Nicholas I. Powell

Synthesis and structures of two isomers of [Re3Ru(S)(C5H4N)(C5H4NS)2(CO)11] which differ in the distribution of pyridine-2-thionato ligands between doubly- and triply-bridging positions

Abstract The pyridine-2-thionato (pyS) bridged compound [Re2(pyS)2(CO)6] reacts with [Ru3(CO)12] to give various tetranuclear compounds built from Re(pyS)(CO)3 and Ru(CO)x (x = 2, 3 or 4) units: [ReRu3(S)(C5H4N)(CO)14], [Re2Ru2(S)(C5H4N)(pyS)(CO)13], and [Re3Ru(S)(C5H4N)(pyS)2(CO)11] as two isomers. X-ray structures of these isomers show that one contains two doubly-bridging pyS ligands and the other one doubly- and one triply-bridging pyS ligands.

Oxygenhydrogen versus nitrogenoxygen bond cleavage in the oxidative addition of oximes to [Os3(CO)10(MeCN)2]: crystal structures of the isomers [Os3H(Me2CNO)(CO)10] and [Os3(OH)(Me2CN) (CO)10]

Acetone oxime (Me2CNOH) reacts with [Os3(CO)10(MeCN)2] to give the bridging oximato cluster [Os3(μ-H)(μ-Me2CNO)(CO)10] (1) resulting from oxidative addition with OH bond cleavage. An X-ray crystal structure determination showed that the oximato ligand is bridging two osmium atoms by bonding to one Os atom through the N-atom and to another through the O-atom. A range of clusters with similarly bonded oximato ligands were synthesised from the oximes derived from benzophenone (Ph2CNOH), cyclohexanone (C6H10NOH), acetaldehyde (MeCHNOH), benzaldehyde (PhCHNOH) (two isomers obtained), and formamide (NH2CHNOH). Compound 1 isomerises at 125°C to the non-hydrido isomer [Os3(μ-OH)(μ-Me2CN)(CO)10] (2) which was characterised spectroscopically and crystallographically and shown to contain the bridging hydroxy and the N-bonded Me2CN ligands. Overall oxidative addition of the oxime with NO bond cleavage has been achieved by an initial oxidative addition with OH cleavage followed by isomerisation.

Conversion of the cluster [Os3(CHCFc)(CO)10] (CHCFc = ethynylferrocene) into [Os3(S)(CHCFc)(CO)9] by reaction with sulphur. Crystal structures of these clusters and of [Os3H(C2Fc)(CO)9]

Abstract By application of a method established for various alkynes, the cluster [Os3(CO)10(MeCN)2] was treated with ethynylferrocene (CHCFc) to give the alkyne cluster [Os3(μ3-CHCFc)(μ-CO)(CO)9] (1). This cluster loses CO thermally and by visible irradiation to form the hydrido-ferrocenylethynyl cluster [Os3H(μ3-C2Fc) (CO)9] (2), but if the decarbonylation is carried out in the presence of sulphur at room temperature under visible irradiation, the cluster [Os3(μ3-S)(μ3-CHCFc)(CO)9] (3) is formed instead. The crystal structures of 1, 2, and 3 are reported. Clusters 1 and 3 are both 48-electron clusters containing μ3-CHCFc ligands but, whereas 1 contains three OsOs bonds, 3 contains only two. In 3 the triply bridging ligands occupy opposite faces of the Os3 triangle, with the osmium atoms at the open edge of the triangle having σ-bonds to the alkyne ligand. The structure of 1 and the known structure of [Os3(PhC2Ph)(CO)10] are closely related, although cluster 1 contains one bridging CO ligand and the latter two semi-bridging CO ligands. The fluxionality of cluster 1 is considered in the light of these different structures.

Intermediates in the conversion of [Os3(CO)11(PRPh2)](R = Me or Ph) into [Os3(µ3-C6H4)(µ3–PR)(CO)9]: crystal and molecular structures of [Os3-(µ-H)(µ3-C6H4PMePh-o)(CO)9] and [Os3(µ3-C6H4PMe-o)(CO)10]

The thermal conversion of [Os3(CO)11(PRPh2)](R = Me or Ph) into [Os3(µ3-C6H4)(µ3-PR)(CO)9](3) by loss of carbon monoxide, and probably benzene, has been reported. By carrying out the reactions at lower temperatures we have been able to isolate [Os3(µ-H)(µ3-C6H4PMePh)(CO)9](1a) and [Os3(µ3-C6H4PMe)(CO)10](2a) from the methyldiphenylphosphine compound and corresponding derivatives (1b) and (2b) from the triphenylphosphine derivative. Both (1) and (2) convert thermally to the µ3-C6H4 clusters (3) and are deduced to be intermediates in the formation of (3). The single-crystal X-ray structures of (1a) and (2a) are reported. In (1a), µ3-C6H4PMePh-o is a five-electron donor bonded through P to one Os atom, by a σ-Os–C bond to another, and by an η2 interaction of the C6H4 ring to the third. Compound (2a) contains the µ3 ligand C6H4PMe-o, as a four-electron donor, and a bridging CO ligand. In the degradation of PRPh2 into the components C6H4, PR, and C6H6, ortho-metallation is the first step, but probably follows an initial loss of CO.

