The substitution kinetics of the aqua ligand by cyanide ions in [Ru(TPPS)(CO)(H2O)]4−

Summary The reaction between the title compound, ,,,-tetra(p-sulphonatophenyl)porphynatoaquacarbonylruthenate(II), [Ru(TPPS)(CO)(H₂O)]^4–, and CN^- revealed that only the aqua ligand is substituted even in the presence of a large excess of the nucleophile. The pK _a1 was spectrophotometrically determined as 13.4(5) (at 33.2 °C) and kinetically as 13.44(5) (at 33.6 °C). The rate of aqua substitution was determined as 89(4)m ^–1 s ^–1 at 35.1 °C and the activation enthalpy and entropy as 55.44(1) kJ mol^–1 and-27.90(4) J K^–1 mol^–1, respectively.     

The mechanism of fluxionality of (1,2,7-η3-2-Me-benzyl)(η5-C5H5)Mo(CO)2

It is shown that (1,2,7-η³-2-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits in solution as one isomer which is fluxional, probably via (7-η¹-2-Me-benzyl)((η⁵-C₅H₅)Mo(CO)₂, with ΔG^≠₃₇₀ = 23.6 ± 1.0 kcal mol⁻¹. In contrast, (1,2,7-η³-3-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits as two isomers at −20°C, which undergo interconversion at room temperature with ΔG^≠ 15.7 kcal mol⁻¹. This dynamic process is an allyl rotation. It is probable that there is also a low energy [1,5]-sigmatropic shift.     

Preparation and crystal structures of [μ-SbPh2]2[Mo(CO)2(η5-C5H5)]2·CHCl3 and SbPh[Fe(CO)2(η5-C5H5)]2

Antimony is reduced when [SbPh₂BrO]₂ is treated with Na[Mo(CO)₃(η⁵-C₅H₅)] to produce [μ-SbPh₂]₂[Mo(CO)₂(η⁵-C₅H₅)]₂. A structure determination shows diphenylstibido groups bridging between two Mo(CO)₂(η⁵-C₅H₅) moieties giving a central ‘butterfly’ shaped Sb₂Mo₂ ring. The cyclopentadiene rings are trans to each other and Mo–Sb and Sb–Sb separations are both short. An iron analogue could not be obtained from [SbPh₂BrO]₂ and Na[Fe(CO)₂(η⁵-C₅H₅)] but a mixture of SbPh[Fe(CO)₂(η⁵-C₅H₅)]₂ and SbPh₂[Fe(CO)₂(η⁵-C₅H₅)] was obtained using SbPh₂Cl. An X-ray structure for SbPh[Fe(CO)₂(η⁵-C₅H₅)]₂ shows an open stibinidine structure.     

Analysis of the metal–ligand bonds in [Mo(X)(NH2)3] (X = P, N, PO, and NO), [Mo(CO)5(NO)]+, and [Mo(CO)5(PO)]+

Quantum chemical calculations at the DFT level have been carried out for model complexes [Mo(P)(NH₂)₃] (1), [Mo(N)(NH₂)₃] (2), [Mo(PO)(NH₂)₃] (3), [Mo(NO)(NH₂)₃] (4), [Mo(CO)₅(PO)]⁺ (5), and [Mo(CO)₅(NO)]⁺ (6). The equilibrium geometries and the vibration frequencies are in good agreement with experimental and previous theoretical results. The nature of the Mo–PO, Mo–NO, Mo–PO⁺, Mo–NO⁺, Mo–P, and Mo–N bond has been investigated by means of the AIM, NBO and EDA methods. The NBO and EDA data complement each other in the interpretation of the interatomic interactions while the numerical AIM results must be interpreted with caution. The terminal Mo–P and Mo–N bonds in 1 and 2 are clearly electron-sharing triple bonds. The terminal Mo–PO and Mo–NO bonds in 3 and 4 have also three bonding contributions from a σ and a degenerate π orbital where the σ components are more polarized toward the ligand end and the π orbitals are more polarized toward the metal end than in 1 and 2. The EDA calculations show that the π bonding contributions to the Mo–PO and Mo–NO bonds in 3 and 4 are much more important than the σ contributions while σ and π bonding have nearly equal strength in the terminal Mo–P and Mo–N bonds in 1 and 2. The total (NH₂)₃Mo–PO binding interactions are stronger than for (NH₂)₃Mo–P which is in agreement with the shorter Mo–PO bond. The calculated bond orders suggest that there are only (NH₂)₃Mo–PO and (NH₂)₃Mo–NO double bonds which comes from the larger polarization of the σ and π contributions but a closer inspection of the bonding shows that these bonds should also be considered as electron-sharing triple bonds. The bonding situation in the positively charged complexes [(CO)₅Mo–(PO)]⁺ and [(CO)₅Mo–(NO)]⁺ is best described in terms of (CO)₅Mo → XO⁺ donation and (CO)₅Mo ← XO⁺ backdonation (X = P, N) using the Dewar–Chatt–Duncanson model. The latter bonds are stronger and have a larger π character than the Mo-CO bonds.     

