Intramolecular rearrangement of the bridging σ,π-acetylide ligand in the Os3H(CO)9(L)(μ-η2-CCPh) (L = CO,PMe2Ph) clusters and crystal structure of Os3H(CO)9(PMe2Ph)(μ-η2-CCPh)

Clusters Os₃H(Cl)(CO)₉(L) (L= CO, PMe₂Ph) react with lithium phenyl-acetylide to yield Os₃H(CO)₉(L)(μ-η²-CCPh),which has a bridging acetylide ligand. The Os₃H(CO)₁₀(μ-η²-CCPh) complex (II) is fluxional owing to rapid π → σ, σ → π interchange of acetylide ligand between the bridged osmium atoms, whereas the phosphine-substituted derivative, Os₃H(CO)₉(PM₂Ph)(μ-η²-CCPh) (III), is stereochemically rigid and exists at room temperature in two isomeric forms. These isomers have been isolated as solids and have been characterized by ¹H and ³¹P{¹H} NMR spectroscopy. According to the spectroscopic data, in the major (IIIa) and minor (IIIb) isomers the phosphine ligand is coordinated to the metal atom which is σ- or π-bonded to the bridging acetylide group, respectively. The isomerization of IIIb into IIIa occurs only at 80°C. The structure of IIIa has been confirmed by an X-ray diffraction study.     

Studies on nucleophilic additions at bridging vinyl ligands in triosmium clusters

The bridging vinyl clusters [HOs₃(CHCHR)(CO)₁₀] (R = H, Ph, or n-Bu) react with PMe₂Ph to give the zwitterionic adducts [HOs₃(CHCHRPMe₂Ph)(CO)₁₀] which contain μ₂-alkylidene ligands. The adducts are not formed so readily when R = Ph or n-Bu but most readily when polar solvents are used. All three CHCHR complexes add cyanide ion irreversibly to give the anionic clusters which were isolated as [N(PPh₃)₂][HOs₃(CHCHRCN)(CO)₁₀]. There is infrared evidence for the addition of various other anions. Acid reverses the addition of methoxide but HCl reacts with the cyanide adduct [HOs₃(CHCH₂CN)(CO)₁₀]^? to give [HOs₃Cl(CO)₁₀] and EtCN. No evidence for nucleophilic addition at [HOs₃(PhCCHPh)(CO)₁₀] was obtained.     

The reaction of H2Os3(CO)10 with trifluoroacetonitrile and the x-ray crystal structure of HOs3(CO)9(μ3-η2-HNCCF3)

The reaction of H₂Os₃(CO)₁₀ with CF₃CN in hexane at 80°C leads to two isomeric products. The isomer constituting the major product contains a 1,1,1-tri-fluoroethylidenimido ligand which bridges one edge of the Os₃ triangle via the nitrogen, atom and may be formulated as (μ-H)Os₃(CO)₁₀(μ-NC(H)CF₃) (I). The minor product, formulated as (μ-H)Os₃(CO)₁₀(μ-η²-HNCCF₃) (II), contains a 1,1,1-trifluoroacetimidoyl ligand which is also edge-bridging, being N-bonded to one Os atom and C-bonded to the other. Thermolysis of I and II in solution results in loss of a CO group in each case to give (μ-H)Os₃(CO)_9^? (μ₃-η²-NC(H)CF₃) (III) and (μ-H)Os₃(CO)₉(μ₃-η²-HNCCF₃) (IV), respectively, which, it is proposed, are structurally related to I and II, but with the CN group coordinated also to the third Os atom in place of a CO group. In the case of IV this proposal has been confirmed by an X-ray crystallographic analysis. The compound crystallises in space group C2/c with a = 14.258(7), b = 13.486(10), c = 18.193(8) Å, β = 92.68(4)°, and Z = 8. The structure was solved by a combination of direct methods and Fourier difference techniques, and refined by full-matrix least squares to R = 0.054 for 2489 unique observed diffractometer data. Reaction of I with Et₃P gives a 1 : 2 adduct which is formulated as (μ-H)Os₃(CO)₁₀[μ-N?C(H)(CF₃)PEt₃] (V) on the basis of NMR evidence.     

