Syntheses and reactivity studies of solvated dirhenium acetonitrile complexes

Fully and partially solvated triply-bonded [Re2]4+ complexes have been synthesized and their X-ray structures are described. A fully solvated dirhenium salt with BArf [tetrakis(3,5-bis(trifluoromethyl)phenyl)borate] as the counter anion [Re2(CH3CN)10][BArf]4 () has been characterized. The solubility of the complex in CH2Cl2 and THF in addition to CH3CN offers the possibility of improved reactivity. The structure of [Re2(micro-O)(CH3CN)10][BF4]4 () that possesses a linear [Re(III)-O-Re(III)]4+ unit is reported. Protonation reactions of cis-Re2Cl2(dppm)2(O2CCH3)2 and trans-Re2Cl4(dppm)2 with HBF4.Et2O in acetonitrile afforded cis and trans [Re2(dppm)2(CH3CN)6][BF4]4 ( and ), respectively. Prolonging the reaction time, however, does not lead to fully solvated complex [Re2(CH3CN)10][BF4]4. The neutral nitrogen donor ligands pynp (2-(2-pyridyl)-1,8-naphthyridine) and tznp (2-(2-thiazolyl)-1,8-naphthyridine) react readily with [Re2(CH3CN)10][BF4]4 to provide trans-[Re2(pynp)2(CH3CN)4][BF4]4 and trans-[Re2(tznp)2(CH3CN)4][BF4]4. The X-ray structures trans-[Re2(pynp)2(CH3CN)4][BF4]4 () and trans-[Re2(tznp)2(CH3CN)4][BF4]3[PF6] () have been determined.     

Systematic preparation of Mo 2 4+ building blocks for supramolecular assemblies

The preparation of additional and useful building blocks for the construction of supramolecular entities with quadruply bonded Mo(2)(4+) units has been explored, and five new mixed-ligand complexes with three types of ligands and various basicities are reported. The ligands used were the DAniF (N,N'-di-p-anisylformamidinate) anion, the acetate anion, and neutral acetonitrile molecules. The formamidinate ligands are the least labile, and the acetonitrile molecules are the most labile. This difference as well as a relatively strong trans directing influence by the formamidinate anions in ligand substitution reactions allows designed synthesis of various mixed-ligand building blocks, including rare pairs of cis and trans isomers. The new compounds are cis-Mo(2)(DAniF)(2)(O(2)CCH(3))(2) (1), trans-Mo(2)(DAniF)(2)(O(2)CCH(3))(2) (2), trans-[Mo(2)(DAniF)(2)(O(2)CCH(3))(CH(3)CN(eq)())(2)]BF(4) (3), trans-[Mo(2)(DAniF)(2)(CH(3)CN(eq)())(4)](BF(4))(2) (4), and [Mo(2)(O(2)CH(3))(CH(3)CN(eq)())(6)(CH(3)CN(ax)())](BF(4))(3) (5), where eq and ax designate equatorial and axial ligands, respectively. A comparison with some previously synthesized complexes is given along with a discussion of the overall reactivity of all compounds.     

Effects of axial coordination on the Ru-Ru single bond in diruthenium paddlewheel complexes

