Monomeric Chini‐Type Triplatinum Clusters Featuring Dianionic and Radical‐Anionic π*‐Systems

Owing to their unique topologies and abilities to self‐assemble into a variety of extended and aggregated structures, the binary platinum carbonyl clusters [Pt₃(CO)₆]_n^2? (“Chini clusters”) continue to draw significant interest. Herein, we report the isolation and structural characterization of the trinuclear electron‐transfer series [Pt₃(μ‐CO)₃(CNAr^Dipp2)₃]^n? (n=0, 1, 2), which represents a unique set of monomeric Pt₃ clusters supported by π‐acidic ligands. Spectroscopic, computational, and synthetic investigations demonstrate that the highest‐occupied molecular orbitals of the mono‐ and dianionic clusters consist of a combined π*‐framework of the CO and CNAr^Dipp2 ligands, with negligible Pt character. Accordingly, this study provides precedent for an ensemble of carbonyl and isocyanide ligands to function in a redox non‐innocent manner.     

The synthesis and characterisation of some mixed-metal carbonyl hydrides containing tungsten: The X-ray crystal structure of [(Ph3P)2N][Os3WH(CO)14]

The mixed-metal cluster anion [Os₃W(μ-H)(μ-CO)(CO)₁₃]^? has been prepared by the reaction of [Os₃(μ-H)(CO)₁₁]^? with W(CO)₃(MeCN)₃, and the dianion, [Os₃W(CO)₁₄]^2?, may be obtained by subsequent deprotonation. An X-ray analysis of the monoanion shows that the metals adopt a closo-tetrahedral geometry with the W atom coordinated to four terminal and one bridging carbonyl groups. The neutral clusters [Os₃WH₂(CO)₁₄] and [Os₃WH(CO)₁₄] are formed upon treatment of the monoanion with sulphuric acid and iodine, respectively.     

The Use of the Electron-Reservoir Complexes [Fe(I)Cp(arene)] for the Electrocatalytic Synthesis of Redox-Reversible Metal-Carbonyl Clusters Containing Ferrocenyldiphenylphosphine

Starting from [M₃(CO)₁₂] (M = Fe or Ru) and [CH₃CCo₃(CO)₉], the electron-tranfer-chain catalyzed synthesis of new Fe, Ru, and Co carbonyl clusters in which one or several carbonyl ligands have been selectively substituted by one or several ferrocenyldiphenylphosphine (FDPP) ligands has been achieved using the electron-reservoir complexes [Fe(I)Cp(arene)] as electrocatalysts. The number of FDPP ligands selectively introduced can be chosen from one per cluster for the three clusters up to one per metal for the Ru and Co clusters. The advantage of this family of electrocatalysts is that the driving force for the initiation step can be varied by changing the number of methyl groups on the rings. The FDPP substituted clusters show one reversible wave by cyclic voltammetry.     

Synthesis and characterisation of phosphane-substituted Co3C clusters having a pendant allyl side-chain

Substituted μ₃-carbido-capped tricobalt carbonyl clusters have been synthesised by reaction of [Co₃(μ₃-C(O)OCH₂CHCH₂)(CO)₉] with a range of monodentate and chelating phosphane ligands. The products have been characterised by microanalysis, IR and NMR spectroscopy, mass spectrometry and, in the case of [Co₃(μ₃-CR)(CO)₇(dppe)], [Co₃(μ₃-CR)(CO)₇(dppm)], [Co₃(μ₃-CR)(CO)₇(PPh₃)₂], [Co₃(μ₃-CR)(CO)₇(PMe₃)₂] and [Co₃(μ₃-CR)(CO)₆(PEt₃)₃] (R=C(O)OCH₂CHCH₂), single crystal X-ray diffraction.     

New Trinuclear Complexes of Group 6, 8, and 9 Metals with a Triply Bridging Borylene Ligand

