Synthesis and reactions of [M(CO)4(Ph2PSiMe3)X] complexes (M = Mn,Re; X = Halogen)

The silylphosphine ligand Ph₂PSiMe₃ reacts readily with a slurry of [Re(CO)₅X] (X  Cl, Br) in polar and in non-polar solvents to yield soluble cis-[Re(CO)₄- (Ph₂PSiMe₃)X] (Ia, X  Cl;Ib, X  Br) via CO substitution. Compound I is readily hydrolyzed by water or silica gel to cis-[Re(CO)₄(Ph₂PH)X]. Compound Ib reacts with [Re(CO)₅Br] to yield [Re₂(CO)₈(μ-PPh₂)- (μ-Br)] (II), and with [Mn(CO)₅Br] to yield [MnRe- (CO)₈(μ-PPh₂)(μ-Br)] (III).The reaction of Ph₂PSiMe₃ with [Mn(CO)₅X] (X=Cl,Br,I) is highly dependent upon reaction conditions.In polar and in non-polar solvents, an excess of ligand gives mainly cis-[Mn(CO)₄(Ph₂PSiMe₃)X] (IVa, X  Cl;IVb, X  Br;IVc, X I). With ligand: [Mn(CO)₅X] reacting ratios in the range 0.5–1.0:1, the products from the three respective halomanganese complexes in THF were: (a) mainly [Mn₂(CO)₈(μ- PPh₂)(μ-Cl) (Va); (b) both [Mn(CO)₄(Ph₂PSiMe₃)Br] and [Mn₂(CO)₈(μ-PPh₂)(μ-Br)] (Vb); and (c) exclusively [Mn(CO)₄(Ph₂PSiMe₃)I]. The compounds IVa-c are stable in solution at ambient temperatures and are readily hydrolyzed by water or methanol to [Mn(CO)₄(Ph₂PH)X]. Compound IVb reacts at room temperature with [Mn(CO)₅Cl] to yield only [Mn₂- (CO)₈(μ-PPh₂)(μ-Br)] (Vb); compound IVc reacts in hot toluene with [Mn(CO)₅Cl] to yield mainly [Mn₂(CO)₈(μ-PPh₂)(μ-I)] (Vc), together with a small amount of the chloro-bridged analog.The dinuclear species II, III and Va-c appear to be formed mainly via an intermolecular elimination of Me₃SiX from the appropriate [M(CO)₄(Ph₂PSiMe₃)X] and metalpentacarbonylhalide (chloride or bromide) complexes.     

Synthesis and spectroscopic properties of some new seven-coordinate thioacetamide complexes of molybdenum(II) and tungsten(II)

The compounds [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with one equivalent of SC(NH₂)Me in CH₂Cl₂ at room temperature to initially give the acetonitrile substituted products [MI₂(CO)₃(NCMe)- {SC(NH₂)Me}] which was isolated for M = W. However, the molybdenum complex rapidly dimerizes with loss of acetonitrile to give the iodide-bridged compound [Mo(σ-I)I(CO)₃ {SC(NH₂)Me}]₂. The tungsten complex does not appear to dimerize, even after stirring at room temperature for 72 h in CH₂Cl₂. Two equivalents of thioacetamide react with [MI₂- (CO)₃(NCMe)₂] in CH₂Cl₂ at room temperature to give the new bisthioacetamide compounds [MI₂- (CO)₃{SC(NH₂)Me}₂] via displacement of the labile acetonitrile ligands. The low temperature (−70 °C) ¹³C NMR spectrum of [WI₂(CO)₃{SC(NH₂)Me}₂] indicates that the geometry of the complex is capped octahedral with a carbonyl ligand in the unique capping position.     

