Structure/reactivity relationships and mechanism from X-ray data and spectroscopic kinetic analysis

Exploring the in vitro anticancer activities of Re(I) picolinic acid and its fluorinated complex derivatives on lung cancer cells: a structural study

Fifteen rhenium(I) tricarbonyl complexes of the form fac-[Re(N,O')(CO)₃(X)], where N,O'-bidentate ligand = 2-picolinic acid (Pico); 3,5-difluoropyridine-2-carboxylic acid (Dfpc); 3-trifluoromethyl-pyridine-2-carboxylic acid (Tfpc) and X = H₂O; pyrazole (Pz); pyridine (Py); imidazole (Im); and methanol (CH₃OH) were synthesized using the '2 + 1' mixed ligand approach with an average yield of 84%. The complexes were characterized using the following spectroscopic techniques: IR, ¹H and ¹³C NMR, UV/Vis, and single-crystal X-ray diffraction. The effect of the fluorine atoms on the backbone of the N,O'-bidentate ligand was investigated and a trend was noticed in the carbonyl stretching frequencies: with Pico < Tfpc < Dfpc. The in vitro biological screening on Vero (healthy mammalian), HeLa (cervical carcinoma) and A549 (lung cancer) cells revealed one toxic complex, fac-[Re(Pico)(CO)₃(H₂O)], with respective LC₅₀ values of 9.0 ± 0.9, 15.8 ± 4.9 (SI = 0.570) and 20.9 ± 0.8 (SI = 0.430) μg/mL. As a result, it can be used as a positive control drug of toxicity.

Structural Study of Model Rhodium(I) Carbonylation Catalysts Activated by Indole-2-/Indoline-2-Carboxylate Bidentate Ligands and Kinetics of Iodomethane Oxidative Addition

The rigid-backbone bidentate ligands Indoline-2-carboxylic acid (IndoliH) and Indole-2-carboxylic acid (IndolH) were evaluated for rhodium(I). IndoliH formed [Rh(Indoli)(CO)(PPh3)] (A2), while IndolH yielded the novel dinuclear [Rh1(Indol’)(CO)(PPh3)Rh2(CO)(PPh3)2] (B2) complex (Indol’ = Indol2−), which were characterized by SCXRD. In B2, the Rh1(I) fragment [Rh1(Indol’)(CO)(PPh3)] (bidentate N,O-Indol) exhibits a square-planar geometry, while Rh2(I) shows a ‘Vaska’-type trans-[O-Rh2(PPh3)2(CO)] configuration (bridging the carboxylate ‘oxo’ O atom of Indol2−). The oxidative addition of MeI to A2 and B2 via time-resolved FT-IR, NMR, and UV/Vis analyses indicated only Rh(III)-alkyl species (A3/B3) as products (no migratory insertion). Variable temperature kinetics confirmed an associative mechanism for A2 via an equilibrium-based pathway (ΔH≠ = (21 ± 1) kJ mol−1; ΔS≠ = (−209 ± 4) J K−1mol−1), with a smaller contribution from a reverse reductive elimination/solvent pathway. The dinuclear complex B2 showed the oxidative addition of MeI only at Rh1(I), which formed a Rh(III)-alkyl, but cleaved the bridged Rh2(I) site, yielding trans-[RhI(PPh3)2(I)(CO)] (5B) as a secondary product. A significantly smaller negative activation entropy [ΔH≠ = (73.0 ± 1.2) kJ mol−1; ΔS≠ = (−21 ± 4) J K−1mol−1] via a more complex/potential interchange mechanism (the contribution of ΔS≠ to the Gibbs free energy of activation, ΔG≠, only ±10%) was inferred, contrary to the entropy-driven oxidative addition of MeI to A2 (the contribution of ΔS≠ to ΔG≠ ± 75%).

The crystal structure of dicarbonyl-(N-nitroso-N-oxido-phenylamine-κ 2 O,O)-rhodium(I), C8H5N2O4Rh

C8H5N2O4Rh, monoclinic, P21/c (no. 14), a = 14.1998(9) Å, b = 3.6516(2) Å, c = 17.7458(11) Å, β = 92.801(2)°, V = 919.06(10) Å3, Z = 4, R gt(F) = 0.0281, wR ref(F 2) = 0.0702, T = 100 K.

