Sn-S and Ru-Ru bonds cleavage reactions between [Ph3SnS(CH2)3SSnPh3] and Ru3(CO)12: X-ray crystal structures of [Ph3SnS(CH2)3SSnPh3] and trans-[Ru(CO)4(SnPh3)2]

The organotin complex [Ph₃SnS(CH₂)₃SSnPh₃] (1) was synthesized by PdCl₂ catalyzed reaction between Ph₃SnCl and disodium-1,3-propanedithiolate which in turn was prepared from 1,2-propanedithiol and sodium in refluxing THF. Reaction of 1 with Ru₃(CO)₁₂ in refluxing THF affords the mononuclear complex trans-[Ru(CO)₄(SnPh₃)₂] (2) and the dinuclear complex [Ru₂(CO)₆(μ-κ²-SCH₂CH₂CH₂S)] (3) in 20 and 11% yields, respectively, formed by cleavage of Sn-S bond of the ligand and Ru-Ru bonds of the cluster. Treatment of pymSSnPPh₃ (pymS = pyrimidine-2-thiolate) with Ru₃(CO)₁₂ at 55-60 °C also gives 2 in 38% yield. Both 1 and 2 have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.     

Bifunctional chelates with mixed aromatic and aliphatic amine donors for labeling of biomolecules with the {Tc(CO)3} and {Re(CO)3} cores

A series of tridentate ligands consisting of mixed aromatic and aliphatic amine derivatives of single amino acid chelates and phenylpiperazine have been developed, and their reactions with [NEt₄]₂[ReBr₃(CO)₃] have been investigated. The compounds [Re(CO)₃{(NC₅H₄CH₂)NCH₃(C₂H₄)NHCH₃}]Br (4), [Re(CO)₃{(NC₅H₄CH₂)NCH₃(C₂H₄)NCH₃(CH₂)_xCOOC₂H₅}]Br (x = 1, 5; x = 4, 6) [Re(CO)₃{(NC₅H₄CH₂)NH(C₂H₄)N(CH₃)₂}]Br (7), [Re(CO)₃{(NC₅H₄CH₂)N(CH ₂COOC₂H₅)(C₂H₄)N(CH₃)₂}]Br (8) and [Re(CO)₃(NC₅H₄CH₂)(C₂H₄NH₂)N(CH₂)₃-CH₃Ophenpip]Br (9) (phenpip: phenylpiperazine, -C₆H₄-(CH₂CH₂)₂N-) were prepared and characterized by elemental analysis, NMR, IR, HSMS and X-ray crystallography. All complexes exhibit fac-{Re(CO)₃N₃} coordination geometry in the cationic molecular unit. Crystal data for C₁₃H₁₇BrN₃O₃Re (4): orthorhombic, Pbca, a = 13.4510(8) Å, b = 10.5728(6) Å, c = 22.5378(13) Å, V = 3205.2(3) ų, Z = 8; C₁₇H₂₃BrN₃O₅Re (5): orthorhombic, Pcca, a = 16.5907(7) Å,b = 14.8387(6) Å, c = 16.7075(7) Å, V = 4113.1(3) ų, Z = 8; C₁₃H₂₅BrN₃O₇Re (7 · 4H₂O): monoclinic, P2₁/n, a = 14.0698(17) Å, b = 9.6760(12) Å, c = 15.6099 (19) Å, β = 114.930(2)°, V = 1927.1(4) ų, Z = 4; C₁₇H₂₃BrN₃O₅Re (8): monoclinic, P2₁/n, a = 7.5312(5) Å, b = 16.0366(10) Å, c = 16.8741(10) Å, β = 98.9990(10)°, V = 2012.9(2) ų, Z = 4.     

On an erroneous view of fluxional behaviour of [Fe3(CO)12]

The idea that the mechanism of the very low energy fluxional behaviour of [Fe₃(CO)₁₂] may be based on the movement of the ligand icosahedron about the central Fe₃ triangle which corresponds to a rotational symmetry operation of the CO ligand icosahedron is discussed and rejected.     

