The RuCl3(dppb)H2O complex: A new metal-assisted oxidative dehydrogenation of the o-phenylenediamine ligand

The trans-[RuCl₂(dppb)(bqdi)] and trans-[RuCl₂(dppb)(opda)] complexes (dppb = 1,4-bis(diphenylphosphine)butane, bqdi = o-benzoquinonediimine, and opda = o-phenylenediamine) were synthesized from the reaction of the mer-[RuCl₃(dppb)(H₂O)] aqua-complex with the opda ligand. The X-ray structural and electrochemical characterizations of the isolated compounds showed that this aqua-complex induces the oxidative dehydrogenation of the amine species (opda) to the imine form (bqdi) of the o-phenylene ligand during the synthetic procedure. In the presence of oxygen, the ³¹P{¹H} NMR experiments confirmed that the trans-[RuCl₂(dppb)(bqdi)] complex is the only product formed.     

Fast and Chemoselective Transfer Hydrogenation of Aldehydes Catalyzed by a Terdentate CNN Ruthenium Complex [RuCl(CNN)(dppb)]

Aromatic, aliphatic and α,β‐unsaturated aldehydes are quickly, quantitatively and chemoselectively reduced to primary alcohols with 2‐propanol using 0.05–0.01 mol % of the terdentate CNN ruthenium complex RuCl(CNN)(dppb) ( 1 ) [HCNN=6‐(4′‐methylphenyl)‐2‐pyridylmethylamine; dppb=Ph₂P(CH₂)₄PPh₂] in the presence of potassium carbonate (K₂CO₃; 1–10 mol %) as a weak base, affording TOF values up to 5.0×10⁵ h⁻¹.     

Synthesis, characterization and crystal structure of a novel thiocyanate–ruthenium(II) complex

The cis-[Ru(dppb)(Me-bipy)(NCS)₂], dppb = 1,4-bis (diphenylphosphino)butane, Me-bipy = 4,4′-dimethyl-2,2′-bipyridine, and NCS = thiocyanate, was synthesized and characterized by spectroscopic and electrochemical techniques and its structure was determined by crystal X-ray analysis. The crystal structure reveals that the coordination geometry around the Ru(II) center is distorted octahedron where two molecules of thiocyanate are bonded to the ruthenium through nitrogen atom in cis orientation. The half-wave formal potential value E_1/2 = 0.8 V (versus Ag/AgCl) observed is considerable higher than that for the cis-[RuCl₂(dppb)(Me-bipy)] complex, E_1/2 = 0.6 V (versus Ag/AgCl), well illustrating the strong π-acceptor effect the NCS ligand toward the backbonding interaction with the Ru(II) metal center. The MLCT absorption bands of the thiocyanate complex present a higher molar absorptivity (about 12%) compared with the cis-[RuCl₂(dppb)(Me-bipy)] complex, in the same experimental conditions. These properties make the complex potentially promising for the photosensitization process.     

A family of thioxanthato ruthenium and osmium aryls

The title complexes of type M(RL²)(PPh₃)₂(CO)(S₂CSEt) ( 2a : M = Ru; 2b : M = Os) have been synthesized in excellent yields by reacting M(RL¹)(PPh₃)₂(CO)X ( 1a : M = Ru, × = Cl; 1b : M = Os, × = Br) with potassium ethyl thioxanthate and have been characterized with the help of spectral and electrochemical data. The RL² ligand in 2 is the imine-phenol tautomer of N-C₆H₄R(p)-4-methylsalicylaldimine (R = Me, MeO, Cl) coordinated at the carbanionic-C2 atom only while RL¹ in 1 is the iminium-phenolato tautomer chelated via carbanionic-C2 and phenolato-O atoms. The synthetic reaction is thus attended with tautomerization of the Schiff base ligand. It is also associated with a rotation of the ligand by ˜180° around the M–C bond in order to exclude steric repulsion. These features have been revealed by structure determination of 2a (R = Me). The metallated aldimine ring is found to be highly noncoplanar (dihedral angle ˜40°) with the thioxanthate chelate ring due to steric repulsion originating from the relatively large size of the sulfur atom. This phenomenon, which is absent in both the precursor 1 (R = Me) and in the carboxylate analogue Ru(MeL²)(PPh₃)₂(CO)(O₂CMe), 7 , has distinctive effects on bond parameters of 2a (R = Me). Thus the two Ru–P bonds in 2a (R = Me) differ in length by as much as 0.06 Å. The thioxanthate 2 is thermodynamically more stable than the precursor 1 as well as the carboxylate 7 . Accordingly, both of these are irreversibly transformed to 2a (R = Me) upon treatment with thioxanthate.     