The crystal structure of (carbonato κ2 O,O′)(2-oxopyridin-1(2H)-olato-κN)tris(trimethylphosphine)rhodium(III) water solvate, C15H33NO5P3Rh

C15H33NO5P3Rh, orthorhombic, Pnma (no. 62), a = 19.8694(11) Å, b = 12.5765(7) Å, c = 8.6990(5) Å, V = 2173.8(2) Å3, Z = 1, Rgt (F) = 0.0394, wRref (F 2) = 0.0941, T = 100 K, α = β = γ = 90°.

Induced fit activity-based sensing: a mechanistic study of pyrophosphate detection with a "flexible" Fe-salen complex

Activity-based sensing of biological targets is attracting increasing attention. In this work, we report detailed UV-Vis and fluorescence mechanistic studies on an Fe-salen based probe, [Fe^III{salenMeCl₂(SO₃)₂}OH₂]⁻ for pyrophosphate (PPi) detection. In the presence of PPi as an analyte, the probe disassembles into its molecular subunits and releases a fluorescent signal. Our studies illustrate that the aqua form of the complex (1-OH2) is the active species and that upon substitution of Fe-coordinated H₂O and an initial end-on coordination of HP₂O₇³⁻, the “trapped” pyrophosphate species switches from a monodentate to a bidentate coordination mode (i.e. linkage isomerism) via a probable equilibrium process. The elusive intermediate is further stabilized by a hydrogen bonding interaction that activates the probe for the subsequent final irreversible rate-limiting step, and allows selective discrimination between the other pyrophosphate (H₂P₂O₇²⁻ and P₂O₇⁴⁻) species in favour of the HP₂O₇³⁻. The flexible mode of molecular recognition and binding of HP₂O₇³⁻ by the tetradentate probe 1-OH2 is unexpected and most effective at physiological pH, and has precedence in enzymatic catalysis (i.e. induced fit principle). These binding properties explain the previously observed outstanding selectivity of 1-OH2 for pyrophosphate over other (poly)oxophosphates and potentially competing analytes.

A detailed mechanistic study of pyrophosphate (PPi) detection with a fluorometric Fe-salen based probe unravels the key structural switch of the Fe-bound PPi (“induced fit principle”) explaining the novel selectivity over other competing analytes.

Crystal structure of monocarbonyl(N-nitroso-N-oxido-phenylamine-κ 2 O,O′)(tricyclohexylphosphine-κP)rhodium(I), C25H39N2O3PRh

C25H39N2O3PRh, triclinic, P21/n (no. 14), a = 13.505(5) Å, b = 14.266(5) Å, c = 13.405(4) Å, β = 91.280(3)°, V = 2574.8(15) Å3, Z = 4, R gt (F) = 0.0399, wR ref (F 2) = 0.1026, T = 100 K.

Crystal structure of carbonyl(2-methylquinolin-8-olato-κ2 N,O)(triphenylarsine-κAs)rhodium(I), C29H23AsNO2Rh

C 29 H 23 AsNO 2 ${\text{C}}_{29}{\text{H}}_{23}{\text{AsNO}}_{2}$ Rh, triclinic, P 1 ‾ $P&#x203e;{1}$ (no. 2), a = 9.2778(18) Å, b = 9.8274(16) Å, c = 14.444(3) Å, α = 99.748(6)°, β = 91.330(7)°, γ = 114.197(6)°, V = 1177.6(4) Å3, Z = 2, R g t ${R}_{gt}$ (F) = 0.0552, w R r e f $w{R}_{ref}$ (F 2) = 0.1005, T = 100 K.

Crystal structure of carbonyl(2-oxopyridin-1(2H)-olato-k2 O,O′)(triphenylarsine-κAs)rhodium(I), C24H19AsNO3Rh

C24H19AsNO3Rh, triclinic, P 1 ‾ $&#x203e;{1}$ (no. 2), a = 9.1358(5) Å, b = 9.6478(6) Å, c = 12.4509(7) Å, α = 92.303(2)°, β = 106.281(2)°, γ = 99.137(2)°, V = 1035.89(1) Å3, Z = 2, R gt (F) = 0.0336, wR ref (F 2) = 0.0900, T = 100 K.