Efficiency enhancement of the electrocatalytic reduction of CO2: fac-[Re(v-bpy)(CO)3Cl] electropolymerized onto mesoporous TiO2 electrodes

As the greenhouse effect increases, the development of systems able to convert with high efficiency CO₂ to energetically rich molecules owns a crucial weight in the technological and environmental domain. As catalyst, rhenium complexes, of the type fac-[Re(L)(CO)₃Cl] (i.e. L = 2,2′-bipyridyl or 4,4′-bipyridyl), have attracted a large interest demonstrating promising catalytic properties. fac-[Re(v-bpy)(CO)₃Cl]-based polymer deposited onto a solid support has been already investigated as heterogeneous catalyst in the reduction of CO₂. Here, we deposited by electrochemical polymerization fac-[Re(v-bpy)(CO)₃Cl] onto a nanocrystalline TiO₂ film on glass and we investigated by cyclic voltammetry the properties of such heterogeneous catalyst in the electrochemical reduction of CO₂. We demonstrated that the nanoporous nature of the substrate allows to increase the two-dimensional number of redox sites per surface area and hence to get a significant enhancement of the catalytic yield.     

Geometrical isomers of bis(benzimidazol-2-ylethyl)sulfide)cobalt(II) diperchlorates: synthesis, structure, spectra and redox behavior of pink-[Co(bbes)2](ClO4)2 and blue-[Co(bbes)2](ClO4)2

1:1 and 1:2 cobalt complexes of bis(benzimidazol-2-ylmethyl)amine (bbma) bis(benzimidazol-2-ylmethyl)sulfide (bbms), bis(benzimidazol-2-ylethyl)sulfide (bbes) and diethylenetriamine (dien) were prepared and their spectral and redox behavior studied. Two geometrical isomers pink-[Co(bbes)₂]²⁺ and blue-[Co(bbes)₂]²⁺ were obtained when the complexes were prepared by using with bbes and they were separated manually and recrystallized. The octahedral structure of pink-[Co(bbes)₂]²⁺ was resolved by X-ray analysis. The electronic spectra show the presence of two geometrical isomers for Co(bbes)₂²⁺ in the solid state; for example, the spectral bands of pink-[Co(bbes)₂]²⁺ differs markedly with those of blue-[Co(bbes)₂]²⁺. This is consistent with the results obtained from magnetic measurements (5.10 BM for pink-Co(bbes)₂²⁺ and 4.72 BM for blue-[Co(bbes)₂]²⁺). Further, the behavior of the ligands (bbma, bbms, bbes) at different pH conditions was determined on the basis of ¹³C NMR studies. The redox potentials [Co(II)/Co(I)] of the complexes follow the trend [Co(bbma)₂]²⁺ < [Co(bbms)₂]²⁺ ≈ [Co(bbes)₂]²⁺ which demonstrates the stabilization of the Co(II) ion is more by both weak σ-donor and weak π-acceptor ligands rather than by σ-donor ligand.     

Ultrafast excited-state dynamics of photoisomerizing complexes fac-[Re(Cl)(CO)3(papy)2] and fac-[Re(papy)(CO)3(bpy)] (papy = trans-4-phenylazopyridine)