Silver(I)-mediated isomerisation of trans-[RuCl2(P-P)2] (P-P=4-membered ring chelate diphosphine ligand) and its application in the syntheses of [RuCl(L)(P-P)2]+ (L=neutral ligand)

Conversion of trans-[RuCl₂(P-P)₂] (P-P=4-membered chelate diphosphine) to cis is facilitated by treatment with AgOTf or AgBF₄ in 1,2-dichloroethane, which gives mixtures of Ru–Cl–Ag heterobimetallic complexes with cis stereochemistry at Ru(II), characterised by ³¹P{¹H} and ¹H NMR spectroscopy and by FAB mass spectrometry. Treatment of these mixtures with neutral ligands (CO, CH₃CN) gives cis-[RuCl(L)(P-P)₂]⁺, whereas simultaneous treatment of trans-[RuCl₂(P-P)₂] with L and Ag(I) salt gives trans-[RuCl(L)(P-P)₂]⁺.     

The Beauty and Complexity of the Mixed-Ligand Pd(II)-containing Monomers,Oligomers and Polymers Built upon Diphosphines and 1,8-Diisocyano-<Emphasis Type="Italic">p</Emphasis>-menthane

The starting materials Pd(diphos)Cl₂ where diphos = bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)propane (dppp), bis(diphenylphosphino)butane (dppb), and Pd₂(diphos′)₂Cl₄ where diphos′ = bis(diphenylphosphino)pentane (dpppen) and bis(diphenylphosphino)hexane (dpph) were reacted with the bridging ligand 1,8-diisocyano-p-menthane (dmb) to form species of the type {Pd₂(diphos)₂(dmb) ₂ ⁴⁺ } _n and {Pd(diphos′)₂(dmb) ₂ ⁴⁺ } _n . Except for Pd₂(dppe)₂(dmb) ₂ ⁴⁺ , which was characterized by X-ray crystallography, the identity of the other weakly soluble dmb-containing materials were exhaustively characterized in solution and in the solid state by ³¹P NMR (Magic Angle Spinning), chemical analyses, MALDI-TOF, DSC, TGA, IR and T ₁/NOE (³¹P NMR spin-lattice relaxation time and nuclear overhauser enhancement constant measurements). Model compounds such as Pd(diphos)(CN-tBu) ₂ ²⁺ (diphos = dppe, dppp, dppb) and Pd₂(diphos′)₂(CN-tBu) ₄ ⁴⁺ (diphos′ = dpppen, dpph; as BF ₄ ⁻ or PF ₆ ⁻ salts), were prepared and also characterized by X-ray crystallography. Evidence for mono- (model complexes only of the type dppe, dppp, and dppb) and dinuclear complexes, as well as oligomers and polymers, are obtained for most cases, as well as the presence of monomer–oligomer (or polymer) equilibrium. During the course of this study, the complexes [Pd(dppp)(CN-tBu)₂](TCNQ)(Cl), [Pd₂(dpppen)₂(CN-tBu)₂(Cl)₂](PF₆)₂, and [Pd₂(dpppen)₂(CN-tBu)₂(CN)₂](TCNQ)₂ (TCNQ⁻ = tetraquinodimethane anion) were isolated and characterized by X-ray crystallography.This paper is dedicated to Professor Richard J. Puddephatt.     