Chemistry of vinylidene complexes: IV. Synthesis and the crystal and molecular structure of (η5-C5H5)MnOs3(μ2-CHCHPh)(μ-H)(μ-CO)(CO)11, an unusual heterometallic cluster

By the reaction of Cp(CO)₂MnCCHPh (I) with H₂Os₃(CO)₁₀ (II) the tetranuclear mixed-metal complex CpMnOs₃(μ₂-CHCHPh)(μ-H)(μ-CO)(CO)₁₁ (III) was prepared. An X-ray study of the structure of III showed that it is a spiked, tetranuclear cluster with the Mn atom linked to one of the vertices of the osmium triangle; the MnOs bond is bridged by CO and CHCHPh groups, the latter being σ-bonded to Os and η²-coordinated by Mn. In the course of the formation of III, hydrogenation and n-π rearrangement of the initial phenylvinylidene ligand take place. In solution, complex III readily eliminates the [CpMn(CO)₂] fragment to give triosmium clusters containing unsaturated organic ligands: HOs₃(μ₂-CHCHPh)(CO)₁₀, H₂Os₃(μ₃-CHCPh)(CO)₉, and H₂Os₃(μ₃-CCHPh)(CO)₉.     

Fragmentierung des schwefeldiimidsystems in tBu2PN=S=NPtBu2 an dreikernigen osmiumclustern. Synthese,feströrperstruktur und dynamische eigenschaften von Os3(CO)11[PtBu2(NH2)] und HOs3(CO)9PtBu2N(H)S]

The phosphino-substituted sulphur diimide, S(NP^tBu₂)₂, reacts with the trinuclear osmium clusters Os₃(CO)₁₁(NCMe) and H₂Os₃(CO)₁₀ with cleavage of one of the NS bonds to give the cluster compounds Os₃(CO)₁₁[P^tBu₂(NH₂)] (I) and HOs₃(CO)₉[P^tBu₂N(H)S] (II), respectively. In the solid state, I contains a closed Os₃ triangle with the phosphine ligand bonded equatorially to an osmium atom through the phosphorus. In solution intramolecular dynamic processes are observed which are explained by carbonyl migration and pseudoration mechanisms. The osmium cluster II, in the solid state, forms an irregular Os₃ triangle which is bridged by a [P^tBu₂N(H)S] system, and the longest edge of which is bridged by a μ₂-hydride. In contrast to I, molecule II is relatively rigid in solution; only pseudorotations are observed as dynamic phenomena.     

Addition reactions of a polynuclear osmium hydrido compound leading to associative carbonyl substitution and catalytic alkene isomerisation

The ability of H₂Os₃(CO)₁₀ to undergo addition reactions under mild conditions allows associative CO substitution via isolable intermediates of the type H₂Os₃(CO)₁₀ (L = CO, PMe₂Ph, PPh₃ or PhCN) whose spectra and structures are discussed. It is probable that simple addition of alkenes to H₂Os₃(CO)₁₀ is in part responsible for its facile catalysis of alkene isomerisation. The kinetics of catalytic conversion of terminal to internal alkenes and of allylic alcohols to aldehydes or ketones are reported and discussed. The reactions of H₂Os₃(CO)₁₀ with allylic halides to give the complexes HOs₃X(CO)₁₀ and Os₃X₂(CO)₁₀ where X = Cl, Br or I are described. Compound H₂Os₃(CO)₁₀ complies with the 18ρ-rule but nevertheless has a chemistry much like that of coordinatively unsaturated molecules.     

Activation of the carbon—nitrogen triple bond of benzonitrile in the presence of triosmium clusters and acetic acid. Crystal structure of (μ-H)Os3(CO)10(μ-O2CCH3), a product of the reaction

The activation of the CN triple bond of benzonitrile in the presence of acetic acid and of Os₃(CO)₁₂ or H₂Os₃(CO)₁₀ has been studied. When Os₃(CO)₁₂ reacts with PhCN and acetic acid in refluxing n-octane the three main products are (μ-H)Os₃(CO)₁₀(μ-O₂CCH₃) (I), (μ-H)Os₃(CO)₁₀(μ-NCHPh) (II) and (μ-H)Os₃(CO)₁₀(μ-NHCH₂Ph) (III); II and III are analogues of (μ-H)Ru₃(CO)₁₀(μ-NCHPh) and (μ-H)Ru₃(CO)₁₀(μ-NHCH₂Ph) obtained from PhCN, Ru₃(CO)₁₂ or H₄Ru₄(CO)]₁₂, and acetic acid. In contrast to the reaction with ruthenium clusters, Os₃(CO)₁₂ and H₂Os₃(CO)₁₀ also give the adduct Os₃(CO)₁₀(CH₃COOH) (I). The structure of I has been fully elucidated by X-ray diffraction. Crystals of I are monoclinic, space group P2₁/m, with unit cell parameters a 7.858(6), b 12.542(8), c 9.867(6) Å, β 109.92(2)°, Z = 2. In I an edge of the triangular cluster of osmium atoms is doubly bridged by a hydride and an acetate ligand. Ten terminal carbonyl groups are bonded to the metal atoms.     