The 1,8-naphthyridine-based (NP-based) ligands with furyl, thiazolyl, pyridyl, and pyrrolyl attachments at the 2-position have been synthesized. Reactions of 3-MeNP (3-methyl-1,8-naphthyridine), fuNP (2-(2-furyl)-1,8-naphthyridine), tzNP (2-(2-thiazolyl)-1,8-naphthyridine), pyNP (2-(2-pyridyl)-1,8-naphthyridine), and prNP(-1) (2-(2-pyrrolyl)-1,8-naphthyridine) with [Ru2(CO)4(CH3CN)6]2+ lead to [Ru2(3-MeNP)2(CO)4(OTf)2] (1), [Ru2(fuNP)2(CO)4]2[BF4]2 (2), [Ru2(tzNP)2(CO)4][ClO4]2 (3), [Ru2(pyNP)2(CO)4][OTf]2 (4), and [Ru2(prNP)2(CO)4] (5). The molecular structures of complexes 1-5 have been established by X-ray crystallographic studies. The modulation of the Ru-Ru single-bond distances with axial donors triflates, furyls, thiazolyls, pyridyls, and pyrrolyls has been examined. A small and gradual increase in the Ru-Ru distance is measured with various donors of increasing strengths. The shortest Ru-Ru distance of 2.6071(9) angstroms is observed for the axially coordinated triflates in complex 1, and the longest Ru-Ru distance of 2.6969(10) angstroms is measured for axial pyrrolyls in complex 5. The Ru-Ru distances in complexes 3 (2.6734(7) angstroms) and 4 (2.6792(9) angstroms), having thiazolyls and pyridyls at axial sites respectively, are similar. The Ru-Ru distance for axial furyls in complex 2 (2.6261(9) angstroms) is significantly shorter than the corresponding distances in 3, 4, and 5. DFT calculations provide insight into the interaction of the Ru-Ru sigma orbital with axial donors. The Ru-Ru sigma orbital is elevated to a higher energy because of the interaction with axial lone pairs. The degree of destabilization depends on the nature of axial ligands: the stronger the ligand, higher the elevation of Ru-Ru orbital. The lengthening of Ru-Ru distances with respect to the axial donors in compounds 1-5 follows along the direction pyrrolyl > pyridyl approximately thiazolyl > furyl > triflate, and the trend correlates well with the computed destabilization of the Ru-Ru sigma orbitals.     

Design and self-assembly of ditopic and tetratopic cavitand complexes

The self-assembly of open ditopic and tetratopic cavitand complexes has been investigated by using monofunctionalized cavitand ligands and suitable metal precursors. In the case of ditopic complexes, self-assembly protocols, leading exclusively to the formation of both thermodynamically stable cis-Pt square-planar complexes 8 and 9 and the kinetically inert fac-Re octahedral complex 14, have been elaborated. The use of cis-[Pt(CH3)CN)2Cl2] as metal precursor led to the formation of monotopic trans-10 and ditopic trans-11 cavitand complexes, while cis-[Pt(dmso)2Cl2] afforded both cis-13 and trans-11 isomers. The self-assembly of tetratopic cavitand complexes has been achieved by using mononuclear [Pd(CH3CN)4(BF4)2] and dinuclear [M2(tppb)(OTf)4] (19: M = Pt; 20: M = Pd) metal precursors. Only the tetratopic dinuclear complexes 21 and 22 were stable. The ligand configuration with two phosphorus and two cavitand ligands at the metal centers is the most appropriate to build tetratopic cavitand complexes with sufficient kinetic stability.     

Dynamics of a cis-dihydrogen/hydride complex of iridium

Insertion of CS2 into one of the Ir-H bonds of [Ir(H)5(PCy3)2] takes place to afford the dihydrido dithioformate complex cis-[Ir(H)2(eta2-S2CH)(PCy3)2] accompanied by the elimination of H2. Protonation of the dithioformate complex using HBF4.Et2O gives cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4] wherein the H atom undergoes site exchange between the dihydrogen and the hydride ligands. The dynamics was found to be so extremely rapid with respect to the NMR time scale that the barrier to exchange could not be measured. Partial deuteration of the hydride ligands resulted in a J(H,D) of 6.5 and 7.7 Hz for the H2D and the HD2 isotopomers of cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4], respectively. The H-H distance (d(HH)) for this complex has been calculated to be 1.05 A, which can be categorized under the class of elongated dihydrogen complexes. The cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4] complex undergoes substitution of the bound H2 moiety with CH(3)CN and CO resulting in new hydride derivatives, cis-[Ir(H)(L)(eta2-S2CH)(PCy3)2][BF4] (L = CH3CN, CO). Reaction of cis-[Ir(H)2(eta2-S2CH)(PCy3)2] with electrophilic reagents such as MeOTf and Me3SiOTf afforded a new hydride aquo complex cis-[Ir(H)(H2O)(eta2-S2CH)(PCy3)2][OTf] via the elimination of CH4 and Me3SiH, respectively, followed by the binding of a water molecule (present in trace quantities in the solvent) to the iridium center. The X-ray crystal structures of cis-[Ir(H)2(eta2-S2CH)(PCy3)2] and cis-[Ir(H)(H2O)(eta2-S2CH)(PCy3)2][OTf] have been determined.     

