On the synthesis and structures of the complexes [RuCl(L)(dppb)(N–N)]PF6 (L = CO,py or 4-NH2py; dppb = 1,4-bis(diphenylphosphino)butane; N–N = 2,2′-bipyridine or 1,10-phenanthroline) and [(dppb)(CO)Cl2-Ru-pz-RuCl2(CO)(dppb)] (pz = pyrazine)

The “Ru(P–P)” unit (P–P = diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl₂Ru-pz-RuCl₂(CO)(dppb)] (pz = pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF₆ (N–N = diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF₆ were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl₂(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and ³¹P{¹H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography.     

The mer-[RuCl3(dppb)(H2O)] complex: A versatile tool for synthesis of Ru compounds

The complex mer-[RuCl₃(dppb)(H₂O)] [dppb = 1,4-bis(diphenylphosphino)butane] was used as a precursor in the synthesis of the complexes tc-[RuCl₂(CO)₂(dppb)], ct-[RuCl₂(CO)₂(dppb)], cis-[RuCl₂(dppb)(Cl-bipy)], [RuCl(2Ac4mT)(dppb)] (2Ac4mT = N(4)-meta-tolyl-2-acetylpyridine thiosemicarbazone ion) and trans-[RuCl₂(dppb)(mang)] (mang = mangiferin or 1,3,6,7-tetrahydroxyxanthone-C2-β-D-glucoside) complexes. For the synthesis of Ru^II complexes, the Ru^III atom in mer-[RuCl₃(dppb)(H₂O)] may be reduced by H₂(g), forming the intermediate [Ru₂Cl₄(dppb)₂], or by a ligand (such as H2Ac4mT or mangiferin). The X-ray structures of the cis-[RuCl₂(dppb)(Cl-bipy)], tc-[RuCl₂(CO)₂(dppb)] and [RuCl(2Ac4mT)(dppb)] complexes were determined.     

Coordination of RuCl3(NO)(H2O)2 by imidazole,histidine and iminodiacetate ligands: a study of complexation of 'Caged NO' by simple bio-cellular donors

The 'caged NO' reagent, RuCl₃NO(H₂O)₂, has been studied by n.m.r. and i.r. methods with imidazole, histidine, histamine, and N-methyliminodiacetate as complexing ligands. These ligands are representative of cellular donors that would be encountered as RuCl₃NO(H₂O)₂ migrates through biological cells. [RuCl₃NO(imH)(H₂O)], [RuCl₃(NO)(imH)₂] and [RuCl₂(NO)(imH)₃]⁺ complexes (imH = imidazole) have been detected by ¹H-n.m.r. and i.r. and electrospray mass spectrometry (e.s.i.–m.s.) methods. Based upon the effect of cis ligand addition on the (NO) frequency causing a decrease in frequency, the 1:1 and 1:2 complexes have the imidazole donors in the plane cis to the NO⁺ moiety, whereas the 1:3 species has the third imidazole trans to the NO⁺. The trans imidazole donor causes 'trans-strengthening' of the N–O bond of the {RuNO}⁶ chromophore. ¹H-n.m.r. shows that the monodentate imidazole donor(s) is (are) in rapid exchange with free imidazole in solution for each of the n = 1–3 species. Histidine and histamine make kinetically more stable 1:1 complexes with the major isomer having an axially-coordinated histidine imidazole donor, but in-plane donation for histamine. The carboxylate of coordinated histidine remains pendant according to i.r. and ¹³C-n.m.r. data. From syntheses carried out at pH ca. 5, the amino donor is H-bonded to an in-plane H₂O in the major species (ca. 75%) and coordinated with displacement of the in-plane H₂O in the lesser isomer (25%). By contrast, the histamine ligand binds with an in-plane bound imidazole and a pendant protonated amino group (94%). The remaining 6% has an in-plane chelated histamine, analogous to the bis imidazole species and the known fac, cis-[RuCl₃NO(en)] complex. N-Methyliminodiacetate is observed to form one main [RuCl(NO)(mida)(H₂O)] complex (85%) with two chelated glycinato donor groups with RuCl₃NO(H₂O)₂, one glycinato group chelated 'in-plane' with the central amine donor and one axial coordinated glycinato donor. A second [RuCl(NO)(mida)(H₂O)] complex (the remaining 15%) has the amine donor trans to NO⁺ and chelated glycinato groups which coordinate in the RuClO₂(OH₂) plane, either cis or trans to each other, in a 60:40 split (ca. 9% and 6%). The presence of one Cl^– and one H₂O in the [RuCl(NO)(mida)(H₂O)] complexes was established by e.s.i.–m.s. These results show that RuCl₃NO(H₂O)₂ is likely to be freely mobile within a cellular environment, forming stable complexes via bidentate chelation with 'two-point' nitrogen donors (en, his, etc).     