Preparation and structural characterization of mercury 21-thiaporphyrin complex: HgII(Stpp)Cl (Stpp=tetraphenyl-21-thiaporphyrin anion)

Treatment of tetraphenyl-21-thiaporphyrin (StppH) with Hg(OAc)₂ in CH₂Cl₂ yields diamagnetic Hg^II(Stpp)Cl complex. The coordination sphere around Hg²⁺ in the monomeric molecule is described as a five-coordinate distorted trigonal bipyramid with the bonding to the three pyrrole nitrogens [Hg(1)–N=2.104(4), 2.626(4), 2.640(4) Å], the thiophene sulfur [Hg(1)–S=2.801(1) Å], and one axial chloride ligand [Hg(1)–Cl(1)=2.318(1) Å]. The plane of the three pyrrole nitrogen atoms [i.e., N(1), N(2), N(3)] bonded to Hg²⁺ is adopted as a reference plane 3N. Because of its larger size, the Hg²⁺ is considerably out of the 3N plane; its displacement of 1.41 Å is in the same direction as that of the apical Cl⁻ ligand. The thiophene ring is slightly folded so that the dihedral angle between the C(13)–C(14)–C(15)–C(16) and C(13)–S(1)–C(16) planes is 7.3°.     

Synthesis,spectral and antibacterial studies on Ni(II) and Zn(II) complexes involving N-furfuryl-N-isopropyldithiocarbamate (f iprdtc) and Lewis bases: X-ray structure of [Ni(f iprdtc)(NCS)(PPh3)]

[Ni(fⁱprdtc)₂] (1), [Ni(fⁱprdtc)(PPh₃)(NCS)] (2), [Ni(fⁱprdtc)(PPh₃)₂]ClO₄ (3), [Zn(fⁱprdtc)₂] (4), [Zn(fⁱprdtc)₂(1,10-phen)] (5) and [Zn(fⁱprdtc)₂(2,2′-bipy)] (6) (f ⁱprdtc=N-furfuryl-N-isopropyldithio- carbamate, 1,10-phen=1,10-phenanthroline and 2,2′-bipy=2,2′-bipyridine) complexes were prepared and characterized by elemental analysis, electronic, IR and NMR spectra and the structure of 2 was determined by single-crystal X-ray crystallography. UV–Vis spectral data of 1–3 are consistent with the formation of square planar complexes. IR spectra of the complexes show the contribution of the thioureide form to the structure. A single-crystal X-ray structural analysis of 2 proved four-coordinated nickel in a distorted square planar arrangement with a S₂PN donor set. Significant asymmetry in Ni–S bond distances was observed in [Ni? S1=2.1655(8); Ni? S2=2.2120(8) Å]. This observation clearly supports the less effective trans of SCN^? over PPh₃. The observed shielding in N¹³CS₂ chemical shifts of heteroleptic nickel complexes 2 and 3 when compared with homoleptic nickel complex 1 indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C? N bond. The N¹³CS₂ chemical shift of 5 and 6 are additionally deshielded compared with 4 owing to the increase in coordination number. Complexes were screened for in vitro antibacterial activity and significant activity has been found.     

Structures of the (4S, 14S)-4, 14-Dimethyl-3,6,9,12,15-pentaoxa-21-azabicyclo[15.3.1] heneicosa-1(21) 17,19-Triene-2,16-dione Complexes of R-and S-α-(1-Naphthyl)ethylammonium Perchlorate