Trinuclear complexes of group 6, 8, and 9 transition metals with a (μ₃‐BH) ligand [(μ₃‐BH)(Cp*Rh)₂(μ‐CO)M′(CO)₅], 3 and 4 ( 3 : M′=Mo; 4 : M′=W) and 5 – 8 , [(Cp*Ru)₃(μ₃‐CO)₂(μ₃‐BH)(μ₃‐E)(μ‐H){M′(CO)₃}] ( 5 : M′=Cr, E=CO; 6 : M′=Mo, E=CO; 7 : M′=Mo, E=BH; 8 : M′=W, E=CO), have been synthesized from the reaction between nido‐[(Cp*M)₂B₃H₇] (nido‐ 1 : M=Rh; nido‐ 2 : M=RuH, Cp*=η⁵‐C₅Me₅) and [M′(CO)₅ ? thf] (M′=Mo and W). Compounds 3 and 4 are isoelectronic and isostructural with [(μ₃‐BH)(Cp*Co)₂(μ‐CO)M′(CO)₅], (M′=Cr, Mo and W) and [(μ₃‐BH)(Cp*Co)₂(μ‐CO)(μ‐H)₂M′′H(CO)₃], (M′′=Mn and Re). All compounds are composed of a bridging borylene ligand (B?H) that is effectively stabilized by a trinuclear framework. In contrast, the reaction of nido‐ 1 with [Cr(CO)₅ ? thf] gave [(Cp*Rh)₂Cr(CO)₃(μ‐CO)(μ₃‐BH)(B₂H₄)] ( 9 ). The geometry of 9 can be viewed as a condensed polyhedron composed of [Rh₂Cr(μ₃‐BH)] and [Rh₂CrB₂], a tetrahedral and a square pyramidal geometry, respectively. The bonding of 9 can be considered by using the polyhedral fusion formalism of Mingos. All compounds have been characterized by using different spectroscopic studies and the molecular structures were determined by using single‐crystal X‐ray diffraction analysis.     

[M(CO)2(NO)], a new core in bioorganometallic chemistry: model complexes of [Re(CO)2(NO)] and [Tc(CO)2(NO)]

In this study selected bidentate (L²) and tridentate (L³) ligands were coordinated to the Re(I) or Tc(I) core [M(CO)₂(NO)]²⁺ resulting in complexes of the general formula fac-[MX(L²)(CO)₂(NO)] and fac-[M(L³)(CO)₂(NO)] (M = Re or Tc; X = Br or Cl). The complexes were obtained directly from the reaction of [M(CO)₂(NO)]²⁺ with the ligand or indirectly by first reacting the ligand with [M(CO)₃]⁺ and subsequent nitrosylation with [NO][BF₄] or [NO][HSO₄]. Most of the reactions were performed with cold rhenium on a macroscopic level before the conditions were adapted to the n.c.a. level with technetium (^99mTc). Chloride, bromide and nitrate were used as monodentate ligands, picolinic acid (PIC) as a bidentate ligand and histidine (HIS), iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA) as tridentate ligands. We synthesised and describe the dinuclear complex [ReCl(μ-Cl)(CO)₂(NO)]₂ and the mononuclear complexes [NEt₄][ReCl₃(CO)₂(NO)], [NEt₄][ReBr₃(CO)₂(NO)], [ReBr(PIC)(CO)₂(NO)], [NMe₄][Re(NO₃)₃(CO)₂(NO)], [Re(HIS)(CO)₂(NO)][BF₄], [⁹⁹Tc(HIS)(CO)₂(NO)][BF₄], [^99mTc(IDA)(CO)₂ (NO)] and [^99mTc(NTA)(CO)₂(NO)]. The chemical and physical characteristics of the Re and Tc-dicarbonyl-nitrosyl complexes differ significantly from those of the corresponding tricarbonyl compounds.     

Structures of homoleptic triply bonded M2(OR)6 compounds where the alkoxide is tertiary: the effect of steric bulk and alkoxide conformation on structural parameters

The structures of three homoleptic metal–metal triply-bonded M₂(OR)₆ compounds {Mo₂(OCMe₂CMe₂O)₃, 1; Mo₂(OCMe₂Ph)₆, 2; and W₂[OCMe(CF₃)₂]₆, 3} containing tertiary alkoxides are reported. The data demonstrate that, overall, the M₂O₆ cores are isomorphous regardless of the substitution pattern of the alkoxide. Dimer 3 is the first example of a W₂(OR)₆ compound containing terminal tertiary alkoxides to be structurally characterized; it is of interest as a close structural analogue of the chemically remarkable W₂(OCMe₃)₆. The hexa(hexafluoro-t-butoxide) dimer, though slightly disordered, displays distances and angles similar to other W₂(OR)₆ species despite the poor electron-donor capacity of the fluoroalkoxide group. The data from these structures, combined with literature data, show that proximal alkoxide ligands generally exhibit shorter M–O bond distances and larger M–M–O and M–O–C angles than do distal alkoxides regardless of metal type, alkoxide steric bulk, and alkoxide π donor ability in a range of compounds. This suggests electrostatic and conformational considerations are of greater importance to the bonding in these dimers than are M–O π interactions.     