Synthesis and structural characterisation of a ruthenium dinitrosyl complex with atrans-chelating bidentate diphosphine (1,10-bis(diphenylphosphinomethyl) [a] benzophenanthrene) chlorodi(nitrosyl)ruthenium tetrafluoroborate, [RuCl(NO)2{(Ph2PCH2)2-C18H10}]BF4

Summary [RuCl(NO)₂(dppbp)]BF₄ (dppbp=(Ph₂PCH₂)_2–) has been synthesised from [RuCl(NO)₂(PPh₃)₂]BF₄ and dppbp and characterised in the solid state by a single crystal x-ray determination. The [RuCl(NO)₂(dppbp)]⁺ cation, has an approximately square-pyramidal co-ordination geometry with the dppbp ligand occupyingtrans-basal sites. The nitrosyl ligand in the apical site is partially bent [Ru–N–O=156.2(7)⁰] and the nitrosyl ligand in the basal side is essentially linear [Ru–N–O=172.5(6)⁰]. The¹Hn.m.r. spectrum of [RuCl(NO)₂(dppbp)]BF₄ in solution has provided some insight into the dynamics of the complex in solution.     

Preparation, characterization and structure of ruthenium phosphine complexes containing non-innocent ligands

Phosphine ruthenate complexes containing the non-innocent ligands 4-chloro-1,2-phenylenediamine (opda-Cl) and 3,3′,4,4′-tetraamminebiphenyl (diopda) were synthesized and characterized by means of X-ray diffraction, electrochemistry, ³¹P{¹H} NMR and electronic spectroscopies. Crystals of cis-[RuCl₂(dppb)(bqdi-Cl)] complex were isolated as a mixture of two conformational isomers due to different positions of the chlorine atoms of the o-phenylene ligand in relation to the P1 atom of the phosphine moiety.     

Syntheses and Structures of Homo‐ and Heterobimetallic Complexes Containing a (Cyclopentadienone)rhodium(I) Fragment

The reaction of [RhCl(η⁴‐Ph₂R₂C₄CO)]₂ (R=Ph, 2‐naphthyl) with the dimeric complexes [RuCl₂(p‐cymene)]₂ p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, [RuCl₂(1,3,5‐Et₃C₆H₃)]₂, [MCl₂(Cp*)]₂ (M=Rh, Ir; Cp*=1,2,3,4,5‐pentamethylcyclopenta‐2,4‐dien‐1‐yl), [RuCl₂(CO)₃]₂, [RuCl₂(dcypb)(CO)]₂ (dcypb=butane‐1,4‐diylbis[dicyclohexylphosphine]), [(dppb)ClRu(μ‐Cl)₂(μ‐OH₂)RuCl(dppb)] (dppb=butane‐1,4‐diylbis[diphenylphosphine]), and [(dcypb)(N₂)Ru(μ‐Cl)₃RuCl(dcypb)] was investigated. In all cases, mixed, chloro‐bridged complexes were formed in quantitative yield (see 5 – 8, 9 – 16, 18, 19, 21 , and 22 ). The six new complexes 5, 8, 9, 13, 15 , and 22 were characterized by single‐crystal X‐ray analysis (Figs. 1–3).     

