Organometallic polymorphism. Synthesis and structural characterization of two forms of [Ru(η6-C6H6)(η6-C6H4(CH3)COOCH3)][BF4]2 and the phase transition in [Ru(η5-C5H5)(η6-C6H5OH)][PF6]

The synthesis and structural characterization of the complex [Ru(η⁶-C₆H₆)(η⁶-C₆H₄(CH₃)COOCH₃)] [BF₄]₂ (2) and of its precursor [Ru(η⁶-C₆H₄(CH₃)COOCH₃)Cl₂]₂ (1) are reported. Compound (2) has been characterized in two polymorphic modifications (2a and 2b) and the molecular organization in the solid state has been investigated. The complex [Ru(η⁵-C₅H₅)(η⁶-C₆H₅OH)][PF₆] (3) has also been investigated; it has been shown to possess a disorder similar to that observed in the high temperature phase of related systems such as [Ru(η⁵-C₅H₅)(η⁶-C₆H₆)][PF₆].     

Some reactions of [(η6-C6Me6)Ru(η6-[2.2]paracyclophane)]-[BF4]2 with nucleophiles

Single addition of the nucleophiles X⁻ (X = H, CN, OH) to the less sterically hindered ring in [(η⁶-C₆Me₆)Ru(η⁶-C₁₆H₁₆)][BF₄]₂ (1) proceeds smoothly to produce, as the sole product, [(exo-η⁵-C₆Me₆X)Ru(η⁶-C₁₆H₁₆)][BF₄]. Use of Na[BD₄] in place of Na[BH₄] gives the expected shift in ν(C-H_exo) in the infrared spectrum.     

Syntheses,spectroscopic and structural studies of indenyl ruthenium complexes incorporating amine and nitrile ligands: molecular structures of [(η5-C9H7) Ru(η2-dppe)(CH3CN)]PF6 and [(η5-C9H7)Ru(η2-dppe)(NH3)]PF6

The reaction of [(η⁵-C₉H₇)Ru(η²-dppe)Cl] (1) with monodentate nitriles, (L) in the presence of NH₄PF₆ afforded the complexes [(η⁵-C₉H₇)Ru(η²-dppe)(L)]PF₆, with L?=?CH₃CN (2a), CH₃CH=CHCN (2b), NCC₆H₄CN (2c), C₆H₅CH₂CN (2d), respectively. However, reaction of 1 with NH₄PF₆ in methanol yielded an amine complex of the type [(η⁵-C₉H₇) Ru(η²-dppe)(NH₃)]PF₆ (3a). The complexes were fully characterized by spectroscopy and analytical data. The molecular structures of the complexes [(η⁵-C₉H₇)Ru(η²-dppe) (CH₃CN)]PF₆ (2a) and [(η⁵-C₉H₇)Ru(η²-dppe)(NH₃)]PF₆ (3a) have been determined by single crystal X-ray analyses.     

The Thermolysis of [Ru3(CO)12] in Cyclohexene: Synthesis and Charaterisation of the New Clusters [Ru3H2(CO)9(μ3-η1:η2:η1-C6H8)] and [Ru5(CO)12(μ4-η2-C6H8)(η4-C6H8)]

Thermolysis of [Ru₃(CO)₁₂] in cyclohexene for 24 h affords the complexes [Ru(CO)₃(η⁴-C₆H₈)] (1), [Ru₃H₂(CO)₉(μ₂-η¹:η²:η¹-C₆H₈)] (2), [Ru₄(CO)₁₂(μ₄-C₆H₈)] (3) [Ru₄(CO)₉(μ₄-C₆H₈)(η⁶-C₆H₆)] (4a and 4b, two isomers) and [Ru₅(CO)₁₂(μ₄-η²-C₆H₈)(η⁴-C₆H₈)] (5), where 1, 3, 4a and 4b have been previously characterised as products of the thermolysis of [Ru₃(CO)₁₂] with cyclohexa-1,3-diene. The molecular structures of the new clusters 2 and 5 were determined by single-crystal X-ray crystallography, showing that two conformational polymorphs of 5 exist in the solid state, differing in the orientation of the cyclohexa-1,3-diene ligand on a ruthenium vertex.     