Copper(II) PMDTA and copper(II) TMEDA complexes: precursors for the synthesis of dinuclear dicationic copper(II) complexes

Copper(II) cations coordinated with PMDTA (pentamethyldiethylenetriamine) and TMEDA (tetramethylethylenediamine) possess a high synthetic potential. The synthesis of these cations was carried out by metathesis reactions with silver salts. The cationic copper(II) complexes, [Cu(PMDTA)(Me₂CO)Cl]⁺, [Cu(PMDTA)(H₂O)Cl]⁺, [Cu(PMDTA)(DMF)]⁺, [Cu(PMDTA)Cl]⁺, [Cu(PMDTA)OAc]⁺, [Cu(PMDTA)(MeCN)₂]²⁺, [Cu₂(TMEDA)₂Cl₃]⁺ and [Cu(TMEDA)(MeCN)₃]²⁺ were synthesised as PF₆ salts, crystallised and characterised by single-crystal X-ray diffraction.     

Photochemical synthesis method of tungsten(II) complexes [WCl2(CO)3PPh3)2] and [WCl2(CO)2(dppe)]

The photochemical oxidation reaction of W(CO)₆ to [W(CO)₄Cl₂]₂ with CCl₄ was applied in the synthesis of [WCl₂(CO)₃(PPh₃)₂] and [WCl₂(CO)₂₋- (dppe)].     

Coordination of 4-mercapto-1,2-dithiole-3-thione heterocycles to ruthenium(II) and molybdenum(VI) centres

Deprotonation of 4-mercapto-1,2-dithiole-3-thiones with NEt₃ followed by reaction with [Ru(H)(Cl)(CO)(PPh₃)₃] affords virtually quantitative yields of turquoise [Ru(H)(RC₃S₄)(CO)(PPh₃)₂] (R = Ph, Mes) in which the heterocycle is bound as a bidentate uninegative ligand through the two exocyclic sulfur atoms. The presence of both possible isomers in each case is indicated by NMR spectroscopy. Reaction of the 4-mercapto-1,2-dithiole-3-thiones with [MoO₂(acac)₂] results in displacement of the acac ligands and formation of [MoO₂(RC₃S₄)₂]. The crystal structures of [Ru(H)(MesC₃S₄)(CO)(PPh₃)₂] and [MoO₂(MesC₃S₄)₂] have been determined.     

Crystal structures of the dimeric cobalt compounds [Co(PPhMe2)(CO)3]2 and [Co2(PPhMe2)3(CO)5]

The molecular structures of the dimeric cobalt compounds [Co(PPhMe₂)(CO)₃]₂ and [Co₂(PPhMe₂)₃(CO)₅] have been characterised by X-ray crystallography. The compound [Co₂(PPhMe₂)₃(CO)₅] contains both bridging and terminal carbonyl groups in the solid state.     

Synthesis and properties of new trinuclear Mo(II) complexes containing imidazole and benzimidazole ferrocene units

The reaction of FcCOCl (Fc = (C₅H₅)Fe(C₅H₄)) with benzimidazole or imidazole in 1:1 ratio gives the ferrocenyl derivatives FcCO(benzim) (L1) or FcCO(im) (L2), respectively. Two molecules of L1 or L2 can replace two nitrile ligands in [Mo(η³-C₃H₅)(CO)₂(CH₃CN)₂Br] or [Mo(η³- C₅H₅O)(CO)₂(CH₃CN)₂Br] leading to the new trinuclear complexes [Mo(η³-C₃H₅)(CO)₂(L)₂Br] (C1 for L = L1; C3 for L = L2) and [Mo(η³-C₅H₅O)(CO)₂(L)₂Br] (C2 for L = L1; C4 for L = L2) with L1 and L2 acting as N-monodentade ligands. L1, L2 and C2 were characterized by X-ray diffraction studies. [Mo(η³-C₅H₅O)(CO)₂(L1)₂Br] was shown to be a trinuclear species, with the two L1 molecules occupying one equatorial and one axial position in the coordination sphere of Mo(II). Cyclic voltammetric studies were performed for the two ligands L1 and L2, as well as for their molybdenum complexes, and kinetic and thermodynamic data for the corresponding redox processes obtained. In agreement with the nature of the frontier orbitals obtained from DFT calculations, L1 and L2 exhibit one oxidation process at the Fe(II) center, while C1, C3, and C4 display another oxidation wave at lower potentials, associated with the oxidation of Mo(II).     