The character and dynamics of low-lying electronic excited states of the complexes fac-[Re(Cl)(CO)₃(papy)₂] and fac-[Re(papy)(CO)₃(bpy)]⁺ (papy = trans-4-phenylazopyridine) were investigated using stationary (UV-Vis absorption, resonance Raman) and ultrafast time-resolved (visible, IR absorption) spectroscopic methods. Excitation of [Re(Cl)(CO)₃(papy)₂] at 400 nm is directed to ¹ππ^∗(papy) and Re → papy ¹MLCT excited states. Ultrafast (?1.4 ps) intersystem crossing (ISC) to ³nπ^∗(papy) follows. Excitation of [Re(papy)(CO)₃(bpy)]⁺ is directed to ¹ππ^∗(papy), ¹MLCT(papy) and ¹MLCT(bpy). The states ³nπ^∗(papy) and ³MLCT(bpy) are then populated simultaneously in less then 0.8 ps. The ³MLCT(bpy) state decays to ³nπ^∗(papy) with a 3 ps time constant. ³nπ^∗(papy) is the lowest excited state for both complexes. It undergoes vibrational cooling and partial rotation around the -NN- bond, to form an intermediate with a nonplanar papy ligand in less than 40 ps. This species then undergoes ISC to the ground state potential energy surface, on which the trans and cis isomers are formed by reverse and forward intraligand papy rotation, respectively. This process occurs with a time constant of 120 and 100 ps for [Re(Cl)(CO)₃(papy)₂] and [Re(papy)(CO)₃(bpy)]⁺, respectively. It is concluded that coordination of papy to the Re center accelerates the ISC, switching the photochemistry from singlet to triplet excited states. Comparison with analogous 4-styrylpyridine complexes (M. Busby, P. Matousek, M. Towrie, A. Vl?ek Jr., J. Phys. Chem. A 109 (2005) 3000) reveals similarities of the decay mechanism of excited states of Re complexes with ligands containing -NN- and -CC- bonds. Both involve sub-picosecond ISC to triplets, partial rotation around the double bond and slower ISC to the trans or cis ground state. This process is about 200 times faster for the -NN- bonded papy ligand. The intramolecular energy transfer from the ³MLCT-excited ^∗Re(CO)₃(bpy) chromophore to the intraligand state of the axial ligand occurs for both L = stpy and papy with a comparable rate of a few ps.     

Synthesis and DNA threading properties of quaternary ammonium [Ru(phen)2(dppz)] derivatives

Ruthenium complexes with one dipyrido[3,2-a:2′-3′-c]phenazine (dppz) ligand, e.g. [Ru(phen)₂(dppz)]²⁺ (phen = phenanthroline), shows strong binding to double helical DNA and are well-known DNA “light-switch” molecules. We have here investigated four new [Ru(phen)₂(dppz)]²⁺ derivatives with different bulky quaternary ammonium substituents on the dppz ligand to find relationships between molecular structure and intercalation kinetics, which is considered to be of importance for antitumor applicability. Linear dichroism spectroscopy shows that the enantiomers of the new complexes exhibit very similar binding geometries (intercalation of dppz moiety between adjacent DNA base pairs) as the enantiomers of the parent [Ru(phen)₂(dppz)]²⁺ complex. Absorption spectra and luminescence properties provide further evidence for a final intercalative binding mode which has to be reached by threading of a bulky moiety between the strands of the DNA. Δ-enantiomers of all the new complexes show much slower association and dissociation kinetics than that of a reference complex without a cationic substituent. Kinetics were not very different whether the bulky quaternary group was derived from hexamethylene tetramine or 1,4-diazabicyclo-(2,2,2)octane (DABCO) or whether it had one or two positive charges. However, a complex in which the hexamethylene tetramine substituent is attached via a phenyl group showed a lowered association rate, in addition to an improved quantum yield of luminescence. A second positive charge on the DABCO substituent resulted in a much slower dissociation rate, suggesting that the distance from the Ru-centre and the amount of charge are both important for threading intercalation kinetics.     