Substitution effects at bridging vinyl ligands: Molecular structures of [Os3H(CHCHR)(CO)10] where R = OEt or ferrocenyl

Abstract The two related compounds [Os3H(μ,η2-trans-CHCHR)(CO)10] (R = OEt or ferrocenyl C5H4FeC5H5, Fc), have been prepared, the first by insertion of ethyl ethynyl ether (CHCOEt) into [Os3H2(CO)10] and the second by oxidative addition of ethynylferrocene (CH2 = CHFc) to [Os3(CO)10(MeCN)2] respectively. Spectroscopically both compounds are similar to known related compounds with alkyl- or aryl-substituted vinyl ligands. A single-crystal X-ray structural study of each was made in an attempt to detect any structural effects of π-donation by the substituents at the vinyl group, such as was observed for [Os3H(CHCHNEt2)(CO)10]. The latter compound has been shown to have a zwitterionic structure with an alkylidene bridge between two osmium atoms rather than the normal μ,η2-vinyl mode of bondiong. The two compounds studied here have essentially normal μ,η2-vinyl bridges, but with some distortion towards the alkylidene bonding type, more pronounced for R = OEt.

Linkage of two trimetallic clusters through the bridging ligands C3HO2 and C3O2. Crystal structures of three clusters containing the components Os3CHCCO2Os3, Ru3CHCCO2Os3, and Os3CCCO2Os3

Abstract Reaction of propynoic acid (CHCCO2H) with [Os3(CO)10(MeCN)2] gives the species [Os3H(CHCCO2)(CO)10] containing a μ-carboxylato ligand and a non-coordinated acetylenic function which may be coordinated further. Reaction of this compound with [M3(CO)10(MeCN)2] (M = Os or RU) gives the linked cluster compounds [Os3(CO)10(CHCCO2)Os3H(CO)10] (1) and [Ru3(CO)10 (CHCCO2)Os3H(CO)10] (2), the crystal structures of which are reported. A comparison of the geometries of the compounds [M3(CO)10(alkyne)] (M = Os or Ru) is possible for the first time; each contains a μ-CO ligand, which is more symmetrical for M = Ru than for M = Os. The coordination geometries of the μ3-alkyne and the overall conformations of the linked clusters are very similar. Decarbonylation of 1 and 2 leads to [Os3H(CO)9(C3O2)Os3H(CO)10] (3) (crystal structure reported) and [Ru3H(CO)9(C3O2)Os3H(CO)10] (4) respectively.

Ring opening versus phenyl–phosphorus bond cleavage in incorporating a phosphole into triosmium clusters

The five-membered heterocyclic compound 3,4-dimethyl-1-phenylphosphole (Ph[graphic omitted]H) reacts with [Os3(CO)11(MeCN)] or [Os3(CO)10(MeCN)2] to give the simple substitution products [Os3(CO)12–x(PhPC4H2Me2)x](x= 1 or 2) in which the phospholes are co-ordinated as tertiary phosphines through the phosphorus atoms. Thermolysis of these compounds gives decarbonylation compounds containing modified phosphole ligands. Phosphorus–carbon bonds either to the phenyl group or within the five-membered ring have been cleaved. The X-ray structure of the main product [Os3(CO)9(µ3-PhPCHCMeCMeCH)]1 shows that the organic µ3 ligand is a six-electron donor which is co-ordinated differently from the corresponding eight-electron donating ligand derived from 1-phenylphosphole in the cluster [Os3(CO)9(µ3-PhPCHCHCHCH)]. There is evidence for the reversible generation of this alternative from, 3, of the methylated compound 1 by photolysis. A minor product of the thermolysis is the hydrido cluster [Os3(µ-H)(µ-[graphic omitted]H)(µ3-C6H4)(CO)9]2 which contains a five-membered phospholyl ring and an o-phenylene (benzyne) ligand which originated from the phenyl group. The X-ray structure shows that the phospholyl ligand bridges two osmium atoms as a phosphido ligand through the phosphorus atom. The major and minor products, 1 and 2, are both derived by C–P bond cleavage, either in the phosphole ring or to the phenyl substituent respectively.