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.     

Synthesis, spectroscopy, structure and photophysical properties of dinaphthylmethylarsine complexes of palladium(II) and platinum(II)

Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX₂L₂] (M = Pd, Pt; L = di(1-naphthyl)methylarsine = Nap₂AsMe and X = Cl, Br, I), [M₂Cl₂(μ-Cl)₂L₂], [PdCl(S₂CNEt₂)L], [Pd₂Cl₂(μ-OAc)₂L₂] and [MCl₂(PR₃)L] (PR₃ = PEt₃, PPr₃, PBu₃, PMePh₂) have been prepared. These complexes have been characterized by elemental analyses, IR, Raman, NMR (¹H, ¹³C, ³¹P) and UV-vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The crystal structures of trans-[PdCl₂(PEt₃)(Nap₂AsMe)] and of [Pd(S₂CNEt₂)₂], a follow-up product, were determined. The UV-vis spectra of [MX₂L₂] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX₂L₂] and [PtX₂L₂] are strongly luminescent in fluid solution and in the solid at ambient temperature.     

Molecular sensing behavior of the first Mn(I)-compound of di-2-pyridylketone-p-nitrophenylhydrazone (dpknph), fac-[Mn(CO)3(dpknph)Br]

The reaction between [Mn(CO)₅Br] and di-2-pyridylketone-p-nitrophenylhydrazone (dpknph) in diethyl ether under ultrasonic conditions gave fac-[Mn(CO)₃(dpknph)Br] in good yield. Optical and thermodynamic measurements on fac-[Mn(CO)₃(dpknph)Br] in non-aqueous polar solvents revealed reversible interconversion between two intense charge transfer absorption bands due to π-π* (dpk), followed by dpk → nitro intraligand charge transfer transition (ILCT), mixed with metal ligand charge transfer transition (MLCT) due to . In non-polar solvents, a single absorption band appeared. Extinction coefficients of 46 200 ± 2000 and 28 400 ± 2000 M⁻¹ cm⁻¹ were calculated in DMSO for the low- and high-energy electronic states of fac-[Mn(CO)₃(dpknph)Br] using excess NaBF₄. Changes in enthalpy (ΔH^ø) of +14.0 and −12.1 kJ mol⁻¹, entropy (ΔS^ø) of +28.65 and −64.30 J mol⁻¹ K⁻¹, and free energy (ΔG^ø) of +5.48 and +7.08 kJ mol⁻¹ at 298 K were calculated for the interconversion between the high and low energy electronic states of fac-[Mn(CO)₃(dpknph)Br]. These results allow for the use of these systems (fac-[Mn(CO)₃(dpknph)Br] and surrounding solvent or solute molecules) as optical sensors for a variety of physical and chemical stimuli that include metal ions. Group 12 metal ions in concentrations as low as 1.00 × 10⁻⁹ M can be detected and determined using fac-[Mn(CO)₃(dpknph)Br] in dmso in the presence and absence of NaBH₄.     

Cobalt(II) and nickel(II) complexes with nitrogen-sulfur tripod ligands. Crystal and molecular structure of the five-coordinate complex bromotris(2-tert-butylthioethyl)aminecobalt(II) hexafluorophosphate (NS3Br donor set)

