Hydrogen-deuterium exchange between TpRu(PMe3)(L)X (L = PMe3 and X = OH, OPh, Me, Ph, or NHPh; L = NCMe and X = Ph) and deuterated arene solvents: evidence for metal-mediated processes

At elevated temperatures (90-130 degrees C), complexes of the type TpRu(PMe3)2X (X = OH, OPh, Me, Ph, or NHPh; Tp = hydridotris(pyrazolyl)borate) undergo regioselective hydrogen-deuterium (H/D) exchange with deuterated arenes. For X = OH or NHPh, H/D exchange occurs at hydroxide and anilido ligands, respectively. For X = OH, OPh, Me, Ph, or NHPh, isotopic exchange occurs at the Tp 4-positions with only minimal deuterium incorporation at the Tp 3- or 5-positions or PMe3 ligands. For TpRu(PMe3)(NCMe)Ph, the H/D exchange occurs at 60 degrees C at all three Tp positions and the phenyl ring. TpRu(PMe3)2Cl, TpRu(PMe3)2OTf (OTf = trifluoromethanesulfonate), and TpRu(PMe3)2SH do not initiate H/D exchange in C6D6 after extended periods of time at elevated temperatures. Mechanistic studies indicate that the likely pathway for the H/D exchange involves ligand dissociation (PMe3 or NCMe), Ru-mediated activation of an aromatic C-D bond, and deuteration of basic nondative ligand (hydroxide or anilido) or Tp positions via net D+ transfer.     

Reactions of TpRu(CO)(NCMe)(Ph) with electron-rich olefins: examples of stoichiometric C-S, C-O and C-H bond cleavage

Stoichiometric reactions of TpRu(CO)(NCMe)(Ph) with electron-rich olefins result in metal-mediated cleavage of C-S and C-O bonds.     

Octahedral Ru(II) amido complexes TpRu(L)(L')(NHR) (Tp = hydridotris(pyrazolyl)borate; L = L' = P(OMe)3 or PMe3 or L = CO and L' = PPh3; R = H,Ph, or tBu): synthesis,characterization, and reactions with weakly acidic C-H bonds

The octahedral Ru(II) amine complexes [TpRu(L)(L')(NH(2)R)][OTf] (L = L' = PMe(3), P(OMe)(3) or L = CO and L' = PPh(3); R = H or (t)Bu) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(L')(NH(3))][OTf] or [TpRu(PMe(3))(2)(NH(2)(t)Bu)][OTf] yields the Ru(II) amido complexes TpRu(L)(L')(NH(2)) and TpRu(PMe(3))(2)(NH(t)Bu). Reactions of the parent amido complexes or TpRu(PMe(3))(2)(NH(t)Bu) with phenylacetylene at room temperature result in immediate deprotonation to form ruthenium-amine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] ion pair results in the formation of the Ru(II) phenylacetylide complex TpRu(PMe(3))(2)(C[triple bond]CPh) in >90% yield. The observation that [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] converts to the Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(L')(NH(3))][PhC(2)] yields multiple products is attributed to reluctant dissociation of ammonia compared with the (t)butylamine ligand (i.e., different rates for acetylide/amine exchange). These results are consistent with ligand exchange reactions of Ru(II) amine complexes [TpRu(PMe(3))(2)(NH(2)R)][OTf] (R = H or (t)Bu) with acetonitrile. The previously reported phenyl amido complexes TpRuL(2)(NHPh) [L = PMe(3) or P(OMe)(3)] react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL(2)(C[triple bond]CPh) in quantitative yields. Kinetic studies indicate that the reaction of TpRu(PMe(3))(2)(NHPh) with phenylacetylene occurs via a pathway that involves TpRu(PMe(3))(2)(OTf) or [TpRu(PMe(3))(2)(NH(2)Ph)][OTf] as catalyst. Reactions of 1,4-cyclohexadiene with the Ru(II) amido complexes TpRu(L)(L')(NH(2)) (L = L' = PMe(3) or L = CO and L' = PPh(3)) or TpRu(PMe(3))(2)(NH(t)Bu) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe(3))(2)(H), [Tp(PMe(3))(2)Ru[double bond]C[double bond]C(H)Ph][OTf], [Tp(PMe(3))(2)Ru=C(CH(2)Ph)[N(H)Ph]][OTf], and [TpRu(PMe(3))(3)][OTf] have been independently prepared and characterized. Results from solid-state X-ray diffraction studies of the complexes [TpRu(CO)(PPh(3))(NH(3))][OTf], [TpRu(PMe(3))(2)(NH(3))][OTf], and TpRu(CO)(PPh(3))(C[triple bond]CPh) are reported.     

