Fast hydrogen elimination from the [Ru(PH3)3(CO)(H)2] and [Ru(PH3)4(H)2] complexes in the first singlet excited states: a diabatic quantum dynamics study

The photodissociation dynamics of [Ru(PH3)3(CO)(H)2] and cis-[Ru(PH3)4(H)2] is theoretically analyzed in the lowest two excited singlet states. Energies obtained through electronic density functional theory calculations that use the time-dependent formalism are fitted to analytical reduced two-dimensional potential energy surfaces (2D-PES). The metal-H2 (R) and H-H (r) distances are the variables of these 2D-PES, the rest of the parameters being kept frozen at the values of the minimum energy structure in the ground electronic state. The time evolution in these 2D-PES is exactly followed by means of a fast Fourier transform algorithm applied to solve the time-dependent Schr?dinger equation. A simple diabatization scheme is devised to take into account the probability of transitions between both excited states. The quantum dynamics results point out that photoelimination is almost inexistent if the H2 fragment is to be expelled without further rearrangement of the rest of the complex. Conversely, when the geometries of the complex are optimized by keeping r and R frozen at the hydrogen elimination barrier coordinates, the new 2D-PES so obtained are highly dissociative, the H2 fragment being expelled in less than 100 fs. Finally the picture of the whole reaction that emerges from our theoretical results is described and the main differences between both complexes are examined.     

Substitution reactions of [Ru(dppe)(CO)(H(2)O)(3)][OTf](2)

The labile nature of the coordinated water ligands in the organometallic aqua complex [Ru(dppe)(CO)(H(2)O)(3)][OTf](2) (1) (dppe = Ph(2)PCH(2)CH(2)PPh(2); OTf = OSO(2)CF(3)) has been investigated through substitution reactions with a range of incoming ligands. Dissolution of 1 in acetonitrile or dimethyl sulfoxide results in the facile displacement of all three waters to give [Ru(dppe)(CO)(CH(3)CN)(3)][OTf](2) (2) and [Ru(dppe)(CO)(DMSO)(3)][OTf](2) (3), respectively. Similarly, 1 reacts with Me(3)CNC to afford [Ru(dppe)(CO)(CNCMe(3))(3)][OTf](2) (4). Addition of 1 equiv of 2,2'-bipyridyl (bpy) or 4,4'-dimethyl-2,2'-bipyridyl (Me(2)bpy) to acetone/water solutions of 1 initially yields [Ru(dppe)(CO)(H(2)O)(bpy)][OTf](2) (5a) and [Ru(dppe)(CO)(H(2)O)(Me(2)bpy)][OTf](2) (6a), in which the coordinated water lies trans to CO. Compounds 5a and 6a rapidly rearrange to isomeric species (5b, 6b) in which the ligated water is trans to dppe. Further reactivity has been demonstrated for 6b, which, upon dissolution in CDCl(3), loses water and coordinates a triflate anion to afford [Ru(dppe)(CO)(OTf)(Me(2)bpy)][OTf] (7). Reaction of 1 with CH(3)CH(2)CH(2)SH gives the dinuclear bridging thiolate complex [[(dppe)Ru(CO)](2)(mu-SCH(2)CH(2)CH(3))(3)][OTf] (8). The reaction of 1 with CO in acetone/water is slow and yields the cationic hydride complex [Ru(dppe)(CO)(3)H][OTf] (9) via a water gas shift reaction. Moreover, the same mechanism can also be used to account for the previously reported synthesis of 1 upon reaction of Ru(dppe)(CO)(2)(OTf)(2) with water (Organometallics 1999, 18, 4068).     

NMR studies of Ru(3)(CO)(10)(PMe(2)Ph)(2) and Ru(3)(CO)(10)(PPh(3))(2) and their H(2) addition products: detection of new isomers with complex dynamic behavior

The clusters Ru(3)(CO)(10)L(2), where L = PMe(2)Ph or PPh(3), are shown by NMR spectroscopy to exist in solution in at least three isomeric forms, one with both phosphines in the equatorial plane on the same ruthenium center and the others with phosphines in the equatorial plane on different ruthenium centers. Isomer interconversion for Ru(3)(CO)(10)(PMe(2)Ph)(2) is highly solvent dependent, with DeltaH decreasing and DeltaS becoming more negative as the polarity of the solvent increases. The stabilities of the isomers and their rates of interconversion depend on the phosphine ligand. A mechanism that accounts for isomer interchange involving Ru-Ru bond heterolysis is suggested. The products of the reaction of Ru(3)(CO)(10)L(2) with hydrogen have been monitored by NMR spectroscopy via normal and para hydrogen-enhanced methods. Two hydrogen addition products are observed with each containing one bridging and one terminal hydride ligand. EXSY spectroscopy reveals that both intra- and interisomer hydride exchange occurs on the NMR time scale. On the basis of the evidence available, mechanisms for hydride interchange involving Ru-Ru bond heterolysis and CO loss are proposed.     