C7 and C9 carbon-rich bridges in diruthenium systems: synthesis, spectroscopic, and theoretical investigations of different oxidation States

Two methodologies of C-C bond formation to achieve organometallic complexes with 7 or 9 conjugated carbon atoms are described. A C7 annelated trans-[Cl(dppe)2Ru=C=C=C-CH=C(CH2)-C[triple bond]C-Ru(dppe)2Cl][X] (X = PF6, OTf) complex is obtained from the diyne trans-[Cl(dppe)2Ru-(C[triple bond]C)2-R] (R = H, SiMe3) in the presence of [FeCp2][PF6] or HOTf, and C7 or C9 complexes trans-[Cl(dppe)2Ru-(C[triple bond]C)n-C(CH3)=C(R1)-C(R2)=C=C=Ru(dppe)2Cl][X] (n = 1, 2; R1 = Me, Ph, R2 = H, Me; X = BF4, OTf) are formed in the presence of a polyyne trans-[Cl(dppe)2Ru-(C[triple bond]C)n-R] (n = 2, 3; R = H, SiMe3) with a ruthenium allenylidene trans-[Cl(dppe)2Ru=C=C=C(CH2R1)R2][X]. These reactions proceed under mild conditions and involve cumulenic intermediates [M+]=(C=)nCHR (n = 3, 5), including a hexapentaenylidene. A combination of chemical, electrochemical, spectroscopic (UV-vis, IR, NIR, EPR), and theoretical (DFT) techniques is used to show the influence of the nature and conformation of the bridge on the properties of the complexes and to give a picture of the electron delocalization in the reduced and oxidized states. These studies demonstrate that the C7 bridging ligand spanning the metal centers by almost 12 angstroms is implicated in both redox processes and serves as a molecular wire to convey the unpaired electron with no tendency for spin localization on one of the halves of the molecules. The reactivity of the C7 complexes toward protonation and deprotonation led to original bis(acetylides), vinylidene-allenylidene, or carbyne-vinylidene species such as trans-[Cl(dppe)2Ru[triple bond]C-CH=C(CH3)-CH=C(CH3)-HC=C=Ru(dppe)2Cl][BF4]3.     

Alcohol addition to acetonitrile activated by the [Re6(mu3-Se)8]2+ cluster core

The addition of methanol and ethanol to the previously reported cluster solvates [Re6(mu3-Se)8(PEt3)5(MeCN)](SbF6)2 and trans-[Re6(mu3-Se)8(PEt3)4(CH3CN)2][SbF6]2 afforded three cluster complexes with imino ester ligands: {Re6(mu3-Se)8(PEt3)5[HN=C(OCH3)(CH3)]}(SbF6)2, {Re6(mu3-Se)8(PEt3)5[HN=C(OCH2CH3)(CH3)]}{SbF6}2, and trans-{Re6(mu3-Se)8(PEt3)4[HN=C(OCH3)(CH3)]2}{SbF6}2. In all cases, predominant formation of the Z isomers was observed.     