Carbonyl substitution chemistry of some trimetallic transition metal cluster complexes with polyfunctional ligands

The trimetallic clusters [Ru₃(CO)₁₀(dppm)], [Ru₃(CO)₁₂] and [RuCo₂(CO)₁₁] react with a number of multifunctional secondary phosphine and tertiary arsine ligands to give products consequent on carbonyl substitution and, in the case of the secondary phosphines, PH activation. The reaction with the unresolved mixed P/S donor, 1-phenylphosphino-2-thio(ethane), HSCH₂CH₂PHPh ( LH₂), gave two products under various conditions which have been characterised by spectroscopic and crystallographic means. These two complexes [Ru₃(μ-dppm)(H)(CO)₇(LH)] and [Ru₃(μ-dppm)(H)(CO)₈(LH)Ru₃(μ-dppm)(CO)₉], show the versatility of the ligand, with it chelating in the former and bridging two Ru₃ units in the latter. The stereogenic centres in the molecules gave rise to complicated spectroscopic data which are consistent with the presence of diastereoisomers. In the case of [Ru₃(CO)₁₂] the reaction with LH₂ gave a poor yield of a tetranuclear butterfly cluster, [Ru₄(CO)₁₀(L)₂], in which two of the ligands bridge opposite hinge wingtip bonds of the cluster. A related ligand, HSCH₂CH₂AsMe(C₆H₄CH₂OMe), reacted with [RuCo₂(CO)₁₁] to give a low yield of the heterobimetallic Ru-Co adduct, [RuCo(CO)₆(SCH₂CH₂AsMe(C₆H₄CH₂OMe))], which appears to be the only one of its type so far structurally characterised.The secondary phosphine, HPMe(C₆H₄(CH₂OMe)) and its oxide HP(O)Me(C₆H₄(CH₂OMe)) also react with the cluster [Ru₃(CO)₁₀(dppm)] to give carbonyl substitution products, [Ru₃(CO)₅(dppm)(μ₂-PMe(C₆H₄CH₂OMe))₄], and [Ru₃H(CO)₇(dppm)(μ₂,η¹-P(O)Me(C₆H₄CH₂OMe))]. The former consists of an open Ru₃ triangle with four phosphide ligands bridging the metal-metal bonds; the latter has the O atom symmetrically bridging one Ru-Ru bond, the P atom being attached to a non-bridged Ru atom.     

Facile Access to Transition‐Metal–Carbonyl Complexes with an Amidinate‐Stabilized Chlorosilylene Ligand

Three transition‐metal–carbonyl complexes [V( L )(CO)₃(Cp)] ( 1 ), [Co( L )(CO)(Cp)] ( 2 ), and [Co( L₂ )(CO)₃]⁺[CoCO)₄]^? ( 3 ), each containing stable N‐heterocyclic‐chlorosilylene ligands ( L ; L =PhC(NtBu)₂SiCl) were synthesized from [V(CO)₄(Cp)], [Co(CO)₂(Cp)], and Co₂(CO)₈, respectively. Complexes 1 , 2 , 3 were characterized by NMR and IR spectroscopy, EI‐MS spectrometry, and elemental analysis. The molecular structures of compounds 1 , 2 , 3 were determined by single‐crystal X‐ray diffraction.     

Reactions of [Ru(CO)3Cl2]2 with aromatic nitrogen donor ligands in alcoholic media

The reactions of mono‐ and bidentate aromatic nitrogen‐containing ligands with [Ru(CO)₃Cl₂]₂ in alcohols have been studied. In alcoholic media the nitrogen ligands act as bases promoting acidic behaviour of alcohols and the formation of alkoxy carbonyls [Ru(N–N)(CO)₂Cl(COOR)] and [Ru(N)₂(CO)₂Cl(COOR)]. Other products are monomers of type [Ru(N)(CO)₃Cl₂], bridged complexes such as [Ru(CO)₃Cl₂]₂(N), and ion pairs of the type [Ru(CO)₃Cl₃]^? [Ru(N–N)(CO)₃Cl]⁺ (N–N = chelating aromatic nitrogen ligand, N = non‐chelating or bridging ligand). The reaction and the product distribution can be controlled by adjusting the reaction stoichiometry. The reactivity of the new ruthenium complexes was tested in 1‐hexene hydroformylation. The activity can be associated with the degree of stability of the complexes and the ruthenium–ligand interaction. Chelating or bridging nitrogen ligands suppresses the activity strongly compared with the bare ruthenium carbonyl chloride, while the decrease in activity is less pronounced with monodentate ligands. A plausible catalytic cycle is proposed and discussed in terms of ligand–ruthenium interactions. The reactivity of the ligands as well as the catalytic cycle was studied in detail using the computational DFT methods. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of solvents on the stability of the products of electrochemical reactions of iron, ruthenium, and osmium carbonyl cluster compounds

