Photoinduced Catalytic Organic-Hydride Transfer to CO2 Mediated with Ruthenium Complexes as NAD+ /NADH Redox Couple Models.

The catalytic organic-hydride transfer to CO2 was first achieved through the photoinduced two-electron reduction of the [Ru(bpy)2 (pbn)]2+ /[Ru(bpy)2 (pbnHH)]2+ (bpy=2,2'-bipyridine, pbn=2-(pyridin-2-yl)benzo[b]-1,5-naphthyridine, and pbnHH=2-(pyridin-2-yl)-5,10-dihydrobenzo[b]-1,5-naphthyridine) redox couple in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH). The active species for the catalytic hydride transfer to carbon dioxide giving formate is [Ru(bpy)(bpy⋅- )(pbnHH)]+ formed by one-electron reduction of [Ru(bpy)2 (pbnHH)]2+ with BI⋅.

Ferrocene-Containing Pseudorotaxanes in Crystals: Aromatic Interactions with Hammett Correlation.

Single crystals of pseudorotaxanes, [(FcCH2NH2CH2Ar)(DB24C8)][PF6] (DB24C8 = dibenzo[24]crown-8, Fc = Fe(C5H4)(C5H5), Ar = -C6H3-3,4-Cl2, -C6H3-3,4-F2, -C6H4-4-F, -C6H4-4-Cl, -C6H4-4-Br, -C6H3-3-F-4-Me, -C6H4-4-I) and [(FcCH2NH2CH2C6H4-4-Me)(DB24C8)][Ni(dmit)2] (dmit = 1,3-dithiole-2,4,5-dithiolate), were obtained from solutions containing DB24C8 and ferrocenylmethyl(arylmethyl)ammonium. X-ray crystallographic analyses of the pseudorotaxanes revealed that the aryl ring of the axle moiety and the catechol ring of the macrocyclic component were at close centroid distances and parallel or tilted orientation. The structures with parallel aromatic rings showed correlation of the distances between the centroids to Hammett substituent constants of the aryl groups.

Digold(I) Thianthrenyl Complexes. Effect of Diphosphine Ligands on Molecular Structures in the Solid State and in Solution.

A series of digold complexes possessing two thianthrenyl ligands, Au2(Thi)2(Ph2P(CH2) n PPh2) (Thi: 1-thianthrenyl; 1: n = 1, 2: n = 2, 3: n = 3, 4: n = 4), were prepared and characterized by crystallographic and spectroscopic measurements. X-ray crystallography of complexes 1 and 3 revealed U-shaped structures with short Au-Au distances [3.2171(3) Å and 3.0735(2) Å]. Complex 2 and three of the four structure-determined molecules of complex 4 showed structures without Au-Au contacts. UV-vis spectroscopic measurements of 1-4 and TD-DFT calculations of the two conformers of 1 revealed that complexes 1 and 3 in the solution phase contained conformers with Au(I)-Au(I) interactions in a much higher proportion than complexes 2 and 4. As a result, complexes with diphosphine ligands containing an odd number of methylene groups preferred structures with Au-Au interactions in the solid state and in solution. Oxidation of 1 with 2 equiv of PhICl2 yielded a mixture of monomeric and dimeric thianthrenes and its dimer via ligand elimination and C-C coupling, respectively.

Crystal structure of 2,6-bis-(3-hy-droxy-3-methyl-but-1-yn-1-yl)pyridine monohydrate.

In the title pyridine derivative, C15H17NO2·H2O, the two OH groups are oriented in directions opposite to each other with respect to the plane of the pyridine ring. In the crystal, hydrogen bonds between the pyridine mol-ecule and the water mol-ecule, viz. Ohy-droxy-H⋯Owater, Ohy-droxy-H⋯Ohy-droxy, Owater-H⋯Ohy-droxy and Owater-H···Npyridine, result in the formation of a ribbon-like structure running along [011].

Bimolecular fusion of [Pd3(µ-CN-C6H3Me2-2,6)3(CN-C6H3Me2-2,6)3] induced by Ph2GeH2: formation of the redox-active Pd6Ge2 complex.

The reaction of Ph2GeH2 with a planar tripalladium(0) complex, [Pd3(µ-CN-C6H3Me2-2,6)3(CN-C6H3Me2-2,6)3], selectively afforded a hexagonal bipyramidal Pd6Ge2 complex, [Pd6(µ-GePh2)2(CN-C6H3Me2-2,6)8(µ-CN-C6H3Me2-2,6)2]. The molecule is stabilized by bridging coordination of isonitrile and GePh2 ligands, although all the Pd-Pd bonds are weak, as revealed by DFT calculations. The resulting complex undergoes two successive redox processes at E1/2 = -1.35 and -1.03 V (vs. Fc+/Fc), which correspond to the stepwise oxidation of the Pd(0)6 complex.

Electrochemical behavior of a Rh(pentamethylcyclopentadienyl) complex bearing an NAD+/NADH-functionalized ligand.