Kinetic studies of the reduction of hexaaquacobalt(III) perchlorate by a cobaloxime, [Co(dmgBF2)2(H2O)2]

The reaction of with Co(dmgBF₂)₂(H₂O)₂ in 1.0 M HClO₄/LiClO₄ was found to be first-order in both reactants and the [H⁺] dependence of the second-order rate constant is given by k_2obs = b/[H⁺], b at 25 °C is 9.23 ± 0.14 × 10² s⁻¹. The [H⁺] dependence at lower temperatures shows some saturation effect that allowed an estimate of the hydrolysis constant for as K_a = 9.5 × 10⁻³ M at 10 and 15 °C. Marcus theory and the known self-exchange rate constant for Co(OH₂)₅OH^2+/+ were used to estimate an electron self-exchange rate constant of k₂₂ = 1.7 × 10⁻⁴ M⁻¹ s⁻¹ for .     

Synthesis and characterization of some oxovanadium(V) complexes with internally functionalized oximes: Crystal and molecular structures of heptacoordinated [VO{ONC(CH3)(C4H3O-2)}3] and [VO{ONC(CH3)(C4H3S-2)}3] · 0.5C6H6

New oxovanadium(V) complexes with internally functionalized oximes of the type VO{OPrⁱ}_3−n{ONC(CH₃)(Ar)}_n] (where Ar = C₄H₃O-2, C₄H₃S-2 and C₅H₄N-2 and n = 1-3) have been prepared in quantitative yields by the reaction of VO(OPrⁱ)₃ with the corresponding oximes in various stoichiometric ratios in refluxing anhydrous benzene. The products have been characterized by elemental analyses and spectroscopic (FT IR, ¹H, ¹³C{¹H} and ⁵¹V NMR) studies. FAB mass spectral analysis of [VO{OPrⁱ}{ONC(CH₃)C₄H₃S}₂] indicates the monomeric nature of the complex. ⁵¹V NMR values for these complexes suggest the formation of tetra-coordinate species in solution. However, the single crystal X-ray diffraction studies of [VO{ONC(CH₃)(C₄H₃O-2)}₃] and [VO{ONC(CH₃)(C₄H₃S-2)}₃] · 0.5C₆H₆ exhibit the presence of vanadium(V) atoms in a unique hepta-coordination state with distorted pentagonal bipyramidal geometry in the solid state. The oxo- atom occupies the axial position while the oximato ligands are bonded in a dihapto (η²-N,O) manner with the formation of three membered rings.     

1D chain coordination assembly of [Mn4(hmp)6(NO3)2] single-molecule magnets linked by the photochromic [FeNO(CN)5] precursor

The first heterometallic chain cluster {[Mn₄(hmp)₆(NO₃)₂FeNO(CN)₅·4CH₃CN}_n (1) based on the [Mn₄(hmp)₆] SMM has been synthesized. 1 has one-dimensional chain structure: the [Mn₄(hmp)₆] units are linked via CN-groups of nitroprusside anions. Its magnetic and relaxation properties and low temperature IR spectra under light irradiation have been investigated. The ferromagnetic exchange constants have been calculated.     

Solution-mediated syntheses and characterizations of two new zincophosphites [C6H14N2]0.5[Zn(H2PO3)2] and [C4H12N2]0.5[(CH3)2NH2][Zn2(HPO3)3]

Two new zincophosphites [C₆H₁₄N₂]_0.5[Zn(H₂PO₃)₂] 1 and [C₄H₁₂N₂]_0.5[(CH₃)₂NH₂][Zn₂(HPO₃)₃] 2 have been solvothermally synthesized in mixed solvents of N,N-dimethylformamide (DMF) and 1,4-dioxane (DOA), respectively. Single-crystal X-ray diffraction analysis reveals that compound 1 exhibits a neutral inorganic chain formed by ZnO₄ and HPO₂(OH) units. Interestingly, the left- and right-handed hydrogen-bonded helical chains are alternately formed via the hydrogen-bonds between two adjacent chains. Compound 2 exhibits a layer structure with 4- and 12-MRs formed by ZnO₄ and HPO₃ units, in which two kinds of organic amine molecules both act as countercations to compensate the overall negative electrostatic charge of the anionic network.     