Crystal structure of twinned (η5-C5(CH3)4CF3) (η5-C5(CH3)5)Ru

The substituted sandwich complex crystallizes in monoclinic space groupP2₁/m withZ=2. Twinning to the (001) direction with the special conditionc ^*/4a ^* = cos ^* causes systematic superposition of the reciprocal lattices of both domains and results in an apparent unit cell with double volume and the reflection condition (2h)kl, l=2n. The structure solution was obtained with the subset of intensity data for the predominant individuum and converged atR = 0.040,R _w =0.046 for 832 independent observations and 122 variables. The molecules show disorder with respect to the crystallographic mirror plane. The structure is closely related to that of decamethylruthenocene.     

Ditropylmolybdenum complexes by the sodium reduction of [Mo(CO)3(η-C7H7)][BF4]. X-Ray crystal structure of the ditropyl complex “Mo(CO)3”2(η6,η′6-C14H14)

Treatment of [Mo(CO)₃(η-C₇H₇)][BF₄] with either sodium amalgam or sodium naphthalide results in a reductive dimerisation to the ditropyl complex “Mo(CO)₃”₂(η₆,η′⁶-C₁₄H₁₄). The results of an X-ray crystallographic study confirm that the hydrogen atoms of the linking carbon atoms are both endo with respect to molybdenum. The reaction of Mo(CO)₆ with ditropyl, C₁₄H₁₄, leads to all three possible isomers of “Mo(CO)₃”²(η⁶,η′⁶-C₁₄-H₁₄). The structure of each is assigned by its ¹H NMR spectrum.     

Study of the origin of enantioselectivity in cyclopropanation reactions using the chiral iron carbene complex [(η5-C5H5)(CO)2FeCH[(η6-o-MeOC6H4)Cr(CO)3]]+

During our low temperature NMR studies we observed two rotational isomers of the carbene complex [(η⁵-C₅H₅)(CO)₂FeCH[(η⁶-o-MeOC₆H₄)Cr(CO)₃]]+ (3) with the O–Me group either anti or anti to the Fp moiety. While the Cr(CO)₃ group very effectively shields one face of the carbene complex from attack by the olefin, the presence of anti and anti isomers allows for the formation of both R and S configuration on C-1 of the cyclopropane through a backside or a frontside ring closure mechanism. The reaction of olefin with anti R-3 can result in R-configuration of the cyclopropane carbon C-1 through a frontside closure mechanism, or in S-configuration if backside closure takes place. In a similar manner, anti R-3 may produce S-configuration through frontside closure or R-configuration through backside closure. We previously have shown by crystallography that reaction the R-isomer of 3 with 2-methyl-propene induces predominantly a R-configuration at C-1 of the resulting cyclopropane (RR-(−)-2,2 dimethyl-1-o-methoxyphenyl(tricarbonyl chromium)cyclopropane, whereas the S-carbene results in the corresponding SS isomer. These findings are consistent with cyclopropane formation from the syn isomer through a frontside closure mechanism or from anti isomer through a backside closure mechanism. In the case of [(η⁵-C₅H₅)(CO)₂FeCH[(η⁶-o-MeC₆H₄)Cr(CO)₃]]+ (4), only anti isomer is observed and optical rotation data indicate that the methylcarbene exhibits the same asymmetric induction (i.e., R-carbene yields R-cyclopropane C-1 and S-carbene yields S-cyclopropane C-1) as the methoxy analogue, and the assumption of the anti isomer being the reactive one then implies that the reaction proceeds through a backside closure mechanism rather a frontside mechanism. It is very likely that this preference is also valid for the methoxy substituted complex 4. Our results on 4 indicate that the enantioselectivity of the cyclopropanation reaction is not determined by the relative abundance of the isomers. As the syn isomer is the more abundant one, the anti isomer has to be the more reactive one compared to the syn isomer. Interchange of syn and anti isomers occurs fast compared to the rate of reaction of the carbene with olefin. The fast rate of interchange of syn and anti isomers relative to the rate of reaction with olefin precludes the direct observation of any differential reactivity form a change in the syn to anti ratio in the NMR spectrum. However, the in general lower ee values observed for 3 compared with 4 are consistent with the fact that the reactive isomer is less abundant in this case. Our data thus show that enantioselectivity of cyclopropanation with “chiral at carbene” complexes is controlled by the higher reactivity of the anti isomer and occurs through a backside ring closure mechanism.     