Crystal structure of monocarbonyl[2-((cyclopentylmethylene)amino)-5-methylphenolato-κ2N,O] (tricyclohexylphosphine)rhodium(I), C32H48NO2PRh

C32H48NO2PRh, orthorhombic, P212121 (no. 19), a = 26.784(10) Å, b = 8.837(3) Å, c = 12.759(4) Å, V = 3020.0(18) Å3, Z = 4, R gt(F) = 0.0400, wR ref(F 2) = 0.0920, T = 100(2) K.

The crystal structure of trans-carbonyl-(diphenylcyclohexyl-phosphine-κP)iodidomethyl-(2-oxopyridin-1(2H)-olato-κ2 O,O′)rhodium(III), C25H28INO3PRh

C25H28INO3PRh, monoclinic, P21/c (no. 14), a = 11.339(4) Å, b = 9.887(5) Å, c = 23.069(9) Å, β = 91.125(5)°, Z = 4, V = 2585.7(19) Å3, R gt(F) = 0.0463, wR ref(F 2) = 0.1093, T = 293(2) K.

Why is interoperability between the two fields of chemical crystallography and protein crystallography so difficult?

The interoperability of chemical and biological crystallographic data is a key challenge to research and its application to pharmaceutical design. Research attempting to combine data from the two disciplines, small-molecule or chemical crystallography (CX) and macromolecular crystallography (MX), will face unique challenges including variations in terminology, software development, file format and databases which differ significantly from CX to MX. This perspective overview spans the two disciplines and originated from the investigation of protein binding to model radiopharmaceuticals. The opportunities of interlinked research while utilizing the two databases of the CSD (Cambridge Structural Database) and the PDB (Protein Data Bank) will be highlighted. The advantages of software that can handle multiple file formats and the circuitous route to convert organometallic small-molecule structural data for use in protein refinement software will be discussed. In addition some pointers to avoid being shipwrecked will be shared, such as the care which must be taken when interpreting data precision involving small molecules versus proteins.

Ambient and high-pressure kinetic investigation of methanol substitution in fac-[Re(Trop)(CO)3(MeOH)] by different monodentate nucleophiles

First report of high-pressure methanol substitution by entering monodentate L forms fac-[Re(CO)₃(Trop)(L)] {ΔV^≠_(kL) = +9 – +14 cm⁻³ mol⁻¹}, indicating dissociative/dissociative interchange activation.

Mechanism of generation of closo-decaborato amidrazones. Intramolecular non-covalent B–H⋯π(Ph) interaction determines stabilization of the configuration around the amidrazone CN bond

Three types of N(H)-nucleophiles were used to study the nucleophilic addition to the CN group of the 2-propanenitrilium closo-decaborate cluster giving N-closo-decaborato amidrazones.

Crystal structure of hexacarbonyl bis(μ2-2-methoxybenzenethiolato-κ2S)pyridine(triphenylphosphane)dirhenium(I), C43H34NO8PS2Re2

C43H34NO8PS2Re2, monoclinic, P21/c (no. 14), a = 12.165(8) Å, b = 19.027(11) Å, c = 18.848(14) Å, β = 108.735(2)°, V = 4131(5) Å3, Z = 4, Rgt(F) = 0.0308, wRref(F2) = 0.0683, T = 100(2) K.

Crystal structure of bis(μ2-2-((3-methylphenyl)imino)methylphenolato-κ2 N,O:O)hexacarbonyldimanganese(I), C34H24Mn2N2O8

C34H24Mn2N2O8, triclinic, P1̅ (no. 2) a = 7.737(5) Å, b = 9.483(5) Å, c = 11.309(5) Å, β = 102.514(5)°, V = 766.6(7) Å3, Z = 1, R gt (F) = 0.0478, wR ref (F 2 ) = 0.1297, T = 100(2) K

Crystal structure of tetraethylammonium hexachloridotantalate(V), C8H20Cl6NTa

C8H20Cl6N1Ta1, monoclinic, P 2 1/n (no. 14), a = 7.1550(4) Å, b = 10.0090(6) Å, c = 11.6290(4) Å, β = 98.487(5)°, V = 823.7(8) Å3, Z = 2, R gt (F) = 0.0207, wR ref (F 2 ) = 0.0531, T = 100(2) K.