Kinetics study of the substitution reaction of fac-[Fe(CN)2(CO)3I] with PPh3

Substitution reaction of fac-[Fe^II(CN)₂(CO)₃I]⁻ with triphenylphosphine (PPh₃) produced mono phosphine substituted complex cis-cis-[Fe^II(CN)₂(CO)₂(PPh₃)I]⁻. Crystal structure of the product showed that carbonyl positioned trans- to iodide was replaced by PPh₃. The substitution reaction was monitored by quantitative infrared spectroscopic method, and the rate law for the substitution reaction was determined to be rate = k[[Fe^II(CN)₂(CO)₂(PPh₃)I]⁻][PPh₃]. Transition state enthalpy and entropy changes were obtained from Eyring equation k = (k_BT/h)exp(−ΔH^≠/RT + ΔS^≠/R) with ΔH^≠ = 119(4) kJ mol⁻¹ and ΔS^≠ = 102(10) J mol⁻¹ K⁻¹. Positive transition state entropy change suggests that the substitution reaction went through a dissociative pathway.     

Synthesis and characterization of three group 10 complexes containing nido-carborane diphosphine: [MCl(PPh3){7,8-(PPh2)2-7,8-C2B9H10}] (M = Ni, Pd, Pt)

Three group 10 complexes containing nido-carborane diphosphine, [NiCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (1), [PdCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] · 1.25CH₂Cl₂ (2) and [PtCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] · 2.5CH₂Cl₂ (3) have been synthesized by the reactions of [M(PPh₃)₂Cl₂] (M = Ni, Pd, Pt) with closo carborane diphosphine 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ in ethanol. For complex 3, it could also be obtained under solvothermal condition. All three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal structures show that their structures are similar to each other. In each complex, the nido [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻, which resulted from the degradation of the initial closo ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ during the reaction process, was coordinated bidentately through the P atoms to M(II) ion, and this resulted in a stable five-membered chelating ring between the bis-diphosphine ligand and the metal. The coordination mode of the metal can be described as a slightly distorted square-planar, in which the remaining two positions were occupied by one Cl⁻ and one PPh₃ group.     

A new arylimido derivative of polyoxometalate (Bu4N)2[Mo6O17(NAr)2] [Ar = 2,6-(CH3)2C6H3]: Synthesis, structure and physicochemical properties

A novel bifunctionalized arylimido derivative of hexamolybdate, (Bu₄N)₂[Mo₆O₁₇(NAr)₂] [Ar = 2,6-(CH₃)₂C₆H₃] (1), in which the two 2,6-dimethylaniline groups are bounded to hexamolybdate at the cis positions, was synthesized by a facile reaction of α-octamolybdate with 2,6-dimethylaniline using DCC as a dehydration agent. The existence of strong non-typical C-H?O hydrogen bonds plays an important role in crystal structure stabilization of compound 1. The results of fluorescence spectra show that the formation of a covalent bond between 2,6-dimethylaniline molecule and hexamolybdate could efficiently quench the fluorescence intensity of 2,6-dimethylaniline molecule, with a fluorescence quencher efficiency of 87.7%. Thermal analysis results indicate that two substituted 2,6-(CH₃)₂C₆H₃ molecules bonding to the same cluster dissociated at different temperature, in well agreement with the different MoN bond length in compound 1. The electrochemical behavior of modified 1-CPE has been studied in detail. Compared with the conventional polyoxometalate (POM)-modified electrode, 1-CPE presents a merit of remarkable stability over 500 cycles due to the insolubility of the POM nanoparticles, which is especially important for practical applications.     