Os3(CO)9(μ3-AsC6H4CH3)(μ3-C6H3CH3) synthesis and crystal structure

One of the products of the reaction of the activated cluster Os₃(CO)₁₁(NCMe) with As(p-tol)₃ in refluxing nonane has been shown by spectroscopic and X-ray crystallographic methods to be Os₃(CO)₉(μ₃-AsC₆H₄CH₃)(μ₃-C₆H₃CH₃), which contains a benzyne moiety bonded asymmetrically from one carbon to one osmium via a σ bond and from a second carbon to form a bridge between the remaining two osmium atoms.     

The chemistry of cyclopentadienyl-ruthenacyclopentatrienes: novel carbon monoxide and isocyanide insertion reactions in [η5-C5H5)Ru(η4-C5Ph2H2NBut)Br]

Reaction of the novel ruthenacyclopentatriene [(η⁵-C₅H₅)Ru(C₄Ph₂H₂)Br] (1) with isocyanides gives the imino-2,5-diphenylcyclopentadiene complexes [(η⁵-C₅H₅Ru(η⁴-C₅Ph₂H₂NR)Br] (2, R = Me, Et, Cy, t-Bu, 2,6-Me₂C₆H₃); a novel fluxional process involving phenyl substituent rotation and imino nitrogen inversion has been identified for 2 (R = t-Bu, 2,6-Me₂C₆H₃), the interpretation of which is supported by the X-ray crystal structure determination of 2 (R = t-Bu).     

Synthesis and reactivity of 2-(tert-butylcyclopentadienyl)-indenyl dinuclear ruthenium complex [η5:η5-(tBuC5H3)(C9H6)]Ru2(CO)4: Halogen induced Ru cleavage from indenyl ring

Thermal reaction of Ru₃(CO)₁₂ with unsymmetrical Fv ligand 2-(tert-butylcyclopentadienyl)-indene provided [η⁵:η⁵-(^tBuC₅H₃)(C₉H₆)]Ru₂(CO)₄ (2) in good yield. When 2 reacted with three or more equivalent of halogen X₂, compounds [(η⁵-^tBuC₅H₃)(C₉H₆X)]Ru(CO)₂X (X = Br, 3; I, 4) were isolated in moderate yield. In complexes 3 and 4 only the Cp rings were coordinated with Ru(CO)₂X, along with uncomplexed halogenated-indenyl rings. All the new complexes have been fully characterized. X-ray characterization of 2, 3, and 4 are also provided.     

Cluster build-up in aqueous solution: synthesis,structure, protonation and catalytic properties of the trinuclear cation [(η6-C6H6)(η6-C6Me6)2Ru3(μ2-H)3(μ3-O)]+

The trinuclear oxo-capped cluster cation [(η⁶-C₆H₆)(η⁶-C₆Me₆)₂Ru₃(μ₂-H)₃(μ₃-O)]⁺ (2) was synthesised by reacting [(η⁶-C₆Me₆)Ru(H₂O)₃]²⁺ with [(η⁶-C₆Me₆)₂Ru₂(μ₂-H)₃]⁺ in aqueous solution. The single-crystal X-ray structure analysis of the tetrafluoroborate salt shows the cation to contain a H₂O molecule hydrogen-bonded to the μ₃-oxo ligand. Acidification experiments show two protonation steps occuring at this H₂O molecule and the oxo cap of the triruthenium cluster. The cluster cation 2 catalyses the hydrogenation of aromatic compounds in aqueous solution under biphasic conditions.     