Transition Metal Complexes with Bidentate Ligands Spanning trans-Positions. VIII. The reactions of the nucleophile trans-[RuCl(NO)(1)] (1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]-phenanthrene) with carbon monoxide and the phosphite ligand (2) (2 = 1-ethyl-3,5,8-trioxa-4-phosphabicyclo (2.2.2)octane)

The preparation of the nucleophile trans-[RuCl(NO)( 1 )], where 1 is the bidentate ligand Ph₂PCH₂C₁₈CH₂PPh₂, and of the five-coordinate species [RuCl(CO)(NO)( 1 )], [RuCl(CO)(NO)(Ph₂PCH₂Ph)₂] and [RuCl(NO)( 2 )( 1 )] are reported. The crystal structure of [RuCl(CO)(NO)( 1 )] shows that the coordination around the metal atom is distorted trigonal bipyramidal with the phosphorus atoms in axial positions. The Ru? N? O bond angle is 142.8°. ¹H- and ³¹P-NMR. and \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \nu $\end{document}_NO IR.-data for the above complexes are reported and related to the coordination geometry.     

Dependence of the product on the P–P ligand in reactions of [RuCl3(NO)(P–P)] complexes (P–P = aromatic diphosphines) with 2-mercaptopyridine

This study presents the syntheses and characterization of 2-mercaptopyridine (pyS⁻) complexes containing ruthenium(II) with the following general formula [Ru(pyS)₂(P–P)], P–P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl₃(NO)(P–P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P–P ligand. The reaction of pyS⁻ with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)₂(NO)(η¹-dppbO-P)]PF₆(5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1–5, and report the X-ray structures for 1 and 5.     

Synthese und Struktur von Ruthenium(II)‐Komplexen mit Triazenido‐ und Pentaazadienido‐Liganden

Synthesis and Crystal Structure of Ruthenium(II) Complexes with Triazenido and Pentaazadienido Ligands The ruthenium(II) triazenido complex [RuCl(ClC₆H₄N₃C₆H₄Cl)(p‐cymene)] ( 1 ) is obtained by the reaction of silver bis(p‐chlorphenyl)triazenid with [RuCl₂(p‐cymene)]₂ in CH₂Cl₂, and forms air stable, orange yellow crystals. It crystallizes as 1 ·CH₂Cl₂ in the orthorhombic space group Pbca with the lattice parameters a = 3134.3(3), b = 2105.7(2), c = 769.15(4) pm and Z = 8. In the diamagnetic mononuclear complex 1 the chelating triazenido ligand coordinates with the atoms N(1) and N(3). p‐Cymene binds η⁶ with its C₆ ring. The reaction of the etherphosphane complex [RuCl₂(Ph₂PCH₂C₄H₇O₂)₂] with 1, 3‐bis(p‐tolyl)triazenid in THF yields the complex [RuCl(tolyl‐N₃‐tolyl)(Ph₂PCH₂C₄H₇O₂)₂] ( 2 ). 2 forms monoclinic, red crystals with the space group P2₁/c and a = 1521.0(2), b = 1451.8(2), c = 2073.7(2) pm, β = 99.29(1)° and Z = 4. It is air stable and diamagnetic. The triazenide ion coordinates with the atoms N(1) and N(3). One of the two etherphosphane ligands is chelating and coordinates with the P atom and one O atom, while the other ligand binds in a monodentate fashion with its P atom, resulting in a coordination number of six for the Ru^II. [Ag(tolyl‐N₅‐tolyl)]₂ reacts in THF with [RuCl₂(C₆H₆)]₂ to afford the air stable, diamagnetic pentaazadienido complex [RuCl(tolyl‐N₅‐tolyl)(C₆H₆)] ( 3 ). 3 forms monoclinic, red crystals with the space group P2₁/c and a = 1462.4(1), b = 1056.51(8), c = 1371.4(1) pm, β = 114.36(1)° and Z = 4. The chelating pentaazadienido ligand coordinates with the atoms N(1) and N(3) at the divalent Ru atom. The benzene molecule binds η⁶ with its π system.     