The stereoselective reaction of sodium cyanide with the cationic ruthenium vinylidene complex [(η5-C5H5)(PMe3)2RuCC(Me)Ph]+

The reaction of sodium cyanide with [(η⁵-C₅H₅)(PMe₃)₂RuCC(Me)Ph]PF₆ (1) proceeds with high stereoselectivity (> 95 : 5) to give (Z)-(η⁵-C₅H₅)(PMe₃)₂RuC(CN)C(Me)Ph, which under acid conditions isomerises (< 5 : 95) to the E isomer.     

Zur reaktion von metallkoordiniertem kohlenmonoxid mit yliden: XIV. Eisenacyl-phosphor-ylide mit elektronenreicher organometallgruppierung

Treatment of [C₅Me₅(CO)₃Fe]BF₄ (I) with the phosphines Me₃P and Et₃P under thermal or photochemical conditions yields the novel iron salts [C₅Me₅-(CO)₂(R₃P)Fe]BF₄ (R = Me (IIa), R = Et (IIb)) and [C₅Me₅(CO)(Me₃P)₂Fe]BF₄ (IIc). The reaction of I and IIa with two mol of the ylide Me₃PCH₂ leads to the formation of the ironacyl-ylides C₅Me₅(CO)(L)FeC(O)CHPMe₃ (L = CO (IVa), Me₃P (IVb)). IVa selectively reacts at the “ylidic” carbon with the electrophilic reagents MeI, MeOSO₂F, Me₃SiOSO₂CF₃ to give the ironacyl-phosphonium salts [C₅Me₅(CO)₂FeC(O)CH(R)PMe₃] X (VaVc), while IVb is partially converted to [C₅Me₅(CO)₂FeC(O)CH₂PMe₃]BF₄ (IIIa) is obtained together with [C₅Me₅-(CO)₂Fe]₂ from I and IVa.     

η2-dithiomethyliron(II) ionic complexes. Evidence for a strong dependence on the nature of the trans-phosphorus ligands bonded to iron

Cationic η²-dithiomethyliron(II) complexes have been made by alkylation of the uncoordinated sulfur atom of Fe(CO)₂[η²-CS₂](L)₂. Surprisingly, only when the phosphorus ligands L are strong donors (PMe₃, PMe₂Ph) does coordination of iodide take place to give the neutral Fe(η²-CS₂CH₃)(I)(CO)(L)₂ derivatives. The ¹³C NMR spectra of the latter at 215 K indicated the presence of both isomers when L was PMe₂Ph. Reaction with iodine under carbon monoxide regenerated the cationic precursor.     

The partial hydrogenation of small unsaturated molecules by osmium cluster compounds. The reaction of diispropylcarbodiimide with H2Os3(CO)10

The products (μ-H)[μ-η²-(CH₃)₂CHNHCNCH(CH₃)₂]Os₃(CO)₁₀, I, and (μ-H)- [μ-η²-(CH₃)₂CHNHCO]Os₃(CO)₉[CNCH(CH₃)₂], II have been obtained from the reaction of H₂Os₃(CO)₁₀ with diisopropylcarbodiimine. Both products have been investigated by infrared and ¹H NMR spectroscopies, and by single crystal X-ray diffraction analyses. For I: Space group, P2₁/c, a12.840(4), b  15.724(4), c 12.638(4) Å, β 106.91(2)°, V  2441(2) ų, Z4, ? calc  2.66 g/cc. For 2869 reflections, R  0.051 and R_w  0.052. I contains an N-hydrido, N-isopropylamidinyl ligand bridging one edge of a triangular cluster of three osmium atoms. It was apparently formed by the incorporation of one carbodiimide molecule into the coordination sphere of the cluster followed by the transfer of one hydride ligand to one of the nitrogen atoms. For II: Space group P2 ₁/n;a  13.936(7), b  12.146(2), c  15.509(6) Å, β  105.20(4)°, V  2533(3) Å, Z  4, ?calc  2.57 g/cc. For 3065 reflections, R  0.052 and R_w  0.057. II contains an N-hydrido, N-isopropylformamido ligand bridging one edge of a triangular cluster of three osmium atoms and an isopropylisocyanide ligand. The molecule appears to have been formed by the cleavage of an NCH(CH₃)₂ moeity from one carbodiimide molecule and the transfer of it together with one hydride ligand to the carbon atom of a carbonyl group. The resultant formamido ligand bridges an edge of the cluster. The remaining fragment of the carbodiimide molecule bonds to one of the metal atoms of the cluster as a terminal isocyanide ligand. When heated, I loses one mole of carbon monoxide and forms the new cluster complex (μ-H)[μ₃-η²-(CH₃)₂CHNHCNCH-(CH₃)₂]Os₃(CO)₉ III. On the basis of electron counting schemes, III is believed to contain a triply-bridging amidinyl ligand serving as a five electron donor. Most importantly, no II was formed from I indicating that it is not a precursor -to II. A mechanism for the formation of I and II is presented and discussed.     