Comparison of the Bonding of Benzene and C60 to a Metal Cluster: Ru3(CO)9(μ3-η2,η 2,η2-C6H6) and Ru3(CO)9(μ3-η2,η2,η2-C60)

The electron distributions and bonding in Ru₃(CO)₉( ³- ², ², ²-C₆H₆) and Ru₃(CO)₉( ³- ², ², ²-C₆₀) are examined via electronic structure calculations in order to compare the nature of ligation of benzene and buckminsterfullerene to the common Ru₃(CO)₉ inorganic cluster. A fragment orbital approach, which is aided by the relatively high symmetry that these molecules possess, reveals important features of the electronic structures of these two systems. Reported crystal structures show that both benzene and C₆₀ are geometrically distorted when bound to the metal cluster fragment, and our ab initio calculations indicate that the energies of these distortions are similar. The experimental Ru–C_fullerene bond lengths are shorter than the corresponding Ru–C_benzene distances and the Ru–Ru bond lengths are longer in the fullerene-bound cluster than for the benzene-ligated cluster. Also, the carbonyl stretching frequencies are slightly higher for Ru₃(CO)₉( ³- ², ², ²-C₆₀) than for Ru₃(CO)₉( ³- ², ², ²-C₆H₆). As a whole, these observations suggest that electron density is being pulled away from the metal centers and CO ligands to form stronger Ru–C_fullerene than Ru–C_benzene bonds. Fenske-Hall molecular orbital calculations show that an important interaction is donation of electron density in the metal–metal bonds to empty orbitals of C₆₀ and C₆H₆. Bonds to the metal cluster that result from this interaction are the second highest occupied orbitals of both systems. A larger amount of density is donated to C₆₀ than to C₆H₆, thus accounting for the longer metal–metal bonds in the fullerene-bound cluster. The principal metal–arene bonding modes are the same in both systems, but the more band-like electronic structure of the fullerene (i.e., the greater number density of donor and acceptor orbitals in a given energy region) as compared to C₆H₆ permits a greater degree of electron flow and stronger bonding between the Ru₃(CO)₉ and C₆₀ fragments. Of significance to the reduction chemistry of M₃(CO)₉( ³- ², ², ²-C₆₀) molecules, the HOMO is largely localized on the metal–carbonyl fragment and the LUMO is largely localized on the C₆₀ portion of the molecule. The localized C₆₀ character of the LUMO is consistent with the similarity of the first two reductions of this class of molecules to the first two reductions of free C₆₀. The set of orbitals above the LUMO shows partial delocalization (in an antibonding sense) to the metal fragment, thus accounting for the relative ease of the third reduction of this class of molecules compared to the third reduction of free C₆₀.     

Syntheses and characterization of [Ru(η5-C5H5) (AsPh3)(L)X] and [Ru(η5-C5H5)(AsPh3)(L)(MeCN)]+mY− (L = PPh3 or AsPh3; X = F,Cl, Br,I, CN,H or SnCl3; Y = HgCl3, Zn2Cl6 or BPh4; m = 1 or 2)

The syntheses of the complexes [(η⁵-C₅H₅)Ru(AsPh₃)(L)X] (L = PPh₃ or AsPh₃; X = Cl, F, Br, I, H, CN or SnCl₃) and [(η⁵-C₅H₅)Ru(AsPh₃)(L)(MeCN)]⁺Y⁻ (Y = HgCl₃, BPh₄ or Zn₂Cl₆) are described. They were characterized by elemental analyses, IR, UV and visible, PMR spectroscopy, X-ray powder diffraction, and mass spectral studies.     

Regioselective permethylation,perallylation and perbenzylation of the arene ligand in [Ru(η5-C5Me5)(η6-C6Me6)][PF6]: a remarkable periodic effect

The reactions of [MCp^*(η⁶-C₆Me₆)][PF₆], M = Fe: 1, Ru: 2, Cp^* = η⁵-C₅Me₅, with KOH (in DME) or tert-BuOK (in THF) and methyl iodide, allyl bromide or benzyl bromide are regioselective on the arene ligand only for 2, giving the complexes [RuCp^*{η⁶-C₆(CH₂R)₆}][PF₆], R = methyl (3), allyl (4) or benzyl (5), although some formations of C-C bonds also occur on the Cp^* ligand in the case of the reactions of allyl and benzyl bromides. This contrasts with the complete lack of regioselectivity formerly observed with the iron analogue 1, and is best taken into account by the difference of steric effects which are less marked in 2 than in 1.     