Stoichiometric and catalytic reactivity of the N-heterocyclic carbene ruthenium hydride complexes [Ru(NHC)(L)(CO)HCl] and [Ru(NHC)(L)(CO)H(eta2-BH4)] (L=NHC, PPh3)

Thermolysis of [Ru(AsPh3)3(CO)H2] with the N-aryl heterocyclic carbenes (NHCs) IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) or the adduct SIPr.(C6F5)H (SIPr=1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene), followed by addition of CH2Cl2, affords the coordinatively unsaturated ruthenium hydride chloride complexes [Ru(NHC)2(CO)HCl] (NHC=IMes , IPr , SIPr ). These react with CO at room temperature to yield the corresponding 18-electron dicarbonyl complexes . Reduction of and [Ru(IMes)(PPh3)(CO)HCl] () with NaBH4 yields the isolable borohydride complexes [Ru(NHC)(L)(CO)H(eta2-BH4)] (, L=NHC, PPh3). Both the bis-IMes complex and the IMes-PPh3 species react with CO at low temperature to give the eta1-borohydride species [Ru(IMes)(L)(CO)2H(eta1-BH4)] (L=IMes , PPh3), which can be spectroscopically characterised. Upon warming to room temperature, further reaction with CO takes place to afford initially [Ru(IMes)(L)(CO)2H2] (L=IMes, L=PPh3) and, ultimately, [Ru(IMes)(L)(CO)3] (L=IMes , L=PPh3). Both and lose BH3 on addition of PMe2Ph to give [Ru(IMes)(L)(L')(CO)H2](L=L'=PMe2Ph; L=PPh3, L'=PMe2Ph). Compounds and have been tested as catalysts for the hydrogenation of aromatic ketones in the presence of (i)PrOH and H2. For the reduction of acetophenone, catalytic activity varies with the NHC present, decreasing in the order IPr>IMes>SIMes.     

On the excited states involved in the luminescent probe [Ru(bpy)2dppz]2+

The nature of the excited states of [Ru(bpy)2dppz]2+ has been investigated using density functional theory with the hybrid functional B3LYP. The excitations were studied via linear response theory (TDDFT) and DeltaSCF calculations and the solvent effects were introduced by embedding the molecule in a continuum dielectric medium. It was found that the solvent effects are critical in understanding the nature of the excitations. For the molecule in ethanol, the lowest absorption predicted by TDDFT is a dark state 3pi --> pi with the electron and hole spread over the dppz ligand. Next come the excitations of 3MLCT between the ruthenium and the dppz and finally the 3MLCT excitations between the ruthenium and the bpy ligands not associated with the phenazine. Using deltaSCF calculations two low-lying excited states were identified and the geometry optimized in the presence of the continuum medium. At the optimal geometry the lowest excited state is 3MLCT (Ru --> dppz). The 3pi --> pi state is found only 0.026 eV higher.     

Quantitative Formation in Water of [Ru(CO)(H2O)5]2+ from Hexaaquaruthenium(II) and Carbon Monoxide

High-pressure ¹⁷O- and ¹³C-NMR show that [Ru(H₂O)₆]²⁺ reacts quantitatively with carbon monoxide (50 bar) in water to form [Ru(CO)(H₂O)₅]²⁺.     

Rhenium-to-benzoylpyridine and rhenium-to-bipyridine MLCT excited states of fac-[Re(Cl)(4-benzoylpyridine)(2)(CO)(3)] and fac-[Re(4-benzoylpyridine)(CO)(3)(bpy)](+): a time-resolved spectroscopic and spectroelectrochemical study

The lowest allowed electronic transition of fac-[Re(Cl)(CO)(3)(bopy)(2)] (bopy = 4-benzoylpyridine) has a Re --> bopy MLCT character, as revealed by UV-vis and stationary resonance Raman spectroscopy. Accordingly, the lowest-lying, long-lived, excited state is Re --> bopy (3)MLCT. Electronic depopulation of the Re(CO)(3) unit and population of a bopy pi orbital upon excitation are evident by the upward shift of nu(CO) vibrations and a downward shift of the ketone nu(C=O) vibration, respectively, seen in picosecond time-resolved IR spectra. Moreover, reduction of a single bopy ligand in the (3)MLCT excited state is indicated by time-resolved visible and resonance Raman (TR(3)) spectra that show features typical of bopy(*)(-). In contrast, the lowest allowed electronic transition and lowest-lying excited state of a new complex fac-[Re(bopy)(CO)(3)(bpy)](+) (bpy = 2,2'-bipyridine) have been identified as Re --> bpy MLCT with no involvement of the bopy ligand, despite the fact that the first reduction of this complex is bopy-localized, as was proven spectroelectrochemically. This is a rare case in which the localizations of the lowest MLCT excitation and the first reduction are different. (3)MLCT excited states of both fac-[Re(Cl)(CO)(3)(bopy)(2)] and fac-[Re(bopy)(CO)(3)(bpy)](+) are initially formed vibrationally hot. Their relaxation is manifested by picosecond dynamic shifts of nu(C(triple bond)O) IR bands. The X-ray structure of fac-[Re(bopy)(CO)(3)(bpy)]PF(6).CH(3)CN has been determined.     

