Synthesis and characterization of new imidorhenium(V) and imidorhenium(VI) complexes of pyridyltriazines and pyrazinyltriazine with halide coligands including rare iodide

The blue colored imido complexes [Re(NC₆H₄Cl)X₃(L)] have been synthesized by three methods: (i) reaction of [Re^VOX₃(L)] with p-ClC₆H₄NH₂, (ii) reaction of [Re^III(OPPh₃)X₃(L)] with p-ClC₆H₄NH₂ and (iii) reaction of [Re^VOX₃(PPh₃)₂] with L followed by the addition of p-ClC₆H₄NH₂ in boiling toluene. Here, X = Cl, Br, I and L are 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (L²) and its dimethyl (L¹) and pyrazinyl (L³) analogues. The [Re(NC₆H₄Cl)Cl₃(L¹)] (1a), [Re(NC₆H₄Cl)Cl₃(L²)] (1b), [Re(NC₆H₄Cl)Br₃(L²)] (1c), [Re(NC₆H₄Cl)I₃(L²)] (1d), [Re(NC₆H₄Cl)Cl₃(L³)] (1e), [Re(NC₆H₄Cl)Br₃(L³)] (1f), [Re(NC₆H₄Cl)I₃(L³)] (1g), complexes have been characterized electrochemically and spectroscopically. The X-ray structures of [Re(NC₆H₄Cl)Cl₃(L²)] and [Re(NC₆H₄Cl)I₃(L³)] reveal that the ReCl₃ fragment is meridionally disposed and that the L ligand is N,N-coordinated such that the pyridine/pyrazine nitrogen lies trans to the imide nitrogen. The feasibility of generating the rhenium(VI) congener of the imidorhenium(V) complex is also examined with the help of six-line EPR spectra at room temperature.     

On the interaction of compounds of chromium(VI) with hydrogen peroxide. A study of chromium(VI) and (V) peroxides in the acid-basic pH range

A computational study of chromium(VI) and (V) peroxides, which exhibit important genotoxic and mutagenic activity, is reported. Energies and equilibrium geometries for [Cr^VI(O)(O₂)₂(OH)]⁻, [Cr^VI(O)(O₂)₂(OH₂)], [Cr^VI(O)(O₂)₂(py)], [Cr^VI(OH)(O₂)₂(OH₂)]⁺, [Cr^V(O)(O₂)₂(OH₂)]⁻ and species were calculated using molecular mechanics calculations (MMFF94 and MM⁺), quantum calculations with semi-empirical methods (RHF and UHF/PM3) and density functional theory (pBP86/DN* or pBP/DN* and B3LYP/6-31G(d). Equilibrium geometries for the compounds [Cr^V(O₂)₃(OH)]²⁻ and [Cr^V(O₂)₄]³⁻ were determined by molecular mechanics. Vibrational frequencies, standard thermodynamic quantities and electronic spectra were calculated using B3LYP/6-31G(d). The structural relationship between all these species and an explanation of the formation of peroxo species in the acid-basic pH range are given. An experimental study of peroxo species in basic medium was also performed (synthesis, X-ray powder diffraction patterns and infrared spectra of the peroxo complexes isolated) but did not confirm the existence of a tri-peroxo complex in the solid phase.     

Aqua bridge cleavage and metal ion extrusion by thiocyanate anions in a dicopper complex