A study of structural and bonding variations in the homologous series [Mo(2)(CN)(6)(dppm)(2)](n-) (n = 2, 1, 0)

Reaction of Mo(2)Cl(4)(dppm)(2) (dppm = bis(diphenylphosphino)methane) with 6 equiv of [n-Bu(4)N][CN] or [Et(4)N][CN] in dichloromethane yields [n-Bu(4)N](2)[Mo(2)(CN)(6)(dppm)(2)] (1) and [Et(4)N](2)[Mo(2)(CN)(6)(dppm)(2)] (2), respectively. The corresponding one- and two-electron oxidation products [n-Bu(4)N][Mo(2)(CN)(6)(dppm)(2)] (3) and Mo(2)(CN)(6)(dppm)(2) (4)were prepared by reactions of 1 with the oxidant NOBF(4). Single-crystal X-ray structures of 2.2CH(3)CN, 3.2CH(3)CN.2H(2)O, and 4.2CH(3)NO(2) were performed, and the results confirmed that all three complexes contain identical ligand sets with trans dppm ligands bisecting the Mo(2)(mu-CN)(2)(CN)(4) equatorial plane. The binding of the bridging cyanide ligands is affected by the oxidation state of the dimolybdenum core as evidenced by an increase in side-on pi-bonding overlap of the mu-CN in going from 1 to 4. The greater extent of pi-donation into Mo orbitals is accompanied by a lengthening of the Mo-Mo distance (2.736(1) A in Mo(2)(II,II) (2), 2.830(1) A in Mo(2)(II,III) (3), and 2.936(1) A in Mo(2)(III,III) (4)). A computational study of the closed-shell members of this homologous series, [Mo(2)(CN)(6)(dppm)(2)](n)() (n = 2-, 0), indicates that the more pronounced side-on pi-donation evident in the X-ray structure of 4 leads to significant destabilization of the delta orbital and marginal stabilization of the delta() orbitals with respect to nearly degenerate delta and delta orbitals in the parent compound, 2. The loss of delta contributions combined with the reduced orbital overlap due to higher charges on molybdenum centers in oxidized complexes 3 and 4 is responsible for the observed increase in the length of the Mo-Mo bond.     

Reductive coupling of metal triangles in sandwich complexes

The one-electron reduction of [Pd3(C7H7)2(CH3CN)3][BF4]2 in acetonitrile resulted in the formation of the dimer dication [Pd6(C7H7)4(CH3CN)4][BF4]2, whose structure containing a novel bitriangle hexapalladium skeleton was determined by X-ray crystallographic analysis. The dimer is stable in CD3CN at ambient temperature for several days but is highly air-sensitive. Similarly, the cycloheptatriene tripalladium complex [Pd3(C7H7R)2(CH3CN)3][BF4]2 (R = H, t-Bu) dimerized upon one-electron reduction. Both monomer and dimer of cycloheptatriene complexes were structurally determined by X-ray crystallographic analyses.     

Trans ruthenium(II) complexes with NH-bridged tetradentate symmetric and asymmetric polypyridyl ligands

NH-Bridged tetradentate ligands were synthesized to achieve stable trans Ru(II) bis(polypyridyl) complexes. The polypyridyl part of the ligand was either symmetric, as in N,N-bis(1,10-phenanthroline-2-yl)amine (phen-NH-phen), or asymmetric, as in N-(1,10-phenanthroline-2-yl)-N-(6-yl-dipyridyl[2,3-a:2',3'-c]phenazine)amine (dppz-NH-phen). Protonation of phen-NH-phen with trifluoroacetic acid and the subsequent reaction with RuCl3 yield trans-[Ru(phen-NH-phen)Cl2]. The chloro ligands in this compound can easily be replaced by stronger ligands, such as CH3CN and DMSO. In this way, complexes trans-[Ru(phen-NH-phen)(CH3CN)(DMSO)](PF6)2 (1), trans-[Ru(phen-NH-phen)(DMSO)2](PF6)2 (2), and trans-[Ru(phen-NH-phen)(CH3CN)2](PF6)2 (3) were obtained. X-ray structures were determined for 1 and 3. Following a procedure similar to that used with phen-NH-phen, the complex trans-[Ru(dppz-NH-phen)(CH3CN)2](PF6)2 (4) was obtained. To our knowledge, this is the first reported trans ruthenium(II) bis(polypyridyl) complex with two different polypyridyl ligands in the equatorial plane.     