等渗NaCl和Ca(NO_3)_2胁迫对黄瓜幼苗生长和生理特性的影响

以盐敏感型的黄瓜品种‘津春2号’为材料,采用营养液栽培方法,研究了等渗NaCl和Ca(NO3)2胁迫对黄瓜幼苗生长和生理特性的影响。结果表明,NaCl胁迫不仅抑制黄瓜幼苗地上部生长,而且对根系生长也具有抑制作用;而Ca(NO3)2胁迫主要抑制黄瓜幼苗地上部生长,对根系生长没有明显影响。NaCl胁迫下,黄瓜幼苗净光合速率(Pn)降低不仅由非气孔因素引起,而且碳同化能力也降低;而Ca(NO3)2胁迫下Pn降低主要由非气孔因素引起,对植株的碳同化能力没有明显影响。等渗NaCl和Ca(NO3)2胁迫导致黄瓜幼苗叶片光系统Ⅱ(PSⅡ)反应中心过剩光能(Ex)显著升高,致使叶片超氧阴离子自由基(O-·2)产生速率加快,过氧化氢(H2O2)含量显著升高,但NaCl胁迫的升高幅度均大于Ca(NO3)2胁迫。NaCl胁迫在提高过氧化物酶(POD)和过氧化氢酶(CAT)活性的同时,降低了超氧化物歧化酶(SOD)活性,对活性氧(ROS)的清除能力有限,致使叶片ROS大量积累,膜质过氧化伤害严重;而Ca(NO3)2胁迫显著提高了SOD、POD和CAT活性,有效清除了ROS,对叶片未造成严重的膜质过氧化伤害。NaCl和Ca(NO3)2胁迫分别导致黄瓜幼苗体内Na+和Ca2+大量积累,致使离子平衡被打破,但过多Na+要比过多的Ca2+对植物体的伤害作用大。上述结果说明,黄瓜幼苗对等渗NaCl和Ca(NO3)2胁迫的生理响应存在差异。NaCl胁迫下黄瓜幼苗体内Na+大量积累,不仅限制了环境中CO2进入叶肉细胞,而且使碳同化能力降低,加之ROS清除能力有限,不能有效清除PSⅡ反应中心过剩能量所导致的ROS,因而产生了严重的膜质过氧化,影响了植株生长和光合速率;而Ca(NO3)2胁迫下,黄瓜幼苗碳同化能力没有受到影响,ROS也能够被抗氧化系统有效清除,植株没有产生严重的膜质过氧化,因而对生长和光合速率的影响没有NaCl胁迫大。     

Quantifying the trans influence of triphenylarsine. Crystal and molecular structures of cis-[PtCl2(SMe2)(AsPh3)] and cis-[PtCl2(AsPh3)2]·CHCl3

Reaction between a mixture of cis-trans-[PtCl₂(SMe₂)₂] and 1 equiv. AsPh₃ in chloroform gives cis-[PtCl₂(SMe₂)(AsPh₃)] crystallizing in P2₁/n with a=10.397(2), b=14.876(3), c=13.956(3) Å, β=90.86(3)° and Z=4. Selected geometrical parameters are PtAs 2.3531(10), PtS 2.262(2), PtCl (trans to S) 2.301(2), PtCl (trans to As) 2.328(2) Å and SPtAs 88.85(6), SPtCl(2) 90.77(8), AsPtCl(1) 91.07(6) and ClPtCl 89.42(7)°. cis-[PtCl₂(AsPh₃)₂]·CHCl₃ crystallizes in P2₁/c with a=20.557(4), b=9.5951(19), c=20.147(4) Å, β=96.77(3)° and Z=4. Selected geometrical parameters are PtAs(1) 2.3599(9), PtAs(2) 2.3770(9), PtCl(1) (trans to As(1)) 2.3515(18), PtCl(2) (trans to As(2)) 2.3251(18) Å and AsPtAs 97.87(3), As(1)PtCl(2) 88.67(5), As(2)PtCl(1) 84.30(5) and ClPtCl 89.32(7)°. By comparison with related structures from the literature the following trans influence series was established PMe₂Ph>PPh₃>AsPh₃≈SbPh₃>Me₂SO≈SMe₂≈SPh₂>NH₃≈olefin>Cl⁻>MeCN.     