The tripod ligands tris(2-alkylthioethyl)amine, with alkyl = ethyl, iso-propyl, and tert-butyl, give with cobalt(II) and nickel(II) halides high-spin complexes with formulae [MLX₂], [MLX]Y, and [MLX]₂[MX₄] (where X = Cl, Br, I; Y = BPh₄, PF₆). The nickel complexes are either six- or five-coordinate: the coordination number decreases as the bulkiness of the alkyl group bound to the sulfur is increased. All the cobalt complexes contain the five-coordinate cation [CoLX]⁺. The crystal and molecular structure of the [Co(NS₃-t-Bu)Br]PF₆ complex has been determined by standard X-ray methods, and refined to R = 0.061. The crystals are monoclinic, space group P2¹/n. The unit cell dimensions are: a = 27.420 (2), b = 11.923 (4), c = 17.082 (1) Å, β = 102.40 (1)°, Z = 8. The complex cation has a trigonal bipyramidal geometry with the nitrogen and bromine atoms at the apexes, and the three sulfur atoms in the equatorial plane. The tetrahedral distortion is relatively small (mean BrCoS angle = 98.5°), and similar to that found for the [Co (Me₆tren)Br]Br complex [Me₆tren = tris(2-dimethylaminoethyl)amine).     

Synthesis of fac-[Os(CO)3(L)Me2] (L = THF or MeCN) and some reactions with PPh3 and trityl salts

The reaction of cis-[Os(CO)₄Me₂] with Me₃NO in the THF or MeCN yields the complexes fac-[Os(CO)₃(L)Me₂] (where L = THF or MeCN). Whereas the THF complex is unstable and only characterised spectroscopically, fac-[Os(CO)₃(MeCN)Me₂] has been isolated as a white solid and fully characterized by both analytical and spectroscopic methods. These complexes fac-[Os(CO)₃(L)Me₂] are shown to be useful intermediates. Thus, reaction with PPh₃ gives fac-[Os(CO)₃(PPh₃)Me₂] in good yield.Reactions of fac-[Os(CO)₃(L)Me₂] (L = CO or MeCN) with CPh₃PF₆ or B(C₆F₅)₃ have been investigated. Whereas cis-[Os(CO)₄Me₂] showed no reaction with either CPh₃PF₆ or B(C₆F₅)₃, the reaction of fac-[Os(CO)₃(MeCN)Me₂] with CPh₃PF₆ in CH₂Cl₂ occurred over 16 h at room temperature to give an unstable cationic product and CPh₃Me. The reaction was monitored by both IR and NMR spectroscopies. When this reaction of fac-[Os(CO)₃(MeCN)Me₂] was carried out in the presence of a trapping ligand such as MeCN, the stable cationic product [Os(CO)₃(MeCN)₂Me]⁺ could be isolated and identified spectroscopically.     

Heptacoordinate dithiophosphate W(II) and Mo(II) complexes of diphosphines and iodide

New complexes [MI(CO)₂(dppe){S₂P(OEt)₂}] (M=W, 1a; M=Mo, 1b), [MI(CO)₂(dppm){S₂P(OEt)₂}] (M=W, 2a; M=Mo, 2b) and [W(CO)(dppe){S₂P(OEt)₂}₂][O₂dppe] (3a), were synthesised from [MI₂(CO)₃(NCMe)₂] (M=Mo, W), after treatment with ammonium diethyldithiophosphate and phosphine under different conditions. The structure of the tungsten complexes was determined by single crystal X-ray diffraction. During the synthesis of 3a, oxidation of the phosphine took place and a molecule of oxidised phosphine occupies channels in the crystal. DFT/B3LYP calculations on models of 1a and 2a showed the capped octahedron structure, observed in most dicarbonyl complexes of this family, to be preferred by 1.4 and 2.6 kcal mol⁻¹ for the dppm and the dppe complexes, respectively. Strong steric repulsions can reverse this trend, as happens with the rigid dppm ligand. Complex 1a adopts a pentagonal bipyramidal geometry, which is often found in related monocarbonyl complexes.     