Crystal data for the more stable (R) and less stable (S) 1:1 macrocycle-cation complexes are as follows: R cation: M_r = 625.08, orthorhombic P2₁2₁2₁, a = 8.47(1), b = 11.78(1), c = 31.19(6) A, V = 3112.0(123) ų, Z = 4, D_x = 1.333 kg m⁻³, λ(Mo Kα) = 0.71073 μ = 1.90 cm⁻¹, F(000) = 1320, T = 295 K, R = 0.17 for 1680 reflections. S Cation: M_r = 625.08, monoclinic, P2₁, a = 8.654(2), b = 11.954(3), c = 15.130(4) Å, β = 97.39(2)°, V = 1552.2(12) ų, Z = 2, D_x = 1.337 kg m⁻³, λ(Mo Kα) = 0.71073, μ = 1.91 cm⁻¹, F(000) = 660, T = 295K, R = 0.081 for 2751 unique reflections. Crystals of the complexes were prepared by the authors. The greater thermodynamic stability of the R cation complex is consistent with the observation that this cation experiences less steric interaction with the methyl substituent of the ligand than does the S cation.     

The formation of [RuCl(p-cymene)(Me2HPz)(PPh2OR)]Cl (Me2HPz=3, 5-dimethylpyrazole; R=H,Me and p-Tol) complexes from the cleavage of the P–N bond of a P-coordinated P(Me2Pz)Ph2 ligand by ROH molecules in a ruthenium(II) complex. Crystal structure of [RuCl(p-cymene)(Me2HPz)(PPh2OH)]Cl

The complex [RuCl₂(p-cymene)]₂ reacts with 1-(3,5-dimethyl)pyrazolyldiphenylphosphine (P(Me₂Pz)Ph₂) to give the complex RuCl₂(p-cymene)(P(Me₂Pz)Ph₂). This compound reacts with ROH molecules (R=H, Me and p-Tol) to give [RuCl(p-cymene)(Me₂HPz)(PPh₂OR)]Cl (R=H, Me and p-Tol) complexes, which contain both Me₂HPz and PPh₂OR coordinated molecules.     

Ring‐opening polymerization of lactones using RuCl2(PPh3)3 as initiator: Effect of hydroxylic transfer agents

ε‐Caprolactone and δ‐valerolactone were polymerized in bulk at 150°C using the ruthenium(II) complex RuCl₂(PPh₃)₃ as initiator in the presence of 1,3‐propanediol (PD) with a series of alcohols as coinitiators. Polymerization of lactones proceeds via ruthenium(II) alkoxide active centers. ¹H‐NMR analysis revealed that the ruthenium complex reacted with the alcohol, generating in situ a ruthenium alkoxide. This species became a more active initiator of ring‐opening polymerization than was RuCl₂(PPh₃)₃. The obtained polylactones were characterized by ¹H‐ and ¹³C‐NMR and matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF). The results showed the formation had occurred of α,ω‐telechelic PCL and PVL diols, in which PD had been incorporated into the polymer backbone. Depending on the nature of the alcohol used as coinitiator, PCLs with different end groups could be synthesized. Insertion of an alcohol as an end group (benzyl alcohol, n‐octanol, or isopropanol) or into the polymeric backbone (propanediol) provided support for the conclusion that a classical coordination–insertion mechanism was operating during lactone polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

One-pot template synthesis and crystal structure of two new polyaza copper(II) complexes

A new 14-membered hexazamacrocyclic copper(II) complex [Cu(H₂L¹)](ClO₄)₄(L¹=1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been prepared by the one-pot reaction of ethylenediamine and formaldehyde in the presence of the Cu(II) ion. The crystal structure of [Cu(H₂L¹)](ClO₄)₄ was determined by X-ray diffraction. It crystallizes in the triclinic space group P−1 with a=12.118(2) Å, b=12.438(2) Å, c=12.466(2) Å, α=102.26(1)°, β=112.82(1)°, γ=111.51(1)°, and Z=2. The coordination geometry around the copper(II) ions is axially elongated octahedral with four nitrogen atoms of the macrocycle [Cu–N 2.012(7) Å for Cu(1) and 2.013(6) Å for Cu(2), average value] and two oxygen atoms of two ClO₄⁻ anions [Cu–O=2.550 Å for Cu(1) and 2.601(6) Å for Cu(2)]. [CuL²](ClO₄)₂(L²=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3,3,2]decane) with a novel tetraazabicyclic ligand was obtained from the same reaction system as an additional product. Crystal structure of [CuL²](ClO₄)₂: monoclinic space group Cc, a=16.393(3) Å, b=8.8640(18) Å, c= 13.085(3) Å, β=105.01(3)°, and Z=4.     