Syntheses and Structures of Ruthenium(II) N,S‐Heterocyclic Carbene Diphosphine Complexes and their Catalytic Activity towards Transfer Hydrogenation

Phosphine exchange of [Ru^IIBr(MeCOO)(PPh₃)₂(3‐RBzTh)] (3‐RBzTh=3‐benzylbenzothiazol‐2‐ylidene) with a series of diphosphines (bis(diphenylphosphino)methane (dppm), 1,2‐bis(diphenylphosphino)ethylene (dppv), 1,1′‐bis(diphenylphosphino)ferrocene (dppf), 1,4‐bis(diphenylphosphino)butane (dppb), and 1,3‐(diphenylphosphino)propane (dppp)) gave mononuclear and neutral octahedral complexes [RuBr(MeCOO)(η²‐P₂)(3‐RBzTh)] (P₂=dppm ( 2 ), dppv ( 3 ), dppf ( 4 ), dppb ( 5 ), or dppp ( 6 )), the coordination spheres of which contained four different ligands, namely, a chelating diphosphine, carboxylate, N,S‐heterocyclic carbene (NSHC), and a bromide. Two geometric isomers of 6 ( 6a and 6 b ) have been isolated. The structures of these products, which have been elucidated by single‐crystal X‐ray crystallography, show two structural types, I and II, depending on the relative dispositions of the ligands. Type I structures contain a carbenic carbon atom trans to the oxygen atom, whereas two phosphorus atoms are trans to bromine and oxygen atoms. The type II system comprises a carbene carbon atom trans to one of the phosphorus atoms, whereas the other phosphorus is trans to the oxygen atom, with the bromine trans to the remaining oxygen atom. Complexes 2 , 3 , 4 , and 6a belong to type I, whereas 5 and 6 b are of type II. The kinetic product 6 b eventually converts into 6a upon standing. These complexes are active towards catalytic reduction of para‐methyl acetophenone by 2‐propanol at 82 °C under 1 % catalyst load giving the corresponding alcohols. The dppm complex 2 shows the good yields (91–97 %) towards selected ketones.     

Olefin epoxidation catalyzed by [Ru(TDL)(tmeda)H2O] complexes (TDL = tridentate Schiff-base ligand; tmeda = tetramethylethylenediamine)

Mixed-chelate complexes of ruthenium have been synthesized using tridentate Schiff-base ligands (TDLs) derived from condensation of 2-aminophenol or 2-aminobenzoic acid with aldehydes (salicyldehyde, 2-pyridinecarboxaldehyde), and tmeda (tetramethylethylenediamine). [Ru^III(hpsd)(tmeda)(H₂O)]⁺ (1), [Ru^III(hppc)(tmeda)(H₂O)]²⁺ (2), [Ru^III(cpsd)(tmeda)(H₂O)]⁺ (3) and [Ru^III(cppc)(tmeda)(H₂O)]²⁺ (4) complexes (where hpsd²⁻ = N-(hydroxyphenyl)salicylaldiminato); hppc⁻ = N-(2-hydroxyphenylpyridine-2-carboxaldiminato); cpsd²⁻ = (N-(2-carboxyphenyl)salicylaldiminato); cppc⁻ = N-2-carboxyphenylpyridine-2-carboxaldiminato) were characterized by microanalysis, spectral (IR and UV–vis), conductance, magnetic moment and electrochemical studies. Complexes 1–4 catalyzed the epoxidation of cyclohexene, styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 4-nitrostyrene, cis- and trans-stilbenes effectively at ambient temperature using tert-butylhydroperoxide (t-BuOOH) as terminal oxidant. On the basis of Hammett correlation (log k_rel vs. σ⁺) and product analysis, a mechanism involving intermediacy of a [Ru–O–OBu^t] radicaloid species is proposed for the catalytic epoxidation process.     

Observation of vinylidene emission in mixed phosphine/diimine complexes of Ru(II) at room temperature in solution