Comparative studies of the photochemical and thermal reactivities of the molybdenum-molybdenum single bond in [Mo2(η5-C5H5)2(CO)6] and triple bond in [Mo2(η5-C5H5)2(CO)4] towards nitrite and nitrate

Irradiation at λ = 507 and 391 nm of [Mo₂(η⁵-C₅H₅)₂(CO)₆] in a degassed tetrahydrofuran (THF) or THF-MeOH solution containing nitrite gives [Mo(η⁵-C₅H₅)₂NO] and several oxo complexes including [{Mo(η⁵-C₅H₅)(O)₂}₂O] in good yields. The quantum yields for the disappearance of [Mo₂(η⁵-C₅H₅)₂(CO)₆] in the reaction with NO₂⁻ depend on the nitrite concentration, thus suggesting participation of the metal-radical intermediate in the reduction of nitrite. Reactions of [Mo₂(η⁵-C₅H₅)₂(CO)₄] with nitrite or nitrate in the dark give the same nitrosyl and oxo complexes as above. An oxygen atom in nitrite or nitrate is mainly transferred onto the molybdenum atom both in the photochemical and the dark reactions.     

The X-ray crystal structure of di-η5-cyclopentadienylthiophenolatoamminemolybdenum(IV) hexafluorophosphate solvate [Mo(η5-C5H5)2(NH3)(SC6H5)][PF6] · (CH32CO

Crystals of [Mo(η⁵-C₅H₅)₂(NH₃)(SC₆H₅)][PF₆] · (CH₃)₂CO solvate are monoclinic, space group P2₁/n, a 9.777(1), b 11.6343(2), c 19.656(4) Å, β 93.60(1)°, V 2231-46 ų, Z  D_c 1.617 g cm⁻³, μ(Mo-K_α) 7.21 cm⁻¹. The structure was solved by Patterson and difference Fourier electron density synthesis and refined to R (F)  0.047 and R_w(F)  0.057 for 3293 observed reflections. The molybdenum atom has the usual distorted tetrahedral geometry comprising the two MoCp (Cp  η⁵-C₅H₅) ring normals (MoCp 1.988(13), 1.989(15) Å), one Mo-NH₃ (MoN 2.226(12) Å), and one MoSc₆H₅ (MoS 2.465(5) Å). Extended HMO and steric energy calculations were made in order to account for the geometry adopted by the thiolato ligand in this complex.     

Kinetic studies on spontaneous ligand substitution in [Cr(S-pdtra)(H2O)]–NCS– and [Cr(edtrp)(H2O)]–NCS– systems

The kinetics of anation of [Cr(S-pdtra)(H2O)] and [Cr(edtrp)(H2O)] complexes (S-pdtra=S-propane-1,2-diamine-N,N,N -triacetate, edtrp=ethylenediamine-N, N,N-tripropionate) by thiocyanates and aquation of the [Cr(NCS)(S-pdtra)]– and [Cr(NCS)(edtrp)]– ions have been studied in aqueous HClO4 solutions. The rate laws and the activation parameters have been determined and discussed. The observed decrease in reactivity for the edtrp complexes corresponds with a changeover of the reaction mechanism from Ia to Id for reactions of the CrIII-S-pdtra and CrIII-edtrp species, respectively.     

The Thermolysis of [Ru3(CO)12] in Cyclohexene: Synthesis and Charaterisation of the New Clusters [Ru3H2(CO)9(μ3-η1:η2:η1-C6H8)] and [Ru5(CO)12(μ4-η2-C6H8)(η4-C6H8)]

Thermolysis of [Ru₃(CO)₁₂] in cyclohexene for 24 h affords the complexes [Ru(CO)₃(η⁴-C₆H₈)] (1), [Ru₃H₂(CO)₉(μ₂-η¹:η²:η¹-C₆H₈)] (2), [Ru₄(CO)₁₂(μ₄-C₆H₈)] (3) [Ru₄(CO)₉(μ₄-C₆H₈)(η⁶-C₆H₆)] (4a and 4b, two isomers) and [Ru₅(CO)₁₂(μ₄-η²-C₆H₈)(η⁴-C₆H₈)] (5), where 1, 3, 4a and 4b have been previously characterised as products of the thermolysis of [Ru₃(CO)₁₂] with cyclohexa-1,3-diene. The molecular structures of the new clusters 2 and 5 were determined by single-crystal X-ray crystallography, showing that two conformational polymorphs of 5 exist in the solid state, differing in the orientation of the cyclohexa-1,3-diene ligand on a ruthenium vertex.     