NMR spectroscopic and X-ray crystallographic study of methylcobalt(III) compounds with saturated amine ligands

The (13)C chemical shifts of methylcobalt(III) compounds with saturated amine ligands in cis positions to the methyl group and a monodentate ligand, L = CN(-), NH(3), NO(2)(-), N(3)(-), H(2)O, or OH(-), in the trans position are reported. The amine ligands used, 1,2-ethanediamine (en), 1,3-propanediamine (tn), N,N'-bis(2-aminoethyl)-1,3-propanediamine (2,3,2-tet), N,N'-bis(3-aminopropyl)-1,2-ethanediamine (3,2,3-tet), and 1,4,8,11-tetraazacyclotetradecane (cyclam), all exert an apparent cis influence on the (13)C resonance signal of the coordinated methyl group. In the trans-[Co(en)(2)(CH(3))(L)](n+) series the (15)N resonance frequency of the coordinated en has also been measured. The influence of L on the en (15)N chemical shifts is reverse the influence on the methyl (13)C chemical shifts except in the case of L = NO(2)(-), which affects a further deshielding of the amine nitrogen nucleus. The methyl (1)J(CH) coupling constants in the trans-[Co(en)(2)(CH(3))(L)](n+) series range from 128.09 Hz (L = CN(-)) to 134.11 Hz (L = H(2)O). The crystal structures of trans-[Co(en)(2)(CH(3))(ClZnCl(3))], trans-[Co(3,2,3-tet)(CH(3))(N(3))]ClO(4), trans,trans-[(CH(3))(en)(2)Co(CN)Co(en)(2)(CH(3))](PF(6))(3)(CH(3)CN), and cis-[Co(en)(2)(CH(3))(NH(3))]ZnCl(4) were determined from low-temperature X-ray diffraction data.     

Stereoselective preparation, structures, and reactivities of phosphine-bridged mixed-metal trinuclear and pentanuclear complexes with tris[2-(diphenylphosphino)ethyl]phosphine

The phosphine-bridged linear trinuclear and pentanuclear complexes with Pd(II)-Pt(II)-Pd(II), Ni(II)-Pt(II)-Ni(II), and Rh(III)-Pd(II)-Pt(II)-Pd(II)-Rh(III) metal-ion sequences were almost quantitatively formed by the stepwise phosphine-bridging reaction of the terminal phosphino groups of tris[2-(diphenylphosphino)ethyl]phosphine (pp3), which is the tetradentate bound ligand of the starting Pd(II) and Ni(II) complexes. The solid-state structures of the trinuclear complexes were determined by X-ray structural analyses, and the structures of the polynuclear complexes in solution were characterized by NMR spectroscopy. The trans and cis isomers of the trinuclear and pentanuclear complexes, which arise from the geometry around the Pt(II) center, were selectively obtained simply by changing the counteranion of the starting complexes: the tetrafluoroborate salts, [MX(pp3)](BF4) [M = Pd(II) or Ni(II), X = Cl- or 4-chlorothiophenolate (4-Cltp-)], gave only the trans isomers, and the chloride salt, [PdCl(pp3)]Cl, gave only the cis isomers. The formation of the trinuclear complex with the 4-Cltp- and chloro ligands, trans-[Pt(4-Cltp)2{PdCl(pp3)}2](BF4)2, proceeded with exchange between the thiolato ligand in the starting Pd(II) complex, [Pd(4-Cltp)(pp(3))](BF4), and the chloro ligands in the starting Pt(II) complex, trans-[PtCl2(NCC6H5)2], retaining the trans geometry around the Pt(II) center. In contrast, the formation reaction between [PdCl(pp3)]Cl and trans-[PtCl2(NCC6H5)2] was accompanied by the trans-to-cis geometrical change on the Pt(II) center to give the trinuclear complex, cis-[PtCl2{PdCl(pp3)}2]Cl2. The mechanisms of these structural conversions during the formation reactions were elucidated by the 31P NMR and absorption spectral changes. The differences in the catalytic activity for the Heck reaction were discussed in connection with the bridging structures of the polynuclear complexes in the catalytic cycle.     