The mixed ruthenium(II) complexes trans-[RuCl₂(PPh₃)₂(bipy)] (1), trans-[RuCl₂(PPh₃)₂(Me₂bipy)](2), cis-[RuCl₂(dcype)(bipy)](3), cis-[RuCl₂(dcype)(Me₂bipy)](4) (PPh₃ = triphenylphosphine, dcype = 1,2-bis(dicyclohexylphosphino)ethane, bipy = 2,2′-bipyridine, Me₂bipy = 4,4′-dimethyl-2,2′-bipyridine) were used as precursors to synthesize the associated vinylidene complexes. The complexes [RuCl(CCHPh)(PPh₃)₂(bipy)]PF₆ (5), [RuCl(CCHPh)(PPh₃)₂(Me₂bipy)]PF₆ (6), [RuCl(CCHPh)(dcype)(bipy)]PF₆ (7), [RuCl(CCHPh)(dcype)(bipy)]PF₆ (8) were characterized and their spectral, electrochemical, photochemical and photophysical properties were examined. The emission assigned to the π–π1 excited state from the vinylidene ligand is irradiation wavelength (340, 400, 430 nm) and solvent (CH₂Cl₂, CH₃CN, EtOH/MeOH) dependent. The cyclic voltammograms of (6) and (7) show a reversible metal oxidation peak and two successive ligand reductions in the +1.5-(−0.64) V range. The reduction of the vinylidene leads to the formation of the acetylide complex, but due the hydrogen abstraction the process is irreversible. The studies described here suggest that for practical applications such as functional materials, nonlinear optics, building blocks and supramolecular photochemistry.     

Ethylenediamine-N,N"-Diacetate Ion (Edda2–) as a Tridentate Ligand: Synthesis and Structure of the [Co(Edda)(Dien)]ClO4 · H2O and [Co(Edda)(En)(CN)] · 2H2O Complexes

The cobalt(III) complexes with tridentate ethylenediamine-N,N"-diacetate ions (Edda^2–) and additional ligands, namely, diethylenetriamine (Dien) or ethylenediamine (En) and cyanide ions, were synthesized. As follows from X-ray diffraction analysis of [Co(Edda)(Dien)]ClO₄· H₂O (monoclinic crystals with a = 9.243 (2) Å, b = 14.167 (4) Å, c = 13.046 (3) Å, = 91.19 (2)°, Z = 4, space group P2₁/c), the secondary N atom of the Dien ligand occupies the trans-position relative to the N atom of the Edda^2– ligand, which contains a free acetate group. Two fac-isomers of [Co(Edda)(En)(CN)] with the CN^– ion in the cis- and trans-positions relative to the oxygen atom of the carboxyl group were isolated, and the structure of the trans-(O,CN)-[Co(Edda)(En)(CN)]· 2H₂O was determined: monoclinic crystals with a = 9.136 (3) Å, b = 15.484 (3) Å, c = 10.564 (3) Å, = 110.67 (5)°, Z = 4, space group P2₁/c.     

Synthesis and catalytic properties of novel ruthenium N-heterocyclic-carbene complexes

The reaction of [RuCl₂(p-cymene)]₂ with 1,3-dialkylimidazolinium salts 1a–f in the presence of a small excess of cesium carbonate yields chelated η⁶-arene, η¹-carbene ruthenium complexes 2a–f. All synthesised compounds were characterized by elemental analysis, NMR spectroscopy. The catalytic activity of RuCl₂(η⁶-arene, η¹-imidazolinylidene) complexes 2a–f was evaluated in the direct arylation of 2-phenylpyridine with chlorobenzene derivatives.     

Observation of vinylidene emission in mixed phosphine/diimine complexes of Ru(II) at room temperature in solution

The mixed ruthenium(II) complexes trans-[RuCl₂(PPh₃)₂(bipy)] (1), trans-[RuCl₂(PPh₃)₂(Me₂bipy)](2), cis-[RuCl₂(dcype)(bipy)](3), cis-[RuCl₂(dcype)(Me₂bipy)](4) (PPh₃ = triphenylphosphine, dcype = 1,2-bis(dicyclohexylphosphino)ethane, bipy = 2,2′-bipyridine, Me₂bipy = 4,4′-dimethyl-2,2′-bipyridine) were used as precursors to synthesize the associated vinylidene complexes. The complexes [RuCl(CCHPh)(PPh₃)₂(bipy)]PF₆ (5), [RuCl(CCHPh)(PPh₃)₂(Me₂bipy)]PF₆ (6), [RuCl(CCHPh)(dcype)(bipy)]PF₆ (7), [RuCl(CCHPh)(dcype)(bipy)]PF₆ (8) were characterized and their spectral, electrochemical, photochemical and photophysical properties were examined. The emission assigned to the π–π1 excited state from the vinylidene ligand is irradiation wavelength (340, 400, 430 nm) and solvent (CH₂Cl₂, CH₃CN, EtOH/MeOH) dependent. The cyclic voltammograms of (6) and (7) show a reversible metal oxidation peak and two successive ligand reductions in the +1.5-(?0.64) V range. The reduction of the vinylidene leads to the formation of the acetylide complex, but due the hydrogen abstraction the process is irreversible. The studies described here suggest that for practical applications such as functional materials, nonlinear optics, building blocks and supramolecular photochemistry.     