The electrochemical reactions of carbonyl cluster compounds M₃(CO)₁₂ (M = Fe, Ru, Os) were compared with those of [Fe₅C(CO)₁₄]^2? and [Fe₆C(CO)₁₆]^2? in different aprotic solvents. The stability of electrochemically generated products of these clusters in the studied solvents was shown to grow in the following order: tetrahydrofuran < acetone < dichloromethane < acetonitrile.     

Iridium Insertion to Triosmium Cluster Containing Unsaturated Os–Os Bonds

Treatment of the triosmium hydrido cluster, [Os₃(μ-H)₂(CO)₁₀], with one equivalent of [IrCp*Cl₂]₂ (Cp* = pentamethylcyclopentadiene) in refluxing THF afforded four osmium–iridium clusters, including [Os₃Ir₂(μ-CO)(μ-H)₂(CO)₉(Cp*)₂] (1), [Os₃IrCp*(μ-H)₃(μ-Cl)(CO)₉] (2), [Os₃IrCp*(μ-H)(μ-Cl)(μ-CO)(CO)₉] (3) and [Os₂IrCp*(μ-H)(μ-Cl)(CO)₇] (4), in moderate yields. The reactivity of complex 3 with hydrogen, carbon monoxide, and thallium hexafluorophosphate was studied. Complex 4 was found to react with [Os₃(μ-H)₂(CO)₁₀] to give 2 and 3. All of the new compounds were characterized by conventional spectroscopic methods and single-crystal X-ray analysis. This work is dedicated to Professor Frank Albert Cotton for his pioneering contributions to the chemistry of metal clusters     

Formation of Isomeric Tetrathiotungstate Clusters [{Cp*Ru(CO)}2(WS4){W(CO)4}] by the Reaction of [Cp*2Ru2S4] with [W(CO)3(MeCN)3]

Thermal and photochemical interconversion occurs between the isomeric pair of tetrathiotungstate [WS₄]²⁻ clusters 1 and 2 , which were formed by thermolysis of [Cp^*₂Ru₂S₄] and [W(CO)₃(MeCN)₃] [Eq. (1)] and then structurally characterized. During synthesis, a dramatic redistribution of ligands between the Ru and W atoms takes place without the loss of any CO and S ligands.     

Electrocatalysis of hydrogen evolution by synthetic diiron units using weak acids as the proton source: Pathways of doubtful relevance to enzymic catalysis by the diiron subsite of [FeFe] hydrogenase

IR spectroelectrochemical studies of bis(thiolate) and dithiolate-bridged diiron carbonyl compounds, [Fe₂(μ-SR)₂(CO)₆], show that the primary reduction process results in rapid chemical reaction, leading to two-electron reduced products. When the reaction is conducted under an inert atmosphere, the major product is [Fe₂(μ-SR)(μ-CO)(CO)₆]¹⁻, where in the case of dithiolate-bridged neutral compounds the product has one bridging and one non-bound sulfur atom. This product is formed in near-quantitative yield for solutions saturated with CO. Reduction of [Fe₂(μ-SR)(μ-CO)(CO)₆]¹⁻ occurs at potentials near −2.0 V vs. SCE to give a range of products including [Fe(CO)₄]²⁻. Reduction of thiolate-bridged diiron compounds at mild potentials in the presence of CH₃COOH leads to formation of [Fe₂(μ-SR)(μ-CO)(CO)₆]¹⁻ and this is accompanied by an acid-base reaction with the dissociated thiolate. The reaction is largely reversible with recovery of ca. 90% of the starting diiron compound and CH₃COOH. In the presence of acid, reduction of [Fe₂(μ-SR)₂(CO)₆] proceeds without generation of observable concentrations of the structurally related one-electron reduced compound. Electrocatalytic proton reduction is achieved when the potential is stepped sufficiently negative to reduce [Fe₂(μ-SR)(μ-CO)(CO)₆]¹⁻, an observation in keeping with the cyclic voltammetry of the system. Since the catalytic species involved in the weak-acid reactions is structurally distinct from the starting material, and the diiron subsite of the hydrogenase H-cluster, these experiments are of dubious relevance to the biological system.     