Reaction of the imidazolidinyl phenolate-based ligand, H₃L [(2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine)] with Cu(ClO₄)₂·6H₂O produces an aqua-bridged cationic reactant complex [Cu₂(μ-H₂O)(μ-L)][ClO₄]·1.5H₂O (1·1.5H₂O). Solution phase interaction of 1·1.5H₂O with SCN⁻ anions in 1:1 molar ratio leads to [Cu₂(μ-L)(NCS)]·2H₂O (2·2H₂O) that does not possess anymore the reactive aqua bridge but instead a terminal SCN⁻ anion coordinated only to one Cu^II ion. Whereas in 1:2 molar ratio, partial extrusion of the Cu^II ions takes place to generate in situ [Cu(NCS)₃(OH₂)]⁻ anions. These complex anions then quantitatively replace anions in 1·1.5H₂O via ‘anion metathesis’ and concurrently remove the aqua bridge by coordination of linear MeCN to one of the Cu^II ions to give [Cu₂(μ-L)(CH₃CN)][Cu(NCS)₃(OH₂)] (3). The literature unknown [Cu(NCS)₃(OH₂)]⁻ anion forms an intimate H-bonded assembly with the cationic part of 3 to yield a novel [Cu₃] isosceles triangle. The precursor complex is known as antiferromagnetic whereas in 2·2H₂O, the Cu^II (S = 1/2) ions in a dinuclear entity exhibit ferromagnetic interactions (J/k_B = +15.0 K and g = 2.22) to yield an S_T = 1 spin ground state in good agreement with the M versus H data below 8 K.     

Novel six-coordinate oxorhenium(V) ‘3+2’ mixed-ligand complexes carrying the SNO/SN donor atom set

Ligand exchange reactions of oxorhenium(V) precursors with bidentate SN and tridentate Schiff bases derived from the condensation of ketones or aldehydes with dithiocarbazic acid methyl ester (H₂NNHC(S)SCH₃) produce novel ‘3+2’ mixed-ligand complexes carrying the SNO/SN donor atom set. Thus, reactions of either [NBu₄][ReOCl₄] or Na[ReO(Gluconate)₂] with SNO ligands (H₂Lⁿ) or a mixture of bidentate SN (HL^m) and tridentate SNO (H₂Lⁿ) in methanol solutions lead, respectively, to the six-coordinated mixed ligand oxorhenium(V) compounds of types [ReO(Lⁿ)(HLⁿ)] and [ReO(Lⁿ)(L^m)], combining one tridentate dianionic S⁻NO⁻ donor Schiff base (L) and one bidentate anionic S⁻N donor ligand (HL). Coordination geometry around rhenium is distorted octahedral with the two SN donor atom sets of each ligand defining the equatorial plane, while apical positions are occupied by the oxo group and the oxygen atom of the tridentate SNO ligand (L), as shown by single-crystal X-ray diffraction structure of [ReO(L¹)(HL¹)] 1.     

Synthesis and structural studies of mixed-ligand rhenium(V) complexes anchored by tridentate pyrazole-based ligands

The novel oxorhenium dichlorides mer-[ReO(L1)Cl₂] (1) and fac-[ReO(L2)Cl₂] (2) (L1 = 2-[2-(pyrazol-1-yl)ethyliminomethyl]phenolate; L2 = 2-[2-(pyrazol-1-yl)ethylaminomethyl]phenolate) were synthesized by reacting [NBu₄][ReOCl₄] with L1H and L2H, respectively. X-ray structural analysis of 1 and 2 has shown that L1 and L2 act as (N,N,O)-tridentate chelators coordinating to the Re(V) centre in a meridional and in a facial fashion, respectively. The reactivity of 2 towards potential bidentate/dianionic substrates is strongly dependent on the donor atom set, being observed that the presence of sulphur favours the displacement of the ancillary ligand (L2). By contrast, complex 2 reacted with (O,O)-bidentate substrates (1,2-ethanediol and oxalic acid) providing the mixed-ligand complexes fac-[ReO(L2)(OCH₂CH₂O)] (3) and fac-[ReO(L2)(C₂O₄)] (4). Complexes 3 and 4 are air and water-stable and have been characterized by the common spectroscopic techniques (IR, ¹H and ¹³C NMR) and by X-ray diffraction analysis.     