Generation of the dichloromethane complex [(η5-C5Me5)Re(NO)(PPh3)(ClCH2Cl]+ BF4−, and its conversion to the oxidative addition product [(η5-C5Me5)Re(NO)(PPh3)(Cl)(CH2Cl)]+ BF4−

Reaction of (η⁵-C₅Me₅)Re(NO)(PPh₃)(CH₃) and HBF₄ · OEt₂ in CH₂Cl₂ at −78°C gives the dichloromethane complex [η⁵-C₅Me₅Re(NO)(PPh₃)(ClCH₂Cl)]⁺ BF₄⁻, which undergoes the title transformation at −35°C. The ReClCH₂Cl carbon is attacked by halide nucleophiles (X⁻) to give XCH₂Cl and the chloride complex (η⁵-C₅Me₅)Re(NO)(PPh₃)(Cl), and exhibits a ¹³C NMR resonance that is coupled to phosphorus (d, ³J(CP) 5.0 Hz) and geminal hydrogens (t, ¹J(CH) 186 Hz).     

[Ru(NH3)6](MoO4)Cl·3H2O and [M(NH3)6](ReO4)3·2H2O (M = Ru, Ir). Synthesis and crystal structure

X-ray crystallographic analysis is used to determine the crystal structures of [Ru(NH₃)₆](MoO₄)Cl·3H₂O and [M(NH₃)₆](ReO₄)₃·2H₂O (M = Ru, Ir) complex salts. The features of the fragment packing are studied.     

Preparative chemistry with [Ru(η6-arene)(H2O)3]2+: bis-arene and monobenzene complexes with O,N and S donors

The preparation, and electronic, ¹H and ¹³C NMR spectra of the complex ions [Ru(η⁶-C₆H₆)L₃]²⁺ (L = acetonitrile, dimethylsulphoxide, dimethylsulphide or tetrahydrothiophene) from [Ru(η⁶-C₆H₆)(H₂O)₃]²⁺ are reported. The NMR data of coordinated benzene are discussed in terms of the π-backbonding capacity of the monodentate ligand.     

Electron transfer in organometallic clusters: XIV. Crystal and electronic structures of the tricobalt carbon cluster (η5-C5H5)Fe[η5-C5H4-CCo3(CO)9] and the biscarbyne cluster (η5-C5H5)Fe[η5-C5H4CCo3(η5-C5H5)3CH]

The crystal and molecular structures of (η⁵-C₅H₅)Fe[η⁵--C₅H₄CCo₃(CO)₉] (1), Pna2₁, α 17.354, b 11.463, c 11.207 Å Z = 4, R = 0.053, R_w = 0.056 for 939 reflections (I>3σ(I)) at 293 K, and (η⁵-C₅H₅Fe[η⁵--C₅H₄CCo₃(η⁵C₅H₅)₃CH] (2), P2₁/n, a 13.807(9), b 11.254(4), c 13.991(9) Å, β 99.98(5)°, Z = 4, R = 0.033 and R_w = 0.033 for 3051 observed reflections (I>3σ(I)) at 180 K, have been determined by X-ray methods.The results provide a detailed characterisation of related tricobalt-carbon complexes directly bound to ferrocene residues. In 1 the ferrocenyl moiety tops the pyramidal CCo₃ cluster core, while in 2 the CCo₃C core is bipyramidal with a ferrocenyl substituent on one capping carbon atom and a hydrogen atom at the other. In both cases the ferrocenyl group is tilted towards one cobalt atom of the cluster core, a distortion believed to be the consequence of the non-degeneracy of the carbyne p(π) orbitals resulting from a cooperative π-interaction between the clusters and the ferrocenyl substituents.     

Heteronuclear (WFe) and homonuclear (FeFE) μ-alkylidene complexes of transition metals from mononuclear terminal carbene complexes. crystal structures of {WFe[μ-η1, η3-C(OCH2CH3)(CHCHCH3](CO)8} and [fe2{μ-η2,η3-C[OCH2CH3[CHC(OCH2CH3)(CH3]}(CO)6

The reactions of mononuclear carbene complexes of W and Fe of the type CO)_mMC(OR)(CH_2nCHCR′″ (M  = FE, W; m = 4 and 5; n = 0, 2, 3; R′, R″ = C, CH₃, OEt) with Fe(CO)₅ have been studied. In all cases the reaction leads to new hetero (WFe) or homo (FeFe) μ-alkylidene complexes, the position of the double bond depending strongly on n.