of each class of compound has been confirmed by x-ray analysis.     

Steric and Electronic Influences in Os3(CO)11(PR3) Structures

The structures of Os₃(CO)₁₁(PR₃) with R=F, OPh, Et, p-C₆H₄Me, o-C₆H₄Me, p-C₆H₄(CF₃) and C₆H₁₁, and with PR₃=P(OCH₂)₃CMe have been determined. The Os–Os bond lengths in these compounds are compared to the Os–Os lengths for the other structures of Os₃(CO)₁₁(PR₃) clusters reported in the literature. In most cases, the Os–Os bond length remote from the P ligand [range, 2.8666(4)–2.9044(4) Å] and that in the pseudo-trans position [range, 2.8712(5)–2.900(1) Å] show little variation as the steric and electronic properties of the P ligand are varied. The Os–Os length cis to PR₃ shows more variation [range, 2.879(1)–2.9429(4) Å] and is sensitive to both the size and the -donor/-acceptor properties of the PR₃ ligand: larger or better donor PR₃ ligands cause an increase in the Os–Os bond length. The Os–P distances [range, 2.15(2)–2.478(1) Å] show a similar dependence on the steric and electronic properties of the PR₃ ligand.     

Synthesis, Structure, and Nonrigidity of Os7(CO)20(CNBu t )

The cluster Os₇(CO)₂₀(CNBu ^t ) (1) has been prepared in 25% yield by the reaction of Os₆(CO)₁₈ with Me₃NO and Os(CO)₄(CNBu ^t ) at –78°C. The crystal structure of 1 reveals the expected capped octahedral arrangement of metal atoms with the noncarbonyl ligand attached to the capping Os atom. The OsOs lengths in the two independent molecules in the unit cell are in the range 2.823(1)–2.922(1) Å, with the longer bonds associated with the Os₃ triangle farthest from the capping Os atom. The ¹³C NMR spectrum of 1 in solution at room temperature has a 3:3:1 pattern that is consistent with rotation of the individual Os(CO)₂(L) (L=CO or CNBu ^t ) groups in the cluster. This in turn supports the idea that the capping Os(CO)₂(CNBu ^t ) unit binds to the central Os₆ via a centrally directed MO plus two tangential molecular orbitals.     

Determination of (187)Os in molybdenite by ICP-MS with neutron-induced (186)Os and (188)Os spikes

The article describes a method for the determination of (187)Os in molybdenite by isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) with neutron-induced (186)Os and (188)Os spike. The spike used in the present work was prepared in line with the principle by which artificial nuclides are produced in a nuclear reaction. The concentration and isotopic composition of osmium in the prepared spike were evaluated accurately with the isotope dilution method, using negative thermal ion mass spectrometry (N-TIMS). The advantage of this method is that using (186)Os and (188)Os double spikes can effectively compensate for the mass discrimination effects of ICP-MS. Thus, the common correction practice for mass bias in the isotope dilution method with a single spike is unnecessary. In addition, the method enables one to reduce the determined error arising from instrumental instability. The precision for the (187)Os/((186)Os+(188)Os) ratio was approximately 2% (2sigma, RSD), but in the case of (187)Os/(186)Os, (187)Os/(188)Os and (186)Os/(188)Os, precision ranged from 2.0 to 8% (2sigma, RSD). The results for (187)Os concentration in a molybdenite sample determined with this method showed good agreement with reference values.     

The reaction of H2Os5(CO)15 with nucleophilic reagents

The reaction of H₂Os₅(CO)₁₅ with nucleophiles Y leads either to deprotonation (Y = OH^? or Me^?) or addition (Y = I^?, P(OMe)₃, or CO). The geometrical consequences of these reactions are discussed.     