A new bifunctional amino acid chelator targeting the glucose transporter

The coupling reactions of d-glucosamine, 1,3,4,6-tetra-O-acetylglucosamine, and 4-aminophenyl-galactopyranosine with N,N-bis(quinolinoyl)aminovaleric acid (L1) provided a series of conjugates containing a potentially tridentate donor group terminus linked to a sugar moiety, L2′, L2 and L3, respectively. Reactions of the ligands with [NEt₄]₂[Re(CO)₃Br₃] in refluxing methanol provided the rhenium complexes [Re(CO₃)(L1)]Br (ReL1), [Re(CO)₃(L2)]Br (ReL2), [Re(CO)₃(L2′)]Br (ReL2′) and [Re(CO)₃(L3)]Br (ReL3). The ligands and complexes were characterized by elemental analyses, ¹H and ¹³C NMR, mass spectroscopy and, in the case of L1 and ReL1, by X-ray crystallography. The rhenium complexes exhibit fluorescence emissions with long lifetimes, large Stokes shifts, and moderate quantum yields.     

The synthesis and characterisation of phenolate complexes of Cu(II) and Ni(II) that are capable of supporting a phenoxyl radical ligand

New Cu^II and Ni^II complexes of potentially tridentate N₂O Schiff base ligands 1 and 2 have been synthesised and characterised. [Cu(2)(OH₂)]⁺ possesses a square planar geometry in the solid state whereas [Ni(1)₂] possesses a distorted octahedral geometry in which the amine donors of 1 coordinate weakly to the Ni^II centre. EPR spectroscopy demonstrates that the N₂O₂ coordination sphere of [Cu(2)(OH₂)]⁺ is retained in CH₂Cl₂ solution. [Cu(2)(OH₂)]⁺ exhibits a reversible one electron oxidation at E_1/2 = 0.54 V versus [Fc]⁺/[Fc], the product of which has been characterised by UV-Vis absorption and EPR spectroscopies. The spectroscopic signature of the oxidised product is consistent with the formation of a stable phenoxyl radical ligand bound to a Cu^II centre. [Ni(1)₂] possesses a reversible metal-based oxidation process at E_1/2 = 0.03 V versus [Fc]⁺/[Fc] and a further oxidation, attributed to the generation of a phenoxyl radical centre, at  = 0.44 V versus [Fc]⁺/[Fc]. UV-Vis absorption and EPR spectroscopic studies indicate that the lower potential process is a formal Ni^III/II couple. In contrast, the pro-ligands 1H and 2H exhibit chemically irreversible oxidation processes at  = 0.42 and 0.40 V versus Fc⁺/Fc, respectively, and do not support the formation of stable phenoxyl radical species.     

Manganese (III) cyclam complexes with aqua, iodo, nitrito, perchlorato and acetic acid/acetato axial ligands

The syntheses, structures and magnetic properties of five new manganese (III) cyclam complexes, trans-[Mn(cyclam)(OH₂)₂](CF₃SO₃)₃ · H₂O, trans-[Mn(cyclam)I₂]I, trans-[Mn(cyclam)(ONO)₂]ClO₄, trans-[Mn(cyclam)(OClO₃)₂]ClO₄ and trans-[Mn(cyclam)(CH₃COO)(CH₃COOH)](ClO₄)₂, are reported. Cyclam is the tetradentate amine ligand 1,4,8,11-tetraazacyclotetradecane. The complexes all exhibit pronounced tetragonal elongation of the coordination octahedron with the four cyclam nitrogens occupying the four equatorial positions. The magnetic properties are consistent with the formulation of the complexes as high-spin d⁴ systems. trans-[Mn(cyclam)(OH₂)₂](CF₃SO₃)₃ · H₂O is shown to be a convenient starting material for the syntheses of trans cyclam complexes. [Mn(cyclam)(CH₃COO)(CH₃COOH)](ClO₄)₂ exhibits extremely short intermolecular hydrogen bonds resulting in a pseudo-chain structure. The tilt of the axial ligands with respect to the equatorial plane containing the manganese and the cyclam nitrogen atoms is discussed.     