A new family of mono- and dicarboxylic ruthenium complexes [Ru(DIP)2(L2)]2+ (DIP = 4,7-diphenyl-1,10-phenanthroline): synthesis, solution behavior, and X-ray molecular structure of trans-[Ru(DIP)2(MeOH)2][OTf]2

A new family of ruthenium complexes of general formula [Ru(DIP)2(L2)]2+, where DIP = 4,7-diphenyl-1,10-phenanthroline, a bidentate ligand with an extended aromatic system, was prepared and fully characterized. When L is a monodentate ligand, the following complexes were obtained: L = CF3SO3(-1) (2), CH3CN (3), and MeOH (4). When L2 is a bidentate ligand, the compounds [Ru(DIP)2(Hcmbpy)][Cl]2 (5) and [Ru(DIP)2(H2dcbpy)][Cl]2 (6) were prepared (Hcmbpy = 4-carboxy-4'-methyl-2,2-bipyridine, H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine). Complex [Ru(DIP)2(MeOH)2][OTf]2 (4) displayed a trans configuration of the DIP ligands, which is rare for octahedral complexes featuring DIP bidentate ligands. DFT calculations carried out on 4 showed that the cis isomer is more stable by 12.2 kcal/mol relative to the trans species. The solution behaviors of monocarboxylic complex [Ru(DIP)2(Hcmbpy)][Cl]2 (5) and dicarboxylic complex [Ru(DIP)2(H2dcbpy)][Cl]2 (6) were investigated by 1H NMR spectroscopy. VT-NMR, concentration dependence, and reaction with NaOD allowed us to suggest that aggregation of the cationic species in solution, especially for 6, originates mainly from hydrogen bonding interactions.     

Hydride-alkenylcarbyne to alkenylcarbene transformation in bisphosphine-osmium complexes

The elongated dihydrogen complex [formula: see text](1) reacts with 1,1-diphenyl-2-propyn-1-ol and 2-methyl-3-butyn-2-ol to give the hydride-hydroxyvinylidene-pi-alkynol derivatives [OsH{=C=CHC(OH)R2}{eta2-HC(triple bond)CC(OH)R2}(PiPr3)2]BF4 (R = Ph (2), Me (3)), where the pi-alkynols act as four-electron donor ligands. Treatment of 2 and 3 with HBF(4) and coordinating solvents leads to the dicationic hydride-alkenylcarbyne compounds [OsH((triple bond)CCH=CR2)S2(PiPr3)2][BF4]2 (R = Ph, S = H(2)O (4), CH(3)CN (5); R = Me, S = CH(3)CN (6)), which in acetonitrile evolve into the alkenylcarbene complexes [Os(=CHCH=CR2)(CH3CN)3(PiPr3)2][BF4](2) (R = Ph (7), Me (8)) by means of a concerted 1,2-hydrogen shift from the osmium to the carbyne carbon atom. Treatment of 2-propanol solutions of 5 with NaCl affords OsHCl2((triple bond)CCH=CPh2)(PiPr3)2 (10), which reacts with AgBF(4) and acetonitrile to give [OsHCl((triple bond)CCH=CPh2)(CH3CN)(PiPr3)2]BF(4) (11). In this solvent complex 11 is converted to [OsCl(=CHCH=CPh2)(CH3CN)2(PiPr3)2]BF(4) (12). Complex 5 reacts with CO to give [Os(=CHCH=CPh2)(CO)(CH3CN)2(PiPr3)2][BF(4)](2) (15). DFT calculations and kinetic studies for the hydride-alkenylcarbyne to alkenylcarbene transformation show that the difference of energy between the starting compounds and the transition states, which can be described as eta(2)-carbene species [formula: see text] increases with the basicity of the metallic center. The X-ray structures of 4 and 7 and the rotational barriers for the carbene ligands of 7, 8, and 12 are also reported.     

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).     