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.     

Reactivity of TpRu(L)(NCMe)R (L = CO, PMe3; R = Me, Ph) systems with isonitriles: Experimental and computational studies toward the intra- and intermolecular hydroarylation of isonitriles

The Ru(II) phenyl complex TpRu(PMe₃)(NCMe)Ph {Tp = hydridotris(pyrazolyl)borate} reacts with isonitriles to form complexes of the type TpRu(PMe₃)(CNR)Ph (R = ^tBu, CH₂Ph, CH₂CH₂Ph). Neither thermal nor photolytic reactions of these systems with excess isonitrile and benzene resulted in the production of corresponding imines. DFT studies that probed the energetics of the desired catalytic transformations revealed that (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph {Tab = tris(azo)borate} is the most stable species in a proposed catalytic cycle. Exclusive of calculated transition states, the highest points on the calculated free energy surface are 34 kcal/mol, for (Tab)Ru(PH₃)(o,η²-C,C-CNCH₂CH₂Ph)Ph {relative to the starting material (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph}, and 27 kcal/mol for the C-H activation product (Tab)Ru(PH₃)(o-C₆H₄CH₂CH₂NC) and benzene. The substantial increases in free energy result primarily from the loss of the stable ruthenium-η¹-isonitrile interaction.     

Synthesis and reactivity of the monomeric late-transition-metal parent amido complex [Ir(Cp*)(PMe3)(Ph)(NH2)

The late-transition-metal parent amido compound [Ir(Cp*)(PMe3)(Ph)(NH2)] (2) has been synthesized by deprotonation of the corresponding ammine complex [Ir(Cp*)(PMe3)(Ph)(NH3)][OTf] (6) with KN(SiMe3)2. An X-ray structure determination has ascertained its monomeric nature. Proton-transfer studies indicate that 2 can successfully deprotonate p-nitrophenylacetonitrile, aniline, and phenol. Crystallographic analysis has revealed that the ion pair [Ir(Cp*)(PMe3)(Ph)(NH3)][OPh] (8) exists as a hydrogen-bonded dimer in the solid state. Reactions of 2 with isocyanates and carbodiimides lead to overall insertion of the heterocumulenes into the N--H bond of the Ir-bonded amido group, demonstrating the ability of 2 to act as an efficient nucleophile. Intriguing reactivity is observed when amide 2 reacts with CO or 2,6-dimethylphenyl isocyanide. eta4-Tetramethylfulvene complexes [Ir(eta4-C5Me4CH2)(PMe3)(Ph)(L)] (L=CO (15), CNC6H3-2,6-(CH3)2 (16)) are formed in solution through displacement of the amido group by the incoming ligand followed by deprotonation of a methyl group on the Cp* ring and liberation of ammonia. Conclusive evidence for the presence of the Ir-bonded eta4-tetramethylfulvene moiety in the solid state has been provided by an X-ray diffraction study of complex 16.     