Homoleptic mononuclear and binuclear osmium carbonyls Os(CO)n(n = 3-5) and Os2(CO)n (n = 8, 9): comparison with the iron analogues

The structures and energetics of the experimentally known Os(CO)n ( n = 3-5), Os2(CO)9, and Os2(CO)8 have been investigated using density functional theory. For Os(CO)5, the lowest-energy structure is the singlet D(3h) trigonal bipyramid. However, the C(4v) square pyramid for Os(CO)5 lies only approximately 1.5 kcal/mol higher in energy, suggesting extraordinary fluxionality. For the coordinatively unsaturated Os(CO)4 and Os(CO)3, a D(2d) strongly distorted tetrahedral structure and a Cs bent T-shaped structure are the lowest-energy structures, respectively. For Os2(CO)9, the experimentally observed singly bridged Os2(CO)8(mu-CO) structure is the lowest-energy structure. A triply bridged Os2(CO)6(mu-CO)3 structure analogous to the known Fe2(CO)9 structure is a transition state rather than a true minimum and collapses to the singly bridged global minimum structure upon following the corresponding normal mode. An unbridged (OC)5Os --> Os(CO)4 structure with a formal Os --> Os dative bond analogous to known stable complexes of the type (R3P)2(OC)3Os --> W(CO)5 is also found for Os2(CO)9 within 8 kcal/mol of the global minimum. The global minimum for the coordinatively unsaturated Os2(CO)8 is a singly bridged (OC)4Os(mu-CO)Os(CO)3 structure derived from the Os2(CO)9 global minimum by loss of a terminal carbonyl group. However, the unbridged structure for Os2(CO)8 observed in low-temperature matrix experiments lies only approximately 1 kcal/mol above this global minimum. In all cases, the triplet structures for these osmium carbonyls have significantly higher energies than the corresponding singlet structures.     

Reaction of [Os3(CO)10(NCMe)2] with amides and aldehydes; X-ray crystal structure of [Os3(CO)10(μ-H)(COCH2Ph)]

Reaction of [OS₃(CO)₁₀(NCMe)₂] with amides and aldehydes has provided a high-yield route to clusters of the type [OS₃(CO)₁₀H(NHCOR)] (R  H, Me, Ph, Et, Pr) and [OS₃(CO)₁₀H(COR)] (R  Me, Ph, CH₂Ph, C₆H₁₃), respectively; the molecular structure of [OS₃(CO)₁₀H(COCH₂Ph)] has been established by a single-crystal X-ray analysis.     

Bridging versus chelating diphosphine in clusters: Isomers of Os3(CO)10(diphosphine)

Isomers of Os₃(CO)₁₀(diphosphine) (diphosphine = Ph₂P(CH₂)_nPPh₂; n = 2 (dppe), n = 3 (dppp), and n = 4 (dppb)) have been prepared in which the diphosphine is chelating (1,1-isomer) or bridging (1,2-isomer), respectively, by displacing butadiene or acetonitrile from the complexes Os₃(CO)₁₀(cis- or trans-C₄H₆) or Os₃(CO)₁₀(MeCN)₂. Ph₂PCH₂PPh₂ (dppm) gives only the known bridging (1,2-isomer) whichever starting material is used. Structures have been established by infrared, ³¹P and ¹³C NMR methods.     

Clusters containing carbene ligands. 12. The synthesis and transformations of Os3(CO)11[C(Et)NMe2], the first simple carbene derivative of Os3(CO)12

The carbonylation of Os₂(CO)₁₀[-CH₂N(Me)C(Et)](-H),1 at 110°C/1300 psi has yielded the carbene complex Os₃(CO)₁₁[C(Et)NMe₂],2, the first simple carbene derivative of Os₃(CO)₁₂, in 68% yield. Compound2 was characterized by a single crystal structure analysis which showed the position of a dimethylaminocarbene ligand in an equatorial coordination site. Compound2 is decarbonylated at 97°C to reform1 in 59% yield. Compound1 can be decarbonylated further at 125°C to yield the new compound Os₃(CO)₉ [₃-²-C(H)N(Me)C(Et)](-H)₂,3 in 94% yield. Compound3 was characterized by a crystal structure analysis and was shown to possess a triply bridging C(H)N(Me)C(Et) ligand containing two carbene centers. Compounds1 and2 can be regenerated from3 by carbonylation with CO at 110°C/800 psi. The facile activation of the N-methyl CH bonds of the carbene ligand of2 is produced by the metal atoms adjacent to the carbene coordination site, and may be a characteristic feature of the chemistry of carbene ligands in clusters. For2: space group=P ,a=11.407(2) Å,b=12.332(2) Å,c=8.602(1) Å, =103.92(1), =110.56(1)°, =82.57(1),Z=2, 2627 reflections,R=0.031; for3: space group=C2/c,a=17.160(3) Å,b=8.947(2) Å,c=27.034(6) Å, =97.82(1)°,Z=8, 2044 reflections,R=0.038.     