Synthesis and characterization of complexes of the type [Pt(amine)4]I2 and trans-[Pt(CH3NH2)2(H3CNC(CH3)2)2]I2 by crystallography and multinuclear magnetic resonance spectroscopy

Complexes of the type [Pt(amine)₄]I₂ were synthesized and characterized mainly by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In ¹⁹⁵Pt NMR, the signals were observed between −2715 and −2769 ppm in D₂O. The coupling constant ³J(¹⁹⁵Pt-¹H) for the MeNH₂ complex is 42 Hz. In ¹³C NMR, the average values of the coupling constants ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) are 18 and 30 Hz, respectively. The crystal structure of [Pt(EtNH₂)₄]I₂ was determined by X-ray diffraction methods. The Pt atom is located on an inversion center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH₂ was found by crystallographic methods to be [Pt(n-BuNH₂)₄]₂I₃(n-BuNHCOO). The crystal contains two independent [Pt(CH₃NH₂)₄]²⁺ cations, three iodide ions and a carbamate ion formed from the reaction of butylamine with CO₂ from the air. When the compound [Pt(CH₃NH₂)₄]I₂ was dissolved in acetone, crystals identified as trans-[Pt(CH₃NH₂)₂(H₃CNC(CH₃)₂)₂]I₂ were isolated and characterized by crystallographic methods. Two trans bonded MeNH₂ ligands had reacted with acetone to produce the two N-bonded Schiff base Pt(II) compound.     

Syntheses and structures of the heterometallic clusters [(Ph3PAu)3Re(CO)4], [(Ph3PAu)4Re(CO)4], [(Ph3PAu)6AuRe2(CO)8], and [(Ph3PAu)6Re(CO)3]

The reaction of [HRe₃(CO)₁₂]²⁻ with an excess of Ph₃PAuCl in CH₂Cl₂ yields [(Ph₃PAu)₄Re(CO)₄]⁺ as the main product, which crystallizes as [(Ph₃PAu)₄Re(CO)₄]PF₆ · CH₂Cl₂ (1 · CH₂Cl₂) after the addition of KPF₆.The crystal structure determination reveals a trigonal bipyramidal Au₄Re cluster with the Re atom in equatorial position.If [(Ph₃PAu)₄Re(CO)₄]⁺ is reacted with PPh₄Cl, a cation [Ph₃PAu]⁺ is eliminated as Ph₃PAuCl, and the neutral cluster [(Ph₃PAu)₃Re(CO)₄] (2) is formed.It combines with excess [(Ph₃PAu)₄Re(CO)₄]⁺ to afford the cluster cation, [(Ph₃PAu)₆AuRe₂(CO)₈]⁺. It crystallizes from CH₂Cl₂ as[(Ph₃PAu)₆AuRe₂(CO)₈]PF₆ · 4CH₂Cl₂ (3 · 4CH₂Cl₂). In [(Ph₃PAu)₃Re(CO)₄] the metal atoms are arranged in form of a lozenge while in [(Ph₃PAu)₆AuRe₂(CO)₈]⁺ two Au₄Re trigonal bipyramids are connected by a common axial Au atom.The treatment of [(Ph₃PAu)₄Re(CO)₄]⁺ with KOH and Ph₃PAuCl in methanol yields the cluster cation [(Ph₃PAu)₆Re(CO)₃]⁺, which crystallizes with from CH₂Cl₂ as [(Ph₃PAu)₆Re(CO)₃]PF₆ · CH₂Cl₂ (4 · CH₂Cl₂). The metal atoms in this cluster form a pentagonal bipyramid with the Re atom in the axial position.     