Reactions of (PCP)Ru(CO)(NHPh)(PMe3) (PCP = 2,6-(CH2PtBu2)2C6H3) with substrates that possess polar bonds

The Ru(II) amido complex (PCP)Ru(CO)(PMe(3))(NHPh) (1) (PCP = 2,6-(CH(2)P(t)Bu(2))(2)C(6)H(3)) reacts with compounds that possess polar C=N, C triple bond N, or C=O bonds (e.g., nitriles, carbodiimides, or isocyanates) to produce four-membered heterometallacycles that result from nucleophilic addition of the amido nitrogen to an unsaturated carbon of the organic substrate. Based on studies of the reaction of complex 1 with acetonitrile, the transformations are suggested to proceed by dissociation of trimethylphosphine, followed by coordination of the organic substrate and then intramolecular N-C bond formation. In the presence of ROH (R = H or Me), the fluorinated amidinate complex (PCP)Ru(CO)(N(Ph)C(C(6)F(5))NH) (6) reacts with excess pentafluorobenzonitrile to produce (PCP)Ru(CO)(F)(N(H)C(C(6)F(5))NHPh) (7). The reaction with MeOH also produces o-MeOC(6)F(4)CN (>90%) and p-MeOC(6)F(4)CN (<10%). Details of the solid-state structures of (PCP)Ru(CO)(F)(N(H)C(C(6)F(5))NHPh) (7), (PCP)Ru(CO)[PhNC{NH(hx)}N(hx)] (8), (PCP)Ru(CO){N(Ph)C(NHPh)O} (9), and (PCP)Ru(CO){OC(Ph)N(Ph)} (10) are reported.     

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.     

Thermodynamic hydride donor abilities of [HW(CO)4L]- complexes (L = PPh3, P(OMe)3, CO) and their reactions with [C5Me5Re(PMe3)(NO)(CO)]+

The thermodynamic hydride donor abilities of [HW(CO)(5)](-) (40 kcal/mol), [HW(CO)(4)P(OMe(3))](-) (37 kcal/mol), and [HW(CO)(4)(PPh(3))](-) (36 kcal/mol) have been measured in acetonitrile by either equilibrium or calorimetric methods. The hydride donor abilities of these complexes are compared with other complexes for which similar thermodynamic measurements have been made. [HW(CO)(5)](-), [HW(CO)(4)P(OMe(3))](-), and [HW(CO)(4)(PPh(3))](-) all react rapidly with [CpRe(PMe(3))(NO)(CO)](+) to form dinuclear intermediates with bridging formyl ligands. These intermediates slowly form [CpRe(PMe(3))(NO)(CHO)] and [W(CO)(4)(L)(CH(3)CN)]. The structure of cis-[HW(CO)(4)(PPh(3))](-) has been determined and has the expected octahedral structure. The hydride ligand bends away from the CO ligand trans to PPh(3) and toward PPh(3).     

Synthesis of RuHCl(CO)(Hdmpz)(L)2 (L=PPh3, AsPh3, and Hdmpz=3,5-dimethylpyrazole) and crystal structure of RuHCl(CO)(Hdmpz)(AsPh3)2

Treatment of RuHCl(CO)(L)₃ with a slight excess amount of K[HB(3,5-Me₂pz)₃] in boiling MeOH solution yielded unusual 3,5-dimethylpyrzaole (Hdmpz) complexes, RuHCl(CO)(Hdmpz)(L)₂ (L=PPh₃, 1 or AsPh₃, 2). Unexpectedly the dissociation of the bonds between the boron atom and the nitrogen atoms of the potentially tridentate [HB(3,5-Me₂pz)₃]⁻ ligand during the coordination of the ligand to the Ru^II metal has been observed. In a separate preparation, the RuHCl(CO)(Hdmpz)(PPh₃)₂ complex has also been synthesized from the reaction between RuHCl(CO)(PPh₃)₃ and the monodentate Hdmpz ligand. Complexes 1 and 2 have been characterized by elemental analysis, IR and ¹H NMR spectroscopies. Compound 1 has also been prepared by the reaction between RuHCl(CO)(PPh₃)₃ and K[H₂B(3,5-Me₂pz)₂] in boiling toluene solution. The crystal structure of 2 has been studied by X-ray crystallography. The geometrical structure around Ru^II of 2 is a distorted octahedral structure. The crystal structure of 2 consists of a discrete monomeric compound. It is interesting to find that the sterically-demanding [HB(3,5-Me₂pz)₃]⁻ or [H₂B(3,5-Me₂pz)₂]⁻ ligands break up during the reaction with the Ru^II complexes to form the neutral 3,5-dimethylpyrazole complexes. In contrast to these observations, [H₂Bpz₂]⁻ and [H₂B(4-Brpz)₂]⁻ ligands form very stable Ru^II complexes.     