Solid state isostructural behavior and quantified limiting substitution kinetics in Schiff-base bidentate ligand complexes fac-[Re(O,N-Bid)(CO)3(MeOH)](n)

A range of N,O-donor atom salicylidene complexes of the type fac-[M(O,N-Bid)(CO)3(L)](n) (O,N-Bid = anionic N,O-bidentate ligands; L = neutral coordinated ligand) have been studied. The unique feature of the complexes which crystallize in a monoclinic isostructural space group for complexes containing methanol in the sixth position (L = MeOH) is highlighted. The reactivity and stability of the complexes were evaluated by rapid stopped-flow techniques, and the methanol substitution by a range of pyridine type ligands indicates significant activation by the N,O-salicylidene type of bidentate ligands as observed from the variation in the second-order rate constants. In particular, following the introduction of the sterically demanding and electron rich cyclohexyl salicylidene moiety on the bidentate ligand, novel limiting kinetic behavior is displayed by all entering ligands, thus enabling a systematic probe and manipulation of the limiting kinetic constants. Clear evidence of an interchange type of intimate mechanism for the methanol substitution is produced. The equilibrium and rate constants (25 °C) for the two steps in the dissociative interchange mechanism for methanol substitution in fac-[Re(Sal-Cy)(CO)3(MeOH)] (5) by the pyridine type ligands 3-chloropyridine, pyridine, 4-picoline, and DMAP are k3 (s(-1)), 40 ± 4, 13 ± 2, 10.4 ± 0.7, and 2.11 ± 0.09, and K2 (M(-1)), 0.13 ± 0.01, 0.21 ± 0.03, 0.26 ± 0.02, and 1.8 ± 0.1, respectively.

Crystal structure of (N-benzoyl-N'-(2,4,6-trimethylphenyl)thiourea-κS)chlorido(η4-cycloocta-1,5-diene) rhodium(I), C25H30ClN2ORhS

C25H30ClN2ORhS, monoclinic, C2/c (no. 15), a = 22.508(2) Å, b = 8.5005(7) Å, c = 24.884(2) Å, β = 93.551(4)°, V = 4751.7 Å3, Z = 8, Rgt(F) = 0.0355, wRref(F2) = 0.0767, T = 100 K.

Crystal structure of bis(triphenylphosphine)(carbonyl)(N-benzoyl-N'-(2-methyl-4-hydroxyphenyl)thioureato-κS,κN)rhodium(I), C52H43N2O3P2RhS

C52H43N2O3P2RhS, triclinic, P1̅ (no. 2), a = 10.6260(3) Å, b = 11.7305(3) Å, c = 19.6582(5) Å, α = 76.489(1)°, β = 82.027(1)°, γ = 64.848(1)°, V = 2154.4 Å3, Z = 2, Rgt(F) = 0.028, wRref(F2) = 0.0722, T = 100 K.

Activation of rhenium(I) toward substitution in fac-[Re(N,O'-Bid)(CO)3(HOCH3)] by Schiff-base bidentate ligands (N,O'-Bid)

A series of fac-[Re(N,O'-Bid)(CO)3(L)] (N,O'-Bid = monoanionic bidentate Schiff-base ligands with N,O donor atoms; L = neutral monodentate ligand) has been synthesized, and the methanol substitution reactions have been investigated. The complexes were characterized by NMR, IR, and UV-vis spectroscopy. X-ray crystal structures of the compounds fac-[Re(Sal-mTol)(CO)3(HOCH3)], fac-[Re(Sal-pTol)(CO)3(HOCH3)], fac-[Re(Sal-Ph)(CO)3(HOCH3)], and fac-[Re(Sal-Ph)(CO)3(Py)] (Sal-mTol = 2-(m-tolyliminomethyl)phenolato; Sal-pTol = 2-(p-tolyliminomethyl)phenolato; Sal-Ph = 2-(phenyliminomethyl)phenolato; Py = pyridine) are reported. Significant activation for the methanol substitution is induced by the use of the N,O bidentate ligand as manifested by the second order rate constants, with limiting kinetics being observed for the first time. Rate constants (25 °C) (k1 or k3) and activation parameters (ΔHk‡, kJ mol(-1); ΔSk‡, J K(-1) mol(-1)) from Eyring plots for entering nucleophiles as indicated are as follows: fac-[Re(Sal-mTol)(CO)3(HOCH3)] 3-chloropyridine: (k1) 2.33 ± 0.01 M(-1) s(-1); 85.1 ± 0.6, 48 ± 2; fac-[Re(Sal-mTol)(CO)3(HOCH3)] pyridine: (k1) 1.29 ± 0.02 M(-1) s(-1); 92 ± 2, 66 ± 7; fac-[Re(Sal-mTol)(CO)3(HOCH3)] 4-picoline: (k1) 1.27 ± 0.05 M(-1) s(-1); 88 ± 2, 53 ± 6; (k3) 3.9 ± 0.03 s(-1); 78 ± 8, 30 ± 27; (kf) 1.7 ± 0.02 M(-1) s(-1); 86 ± 2, 49 ± 6; fac-[Re(Sal-mTol)(CO)3(HOCH3)] DMAP (k3) 1.15 ± 0.02 s(-1); 88 ± 2, 52 ± 7. An interchange dissociative mechanism is proposed.