Complexes of the fac-{Re(CO)3} core with tridentate ligands derived from arylpiperazines

Arylpiperazines, XC₆H₄N(CH₂CH₂)₂NH, are readily alkylated to give the N-alkylpiperazines of the type XC₆H₄N(CH₂CH₂)₂N(CH₂)_nNH₂. The amine functions of these derivatives are in turn easily subjected to mono- or dialkylation to provide potentially tridentate ligands of the types XC₆H₄N(CH₂CH₂)₂N(CH₂)_nN(H)(CH₂Y) and XC₆H₄N(CH₂CH₂)₂N(CH₂)_nN(CH₂Y)(CH₂Z), respectively. The latter class of dialkylated derivatives may be symmetrically (Y=Z) or unsymmetrically (Y ≠ Z) substituted. The donor groups Y and Z of this study include pyridine, imidazole, methyl-imidazole, thiazole, carboxylate and thiolate.The reactions of these ligands with [NEt₄]₂[Re(CO)₃Br₃] yield complexes of the type [Re(CO)₃{(YCH₂)N(H)(CH₂)_n(H)_xN(CH₂CH₂)₂N(H)_yC₆H₄X}]ⁿ and [Re(CO)₃{(ZCH₂)(YCH₂)N(CH₂)_n(H)_xN(CH₂CH₂)₂N(H)_yC₆H₄X}]ⁿ where the molecular charge n (0, +1, or +2) depends on the nature of the donor groups Y and Z (whether neutral or anionic or a combination of neutral and anionic) and on the degree of protonation of the piperazine unit (x=0 or 1; y=0 or 1). This variety of tridentate chelators provides complexes with fac-{Re(CO)₃N₃}, {Re(CO)₃N₂O}, {Re(CO)₃NO₂}, {Re(CO)₃N₂S} and {Re(CO)₃NS₂} coordination geometries. The structures of the model compound [Re(CO)₃{(CH₃N₂C₃H₂CH₂)N(H)CH₂CH₂-piperidine}]Br · H₂O, [Re(CO)₃{(CH₃N₂C₃H₂CH₂)N(H)CH₂CH₂-Fphenpip}]Br, [Re(CO)₃{(NC₅H₄CH₂)N(H)CH₂CH₂-Fphenpip}]Br, [Re(CO)₃{(O₂CCH₂)₂NCH₂CH₂CH₂-CH₃OphenpipH}] · xCH₃OH (x≈0.875), [Re(CO)₃{(NC₅H₄CH₂)₂NCH₂CH₂CH₂-CH₃OphenpipH}]Br₂ · 2CH₂Cl₂ · H₂O and [Re(CO)₃{(CH₃N₂C₃H₂CH₂)(O₂CCH₂)NCH₂CH₂CH₂-CH₃OphenpipH₂}]BrCl · 1.5CH₃OH · H₂O are discussed (phenpip: phenylpiperazine, -C₆H₄N(CH₂CH₂)₂N-).     

Structure and reactivity of [Ru(2,3-Medpp)2Cl2]

The structure and reactivity of the complex [Ru(2,3-Medpp)₂Cl₂](PF₆)₂ (2,3-Medpp⁺=2-[2-(1-methylpyridiniumyl)]-3-(2-pyridyl)pyrazine) was investigated by X-ray diffraction (XRD), ¹H NMR, redox, and UV-Vis absorption measurements. X-ray analysis shows that crystals obtained from an acetonitrile-toluene solution contain the trans-Cl₂, trans-pyrazine isomeric form, while ¹H NMR and redox measurements on the main product of the synthetic workup indicate the presence of the trans-Cl₂, cis-pyrazine isomer. In the dark at 70 °C, the complex [Ru(2,3-Medpp)₂Cl₂]²⁺ reacts slowly in acetonitrile isomerizing to the cis-[Ru(2,3-Medpp)₂(CH₃CN)Cl]³⁺ species. Under ambient light in the presence of excess AgNO₃ the cis-[Ru(2,3-Medpp)₂(CH₃CN)₂]⁴⁺ species is obtained.