Preparation, characterization and taste sensing properties of Langmuir-Blodgett Films from mixtures of polyaniline and a ruthenium complex

Langmuir-Blodgett (LB) films from a ruthenium complex, mer-[RuCl₃(dppb)(py)] (dppb=PPh₂(CH₂)₄PPh₂; py=pyridine) (Rupy), and from mixtures with varied amounts of polyaniline (PANi) were fabricated. Molecular-level interactions between the two components are investigated by surface potential, dc conductivity and Raman spectroscopy measurements, particularly for the mixed film with 10% of Rupy. For the latter, the better miscibility led to an interaction with Rupy inducing a decrease in the conducting state of PANi, as observed in the Raman spectra and conductivity measurement. The interaction causes the final film properties to depend on the concentration of Rupy, and this was exploited to produce a sensor array made up of sensing units consisting of 11-layer LB films from pure PANi, pure Rupy and mixtures with 10 and 30% of Rupy. It is shown that the combination of only four non-specific sensing units allows one to distinguish the basic tastes detected by biological systems, viz. saltiness, sweetness, sourness and bitterness, at the μM level.     

Solvent/C60 exchange on Ir(CO)(PPH3)2(Cl)(η2-C60) and solvent/solvent’ exchange on Ir(CO)(PPH3)2(Cl)(solvent)

Dissociation of C₆₀ from Ir(CO)(PPh₃)₂(Cl)(η²-C₆₀) in a binary mixture of solvents (solvent₁ and solvent₂) produced non-equilibrium mixtures of Ir(CO)(PPh₃)₂(Cl)(solvent₁) and Ir(CO)(PPh₃)₂(Cl)(solvent₂). Once the solvated species were produced, they underwent a relative fast solvent exchange between them to produce an equilibrium mixture.     

Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

The trans-[RuCl₂(L)₄], trans-[Ru(NO)Cl (L)₄](PF₆)₂ (L = isonicotinamide and 4-acetylpyridine) and trans-[Ru(NO)(OH)(py)₄]Cl₂ (py = pyridine) complexes have been prepared and characterized by elemental analysis, UV–visible, infrared, and ¹H NMR spectroscopies, and cyclic voltammetry. The MLCT band energies of trans-[RuCl₂(L)₄] increase in the order 4-acpy < isn < py. The reduction potentials of trans-[RuCl₂(L)₄] and trans-[Ru(NO)Cl(L)₄]²⁺ increase in the order py < isn < 4-acpy. The stretching band frequency, ν_NO, of the nitrosyl complexes ranges from 1913 to 1852 cm^?1 indicating a nitrosonium character for the NO ligand. Due to the large π-acceptor ability of the equatorial ligands, the coordinated water is much more acidic in the water soluble trans-[Ru(NO)(H₂O)(py)₄]³⁺ than in trans-[Ru(NO)(H₂O)(NH₃)₄]³⁺.     

Asymmetric transfer hydrogenation of ketones by N,N-containing quinazoline-based ruthenium(II) complexes

The novel set of quinazoline-based chiral ligands was synthesized starting from optically pure amino acids. Coordination with RuCl₂(PPh₃)dppb gave ruthenium(II) N-heterocyclic complexes 4b–d. The structure of complex 4b was fully illuminated by X-ray crystallography. The steric environment of these chiral ruthenium complexes 4b–d was evaluated in asymmetric transfer hydrogenation (ATH) of prochiral ketones in the presence of NaOⁱPr by using 2-propanol as the hydrogen source and solvent. The resultant catalytic system can achieve very good enantioselectivities (up to 91%) and high yields (up to 99%).     