Synthesis and reactivity of neodymium(III) amido-tethered N-heterocyclic carbene complexes

The reaction of the heteroleptic Nd(III) iodide, [Nd(L′)(N″)(μ-I)] with the potassium salts of primary aryl amides [KN(H)Ar′] or [KN(H)Ar^*] affords heteroleptic, structurally characterised, low-coordinate neodymium amides [Nd(L′)(N″)(N(H)Ar′)] and [Nd(L′)(N″)(N(H)Ar^*)] cleanly (L′ = t-BuNCH₂CH₂[C{NC(SiMe₃)CHNt-Bu}], N″ = N(SiMe₃)₂, Ar′ = 2,6-Dipp₂C₆H₃, Dipp = 2,6-Prⁱ₂C₆H₃, Ar^* = 2,6-(2,4,6-Prⁱ₃C₆H₂)₂C₆H₃). The potassium terphenyl primary amide [KN(H)Ar^*] is readily prepared and isolated, and structurally characterised. Treatment of these primary amide-containing compounds with alkali metal alkyl salts results in ligand exchange to give alkali metal primary amides and intractable heteroleptic Nd(III) alkyl compounds of the form [Nd(L′)(N″)(R)] (R = CH₂SiMe₃, Me). Attempted deprotonation of the Nd-bound primary amide in [Nd(L′)(N″)(N(H)Ar^*)] with the less nucleophilic phosphazene superbase Bu^tNP{NP(NMe₂)₃}₃ resulted in indiscriminate deprotonations of peripheral ligand CH groups.     

Ab initio investigation of tautomeric stability,molecular structure,and internal rotation of methylphosphonic dicyanide,methoxydicyanophosphine, and their isocyano analogs

The equilibrium geometric parameters and structures of the transition states of internal rotation for MeP(O)(CN)₂, McOP(CN)₂, and their isocyano analogs, MeP(O)(NC)₂ and MeOP(NC)₂, have been calculated by theab initio SCF method and with inclusion of electron correlation effects according to the second-order Muuller-Plesset perturbation theory (MP2). At both levels the 6-31G* basis set has been used. The estimation of relative stability of these tautomeric forms depends largely on the calculation level. The total energies of the cyanides calculated by the MP2 method are 25–30 kcal mol^–1 lower than those of the corresponding isocyanides. The oxo-tautomeric forms containing four-coordinate phosphorus are 15–25 kcal mol^–1 more stable than the three-coordinate phosphorus aci-derivatives. The internal rotation potential curves of the aci-forms are characterized by a deep minimum for thetrans-arrangement of the methoxy group and phosphorus lone electron pair. Two additional less clearly pronounced minima are located symmetrically on both sides of the weak maximum, which corresponds to thecis-arrangement. The equilibrium oxo-form structures have a staggered configuration of the methyl group with respect to the phosphorus atom bonds.Translated from izvestiyaAkademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1104–1115, May, 1996.     

Co(III) complexes of Me-salpn and Me-salbn and the ring size effect on the coordination modes and electrochemical properties: The crystal structures of trans-[Co(Me-salpn)(py)2]PF6 and cis-α-[Co(Me-salbn)(4-Mepy)2]BPh4 · 4-Mepy