Synthesis, structures and photophysical properties of luminescent copper(I) and platinum(II) complexes with a flexible naphthyridine-phosphine ligand

Condensation of Ph(2)PH and paraformaldehyde with 2-amino-7-methyl-1,8-naphthyridine gave the new flexible tridentate ligand 2-[N-(diphenylphosphino)methyl]amino-7-methyl-1,8-naphthyridine (L). Reaction of L with [Cu(CH(3)CN)(4)]BF(4) and/or different ancillary ligands in dichloromethane afforded N,P chelating or bridging luminescent complexes [(L)(2)Cu(2)](BF(4))(2), [(micro-L)(2)Cu(2)(PPh(3))(2)](BF(4))(2) and [(L)Cu(CNN)]BF(4) (CNN = 6-phenyl-2,2'-bipyridine), respectively. Complexes [(L)(2)Pt]Cl(2), [(L)(2)Pt](ClO(4))(2) and [(L)Pt(CNC)]Cl (CNC = 2,6-biphenylpyridine) were obtained from the reactions of Pt(SMe(2))(2)Cl(2) or (CNC)Pt(DMSO)Cl with L. The crystal structures and photophysical properties of the complexes are presented.     

A remarkable anion effect on palladium nanoparticle formation and stabilization in hydroxyl-functionalized ionic liquids

Pd nanoparticles (NPs) with a small size and narrow size distribution were prepared from the decomposition of Pd(OAc)(2) in a series of hydroxyl-functionalized ionic liquids (ILs) comprising the 1-(2'-hydroxylethyl)-3-methylimidazolium cation and various anions, viz. [C(2)OHmim][OTf] (2.4 ± 0.5 nm), [C(2)OHmim][TFA] (2.3 ± 0.4 nm), [C(2)OHmim][BF(4)] (3.3 ± 0.6 nm), [C(2)OHmim][PF(6)] (3.1 ± 0.7 nm) and [C(2)OHmim][Tf(2)N] (4.0 ± 0.6 nm). Compared with Pd NPs isolated from the non-functionalized IL, [C(4)mim][Tf(2)N] (6.2 ± 1.1 nm), it would appear that the hydroxyl group accelerates the formation of the NPs, and also helps to protect the NPs from oxidation once formed. Based on the amount of Pd(OAc)(2) that remains after NP synthesis (under the given conditions) the ease of formation of the Pd NPs in the [C(2)OHmim](+)-based ILs follows the trend [Tf(2)N](-), [PF(6)](-) > [BF(4)](-) > [OTf](-) > [TFA](-). Also, the ability of the [C(2)OHmim](+)-based ILs to prevent the Pd NPs from undergoing oxidation follows the trend [Tf(2)N](-) > [PF(6)](-) > [TFA](-) > [OTf](-) > [BF(4)](-). DFT calculations were employed to rationalize the interactions between Pd NPs and the [C(2)OHmim](+) cation and the various anions.     

Irreversible and reversible formation of a [2]rotaxane containing platinum(II) complex with an N-alkyl bipyridinium ligand as the axis component