Ethylene tri- and tetramerization: a steric parameter selectivity switch from X-ray crystallography and computational analysis

A steric parameter (θN-sub) is introduced to describe the steric bulk at the nitrogen atom on a range of PNP ligands used in ethylene tri- and tetramerization. This parameter was calculated for the free ligands and different metal complexes thereof and compared to catalytic data. A specific tendency is observed for the value of θN-sub and 1-hexene selectivity, and a slight increase in 1-octene selectivity is found with increased bulkiness of the substituents on the nitrogen atom.

N,N'-(4,5-Dimethyl-1,2-phenyl-ene)bis-(pyridine-2-carboxamide)

In the title compound, C₂₀H₁₈N₄O₂, the dihedral angles between the central benzene ring and the pyridine rings are 57.55 (6) and 22.05 (8)°. The mol­ecular conformation is stabilized by intra­molecular N—H⋯N inter­actions and in the crystal structure an inter­molecular asymmetric cyclic hydrogen-bonding association involving both amide N—H donors and a common amide O-atom acceptor gives a chain extending along the c axis.

(N-Benzoyl-N',N'-diphenyl-thio-ureato-κ(2)S,O)(η(4)-cyclo-octa-1,5-diene)rhodium(I)

The title complex, [Rh(C(20)H(15)N(2)OS)(C(8)H(12))], exhibits an essentially square-planar coordination environment around the Rh(I) atom, which bears a bidentate cyclo-octa-diene ligand as well as a monoanionic bidentate benzoyl-thio-ureate ligand. The Rh(I) atom, the S- and O-donor atoms and the alkene centroids of the cyclo-octa-diene ligand do not deviate by more than 0.031 Å from their least mean-squares plane.

Dicarbon-yl[4-(2,6-dimethyl-phenyl-amino)-pent-3-en-2-onato-κ(2)N,O]rhodium(I)

In the title compound, [Rh(C₁₃H₁₆NO)(CO)₂], a square-planar coordination geometry is observed around the Rh^I atom, formed by the N and O atoms of the bidentate ligand and two C atoms from two carbonyl ligands. The Rh^I atom is displaced from the plane through these surrounding atoms by 0.0085 (2) Å. The dihedral angle between the benzene ring and the N—C—C—C—O plane is 89.82 (6)°, and the N—Rh—O bite angle for the bidentate ligand is 90.53 (6)°. An inter­molecular C—H⋯O inter­action is observed between a methyl group of the benzene ring and a carbonyl O atom.

Oxidative addition of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)]: an experimental and computational study

The reaction rate of the oxidative addition and CO insertion steps of methyl iodide with [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)] are presented. Large negative experimental values for the activation entropy and results from a density functional theory computational chemistry study indicated trans addition of the CH3I to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)]. A study of the molecular orbitals gives insight into the flow of electrons during the oxidative addition reaction. CO insertion leads to a square pyramidal [Rh(PhCOCHCOPh)(P(OCH2)3CCH3)(COCH3)(I)] acyl product with the COCH3 moiety in the apical position. The strong electron donation of the P(OCH2)3CCH3 ligand accelerates the oxidation addition step of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)] by ca. 265 times faster (at 35°C) than that of the Monsanto catalyst, but inhibits the CO insertion step.