Synthesis,structures and urease inhibitory activity of cobalt(III) complexes with Schiff bases

A series of new cobalt(III) complexes were prepared. They are [CoL¹(py)₃]·NO₃ (1), [CoL²(bipy)(N₃)]·CH₃OH (2), [CoL³(HL³)(N₃)]·NO₃ (3), and [CoL⁴(MeOH)(N₃)] (4), where L¹, L², L³ and L⁴ are the deprotonated form of N′-(2-hydroxy-5-methoxybenzylidene)-3-methylbenzohydrazide, N′-(2-hydroxybenzylidene)-3-hydroxylbenzohydrazide, 2-[(2-dimethylaminoethylimino)methyl]-4-methylphenol, and N,N′-bis(5-methylsalicylidene)-o-phenylenediamine, respectively, py is pyridine, and bipy is 2,2′-bipyridine. The complexes were characterized by infrared and UV–Vis spectra, and single crystal X-ray diffraction. The Co atoms in the complexes are in octahedral coordination. Complexes 1 and 4 show effective urease inhibitory activities, with IC₅₀ values of 4.27 and 0.35 μmol L⁻¹, respectively. Complex 2 has medium activity against urease, with IC₅₀ value of 68.7 μmol L⁻¹. While complex 3 has no activity against urease. Molecular docking study of the complexes with Helicobacter pylori urease was performed.     

Tungsten complexes of aromatic and aliphatic thioaldehydes

Reaction of PPN[W(CO)₃(R₂PC₂H₄PR₂)(SH)] (PPN=Ph₃PNPPh₃; R=Me, 1; R=Ph, 2) with aromatic aldehydes in the presence of trifluoroacetic acid gave tungsten complexes of thiobenzaldehydes mer-[W(CO)₃(R₂PC₂H₄PR₂)(η²-SCHR^′)] (R=Me, 3a-3f; R=Ph, 4a-4e) in high yields. Analogous complexes of aliphatic thioaldehydes mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-SCHR^′)] (3g-3l) could only be obtained from the highly electron-rich thiolate complex 1. The structure of 3i (R^′=i-Bu) was determined by X-ray crystallography. In solution the complexes 3 and 4 are in equilibrium with small quantities of their isomers fac-[W(CO)₃(R₂PC₂H₄PR₂)(η²-SCHR^′)]. Reaction of complexes 3 with dimethylsulfate followed by salt metathesis with NH₄PF₆ gave the alkylation products mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-MeSCHR^′)]PF₆ (5a-5l) as mixtures of E and Z isomers. The methylated thioformaldehyde complex mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-MeSCH₂)]PF₆ (5m) was prepared similarly. Nucleophilic addition of hydride (from LiAlH₄) to 5 initially gave thioether complexes mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(MeSCH₂R^′)] (mer-6) which rapidly isomerized to fac-[W(CO)₃(Me₂PC₂H₄PMe₂)(MeSCH₂R^′)] (fac-6).     

Pd(II) complexes containing N-alkyl-3-pyridine-5-trifluoromethyl pyrazole ligands: Synthesis, NMR studies and X-ray crystal structures

Palladium [PdCl₂(L)] complexes with N-alkylpyridylpyrazole derived ligands [2-(5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L¹), 2-(1-ethyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L²), 2-(1-octyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L³), and 2-(3-pyridin-2-yl-5-trifluoromethyl-pyrazol-1-yl)ethanol (L⁴) were synthesised. The crystal and molecular structures of [PdCl₂(L)] (L = L², L³, L⁴) were resolved by X-ray diffraction, and consist of monomeric cis-[PdCl₂(L)] molecules. The palladium centre has a typical square-planar geometry, with a slight tetrahedral distortion. The tetra-coordinate metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine ligands in cis disposition. Reaction of L (L², L⁴) with [Pd(CH₃CN)₄](BF₄)₂, in the ratio 1M:2L, gave complexes [Pd(L)]₂(BF₄)₂. Treatment of [PdCl₂(L)] (L = L², L⁴) with NaBF₄ and pyridine (py) and treatment of the same complexes with AgBF₄ and triphenylphosphine (PPh₃) yielded [Pd(L)(py)₂](BF₄)₂ and [Pd(L)(PPh₃)₂](BF₄)₂ complexes, respectively. Finally, reaction of [PdCl₂(L⁴)] with 1 equiv of AgBF₄ yields [PdCl(L⁴)](BF₄).     