Oxidative addition of phenylphosphole: X-ray crystal structures of two ring-opened products [Os3(μ3-PhPC4H4)(CO)x] where x = 8 or 9

Abstract The phenylphosphole complex [Os 3 PhPC 4 H 4 )(CO) 11 ] decarbonylates in refluxing octane to yield the oxidative addition product [Os 3 (μ 3 -PhPC 4 H 4 )(CO) 9 ] ( 1 ) in which ring-opening of both the triosmium and the five-membered phosphole rings has occured, while further thermal decarbonylation to the cluster [Os 3 (μ 3 -PhPC 4 H 4 )(CO) 8 ] ( 2 ) leads to metal ring closure and a major reorganisation of the coordination of the 8-electron donating PhPC 4 H 4 ligand.

Mode of attachment of the triply-bridging C6H4 ligand in open triosmium clusters: Crystal structures and fluxionality of the clusters [Os3(PMe)(C6H4)(CO)8L] (L = CO or PEt3)

Abstract The cluster [Os 3 (PMe)(C 6 H 4 )(CO) 9 ] ( 1 ) reacts with phosphorus(III) ligands L [PEt 3 , PCy 3 , or P(OMe) 3 ] to give the substitution products [Os 3 (PMe)(C 6 H 4 )(CO) 9- x L x ], clusters 2 ( x = 1) and 3 ( x = 2). The crystal structures of 1 and 2 (L = PEt 3 ) are compared with that previously reported for [Os 3 (PEt)(C 6 H 4 )(CO) 9 ]; each has two OsOs bonds and one non-bonding Os ··· Os distance (3.982(1), 4.014(1), and 4.008(2) A, respectively, for the three compounds). A μ 3 -PMe or PEt group caps one face of the Os 3 triangle and the opposite one is capped by a μ 3 -C 6 H 4 ligand coordinated through σ-OsC bonds to two mutually bonded Os atoms and does not span the open Os ··· Os edge by σ-bonds as in other cases such as [Os 3 H(AsMe 2 )(C 6 H 4 )(CO) 9 ]. Bonding to the third Os atom through one carbon atom involves π-orbitals predominantly, and there is evidence against an alkylidene component in the bridging such as was considered previously. The C 6 H 4 ligand is rapidly mobile in 1 , and in one of the two isomers of 2 with the ligand L at the central Os atom. The fluxionality is substantially suppressed when L is coordinated at a terminal Os atom as in the isomer of [Os 3 (PMe)(C 6 H 4 )(CO) 8 (PEt 3 )] whose structure was established crystallographically. The movement of the non-bonded Os ··· Os edge around the metal triangle does occur, but is slow.

New trinuclear and hexanuclear ruthenium clusters derived from the reaction of [Ru3(CO)12] with phenylphosphine or cyclohexylphosphine

Abstract The reaction of [Ru3(CO)12] with RPH2 (R=phenyl or cyclohexyl) has been re-examined and the involvement of the trinuclear clusters [Ru3(μ-H)(μ-PHR)(CO)10], [Ru3H2(μ3-PR)(CO)9], [Ru3H2(μ3-PR)(CO)8(PH2R)] and [Ru3H2(μ-PHR)2(CO)8] in the formation of the bis-capped compound [Ru3(μ3-PR)2(CO)9] has been explored. The single-crystal X-ray structures of [Ru3(μ-H)2(μ3-PPh)(CO)8(PH2Ph)] and [Ru3(μ-H)(μ-PHPh)3(CO)7] are presented. The latter compound was obtained as a single isomer whereas there are four isomers present in solutions of the PHCy analogue (Cy=cyclohexyl). In an unsuccessful attempt to hydrogenate [Ru3(μ3-PR)2(CO)9] to reform one of the isomers, [Ru3H2(μ-PHR)2(CO)8] or [Ru3H2(μ3-PR)(CO)8(PH2R)], we obtained instead a mixture of the known compound [Ru6(μ3-PR)2(μ4-PR)2(CO)12] and the hydrogenated form of this, [Ru6H2(μ3-PR)2(μ4-PR)2(CO)12]. The structures of these hexanuclear clusters are related, both being based on distorted trigonal prismatic Ru6 arrangements, but the distortions are very different and the average RuRu distances in the 90-valence electron dihydride are longer than in the 88-valence electron non-hydride compound. We have identified a restricted rotation about the PPh bonds for the μ4-ligands but not the μ3-ligandwhich is interpreted in terms of clashes of the ortho-phenyl hydrogen atoms with CO ligands.