A convenient one-step synthesis of alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III)

Alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III) were prepared by reactions of [(p-cymene)RuCl₂(PPh₃)] or [C_p^*MCl₂(PPh₃)] (M=Rh, Ir; C_p^*=C₅Me₅) with 1-ethynylbenzene and triphenylphosphine in the presence of KPF₆.     

Multinuclear Metal Carbonyl Alkoxide and Aryloxide Derivatives as Models for Metal Carbonyls Adsorbed on Metal Oxide Supports

The synthesis and characterization of two tungsten carbonyl dimers containing bridging alkoxide or aryloxide ligands are described. The crystal and molecular structures of [PPN]₂[W₂(CO)₈(OCH₂CF₃)₂], 1, and [Et₄N]₃[W₂(CO)₆-(OPh)₃]-CH₃CN, 2 , are reported and compared with the structures of tetranuclear tungsten derivatives previously described. The dimer 1 crystalizes in the triclinic space group P 1 with unit cell parameters a = 13.460(11) Å, b = 12.318(5) Å, c = 13.842(10) Å, α = 82.73(5)°, β = 59.11(5)°, γ= 80.09(5)°, V = 1938(2) ų, and Z = 1. The complex 2 crystalizes in the monoclinic space group P2₁/n with unit cell parameters a = 11.954(2) Å, b = 19.359(4) Å, c = 26.462(5) Å, β = 102.50(16)°, V = 5979(2) ų, Z = 4. Molecular modeling software was utilized to construct a tetranuclear derivative from 1 similar to the structurally characterized [W(CO)₃OH]₄₋⁴ tetramer. The two tetramers were found to possess similar molecular parameters. This supports the contention that dimers of type 1 are the precursors of the tetramers. Comparisons of the tungsten alkoxides and aryloxides with the behavior of W(CO)₆ on γ-alumina are provided.     

Synthesis and characterization of the zinc(II) complex of a bleomycin analogue: a unique polymeric 2-[((2-(4-imidazoyl)ethyl)amino)carbony]-6-[((2-amino-2-methylpropyl)amino)methyl]pyridine zinc(II) nitrate complex

The reaction of 2-[((2-(4-imidazoyl)ethyl)amino)carbonyl]-6-[((2-amino-2-methylpropyl)amino)methyl]pyridine (L) with Zn^II(NO₃)₂·6H₂O has afforded a novel one-dimensional polymeric Zn^II complex, (Zn^II(L)(NO₃)₂)_n (2). Complex 2 crystallizes in the space group P2₁/n with a=8.955(3), b=13.216(3), c=18.941(3) Å, β=103.39(2)°, V=2180.6(10) ų, and Z=4. The geometry of each Zn^II is approximately a trigonal bipyramid: three nitrogens and one oxygen of the amide group are coordinated to the zinc while the fifth site is occupied by the imidazole nitrogen of a neighboring unit.     

Sulfur-assisted chloride and triphenylphosphine dissociation of palladium(II) complex [Pd(PPh3)2(η1-SCNMe2)(Cl)]. X-ray structures of [Pd(PPh3)2(η1-SCNMe2)(Cl)], [Pd(PPh3)(Cl)]2(μ,η2-SCNMe2)2, and [Pd(PPh3)2(η2-SCNMe2)][PF6]

Treatment of Pd(PPh₃)₄ with Me₂NC(S)Cl in dichloromethane at −20 °C produces the complex [Pd(PPh₃)₂(η¹-SCNMe₂)(Cl)], 2. Variable temperature ¹H and ³¹P{H} NMR experiments of complex 2 shows the dissociation of either the chloride or the triphenylphosphine ligand to form complex [Pd(PPh₃)₂(η²-SCNMe₂)][Cl], 3 or the dipalladium complex [Pd(PPh₃)Cl]₂(μ,η²-SCNMe₂)₂, 4. The reaction of complex 2 with NaPF₆ affords complex [Pd(PPh₃)₂(η²-SCNMe₂)][PF₆], 5. Complexes 2, 4, and 5 are characterized by X-ray diffraction analyses.