Redox-active polymers based on nonbridged metal-metal bonds. Electrochemical formation of [Os(bpy)(CO)(L)](n) (bpy = 2,2'-bipyridine; L = CO, MeCN) and of their reduced forms: a spectroelectrochemical study

IR, UV-vis, and EPR spectroelectrochemistry at variable temperatures and in different solvents were applied to investigate in situ the formation of electroactive molecular chains with a nonbridged Os-Os backbone, in particular, the polymer [Os(0)(bpy)(CO)(2)](n) (bpy = 2,2'-bipyridine), from a mononuclear Os(II) carbonyl precursor, [Os(II)(bpy)(CO)(2)Cl(2)]. The one-electron-reduced form, [Os(II)(bpy(.)(-))(CO)(2)Cl(2)](-), has been characterized spectroscopically at low temperatures. This radical anion is the key intermediate in the electrochemical propagation process responsible for the metal-metal bond formation. Unambiguous spectroscopic evidence has been gained also for the formation of [[Os(0)(bpy(*)(-))(CO)(2)](-)](n), the electron-rich electrocatalyst of CO(2) reduction. The polymer species are fairly well soluble in butyronitrile, which is important for their potential utilization in nanoscience, for example, as conducting molecular wires. We have also shown that complete solubility is accomplished for the monocarbonyl-acetonitrile derivative of the polymer, [Os(0)(bpy)(CO)(MeCN)(2)Cl](n).     

Density functional computations of the cyclopropanation of ethene catalyzed by iron (II) carbene complexes Cp(CO)(L)FeCHR,L = CO,PMe3, R = Me,OMe, ph,CO2Me

Density functional theory has been used to study the Fe‐catalyzed cyclopropanation of Fe‐carbene complexes with ethene. All the intermediates and transition states were optimized completely at the B3LYP/6‐31+G(d,p) level. Calculation results confirm that the cyclopropanation of Fe‐carbene complexes with ethene involves the two reaction paths I and II . In the reaction path I , the double bond of ethene attacks directly on the carbene carbon of Fe‐carbene complexes to generate the cyclopropane. In the reaction path II , ethene substitution for PMe₃ or CO in the Fe‐carbene complexes leads to the complexes M2 ; and the attack of one carbon of ethene on the carbene carbon results in the complexes M3 with a Fe? C? C? C four‐membered ring, and then generates the cyclopropane via the elimination reaction. For Fe‐carbene complexes A , C , D , E , and H , the main reaction mode is the reaction path I ; for Fe‐carbene complexes B , F , and G , the main reaction mode is the reaction path II . © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Preparative and electrochemical investigations on the electron sponge behavior of cobalt telluride clusters: CO substitution in [Co11Te7(CO)10]n- ions (n=1, 2) by PMe2Ph and crystal structure of [Co11Te7(CO)5(PMe2Ph)5