Addition and elimination of hydrogen and ligand substitution on triosmium clusters. Kinetics and mechanism

The kinetics of the reversible reaction HOs₃(μ-COMe)(CO)₁₀ + H₂ ? H₃Os₃(μ³-COMe)(CO)₉ + CO has been investigated. The reaction of HOs₃(μ-COMe)(CO)₁₀ with hydrogen involves dissociation of a CO ligand prior to the rate-determining step, which is proposed to be the oxidative addition of molecular hydrogen. The reaction of H₃Os₃(μ₃-COMe)(CO)₉ with CO involves rate-limiting hydrogen loss. The equilibrium constant and the competition ratio for hydrogen and CO for the unsaturated intermediate were determined. The mechanism of substitution by AsPh₃ on HOs₃(μ-COMe)(CO)₁₀ also involves a CO dissociative mechanism. Based upon relative rate constants for CO, AsPh₃, and hydrogen addition to HOs₃(COMe)(CO)₉, CO dissociation and hydrogen addition are proposed to occur at different metal sites.     

Activation of 1,3,5-trimethyl-1,3,5-triazacyclohexane by Os3(CO)12 to form amidino [(MeN)2CH] cluster complexes

Reaction of 1,3,5-trimethyl-1,3,5-triazacyclohexane [(MeNCH₂)₃] with Os₃(CO)₁₂ in refluxing toluene results in C-H and C-N bond activation of the (MeNCH₂)₃ ligand to afford three amidino cluster complexes (μ-H)Os₃(CO)₁₀[μ,η²-CH(NMe)₂] (1), (μ-H)Os₃(CO)₉[μ₃,η²-CH(NMe)₂] (2), and Os₂(CO)₆[μ,η²-CH(NMe)₂]₂ (3). The controlled experiments show that thermolysis of 1 yields 2, and heating 2 in the presence of (MeNCH₂)₃ ligand produces 3. The molecular structures of 1 and 3 have been determined by an X-ray diffraction study.     

Oxide promoted isomerisation of an isonitrile complex,H2Os3(CO)10[CN(CH2)3Si(OEt)3]

The isomerisation of H₂Os₃(CO)₁₀[CN(CH₂)₃Si(OEt)₃] to HOs₃(CO)₁₀-[CN(H)(CH₂)₃Si(OEt)₃] is accelerated by interaction with some oxides; both complexes afford HOs₃(CO)₁₀[CN(H)(CH₂)₃Si(OEt)_3it-x(O)x] as oxide supported clusters.     

Preparation of siloxycarbenemanganese complexes including a chelated siloxycarbene-alkene complex

Reaction of Li{(η⁵-C₅H₄Me)Mn(CO)₂]C(O)Ph]} with one equivalent of RSiMe₂Cl yields (η⁵-C₅H₄Me)Mn(CO)₂[C(Ph)(OSiMe₂R)] for R  CH₃, CHCH₂, and CH₂CHCH₂ (1a–c, respectively). Low temperature photolysis of the vinyl derivative, 1b, results in formation of a chelated manganese siloxycarbene-alkene complex, (η⁵-C₅H₄Me)MN(CO)[C(Ph)(η²-OSiMe₂CHCH₂)]. (2). Photolysis of the allyl derivative, 1c, under similar conditions leads to uncharacterized decomposition products. Infrared, ¹H, ¹³C, and ²⁹Si NMR data are reported for these new siloxycarbenemanganese derivatives.     