Reactions of isonitriles with [Fe3(CO)12] and [Ru3(CO)12] monitored by electrospray mass spectrometry: structural characterisation of [Fe3(CO)10(CNPh)2] and [Ru4(CO)11(μ3-η-CNPh)2(CNPh)]

The reactions of [Fe₃(CO)₁₂] or [Ru₃(CO)₁₂] with RNC (R=Ph, C₆H₄OMe-p or CH₂SO₂C₆H₄Me-p) have been investigated using electrospray mass spectrometry. Species arising from substitution of up to six ligands were detected for [Fe₃(CO)₁₂], but the higher-substituted compounds were too unstable to be isolated. The crystal structure of [Fe₃(CO)₁₀(CNPh)₂] was determined at 150 and 298 K to show that both isonitrile ligands were trans to each other on the same Fe atom. For [Ru₃(CO)₁₂] substitution of up to three COs was found, together with the formation of higher-nuclearity clusters. [Ru₄(CO)₁₁(CNPh)₃] was structurally characterised and has a spiked-triangular Ru₄ core with two of the CNPh ligands coordinated in an unusual μ₃-η² mode.     

Controlled Expansion of a Strong‐Field Iron Nitride Cluster: Multi‐Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity

Multimetallic clusters have long been investigated as molecular surrogates for reactive sites on metal surfaces. In the case of the μ₄‐nitrido cluster [Fe₄(μ₄‐N)(CO)₁₂]^?, this analogy is limited owing to the electron‐withdrawing effect of carbonyl ligands on the iron nitride core. Described here is the synthesis and reactivity of [Fe₄(μ₄‐N)(CO)₈(CNAr^Mes2)₄]^?, an electron‐rich analogue of [Fe₄(μ₄‐N)(CO)₁₂]^?, where the interstitial nitride displays significant nucleophilicity. This characteristic enables rational expansion with main‐group and transition‐metal centers to yield unsaturated sites. The resulting clusters display surface‐like reactivity through coordination‐sphere‐dependent atom rearrangement and metal–metal cooperativity.     

Highly Active,Low‐Valence Molybdenum‐ and Tungsten‐Amide Catalysts for Bifunctional Imine‐Hydrogenation Reactions

The reactions of [M(NO)(CO)₄(ClAlCl₃)] (M=Mo, W) with (iPr₂PCH₂CH₂)₂NH, (PN^HP) at 90 °C afforded [M(NO)(CO)(PN^HP)Cl] complexes (M=Mo, 1a ; W, 1b ). The treatment of compound 1a with KOtBu as a base at room temperature yielded the alkoxide complex [Mo(NO)(CO)(PN^HP)(OtBu)] ( 2a ). In contrast, with the amide base Na[N(SiMe₃)₂], the PN^HP ligand moieties in compounds 1a and 1b could be deprotonated at room temperature, thereby inducing dehydrochlorination into amido complexes [M(NO)(CO)(PNP)] (M=Mo, 3a ; W, 3b ; PNP=(iPr₂PCH₂CH₂)₂N)). Compounds 3a and 3b have pseudo‐trigonal‐bipyramidal geometries, in which the amido nitrogen atom is in the equatorial plane. At room temperature, compounds 3a and 3b were capable of adding dihydrogen, with heterolytic splitting, thereby forming pairs of isomeric amine‐hydride complexes [Mo(NO)(CO)H(PN^HP)] ( 4a(cis) and 4a(trans) ) and [W(NO)(CO)H(PN^HP)] ( 4b(cis) and 4b(trans) ; cis and trans correspond to the position of the H and NO groups). H₂ approaches the Mo/W?N bond in compounds 3a , 3b from either the CO‐ligand side or from the NO‐ligand side. Compounds 4a(cis) and 4a(trans) were only found to be stable under a H₂ atmosphere and could not be isolated. At 140 °C and 60 bar H₂, compounds 3a and 3b catalyzed the hydrogenation of imines, thereby showing maximum turnover frequencies (TOFs) of 2912 and 1120 h^?1, respectively, for the hydrogenation of N‐(4 ‐ methoxybenzylidene)aniline. A Hammett plot for various para‐substituted imines revealed linear correlations with a negative slope of ?3.69 for para substitution on the benzylidene side and a positive slope of 0.68 for para substitution on the aniline side. Kinetics analysis revealed the initial rate of the hydrogenation reactions to be first order in c(cat.) and zeroth order in c(imine). Deuterium kinetic isotope effect (DKIE) experiments furnished a low k_H/k_D value (1.28), which supported a Noyori‐type metal–ligand bifunctional mechanism with H₂ addition as the rate‐limiting step.     