The synthesis and characterization of a series of cobalt(III) complexes of the general type [Co(N₂O₂)(L₂)]⁺ are described. The N₂O₂ Schiff base ligands used are Me-salpn (H₂Me-salpn = N,N′-bis(methylsalicylidene)-1,3-propylenediamine) (1–3) and Me-salbn (H₂Me-salbn = N,N′-bis(methylsalicylidene)-1,4-butylenediamine) (4–5). The two ancillary ligands L include: pyridine (py) 1, 3-metheylpyridine (3-Mepy) 2, 1-methylimidazole (1-MeIm) 3, 4-methylpyridine (4-Mepy) 4 and pyridine (py) 5. These complexes have been characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structures of trans-[Co^III(Me-salpn)(py)₂]PF₆, 1, and cis-α-[Co^III(Me-salbn)(4-Mepy)₂]BPh₄ · 4-Mepy, 4, have been determined by X-ray diffraction. Examination of the solution and crystalline structures revealed that the outer coordination sphere of the complexes exerts a noticeable influence on the inner coordination sphere of the Co(III) ion. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial (R-py)–cobalt bonds. It has also been observed that the Co(III) state is stabilized with increasing the flexibility of the ligand environment.     

Transition metal complexes with thiosemicarbazide-based ligands. Part 56. Square-pyramidal complexes of copper(II) with 2-acetylpyridine S-methylisothiosemicarbazone

The article describes the synthesis and single-crystal X-ray analysis of two sulfato and one thiocyanato copper(II) complex with 2-acetylpyridine S-methylisothiosemicarbazone (HL) of the formulae [Cu(HL)SO₄(H₂O)]·H₂O (1), [Cu₂(HL)₂(μ-SO₄)₂]·2H₂O (2) and [Cu(HL)(NCS)(SCN)] (3), as well as the structure of the protonated ligand H₂L⁺I⁻. Complexes 1 and 2 were obtained from the reaction of aqueous/methanolic CuSO₄·5H₂O and ethanolic/methanolic H₂L⁺I⁻ solutions, respectively. Complex 3 was synthesized by the reaction of methanolic solutions of Cu(ClO₄)₂·6H₂O, the ligand and NH₄SCN, with the addition of triethyl orthoformate. All three complexes have a slightly deformed square-pyramidal structure (τ_av = 0.15) with the tridentate NNN neutral ligand in the basal plane. In complexes 1 and 3 the apical position is occupied by the oxygen atom of the monodentate SO₄ group, or the sulfur atom of the SCN group. Thanks to the hydrogen bonds, complex 3 may be thought of as having a pseudo-dimeric structure. In the authentic centrosymmetric dimer 2, the oxygen atoms of both SO₄ groups occupy also the apical position of both coordination polyhedra, as well as an equatorial position. Complexes 1 and 3 have μ_eff values characteristic of magnetically isolated mononuclear Cu(II) complexes. In contrast to them, complex 2 has a μ_eff value of 1.57 BM, which is in agreement with its dinuclear structure. All the complexes, in addition to the X-ray analysis and magnetic measurements, were characterized by IR and UV–Vis spectroscopy and by thermal analysis.     

Pincer and diamine Ru and Os diphosphane complexes as efficient catalysts for the dehydrogenation of alcohols to ketones

The ruthenium and osmium complexes [MCl₂(diphosphane)(L)] (M=Ru, Os; L=bidentate amino ligand) and [MCl(CNN)(dppb)] (CNN=pincer ligand; dppb=1,4‐bis‐ (diphenylphosphino)butane), containing the N–H moiety, have been found to catalyze the acceptorless dehydrogenation of alcohols in tBuOH and in the presence of KOtBu. The compounds trans‐[MCl₂(dppf)(en)] (M=Ru 7 , Os 13 ; dppf=1,1′‐bis(diphenylphosphino)ferrocene; en=ethylenediamine) display very high activity and different substrates, including cyclic and linear alcohols, are efficiently oxidized to ketones by using 0.8–0.04 mol % of catalyst. The effect of the base and the comparison of the catalytic activity of the Ru versus Os complexes are reported. The ruthenium complex 7 generally leads to a faster conversion into ketones with respect to the osmium complex 13 , which displays better activity in the dehydrogenation of 5‐en‐3β‐hydroxy steroids. The synthesis of new Ru and Os complexes [MCl₂(PP)(L)] (PP=dppb, dppf; L=(±)‐trans‐1,2‐diaminocyclohexane, 2‐(aminomethyl)pyridine, and 2‐aminoethanol) of trans and cis configuration is also reported.