Synthesis and structural characterisation of an unsaturated osmium-gold cluster HOs3Au(CO)10(PR3) (R  Et,Ph); x-ray crystal structures of HOs3Au(CO)10(PPh3) and Os3Au(CO)10(PPh3)(SCN)

The reaction of [HOs₃(CO)₁₁]^? with AuClPR₃ (R  Et, Ph) yields the complex HOs₃Au(CO)₁₀(PR₃), and the PPh₃ derivative has been characterised by an X-ray analysis; the structure is compared with that of Os₃Au(CO)₁₀(PPh₃)-(SCN) and is shown to contain a formally unsaturated OsOs bond.     

Indene in a novel bonding mode in a carbonyl cluster: isolation,characterisation, and crystal and molecular structure of [HOs4(CO)9(C9H6)(C9H7)]

The reaction of [Os₃(CO)₁₂] with indene at 150°C under reflux affords the known compounds [H₂Os₃(CO)₉(C₉H₆)] (2) and [Os₄(CO)₁₂(C₉H₆)] (3). When the reaction temperature is increased to 170°C, the yield of 2 is greatly reduced, and a new tetraosmium cluster [HOs₄(CO)₉(C₉H₆)(C₉H₇)] (1) is isolated. An X-ray diffraction study of 1 has shown that one face of the Os₄ tetrahedron is capped by an indyne ligand coordinated in a μ₃-η²-− bonding mode, while the indenyl ligand (C₉H₇) is coordinated to a single Os atom in a η⁵ bonding mode through the five-membered ring.     

Reactivity of triosmium clusters with 3,4-dimethyl-1-phenylphosphole and cyanoethyldi-tert-butylphosphine ligands: X-ray crystal structures of [Os3(CO)9(μ-OH)(μ-H)(η1-PhPC4H2Me2)] and [Os3(CO)11(η1- t Bu2PC2H4CN)]

Reaction of [Os₃(μ-H)₂(CO)₁₀] with 3,4-dimethyl-1-phenylphosphole in refluxing cyclohexane affords two substituted triosmium clusters: [Os₃(CO)₉(μ-H)(μ³:η¹:η¹:η²-PhPC₄H₃Me₂)] (1) and [Os₃(CO)₉(H)(μ²-η¹:η²-PhPC₄H₄Me₂)] (2), of which cluster 2 exhibits two chromatographically non-separable isomeric forms attributed to terminal and bridging coordination of the hydride ligand, respectively. When this reaction is performed in refluxing THF, the only product is the cluster [Os₃(CO)₉(μ-OH)(μ-H)(η¹-PhPC₄H₂Me₂)] (3). Crystallographic information obtained for cluster 3 shows the phosphole ligand occupying an equatorial position, as expected, while the OH group is asymmetrically bridging unlike previously reported similar compounds. Additionally, interaction of the labile cluster [Os₃(CO)₁₁(CH₃CN)] with cyanoethyldi-tert-butylphosphine in dichloromethane at room temperature was found to give [Os₃(CO)₁₁(η¹- ^t Bu₂PC₂H₄CN)] (4) as the only product; its crystallographic characterization shows that the phosphine ligand coordinates by means of the phosphorus atom in an equatorial fashion, analogous to compound 3.     

Sulfur-containing carbene-metal compounds: General route from carbon disulfide manganese complexes; X-ray structure of 1,3-dithiol-2-ylidenemanganese(I) derivative

Chiral carbene-manganese(I) complexes have been synthesized by the cyclo-addition of dimethyl acetylenedicarboxylate to the coordinated CS₂ ligand in Mn(η²-CS₂)(CO)(L)C₅H₄R (L = P(OMe)₃; PMe₂Ph; PMe₃). Irrespective of the nature of the ligand L, these 1,3-dithiol-2-ylidenemanganese(I) complexes are stable towards isomerisation into heterometallocycles and exhibit low frequency carbonyl absorption bands in the infrared consistent with a strong electron releasing effect of the carbene ligand. The structure of Mn(CS₂C₂(CO₂Me)₂)(CO)(P(OMe)₃)(C₅H₅) has been determined by X-ray analysis of a suitable crystal. The molecule shows a carbene carbonmanganese bond C(7)Mn of length 1.876 Å and a planar carbene which does not adopt the 1,3-dithiolium aromatic-ring geometry but contains a carboncarbon double bond, C(8)C(9), of length of 1.341 Å. The CO₂Me groups are out of the plane of the carbene ligand and two positions with equal occupancy are found for each oxygen atom O(3) and O(5) belonging to the CO groups.