Theoretical studies on the excited states, DNA photocleavage, and spectral properties of complex [Ru(phen)(2)(6-OH-dppz)](2+)

The structures and related properties of the complex [Ru(phen)2(6-OH-dppz)]2+ (phen = 1,10-phenanthroline; dppz = dipyrido [3,2-a:2',3'-c]phenazine) in the ground state (S0), the first singlet excited state (S1), and the first triplet excited state (T1) have been studied using density functional theory (DFT), time-dependent (TD) DFT, Hartree-Fock (HF), and configuration interaction singles (CIS) methods. Three electronic absorption-spectral bands (1MLCT, 1LL, and 1LL) lying in the range of 250-550 nm in vacuo and in aqueous solution were theoretically calculated, simulated, and assigned with TDDFT method. In particular, the theoretical results show the following: (1) The positive charges of central Ru atom in the excited states (S1 and T1) are greatly increased relative to those in the ground state (S0), and thus the Ru atom in the excited states can be regarded as Ru(III). (2) The positive charges on the main ligand (6-OH-dppz) in the excited states are considerably reduced, and thus the interaction between the main ligand (intercalative ligand) and DNA base pairs is considerably weakened. (3) The geometric structures in excited states are also distorted, resulting in obvious increase in the coordination bond length. It is advantageous to the complex forming a high oxidizing center (i.e., Ru(III) ion). On the basis of these results, a theoretical explanation on photoinduced oxidation reduction mechanism of DNA photocleavage by [Ru(phen)2(6-OH-dppz)](2+) has been presented.     

Syntheses of the new trinuclear ions [Ru3(CO)11]2− and [Os3(CO)11]2−

Stoichiometric reduction of Os₃CO)₁₂ and Ru₃(CO)₁₂ with K and Ca, respectively; yields the two new cluster dianions [Os₃(CO)₁₁]^2? and [Ru₃(CO)₁₁]^2? which have been isolated and characterized. Temperature-dependent ¹³C NMR spectra for [Os₃(CO)₁₁]^2? and infrared spectra of [Os₃(CO)₁₁]^2? and [Ru₃(CO)₁₁]^2? suggest a similar structure for these dianions in which there is a single edge-bridging carbonyl.     

Reaction properties of the trans-hyponitrite complex [Ru2(CO)4(mu-H)(mu-PBu(t)2)(mu-Ph2PCH2PPh2)(mu-eta2-ONNO)

The protonation of [Ru(2)(CO)(4)(mu-H)(mu-PBu(t)()(2))(mu-dppm)(mu-eta(2)-ONNO)] (1) with HBF(4) occurs at the oxygen of the noncoordinating side of the trans-hyponitrite ligand to give [Ru(2)(CO)(4)(mu-H)(mu-PBu(t)()(2))(mu-dppm)(mu-eta(2)-ONNOH)][BF(4)] (2) in good yield. The monoprotonated hyponitrite in 2 is deprotonated easily by strong bases to regenerate 1. Furthermore, 1 reacts with the methylating reagent [Me(3)O][BF(4)] to afford [Ru(2)(CO)(4)(mu-H)(mu-PBu(t)()(2))(mu-dppm)(mu-eta(2)-ONNOMe)][BF(4)] (3). The molecular structures of 2 and 3 have been determined crystallographically, and the structure of 2 is discussed with the results of the DFT/B3LYP calculations on the model complex [Ru(2)(CO)(4)(mu-H)(mu-PH(2))(mu-H(2)PCH(2)PH(2))(mu-eta(2)-ONNOH)](+) (2a). Moreover, the thermolysis of 2 in ethanol affords [Ru(2)(CO)(4)(mu-H)(mu-OH)(mu-PBu(t)()(2))(mu-dppm)][BF(4)] (4) in high yield, and the deprotonation of 4 by DBU in THF yields the novel complex [Ru(2)(CO)(4)(mu-OH)(mu-PBu(t)()(2))(mu-dppm)] (5).     