Syntheses and structures of mononuclear manganese(II) complexes bearing bis(1-methylimidazol-2-yl)ketone ligands

The ligand bis(1-methylimidazol-2-yl)ketone (bik) (1) was applied in the synthesis of mononuclear manganese(II) complexes. The complexes [Mn(bik)₂Cl₂] (2), [Mn(bik)₂(OH₂)Br]Br × H₂O (3b) and [Mn(bik)₃](ClO₄) (4) were characterised by X-ray crystallography, ESR and UV-Vis methods.     

Bis(dimethylphosphino)methane complexes of ruthenium carbonyl

Reaction of Me₂PCH₂PMe₂ with [Ru₃(CO)₁₂] in a 1:1 or 2:1 ratio in the presence of [(Ph₃P)₂N]CN catalyst gives [Ru₃(CO)₁₀(μ-Me₂PCH₂PMe₂)] and [Ru₃(CO)₈(μ-Me₂PCH₂PMe₂)₂] respectively. The complexes were characterized by elemental analysis, IR and ¹H and ³¹P NMR spectroscopies.     

Electrochemical oxidation of Mo(CO)4(LL) and Mo(CO)3(LL)(CH3CN): Generation, infrared characterization, and reactivity of [Mo(CO)4(LL)] and [Mo(CO)3(LL)(CH3CN)] (LL = 2,2′-bipyridine, 1,10-phenanthroline and related ligands)

Mo(CO)₄(LL) complexes, where LL = polypyridyl ligands such as 2,2′-bipyridine and 1,10-phenanthroline, undergo quasi-reversible, one-electron oxidations in methylene chloride yielding the corresponding radical cations, [Mo(CO)₄(LL)]⁺. These electrogenerated species undergo rapid ligand substitution in the presence of acetonitrile, yielding [Mo(CO)₃(LL)(CH₃CN)]⁺; rate constants for these substitutions were measured using chronocoulometry and were found to be influenced by the steric and electronic properties of the polypyridyl ligands. [Mo(CO)₃(LL)(CH₃CN)]⁺ radical cations, which could also be generated by reversible oxidation of Mo(CO)₃(LL)(CH₃CN) in acetonitrile, can be irreversibly oxidized yielding [Mo(CO)₃(LL)(CH₃CN)₂]²⁺ after coordination by an additional acetonitrile. Infrared spectroelectrochemical experiments indicate the radical cations undergo ligand-induced net disproportionations that follow first-order kinetics in acetonitrile, ultimately yielding the corresponding Mo(CO)₄(LL) and [Mo(CO)₂(LL)(CH₃CN)₃]²⁺ species. Rate constants for the net disproportionation of [Mo(CO)₃(LL)(CH₃CN)]⁺ and the carbonyl substitution reaction of [Mo(CO)₃(LL)(CH₃CN)₂]²⁺ were measured. Thin-layer bulk oxidation studies also provided infrared characterization data of [Mo(CO)₄(ncp)]⁺ (ncp = neocuproine), [Mo(CO)₃(LL)(CH₃CN)]⁺, [Mo(CO)₃(LL)(CH₃CN)₂]²⁺ and [Mo(CO)₂(LL)(CH₃CN)₃]²⁺ complexes.     

Synthesis, characterization and X-ray crystal structure of [Re(L4)(CO)3]Br · 2CH3OH (L4 = N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine): A model compound for novel cationic Tc(I)-tricarbonyl radiotracers useful for heart imaging