An N-Alkyl bipyridinium having a polymethylene chain and a bulky aryl group at the end, [4,4'-bpy-N-(CH2)10OC6H(3)-3,5-tBu2]Cl (Cl), reacts with K[PtCl3(dmso)] to produce the Pt complex with the N-alkyl bipyridinium ligand [Cl2(dmso)Pt{4,4'-bpy-N-(CH2)10OC6H(3)-3,5-tBu2}][PtCl3(dmso)] as a 6:1 mixture of trans and cis isomers ([trans-][PtCl3(dmso)] and [cis-][PtCl3(dmso)]). Addition of alpha-cyclodextrin (alpha-CD) to a solution of Cl in dmso-d6/D2O (3:1) forms [2]pseudorotaxane [{4,4'-bpy-N-(CH2)10OC6H(3)-3,5-tBu2}.(alpha-CD)]Cl (Cl) which is equilibrated with Cl and alpha-CD in solution. The reaction of K[PtCl3(dmso)] with Cl affords the [2]rotaxane [trans-Cl2(dmso)Pt{4,4'-bpy-N-(CH2)10OC6H(3)-3,5-tBu2}.(alpha-CD)][PtCl3(dmso)] ([trans-][PtCl3(dmso)]) which contains alpha-CD and [trans-][PtCl3(dmso)] as the cyclic and axis components, respectively. Dissolution of a mixture of [trans-][PtCl3(dmso)], [cis-][PtCl3(dmso)] and alpha-CD in dmso-d6/D2O (3:1) forms a mixture of the rotaxanes containing [trans--d6][PtCl3(dmso)] and [cis--d6][PtCl3(dmso)]. The reaction involves partial dissociation of the bipyridinium from Pt of [trans-][PtCl3(dmso)] or [cis-][PtCl3(dmso)] to yield [PtCl3(dmso)] and formation of pseudorotaxane with alpha-CD, followed by recoordination of the bipyridinium to the Pt. The reversible formation of the Pt-N coordination bond is studied in a dmso solution of the N-butyl compounds [trans-Cl2(dmso)Pt{4,4'-bpy-N-nBu}][PtCl3(dmso)] ([trans-][PtCl3(dmso)]).     

cis-trans photoisomerization in [Ru(DIP)2(MeOH)2][OTf]2: synthesis, NMR, X-ray structure of the trans-isomer and photophysical properties

The first trans-ruthenium complex trans-[Ru(DIP)2(MeOH)2][OTf]2 (1b, where DIP = 4,7-diphenyl-1,10-phenanthroline) incorporating a pi-extended ligand was prepared via two methods: either photolysis of cis-[Ru(DIP)2(OTf)2] in MeOH-Et(2)O or via crystallization from MeOH-Et(2)O in direct sunlight. The X-ray molecular structure of is reported and confirmed the trans geometry of the title compound. The cis-trans isomerization process was monitored by 1H-NMR and showed that 1b reverts back to cis-[Ru(DIP)2(MeOH)2][OTf]2 (1a) in methanol-d4 after 15 h at 55 degrees C or several days at room temperature. The absorption spectra recorded in MeOH showed a bathochromic shift of the MLCT band of the trans-isomer 1b relative to that of the cis complex 1a. Interestingly at 77 K the emission spectrum of 1b is red shifted compared to the cis analog 1a. A rational explanation in terms of the energy of the excited states in the cis- and trans-isomers is proposed to explain this behavior.     

Fluoride abstraction and reversible photochemical reduction of cationic uranyl(VI) phosphine oxide complexes

The syntheses, structural and spectroscopic characterization, fluoride abstraction reactions, and photochemical reactivity of cationic uranyl(VI) phosphine oxide complexes are described. [UO2(OPPh3)4][X]2 (1a, X = OTf; 1b, X = BF4) and [UO2(dppmo)2(OPPh3)][X]2 (2a, X = OTf; 2b, X = BF(4)) are prepared from the corresponding uranyl(VI) chloride precursor and 2 equiv each of AgX and phosphine oxide. The BF4- compounds 1b and 2b are prone to fluoride abstraction reactions in methanol, leading to dinuclear fluoride-bridged uranyl(VI) complexes. Fluoride abstraction of 2b in methanol generates two structural isomers of the fluoride-bridged uranyl(VI) dimer [(UO2(dppmo)2)2(mu-F)][BF4]3 (4), both of which have been structurally characterized. In the major isomer 4C, the four dppmo ligands are all chelating, while in the minor isomer 4B, two of the dppmo ligands bridge adjacent uranyl(VI) centers. Photolysis of 2b in methanol proceeds through 4 to form the uranium(IV) fluoride complex [UO2F2(dppmo)3][BF4]2 (5), involving another fluoride abstraction step. X-ray crystallography shows 5 to be a rare example of a structurally characterized uranium(IV) complex possessing terminal U-F bonds. Complex 5 reverts to 4 in solution upon exposure to air.