Indium monohalide insertion reactions into metal—metal bonds. Crystal structure of [InCl(THF){Mo(CO)3(η-C5H5)}2]

The reaction between InCl and [Mo₂(CO)₆(η-C₅H₅)₂] affords [InCl&{;Mo(CO)₃(η-C₅H₅)&};], 6a which has been characterised as a THF adduct [InCl(THF)&{;Mo(CO)₃(η-C₅H₅)&};₂], 10, by X-ray crystallography. An additional complex, [InCl₂&{;Mo(CO)₃(η-C₅H₅)&};₂]⁻, 11, is also formed in this reaction. Similar products are reported for reactions involving [M₂(CO)₆(η-C₅H₅)₂] (M = Cr, W). The reaction between InCl and [Fe₂(CO)₄(η-C₅H₅)₂] affords [InCl{Fe(CO)₂(η-C₅H₅)}₂], 17, and [InCl₂{Fe(CO)₂(η-C₅H₅)}], whilst that between InI and [Fe₂(CO)₄(η-C₅H₅)₂] affords [InI{Fe(CO)₂(η-C₅H₅)}₂], 19.     

The asymmetric sythesis of (-)-actinonin using the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3)]

The asymmetric synthesis of the α-pentyl succinate fragment of (-)-Actinonin is achieved using the chiral iron acetyl S-(+)-[(η⁵-C₅H₅)Fe(CO)(PPh₃)COCH₃] and subsequently converted to (-)-Actinonin in an overall yield of 41%.     

Selective dilithiation of [Ti(η(5)-C5H5)(η(8)-C8H8)] and subsequent conversion into neutral and cationic ansa-complexes

Selective dimetalation of a sandwich complex featuring the cyclooctatetraene ligand has been accomplished for the first time. The isolation of the dilithiated species 1 subsequently enabled the isolation of a paramagnetic [2]stannatitanoarenophane (2) via salt elimination reaction. Chemical oxidation resulted in the formation of a rare example of a cationic ansa-complex (3).     

Replacement of terminal and bridging oxo groups by phenylimido groups in (η-C5H5)OMo(μ-O)2OMo(η-C5H5) giving (η-C5H5)(NPh)Mo(μ-NPh)2Mo(NPh)(η-C5H5)

The treatment of (η-C₅H₅)OMo(μ-O)₂MoO(η-C₅H₅) with excess phenylisocyanate at reflux in tetrahydrofuran yields the arylimido-substituted complex (η-C₅H₅)(NPh)Mo(η-NPh)₂Mo(NPh)(η-C₅H₅), which has been characterized by elemental analysis, and mass, IR and ¹H NMR spectra.     

Comprehensive thermochemistry of W-H bonding in the metal hydrides CpW(CO)2(IMes)H, [CpW(CO)2(IMes)H](•+), and [CpW(CO)2(IMes)(H)2]+. Influence of an N-heterocyclic carbene ligand on metal hydride bond energies