Synthesis, structures, and magnetic properties of dicopper(II) and dinickel(II) complexes with a new bis(macrocycle), 7,7-(2-hydoxypropane-1,3-diyl)bis{3,7,11,17-tetraazabicyclo[11.3.1]- heptadeca-1(17),13,15-triene}

A new bis(macrocycle) ligand, 7,7^′-(2-hydoxypropane-1,3-diyl)-bis{3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene} (HL), and its dicopper(II) ([Cu₂(HL)Cl₂](NO₃)₂ · 4H₂O (4a), [Cu₂(HL)I₂]I₂ · H₂O (4b)) and dinickel(II) ([Ni₂(L)(OH₂)](ClO₄)₃ (5a), [Ni₂(L)(OH₂)]I₃ · 2H₂O (5b), [Ni₂(L)N₃](N₃)₂ · 7H₂O (5c)) complexes have been synthesized. The alkoxide bridged face-to-face structure of the dinickel(II) complex 5c has been revealed by X-ray crystallography, as well as the “half-opened clamshell” form of the bis(macrocyclic) dicopper(II) complex 4b. Variable temperature magnetic susceptibility studies have indicated that there exists intramolecular antiferromagnetic coupling (J=−33.8 cm⁻¹ (5a), −32.5 cm⁻¹ (5b), and −29.7 cm⁻¹ (5c)) between the two nickel(II) ions in the nickel(II) complexes.     

Reaction of [MCl2(CH3CN)2] (M = Pd(II), Pt(II)) compounds with N1-alkylpyridylpyrazole-derived ligands

Palladium(II) and platinum(II) complexes with N-alkylpyridylpyrazole-derived ligands, 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L¹) and 2-(1-octyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L²), cis-[MCl₂(L)] (M = Pd(II), Pt(II)), have been synthesised. Treatment of [PdCl₂(L)] (L = L¹, L²) with excess of ligand (L¹, L²), pyridine (py) or triphenylphosphine (PPh₃) in the presence of AgBF₄ and NaBPh₄ produced the following complexes: [Pd(L)₂](BPh₄)₂, [Pd(L)(py)₂](BPh₄)₂ and [Pd(L)(PPh₃)₂](BPh₄)₂. All complexes have been characterised by elemental analyses, conductivity, IR and NMR spectroscopies. The crystal structures of cis-[PdCl₂(L²)] (2) and cis-[PtCl₂(L¹)] (3) were determined by a single crystal X-ray diffraction method. In both complexes, the metal atom is coordinated by one pyrazole nitrogen, one pyridine nitrogen and two chlorine atoms in a distorted square-planar geometry. In complex 3, π-π stacking between pairs of molecules is observed.     

Amido binding to ReO core: Synthesis, structure and intermolecular interactions

The light green coloured complexes of general formula [Re^VO(L)Cl(OH₂)]Cl have been synthesised in good yields by reacting [Re^VOCl₃(AsPh₃)₂] with HL in dichloromethane in dinitrogen atmosphere. Here, L⁻ is the deprotonated form of N,N-bis(2-pyridylmethyl)amine (HL¹); N-(2-pyridylmethyl)-N′,N′-dimethylethylenediamine (HL²) and N-(2-pyridylmethyl)-N′,N′-diethylethylenediamine (HL³). Single crystal X-ray structure determination of [Re^VO(L¹)Cl(OH₂)]Cl confirms the amido binding of ReO³⁺ species. In the solid state of [Re^VO(L¹)Cl(OH₂)]Cl, the coordinated and counter chloride ions are engaged in Re-Cl…H-C(ring), Cl…H-C(ring) and Re-(OH₂)…Cl hydrogen bonding and forming of a supramolecular network in the solid state. The subunit of the supramolecular network consists of one eight-membered and two nine-membered hydrogen bonded rings. The average diameters of eight-membered and nine-membered rings are ∼3.70 and ∼5.26 Å, respectively.     