Synthesis and structure of [(OC)4Os(PbMe2)]2 and some derivatives of the type Os2(CO)7(SnMe2)2(L)

The complexes [(OC)₄Os(PbMe₂)]₂ (3) and [(OC)₄OsSnBu ₂ ]₂ (4) have been prepared from be reaction of Na₂[Os(CO)₄] with Me₂PbCl₂ and Bu ₂ SnCl₂, respectively, in THF and their X-ray crystal structures determined. The red derivative,3, was light-sensitive in solution. The reactions or [(OC)₄ Os(SnMe₂)]₂ (2), or its decarbonylated derivative [Os₃(CO)₇(SnMe₂)₂]₂ (7), with olefins or phosphorus donor ligands have also been investigated, and the structures of two derivatives, viz. [Os₂(CO)₇(SnMe₂)₂(C₂H₄)] (5a) and [Os₂(CO)₇(SnMe₂)₂(PMe₃)] (6a), have been determined; the noncarbonyl ligand occupies an equatorial site in each case. The X-ray crystal structures of all these compounds, like those of [(OC)₄Os(EMe₂)]₂ (E=Ge (1), Sn (2)) which have been reported previously, show leaning of the axial carbonyl ligands toward the metal tetracycle, i.e., an umbrella effect. Crystallographic data for compound3: space group, P2₁/a;a=13.4404(13) Å,b=10.7494(14) A,c=148967(18) A,=98.204(9)°,R=0.035, 1983 observed reflections. For compound4: space group,P1;a=9.016(1) Å,b=9.370(1),c=11.334(1) A, =103.67(1)°,=100.30(1)°, =115.03(1)°, R=0.046, 2026 observed reflections. For compound5a: space group,P1;a=9.2933(11)Å,b=9.7181(3),c=12.2508(15) A, =89.21(1)°,=87.61(1)°, =86.13(1)°,R=0.038, 2770 observed reflections. For compound6a space groupP1:a=8.7244(9)Å,b=10.9318(6),c=13.2560(13) A, =87.815(6)°,=83.655(8)°, =82.343(6)°, R=0.030, 3497 observed reflections.     

Halogenation behaviour of bidentate ligand-bridged derivatives of [Ru3(CO)12] and [Os3(CO)12]

Reaction of the ligand-bridged derivatives [M₃(CO)₁₀{μ-(RO)₂PN(Et)P(OR)₂}] and [M₃(CO)₈{μ-(RO)₂PN(Et)P(OR)₂}₂] (M = Ru or Os; R = Me or Prⁱ) with halogens leads to the formation of cationic products [M₃(μ-X)(CO)₁₀{μ- (RO)₂PN(Et)P(OR)₂}]⁺ and [M₃(μ-X)(CO)₈{μ-(RO)₂PN(Et)P(OR)₂}₂]⁺ (X = Cl, Br or I) in which the halogen bridges an opened edge of the metal atom framework; the crystal structure of [Ru₃(μ-I)(CO)₈{μ-(MeO)₂PN(Et)P(OMe)₂}₂]PF₆ is reported.     