The free energies interconnecting nine tungsten complexes have been determined from chemical equilibria and electrochemical data in MeCN solution (T = 22 °C). Homolytic W-H bond dissociation free energies are 59.3(3) kcal mol(-1) for CpW(CO)(2)(IMes)H and 59(1) kcal mol(-1) for the dihydride [CpW(CO)(2)(IMes)(H)(2)](+) (where IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), indicating that the bonds are the same within experimental uncertainty for the neutral hydride and the cationic dihydride. For the radical cation, [CpW(CO)(2)(IMes)H](?+), W-H bond homolysis to generate the 16-electron cation [CpW(CO)(2)(IMes)](+) is followed by MeCN uptake, with free energies for these steps being 51(1) and -16.9(5) kcal mol(-1), respectively. Based on these two steps, the free energy change for the net conversion of [CpW(CO)(2)(IMes)H](?+) to [CpW(CO)(2)(IMes)(MeCN)](+) in MeCN is 34(1) kcal mol(-1), indicating a much lower bond strength for the 17-electron radical cation of the metal hydride compared to the 18-electron hydride or dihydride. The pK(a) of CpW(CO)(2)(IMes)H in MeCN was determined to be 31.9(1), significantly higher than the 26.6 reported for the related phosphine complex, CpW(CO)(2)(PMe(3))H. This difference is attributed to the electron donor strength of IMes greatly exceeding that of PMe(3). The pK(a) values for [CpW(CO)(2)(IMes)H](?+) and [CpW(CO)(2)(IMes)(H)(2)](+) were determined to be 6.3(5) and 6.3(8), much closer to the pK(a) values reported for the PMe(3) analogues. The free energy of hydride abstraction from CpW(CO)(2)(IMes)H is 74(1) kcal mol(-1), and the resultant [CpW(CO)(2)(IMes)](+) cation is significantly stabilized by binding MeCN to form [CpW(CO)(2)(IMes)(MeCN)](+), giving an effective hydride donor ability of 57(1) kcal mol(-1) in MeCN. Electrochemical oxidation of [CpW(CO)(2)(IMes)](-) is fully reversible at all observed scan rates in cyclic voltammetry experiments (E° = -1.65 V vs Cp(2)Fe(+/0) in MeCN), whereas CpW(CO)(2)(IMes)H is reversibly oxidized (E° = -0.13(3) V) only at high scan rates (800 V s(-1)). For [CpW(CO)(2)(IMes)(MeCN)](+), high-pressure NMR experiments provide an estimate of ΔG° = 10.3(4) kcal mol(-1) for the displacement of MeCN by H(2) to give [CpW(CO)(2)(IMes)(H)(2)](+).     

Modulation of properties in analogues of Zeise's anion on changing the ligand trans to ethene. X-ray crystal structures of trans-[PtCl2(OH)(η2-C2H4)]- and trans-[PtCl2(η1-CH2NO2)(η2-C2H4)]-

To get further insight in the reaction of nucleophilic substitution upon changing the ligand trans to a η(2)-olefin, the reactivity of some monoanionic platinum(II) complexes (trans-[PtCl(2)X(η(2)-C(2)H(4))](-), X = Cl(-), 1, OH(-), 2, and CH(2)NO(2)(-), 3) towards pyridines with different steric hindrance (py, 4-Mepy, and 2,6-Me(2)py) has been tested. All crystallographic (2 and 3 reported for the first time) and spectroscopic data are in accord with a platinum-olefin interaction decreasing in the order 2 > 1 > 3, paralleling the decreasing electronegativity of the donor atom (O > Cl > C). Not only the platinum-olefin bond but also the bond between platinum and the ligand trans to the olefin appear to be strongest in 2 (Pt-O distance at the lower limit for this type of bond). In the reaction with py, the ligand trans to the olefin is displaced in 1 and 2. Moreover the reaction is in equilibrium in the case of sterically hindered 2,6-Me(2)py, the equilibrium being shifted moderately or prevalently toward the reagents in the case of 1 and 2, respectively. In the case of 3, the reaction with pyridines leads to substitution of the olefin instead of the carbanion. This is in accord with the observation that carbanions strongly weaken the trans Pt-olefin bond.     

Synthesis and crystal structure of Cu(I) π-complexes with N-allyl-5-amino-1-phenyl-1H-1,2,3-triazole-4-carboxamide [Cu(C12H13N5O)(NO3)] · 0.5H2O and [Cu(C12H13N5O)(CF3COOH)]

Copper(I) ??-complexes of the compositions [Cu(C₁₂H₁₃N₅O)(NO₃)] · 0.5H₂O (1) and [Cu(C₁₂H₁₃N₅O)(CF₃COO)] (2) (C₁₂H₁₃N₅O is N-allyl-5-amino-1-phenyl-1H-1,2,3-triazole-4-carboxamide) were obtained by alternating-current electrochemical synthesis, and their crystal structures were studied by X-ray crystallography. Crystals of the compounds are monoclinic, space group C2/c with the unit cell parameters a = 21.3976(15) ?, b = 8.0335(4) ?, c = 18.6027(13) ?, ?? = 114.422(2)°, V = 2911.6(3) ?³, Z = 8 for 1; and a = 18.3578(18) ?, b = 9.8700(10) ?, c = 20.9094(18) ?, ?? = 106.883(3)°, V = 3625.3(6) ?³, Z = 8 for 2. In both structures, N-allyl-5-amino-1-phenyl-1H-1,2,3-triazole-4-carboxamide acts as a bridging tridentate chelating ligand and forms with copper(I) atoms infinite chains containing [CuC₄NO] seven-membered rings. The chains are linked to form a three-dimensional framework due to hydrogen bonds (N)H??O, which involve nitrogen atoms of amino and amide groups of the ligand. The coordination sphere of Cu(I) atoms consists of olefin bond of the allyl C=C group, O atom of the carbonyl group, N(3) atom of the triazole nucleus of the organic ligand, and an oxygen atom of nitrate (compound 1) or trifluoroacetate (compound 2) anion, respectively.     