This report describes synthesis and evaluation of cationic complexes, [^99mTc(CO)₃(L)]⁺ (L = N-methoxyethyl-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L1), N-[(15-crown-5)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L2) and N-[(18-crown-6)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L3)) as potential radiotracers for heart imaging. Preliminary results from biodistribution studies in female adult BALB-c mice indicated that the cationic ^99mTc(I)-tricarbonyl complex, [^99mTc(CO)₃(L2)]⁺, has a significant localization in the heart at 60 min post-injection. To understand the coordination chemistry of these bisphosphine ligands with the ^99mTc(I)-tricarbonyl core, we prepared [Re(CO)₃(L4)]Br (L4: N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine) as a model compound. [Re(CO)₃(L4)]Br has been characterized by elemental analysis, IR, ESI-MS, NMR (¹H, ¹³C, ¹H-¹H COSY, and ¹H-¹³C HMQC) methods, and X-ray crystallography. In solid state, [Re(CO)₃(L4)]⁺ has a distorted octahedron coordination geometry with PNP occupying one facial plane. The chelator backbone adopts a “chair” conformation with phosphine-P atoms at equatorial positions and the amine-N at the apical site. In solution, [Re(CO)₃(L4)]⁺ is able to maintain its cationic nature with no dissociation of carbonyl ligands or any of the three PNP donors.     

Rhenium tricarbonyl complexes of 1-benzyl-4-(5-bipyridyl)-1H-1,2,3-triazoles

Copper(I) catalyzed [3+2] cycloaddition reactions between 5-ethynylbipyridine and benzyl, p-methylbenzyl, or m-bromobenzyl azides yields the corresponding 1-benzyl-4-(5-bipyridyl)-1H-1,2,3-triazoles 1-3. Reaction between 1-3 and [NEt₄]₂[Re(CO)₃Br₃] yields the [1-benzyl-4-(5-bipyridyl)-1H-1,2,3-triazole]Re(CO)₃Br complexes 4-6. The Re(CO)₃Br complexes of 5- and 6-ethynylbipyridine complexes (7-8) are prepared in a similar fashion. Cycloaddition reactions between 7 and benzyl azide yields mixtures of 4 and unreacted starting material.     

Synthesis, structure and properties of copper(II) and manganese(II) coordination polymers with 1,5-dinitronaphthalene-3,7-dicarboxylate

Two new metal-organic coordination polymers with 1,5-dinitronaphthalene-3,7-dicarboxylate (NNDC), [Cu₂(NNDC)₂(DMF)_1.8(DMSO)_2.2(H₂O)₂]·H₂O (1) and [Mn₃(NNDC)₃(DMSO)₄]·2DMSO (2) have been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction and Thermogravimetric Analysis (TGA). The structure of compound 1 consists of one-dimensional chains with copper ions being linked by the dicarboxylate ligands. The coordination chains are associated into ladder-like double chains through O-H?O hydrogen bonds and π-π interactions, and the ladders are packed in a cross fashion through further π-π interactions to give the three-dimensional structure. The Mn(II) compound exhibits a 3D framework with the pcu topology, in which [Mn₃(COO)₆] clusters as octahedral secondary building blocks are linked by the naphthalene spacers. Magnetic analyses were carried out based on both temperature- and field-dependent data, consistently suggesting relatively weak antiferromagnetic interactions within the carboxylate bridged [Mn₃(COO)₆] cluster.     

Bipyrimidine-bridged rhenium(I)/rhenium(I) and ruthenium(II)/rhenium(I) complexes. Synthesis,electronic absorption and emission spectra

The binuclear complexes [Cl(OC)₃Re^I(bipym)Re^I(CO)₃Cl] (bipym=2,2′-bipyrimidine), [(bipy)₂Ru^II(bipym)Re^I(CO)₃Cl](PF₆)₂ (bipy=2,2′-bipyridine) and their mononuclear component [Re(bipym)(CO)₃Cl] were prepared. The electronic absorption spectra of these complexes display low-energy Re(I) →π*(bipym) and Ru(II)→π*(bipym) charge transfer (CT) bands. While [Re(bipym)(CO)₃Cl] shows a strong emission from its lowest CT state, the dimer [Cl(OC)₃Re(bipym)Re(CO)₃Cl] is not luminescent. The cation [(bipy)₂Ru(bipym)Re(CO)₃Cl]²⁺ emits from the lowest-energy Ru→bipym CT state. The emission behavior of the binuclear complexes is described in terms of intramolecular excited state electron or energy transfer.