Synthesis and characterisation of palladium(II) and platinum(II) compounds containing pyrazole-derived ligands: crystal structure of [PdCl2(HL)] (HL = 3-phenyl-5-(2-pyridyl)pyrazole)

Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL¹), 3,5-bis(2-pyridyl)pyrazole (HL²), 3-methyl-5-(2-pyridyl)pyrazole (HL³) and 3-methyl-5-phenylpyrazole (HL⁴) with [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) or [PdCl₂(cod)] gives complexes with stoichiometry [PdCl₂(HL)₂] (HL = HL¹, HL², HL³), [Pt(L)₂] (L = L¹, L², L³) and [MCl₂(HL⁴)₂] (M = Pd(II), Pt(II)). The new complexes were characterised by elemental analyses, conductivity measurements, infrared and ¹H NMR spectroscopies. The crystal and molecular structure of [PdCl₂(HL¹)] was resolved by X-ray diffraction, and consists of monomeric cis-[PdCl₂(HL¹)] molecules. The palladium centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated metal atom is bonded to one pyridine nitrogen, one pyrazolic nitrogen and two chloro ligands in a cis disposition. The ligand HL¹ is not completely planar.     

Syntheses, structures and bioactivities of silver(I) complexes with dithioether ligands that contain a di- or triethylene glycol chain and different terminal groups

A series of flexible dithioethyl ligands that contain ethyleneoxy segments were designed and synthesized, including bis(2-(pyridin-2-ylthio)ethyl)ether (L¹), 1,2-bis(2-(pyridin-2-ylthio)ethoxy)ethane (L²), bis(2-(benzothiazol-2-ylthio)ethyl)ether (L³) and 1,2-bis(2-(benzothiazol-2-ylthio)ethoxy)ethane (L⁴). Reactions of these ligands with AgNO₃ led to the formation of four new supramolecular coordination complexes, [Ag₂L¹(NO₃)₂]₂ (1), [Ag₂L²(NO₃)₂] (2), [AgL³(NO₃)]_∞ (3) and [AgL⁴(NO₃)] (4) in which the length of the (CH₂CH₂O)_n spacers and the terminal groups of ligands cause subtle geometrical differences. Studies of the inhibitory effect to the growth of Phaeodactylum tricornutum show that all four complexes are active and the compound 4 has the highest inhibitory activity.     

Linear and bent oxo-bridged dinuclear rhenium(V) complexes with terminal and bridging pyrazole ligands

The [ReOX₃(AsPh₃)(OAsPh₃)] (X = Cl or Br) complexes react with two equivalents of 3,5-dimetylopyrazole (3,5-Me₂pzH) in acetone at room temperature to give [{Re(O)X₂(3,5- Me₂pzH)₂}₂(μ-O)] (1 and 2). In the case of [ReOBr₃(AsPh₃)(OAsPh₃)], a small quantity of the dinuclear rhenium complex [{Re(O)Br(3,5-Me₂pzH)}₂(μ-O)(μ-3,5-Me₂pz)₂] (3) has been isolated next to the main product 2. Treatment of [ReOX₃(PPh₃)₂] compounds with two equivalents of 3,5-Me₂pzH in acetone at room temperature leads to the isolation of symmetrically substituted dinuclear rhenium complexes [{Re(O)X(PPh₃)}₂(μ-O)(μ-3,5-Me₂pz)₂] (4 and 5). Refluxing of [ReO(OEt)X₂(PPh₃)₂] complexes with 3,5-Me₂pzH in ethanol affords unsymmetrically substituted dinuclear rhenium [{Re(O)X(PPh₃)}(μ-O)(μ-3,5-Me₂pz)₂{Re(O)X(3,5- Me₂pzH)}] complexes (6 and 7). The complexes obtained in these reactions have been characterised by IR, UV-Vis, ¹H and ³¹P NMR. The crystal and molecular structures have been determined for 1, 2, 3, 4, 6 and 7 complexes.     