Kinetics and mechanisms of halide ion catalysis of CO substitution reactions in Os3(CO)12 and Ru3(CO)12 metal carbonyl clusters

The results of kinetic studies on ligand substitution in [M₃(CO)₁₁X]^– complexes (M = Ru, Os; X = Cl, Br, I) are summarized. The [Os₃(CO)₁₁X]^– complexes react with PPh₃ under mild conditions to initially yield monosubstituted products [Os₃(CO)₁₀(PPh₃)X]^–. The rate of CO substitution obeys a first-order equation with respect to the concentration of the complex and does not depend on the ligand concentration. The rates of the reactions decrease in the order Cl > Br > I withH values increasing from 15 to 18 kcal mol^–1 and S values varying from –19 to –13 cal mol^–1 K^–1. The enhanced reactivities of these complexes as well as the low activation energies and negative activation entropies are discussed in terms of the effects of -X bridge formation on the transition state of the reaction. Reactions of PPN[Ru₃(CO)_11–x (Cl)] (PPN is the bis(triphenylphosphine)iminium cation;x=0, 1) and PPN[Ru₃(CO)₉(₃-I)] with alkynes are also reported. The reactivities of alkynes follow the order BuCCH PhCCH EtCCEt PhCCPh. The higher rates of the reactions of monosubstituted acetylenes compared with those of their disubstituted analogs are explained by agostic interaction between the metal atom and the C-H bond in the reaction transition state and by steric effects. The results obtained attest that the reaction with alkynes occursvia intermediates containing halide bridges and that ₃-halide complexes are more reactive than ₂-halide complexes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1540–1545, September, 1994.This work was supported by a Presidential Grant from Northwestern University. One of the authors (F. Basolo) wishes to thank Academician M. E. Vol'pin for the invitation to participate in the Workshop The Modern Problems of Organometallic Chemistry (INEOS-94) and Academician O. M. Nefedov for the invitation to publish a review in theRussian Chemical Bulletin.     

Novel butterfly tungsten-osmium carbido cluster Complexes from the reaction of Os3(CO)10(NCME)2 CPW(CO)3(CH2SMe)

Condensation of be triosmium acetonitrile complex Os₃(CO)₁₀(NCMe)₂ with the sulfido complex CpW(CO)₃(CH₂SMe) in refluxing THF solution produced three sulfur-containing compounds Os₃(C0)₁₀)(µ-H)(µ-SMe) (1), Os₃(CO)₁₁ [S(Me)CH₂W(CO)₃Cp] (2) and CpWOs₃(CO)₁₂(µ-CH₂)(µ-SMe) (3). Clusters 2 and 3 were products involving a 1:1 combination of starting materials and were characterized by X-ray diffraction studies. Crystals of 2 belongs to monoclinic space group P 2₁ /c witha=8.418(2),b = 11.912(2),c = 28.288 Å,=97.64(2)°,Z=4;R _F=0.044,R _W,=0.044. Crystal dara far 3: space group P 2₁/e,a 18.156(4).b=9.255(6),c = 15.347(4) Å. = 103.49(2)°,Z = 4;R _F -=0.047,R _W = 0.045. Upon thermolysis in toluene, the methylene cluster 3 released CO and induced C-H bond activation to afford two tetrametallic carbido clusters with formula CPWOS₃(CO)₉(µ₄-C)(µ-H)₂(µ-SMe) (4) and CPWOs₃(CO)₁₁(µ₄-C)(µ-SMe) (5) as the principle products. The first complex possesses a butterfly framework encapsulating a µ₄-C ligmd and a µ-SMe ligand linking a W-Os edge, whereas the second product adopts a puckered, cyclic arrangement of WOs₃ metal atoms with µ-SMe ligand located on a nonbonding Os-Os vector. Complex4 crystallizes in monoclinic space group P 2₁ /c witha=15.633(4) Å,b = 8.699 (3) Å,c=15.422(4) Å,=93.12(2)=°, Z=4,R=0.036,R _W =0.034 for 2780 observed reflections. Crystal data for5: space groupP nma,a=14.542(3),b=13.710(6),c=11.758(3) Å.Z=4,R _F =0.038,R _W = 0.037 for 1826 observed reflections. A variable temperature¹H NMR study was also presented to demonstrate the solution fluxionality of5.