New Heteronuclear Bridged Borylene Complexes That Were Derived from [{Cp*CoCl}2] and Mono‐Metal?Carbonyl Fragments

The synthesis, structural characterization, and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}₂] with LiBH₄ ? THF at ?70 °C, followed by treatment with [M(CO)₃(MeCN)₃] (M=W, Mo, and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(μ₃‐BH)(Cp*Co)₂(μ‐CO)M(CO)₅] ( 1 – 3 ; 1 : M=W, 2 : M=Mo, 3 : M=Cr). During the syntheses of complexes 1 – 3 , capped‐octahedral cluster [(Cp*Co)₂(μ‐H)(BH)₄{Co(CO)₂}] ( 4 ) was also isolated in good yield. Complexes 1 – 3 are isoelectronic and isostructural to [(μ₃‐BH)(Cp*RuCO)₂(μ‐CO){Fe(CO)₃}] ( 5 ) and [(μ₃‐BH)(Cp*RuCO)₂(μ‐H)(μ‐CO){Mn(CO)₃}] ( 6 ), with a trigonal‐pyramidal geometry in which the μ₃‐BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis‐phosphine ligands, the room‐temperature photolysis of complexes 1 – 3 , 5 , 6 , and [{(μ₃‐BH)(Cp*Ru)Fe(CO)₃}₂(μ‐CO)] ( 7 ) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph₂P(CH₂)_nPPh₂] (n=1–3) yielded complexes 9 – 11 , [3,4‐(Ph₂P(CH₂)_nPPh₂)‐closo‐1,2,3,4‐Ru₂Fe₂(BH)₂] ( 9 : n=1, 10 : n=2, 11 : n=3). Quantum‐chemical calculations by using DFT methods were carried out on compounds 1 – 3 and 9 – 11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO–LUMO gaps, in accordance with the high stabilities of these complexes, and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy, and ¹H, ¹³C, and ¹¹B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1 , 2 , 4 , 9 , and 10 .     

Structural Studies of Several Ru3 and Ru4 Carbonyl Clusters

The preparation, characterisation and single‐crystal XRD molecular structure determinations of the three Ru₃ carbonyl clusters attached to carbon ligands, Ru₃(μ‐H)₃(μ₃‐CBr)(CO)₉ ( 1 ), Ru₃(μ‐H)(μ‐dppm){μ‐C(OMe)}(CO)₈ ( 2 ) and AuRu₃(μ‐H)₂(μ₃‐C=C=CHPh)(CO)₁₀ ( 3 ) are reported, together with the structures of the tetranuclear hydrido‐carbonyls Ru₄(μ‐H)_4–2x(CO)_11+x(PPh₃) (x = 0 4 , 1 5 ).     

New triosmium–iridium clusters: Synthesis and molecular structure of [Os3Ir2(Cp1)2(μ-OH)(μ-CO)2(CO)8Cl] (1), [Os3IrCp1(μ-OH)(CO)10Cl] (2), [Os3IrCp1(μ-H)(μ-Cl)(η3,μ3-C5H2N(NH2)Br)(CO)9] (3) and [Os3IrCp1(μ-Cl)2(η2,μ3-C5H3N(NH)Br)(CO)7] (4)

The trinuclear osmium carbonyl cluster, [Os₃(CO)₁₀(MeCN)₂], is allowed to react with 1 equiv. of [IrCp¹Cl₂]₂ (Cp¹ = pentamethylcyclopentadiene) in refluxing dichloromethane to give two new osmium–iridium mixed-metal clusters, [Os₃Ir₂(Cp¹)₂(μ-OH)(μ-CO)₂(CO)₈Cl] (1) and [Os₃IrCp¹(μ-OH)(CO)₁₀Cl] (2), in moderate yields. In the presence of a pyridyl ligand, [C₅H₃N(NH₂)Br], however, the products isolated are different. Two osmium–iridium clusters with different coordination modes of the pyridyl ligand are afforded, [Os₃IrCp¹(μ-H)(μ-Cl)(η³,μ₃-C₅H₂N(NH₂)Br)(CO)₉] (3) and [Os₃IrCp¹(μ-Cl)₂ (η²,μ₃-C₅H₃N(NH)Br)(CO)₇] (4). All of the new compounds are characterized by conventional spectroscopic methods, and their structures are determined by single-crystal X-ray diffraction analysis.