The first report on specific binding mode of diethylmalonate acting as a bridging ligand between ruthenium (II) ions stabilized by intramolecular hydrogen bonds

Typically 2,2-diethylmalonate (dem) acts as a chelating ligand and binds to the metal in a η² (dem-O, O′) mode. However, when cis,fac-[RuCl₂(TMSO-S)₄] is treated with K₂(dem), it prefers to bind in an unusual bridging mode (μ-dem-O, O′) with the ruthenium (II) cation containing coordinated water, forming a strong hydrogen bond with the non-coordinated oxygen atoms of the 2,2-diethylmalonate ligand. The reaction products of cis,fac-[RuCl₂(TMSO-S)₄] (1) and cis,fac-[RuCl₂(DMSO-S)₃(DMSO-O)] (2) with dem are the dinuclear species with two bridging dem units, fac-[Ru(TMSO-S)₃(H₂O)(μ²-dem-O, O′)]₂ (3) and fac-[Ru(DMSO-S)₃(H₂O)(μ²-dem-O, O′)]₂ (4), respectively. The complex 3 was characterized by X-ray crystallography in which water ligands occupy anti positions with respect to each other. The NMR and X-ray study support each other with respect to dinuclear structure of 3 and 4, indicating that the dinuclear structure observed in the solid state is preserved in solution as well. The mononuclear anionic complex with chelating dem unit, K{fac-[RuCl(η²-dem-O, O′)(TMSO-S)₃} (5), was also isolated from the reaction of 1 and K₂(dem) demonstrating that 5 is an intermediate in the formation of 3.     

Reactions of the fac-[Re(CO)3] and [ReO] moieties with substituted benzothiazoles

The reaction of 2-(2-aminophenyl)benzothiazole (Habt) with [Re(CO)₅Br] led to the isolation of the rhenium(I) complex fac-[Re(Habt)(CO)₃Br] (1). With trans-[ReOCl₃(PPh₃)₂], the ligand Habt decomposed to form the oxofree rhenium(V) complex [Re(itp)₂Cl(PPh₃)] (2) (itp = 2-amidophenylthiolate). From the reaction of trans-[ReOBr₃(PPh₃)₂] with 2-(2-hydroxyphenyl)benzothiazole (Hhpd) the complex [Re^VOBr₂(hpd)(PPh₃)] (3) was obtained. Complexes 1-3 are stable and lipophilic. ¹H NMR and infrared assignments, as well as the X-ray crystal structures, of the complexes are reported.     

New arene ruthenium complexes with planar chirality

1,2,4-Trimethyl-cyclohexadiene reacts with RuCl₃ · nH₂O in refluxing ethanol to afford quantitatively [RuCl₂(1,2,4-C₆H₃Me₃)]₂ (1), the coordination of 1,2,4-trimethylbenzene to the ruthenium atom introducing planar chirality at the η⁶-arene ligand. The dinuclear complex 1 reacts with two equivalents of triphenylphosphine (PPh₃) to give quantitatively, as a racemic mixture of enantiomers, [RuCl₂(1,2,4-C₆H₃Me₃)(PPh₃)] (2), the structure of which has been determined by a single-crystal X-ray structure analysis of (rac)-2. Similarly, 1 reacts with two equivalents of the enantiopure phosphine (1S,2S,5R)-(+)-neomenthyldiphenylphosphine (nmdpp) to afford in good yield [RuCl₂(1,2,4-C₆H₃Me₃)(nmdpp)] (3) as a mixture of diastereoisomers, from which the isomer 3a was isolated by crystallisation. A single-crystal X-ray structure analysis of 3a allowed the determination of the absolute configuration at the planar chiral η⁶-arene moiety. Finally, complex 1 reacts with one equivalent of the diphosphine ligand 1,1^′-bis(diphenylphosphino)ferrocene (dppfc) to give the heteronuclear complex [RuCl₂(1,2,4-C₆H₃Me₃) (dppfc)RuCl₂(1,2,4-C₆H₃Me₃)] (4). All complexes were fully characterised by elemental analysis, mass spectrometry, NMR and IR spectroscopies.