Synthesis and structures of the η5-C5H5Cl(CO)2W-η1,η5-(PPh2)C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3 and MeSi[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)2PPh3]3 complexes

The metallation of the η⁵-C₅H₅(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex with BuⁿLi (THF, ?78 °C) followed by the treatment of the lithium derivative with Ph₂PCl afforded the η⁵-Ph₂PC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex. The reaction of the latter with η⁵-C₅H₅(CO)₃WCl in the presence of Me₃NO produced the trinuclear complex η⁵-C₅H₅Cl(CO)₂W-η¹,η⁵-(Ph₂P)C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃. The structure of the latter complex was established by IR, UV, and 1H and ³¹P NMR spectroscopy and X-ray diffraction. The reaction of MeSiCl₃ with three equivalents of LiC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃ gave the hexanuclear complex MeSi[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃]₃.     

The cleavage of a coordinated SCNR group in [Fe(CO)2L2(η2-SCNR)] by [Co(η-C5H5)(PPh3)2] to give complexes containing μ3-CNR ligand. The preparation and structure of [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S){μ3-CNC(O)C6H5}]

The reaction of [Fe(CO)₂(PPh₃)₂{η²-SCNC(O)Ph}] with [Co(η-C₅H₅)(PPh₃)₂] in benzene solution at room temperature results in the facile cleavage of the CS bond of the SCNC(O)Ph ligand to give [{Co(η-C₅H₅)}₂{Fe(CO)₂(PPh₃)}(μ₃-S{μ₃-CNC(O)Ph}], whereas [Fe(CO)₂(PPh₃)₂(η²-SCNMe)] gives [{Co(η-C₅H₅)} ₂₂{Fe(CO)(CNMe)(PPh₃)(μ₃-S)(μ₃-CO)]. The structure of [{Co(η-C₅H₅)}₂{Fe(CO)₂(PPh₃)} (μ₃-CNC(O)Ph}] has been confirmed by X-ray diffraction.     

Synthesis and molecular structure of [η5-C5H5Mo(CO)2]2(μ,η2-Sb2). Formation of an SbSb double bond from metallic antimony

The complex {[η⁵-C₅H₅Mo(CO)₂]₂(μ,η²-Sb₂)} (1), synthesized from the thermolytic reaction of [η⁵-C₅H₅Mo(CO)₃]₂ and elemental antimony, is the first example of μ,η² coordination of a four-electron diantimony fragment to a transition metal dimer. As determined by X-ray crystallography, 1 is a tetrahedral cluster characterized by a very short SbSb bond of 2.678(1) Å bound side-on to form a plane nearly perpendicular to an elongated MoMo bond of 3.114(1) Å.     

The Significant Influence of a Second Metal on the Antiproliferative Properties of the Complex [Ru(η6−C10H14)(Cl2)(dmoPTA)]

Complexes [Ru(η⁶−C₁₀H₁₄)(Cl₂)(HdmoPTA)](OSO₂CF₃) ( 1 ), [Ru(η⁶−C₁₀H₁₄)(Cl₂)(dmoPTA)] ( 2 ) and [Ru(η⁶−C₁₀H₁₄)(Cl₂)-μ-dmoPTA-1κP:2κ²N,N’-MCl₂] (M=Zn ( 3 ), Co ( 4 ), Ni ( 5 ), dmoPTA=3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) have been synthesized and characterized by elemental analysis and spectroscopic techniques. The crystal structures of 1 , 3 and 5 were obtained by single-crystal X-ray diffraction. The antiproliferative activity of the complexes was evaluated against colon cancer cell line Caco-2/TC7 by using the MTT protocol. The monometallic ruthenium complexes 1 and 2 were found to be inactive, but the bimetallic complexes 3 , 4 and 5 display an increased activity (IC₅₀ 3 : 9.07±0.27, 4 : 5.40±0.19, 5 : 7.15±0.30 μM) compared to cisplatin (IC₅₀=45.6±8.08 μM). Importantly, no reduction in normal cell viability was observed in the presence of the complexes. Experiments targeted to obtain information on the possible action mechanism of the complexes, such as cell cycle, ROS and gene expression studies, were performed. The results showed that the complexes display different properties and action mechanism depending on the nature of metal, M, bonded to the CH₃N_dmoPTA atoms.