The reaction of the cluster salts [Cp(2*) Nb(CO)(2)](n)[Co(11)Te(7)(CO)(10)] (Cp*=C(5)Me(5); n=1, 2) with excess PMe(2)Ph gave the neutral, dark brown clusters [Co(11)Te(7)(CO)(6)(PMe(2)Ph)(4)] (5) and [Co(11)Te(7)(CO)(5)(PMe(2)Ph)(5)] (6) with 147 metal valence electrons. The new compounds were characterized by IR spectroscopy, elemental analyses, and mass spectrometry. The molecular structure of 6 was determined by X-ray crystallography. Like its precursor anion, it consists of a pentagonal-prismatic [Co(11)Te(7)] core, but with a ligand sphere composed of five CO and five PMe(2)Ph ligands. Detailed electrochemical studies of both reactions reveal that a stepwise substitution of CO ligands in the initial cluster anions takes place leading to intermediate [Co(11)Te(7)(CO)(10-m)(PMe(2)Ph)(m)](n-) ions (m=1-5; n=1, 2). Each of these intermediates is distinguished by at least one oxidation and two reduction waves, giving rise to a total of 21 redox couples and 27 electroactive species. The electron sponge character of the new compounds is particularly pronounced in 5, which exhibits charges n between +1 and -4 corresponding to metal valence electron counts of between 146 and 151.     

Reaction of [Os3(CO)10(NCMe)2] with amides and aldehydes; X-ray crystal structure of [Os3(CO)10(μ-H)(COCH2Ph)]

Reaction of [OS₃(CO)₁₀(NCMe)₂] with amides and aldehydes has provided a high-yield route to clusters of the type [OS₃(CO)₁₀H(NHCOR)] (R  H, Me, Ph, Et, Pr) and [OS₃(CO)₁₀H(COR)] (R  Me, Ph, CH₂Ph, C₆H₁₃), respectively; the molecular structure of [OS₃(CO)₁₀H(COCH₂Ph)] has been established by a single-crystal X-ray analysis.     

Excited-state dynamics of fac-[ReI(L)(CO)3(phen)]+ and fac-[ReI(L)(CO)3(5-NO2-phen)]+ (L = imidazole, 4-ethylpyridine; phen = 1,10-phenanthroline) complexes

The nature and dynamics of the lowest excited states of fac-[Re(I)(L)(CO)(3)(phen)](+) and fac-[Re(I)(L)(CO)(3)(5-NO(2)-phen)](+) [L = Cl(-), 4-ethyl-pyridine (4-Etpy), imidazole (imH); phen = 1,10-phenanthroline] have been investigated by picosecond visible and IR transient absorption spectroscopy in aqueous (L = imH), acetonitrile (L = 4-Etpy, imH), and MeOH (L = imH) solutions. The phen complexes have long-lived Re(I) --> phen (3)MLCT excited states, characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widely split IR bands due to the out-of-phase A'(2) and A"nu(CO) vibrations. The lowest excited states of the 5-NO(2)-phen complexes also have (3)MLCT character; the larger upward nu(CO) shifts accord with much more extensive charge transfer from the Re(I)(CO)(3) unit to 5-NO(2)-phen in these states. Transient visible absorption spectra indicate that the excited electron is delocalized over the 5-NO(2)-phen ligand, which acquires radical anionic character. Similarly, involvement of the -NO(2) group in the Franck-Condon MLCT transition is manifested by the presence of an enhanced nu(NO(2)) band in the preresonance Raman spectrum of [Re(I)(4-Etpy)(CO)(3)(5-NO(2)-phen)](+). The Re(I) --> 5-NO(2)-phen (3)MLCT excited states are very short-lived: 7.6, 170, and 43 ps for L = Cl(-), 4-Etpy, and imH, respectively, in CH(3)CN solutions. The (3)MLCT excited state of [Re(I)(imH)(CO)(3)(5-NO(2)-phen)](+) is even shorter-lived in MeOH (15 ps) and H(2)O (1.3 ps). In addition to (3)MLCT, excitation of [Re(I)(imH)(CO)(3)(5-NO(2)-phen)](+) populates a (3)LLCT (imH --> 5-NO(2)-phen) excited state. Most of the (3)LLCT population decays to the ground state (time constants of 19 (H(2)O), 50 (MeOH), and 72 ps (CH(3)CN)); in a small fraction, however, deprotonation of the imH.+ ligand occurs, producing a long-lived species, [Re(I)(im.)(CO)(3)(5-NO(2)-phen).-]+.