A [2]catenane constructed around a Ru(diimine)(3)(2+) complex used as a template

A [2]catenane has been constructed using an octahedral complex of the Ru(diimine)( 2+)(3) family as a scaffold. Two diimine chelates have been incorporated in a ring prior to the ruthenium(II) complexation reaction. The macrocyclic complex thus obtained has been subsequently threaded by a long linear fragment containing the third chelate. The rutheniuml(II)-complexed catenane, cyclized by ring-closing metathesis, is the first example of an interlocking ring system built around an octahedral tris-chelate complex.     

Mechanism of protonation of [Pt(3)(mu-PBu(t)(2))3(H)(CO)2], yielding the hydride-bridged [Pt(3)(mu-PBu(t)(2))2(mu-H)(PBu(t)(2)H)(CO)2]OTf (Tf=CF(3)SO(2)), and the spectroscopic and theoretical characterization of a kinetic intermediate

The reaction of the Pt(I)Pt(I)Pt(II) triangulo cluster Pt(3)(micro-PBu(t)()(2))(3)(H)(CO)(2) (1) with TfOH (Tf = CF(3)SO(2)) affords the hydride-bridged cationic derivative [Pt(3)(mu-PBu(t)()(2))(2)(mu-H)(PBu(t)()(2)H)(CO)(2)]OTf (2). With TfOD the reaction gives selectively [Pt(3)(mu-PBu(t)(2))(2)(mu-D)(PBu(t)(2)H)(CO)(2)]OTf (2-D(1)), implying that the proton is transferred to a metal center while a P-H bond is formed by the reductive coupling of one of the bridging phosphides and the terminal hydride ligand of the reagent. The reaction proceeds through the formation of a thermally unstable kinetic intermediate which was characterized at low temperatures, and was suggested to be the CO-hydrogen-bonded (or protonated) [Pt(3)(mu-PBu(t)(2))(3)(H)(CO)(2)].HOTf (3). An ab initio theoretical study predicts a hydrogen-bonded complex or a proton-transfer tight ion pair as a possible candidate for the structure of the kinetic intermediate.     

The reaction of Ru3(CO)12 with HC9PPh2)3. Characterisation of Ru3(CO)9[HC(PPh2)3], and crystal and molecular structure of Ru3(CO)9[HC(PPh2)(PhPC6H4PPh)]·CHCl3

Reaction of Ru₃(CO)₁₂ with HC(PPh₂)₃ leads to a variety of products, two of which have been characterised. One is the symmetrically capped product Ru₃(CO)₉[HC(PPh₂)₃], which was characterised spectroscopically. The second product was characterised crystallographically as Ru₃(CO)₉[HC(PPh₂)-(PhPC₆H₄PPh)]-CHCl₃.     

Correlated v(H(2) ) and j(CO) product states from formaldehyde photodissociation: dynamics of molecular elimination

A detailed study of the photoinduced molecular elimination pathway of formaldehyde on the ground state surface was carried out using high-resolution dc slice ion imaging. Detailed correlated H(2) rovibrational and CO rotational product quantum state distributions were measured by imaging spectroscopically selected CO velocity distributions following photodissociation at energies from approximately 1800 to approximately 4100 cm(-1) above the barrier to molecular elimination. Excitation to the 2(1)4(1), 2(1)4(3), 2(2)4(1), 2(2)4(3), and 2(3)4(1) bands of H(2)CO are reported here. The dependence of the product rovibrational distributions on excitation energy are discussed in light of a dynamical model which has been formulated to describe the strong product state correlations observed.     

Reactivity of Ph2P(Se)CH2C6H4CH2P(Se)Ph2 with [M3(CO)12] (M=Ru or Fe). Synthesis and characterization of the new carbene cluster [Ru3(mu3-Se)(mu3-H)(mu2-PPh2)(CO)6(mu2-CHC6H4CH2PPh2)

The reactions of [M3(CO)12] (M=Ru or Fe) with 1,2 bis[(diphenylphosphino)methyl]benzene diselenide (dpmbSe2) in hot toluene afford a variety of phosphine-substituted selenido carbonyl clusters. They belong to the following three families: (i) 50-electron clusters with a M3Se2 core (2, 3, 5-7), (ii) 48-electron clusters with a M3Se core (1, 8), (iii) 34-electron clusters with a M2Se2 core (4). All these species derive from the P=Se bond cleavage. Cluster 1, which contains a hydrido, a phosphido, and a carbene ligand, is produced by multiple fragmentation of the diphosphine. This fragmentation appears related to the presence of the selenido ligand on the cluster, as the reaction of [Ru3(CO)12] with dpmb (not selenized) produces only carbonyl substitution by the phosphine to give [Ru3(CO)10(mu-dpmb)] (9). All the clusters synthesized have been characterized by spectroscopic techniques, and in some cases fluxional behavior has been detected in solution by NMR analysis. The structures of 1, 2, and 7-9 have been determined by X-ray diffraction methods.