A RhCp* (Cp* = pentamethylcyclopentadienyl) complex bearing an NAD+/NADH-functionalized ligand, [RhCp*(pbn)Cl]Cl ([1]Cl, pbn = (2-(2-pyridyl)benzo[b]-1,5-naphthyridine)), was synthesized. The cyclic voltammogram of [1]Cl in CH3CN shows two reversible redox waves at E1/2 = -0.58 and -1.53 V (vs. the saturated calomel electrode (SCE)), which correspond to the RhIII/RhI and pbn/pbn˙- redox couples, respectively. The addition of acetic acid to the solution afforded the proton-coupled two-electron reduction of [1]Cl at -0.62 V, from which [RhCp*(pbnHH)Cl]+ was selectively generated, probably via a hydride transfer from a RhIII-hydride intermediate to the pbn ligand. Complex [1]Cl is stable under acidic conditions, whereas a methyl proton of the Cp* moiety dissociates under basic conditions. The resulting anionic methylene group attacks the para carbon of the free pyridine of pbn, accompanied by protonation of the nitrogen atom of the ligand. As a result, treatment of [1]Cl with a base produces selectively the cyclic complex [1CH]Cl, which bears a reduced pbn framework (pbnCH). [1CH]Cl forms 1 : 1 adducts with PhCOO-via hydrogen bonding. A similar adduct, formed by a Ru-pbnHH scaffold and RCOO- (R = CH3, C6H5), has been reported to react with CO2 to produce HCOO- under concomitant regeneration of Ru-pbn. The adduct of [1CH]Cl with PhCOO-, however, lacks such hydride-donor ability, due to a steric barrier in the molecular structure of [1CH]Cl, which hampers the hydride transfer.

Crystal structure of 1,13,14-tri-aza-dibenz[a,j]anthracene 1,1,2,2-tetra-chloro-ethane monosolvate.

The asymmetric unit of the title compound, C19H11N3·C2H2Cl4, consists of one half-mol-ecule of 1,13,14-tri-aza-dibenz[a,j]anthracene (dibenzo[c,h]-1.9,10-anthyridine, dbanth) and one half of 1,1,2,2-tetra-chloro-ethane (TCE), both of which are located on a crystallographic twofold rotation axis. The dihedral angle between the planes of the terminal benzene rings in dbanth is 3.59 (7)° owing to the steric repulsion between the H atoms in the two benzo groups and the H atom in the central pyridine ring of the anthridine skeleton. In the crystal, π-π inter-actions between pyridine rings [centroid-centroid distances = 3.568 (2) and 3.594 (2) Å] link the dbanth mol-ecules to form a one-dimensional columnar structure along the c axis. The dbanth and TCE mol-ecules are connected through weak bifurcated C-H⋯(N,N) hydrogen bonds.

Synthesis and dynamic behavior of an anthyridine-ligated ruthenium complex.

A ruthenium complex containing a 1,9,10-anthyridine derivative, [Ru(L)(bpy)2](PF6)2 ([1](PF6)2; L = 1,13,14-triazadibenz[a,j]anthracene, bpy = 2,2'-bipyridyl), was synthesized. X-ray crystal structural analysis of [1](PF6)2 showed that L is coordinated to the Ru center as a bidentate ligand. When [1](PF6)2 was dissolved in acetonitrile, a new complex incorporating one acetonitrile molecule, [Ru(L)(CH3CN)(bpy)2](PF6)2 ([2](PF6)2), was formed. X-ray crystallographic data revealed that, in [2](PF6)2, L is coordinated to the Ru center in a monodentate fashion. The coordinated L in [2](PF6)2 shows a unique haptotropic rearrangement in an acetonitrile solution.

Deprotonation/protonation of coordinated secondary thioamide units of pincer ruthenium complexes: modulation of voltammetric and spectroscopic characterization of the pincer complexes.

New pincer ruthenium complexes, [Ru(SCS)(tpy)]PF(6) (1) (SCS = 2,6-bis(benzylaminothiocarbonyl)phenyl), tpy = 2,2':6',2''-terpyridyl) and [Ru(SNS)(tpy)]PF(6) (2) (SNS = 2,5-bis(benzylaminothiocarbonyl)pyrrolyl), having κ(3)SCS and κ(3)SNS pincer ligands with two secondary thioamide units were synthesized by the reactions of [RuCl(3)(tpy)] with N,N'-dibenzyl-1,3-benzenedicarbothioamide (L1) and N,N'-dibenzyl-2,5-1H-pyrroledicarbothioamide (L2), respectively, and their chemical and electrochemical properties were elucidated. The structure of 1 was determined by X-ray crystallography. The complexes 1 and 2 showed a two-step deprotonation reaction by treatment with 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), and the addition of DBU led to a shift of the metal-centered redox couples to a lower potential by 720 and 550 mV, respectively. The di-deprotonated complexes were also studied by (1)H-NMR and UV-vis spectroscopy. The addition of methanesulfonic acid (MSA) to the di-deprotonated complexes enabled the recovery of 1 and 2, indicating that the thioamide moiety underwent a reversible deprotonation-protonation process, which resulted in regulating the redox potentials of the metal center. The Pourbaix diagram of 1 revealed that 1 underwent a one-proton/one-electron transfer process in the pH range of 5.83-10.35, and a two-proton/one-electron process at a pH of over 10.35, indicating that the deprotonation/protonation process of the complexes is related to proton-coupled electron transfer (PCET).

Reductive elimination of C6F5-C6F5 in the reaction of bis(pentafluorophenyl)palladium(II) complexes with protic acids.

Reductive elimination of C6F5-C6F5 from cis-[Pd(C6F5)2L] (L = cod, bpy, and dppb) was promoted by Brønsted acids. HNO3 is a convenient acid for the formation of C6F5-C6F5 from [Pd(C6F5)2(cod)]. The products are controlled by the auxiliary ligand.

A Symmetrically Bridging Triarylsilyl Ligand in a Dinuclear Rhodium Complex: Synthesis and Structure of [LRh(H)(µ-Cl)(µ-SiAr2 )(µ-SiAr3 )Rh(H)L] (Ar=Ph, p-FC6 H4 ; L=PiPr3 ).

Simply warming solutions of the dinuclear complexes 1 provides novel complexes 2 [Eq. (a); Ar = Ph, p-FC6 H4 ; L = PiPr3 ], which contain a bridging triarylsilyl ligand and show unusual thermal stability. Compounds with this type of symmetric structure are of interest as models of the transition state for the migration of tertiary silyl groups in a bimetallic framework.