5-(3,4-Dimeth-oxy-benzyl-idene)-1,3-dimethyl-1,3-diazinane-2,4,6-trione

In the title compound, C(15)H(16)N(2)O(5), the dihedral angle between 1,3-diazinane and benzene rings is only 4.27 (1)°. The essentially planar mol-ecular structure is characterized by a short intra-molecular C-H⋯O separation and by an exceptionally large bond angle of 138.25 (14)° at the bridging methine C atom. The meth-oxy groups deviate somewhat from the plane of the benzene ring, with C-C-O-C torsion angles of -15.6 (1) and 9.17 (6)°. In the crystal, mol-ecules form centrosymmetric dimers via donor-acceptor π-π inter-actions, with a centroid-centroid distance of 3.401 (1) Å.

Dimethyl 2,6-dimethyl-4-phenylpyridine-3,5-dicarboxylate

In the title compound, C₁₇H₁₇NO₄, the dihedral angle between the benzene and pyridine rings is 75.51 (4)°. The benzene and pyridine rings are both approximately planar (r.m.s. deviations of 0.0040 and 0.0083 Å, respectively), indicating that the pyridine N atom is not protonated. The crystal structure is stabilized by weak inter­molecular C—H⋯O and C—H⋯N inter­actions.

cyclo-Tetra-μ-oxido-tetra-kis-[(acetyl-acetonato-κO,O')bis-(ethano-lato-κO)niobium(V)]

The asymmetric unit of the title tetra­nuclear niobium(V) compound, [Nb₄(C₂H₅O)₈(C₅H₇O₂)₄O₄], contains two Nb^V atoms, two bridging O atoms, two acetyl­acetonate and four ethano­late ligands. Each Nb^V atom is six-coordinated by the bridging O atoms, two ethano­late and one chelating acetyl­acetonate ligands. The Nb—O distances vary between 1.817 (2) and 2.201 (2) Å and the O—Nb—O angles vary between 78.88 (8) and 102.78 (9)°, illustrating the significant distortion from ideal ocahedral geometry. The rest of the tetra­nuclear unit is generated through an inversion centre. The C atoms of two of the ethano­late mol­ecules are disordered over two sites [occupancy ratio 0.601 (12):0.399 (12)].

Tuning the reactivity in classic low-spin d6 rhenium(I) tricarbonyl radiopharmaceutical synthon by selective bidentate ligand variation (L,L'-Bid; L,L'= N,N', N,O, and O,O' donor atom sets) in fac-[Re(CO)3(L,L'-Bid)(MeOH)]n complexes

A range of fac-[Re(CO)(3)(L,L'-Bid)(H(2)O)](n) (L,L'-Bid = neutral or monoanionic bidentate ligands with varied L,L' donor atoms, N,N', N,O, or O,O': 1,10-phenanthroline, 2,2'-bipydine, 2-picolinate, 2-quinolinate, 2,4-dipicolinate, 2,4-diquinolinate, tribromotropolonate, and hydroxyflavonate; n = 0, +1) has been synthesized and the aqua/methanol substitution has been investigated. The complexes were characterized by UV-vis, IR and NMR spectroscopy and X-ray crystallographic studies of the compounds fac-[Re(CO)(3)(Phen)(H(2)O)]NO(3)·0.5Phen, fac-[Re(CO)(3)(2,4-dQuinH)(H(2)O)]·H(2)O, fac-[Re(CO)(3)(2,4-dQuinH)Py]Py, and fac-[Re(CO)(3)(Flav)(CH(3)OH)]·CH(3)OH are reported. A four order-of-magnitude of activation for the methanol substitution is induced as manifested by the second order rate constants with (N,N'-Bid) < (N,O-Bid) < (O,O'-Bid). Forward and reverse rate and stability constants from slow and stopped-flow UV/vis measurements (k(1), M(-1) s(-1); k(-1), s(-1); K(1), M(-1)) for bromide anions as entering nucleophile are as follows: fac-[Re(CO)(3)(Phen)(MeOH)](+) (50 ± 3) × 10(-3), (5.9 ± 0.3) × 10(-4), 84 ± 7; fac-[Re(CO)(3)(2,4-dPicoH)(MeOH)] (15.7 ± 0.2) × 10(-3), (6.3 ± 0.8) × 10(-4), 25 ± 3; fac-[Re(CO)(3)(TropBr(3))(MeOH)] (7.06 ± 0.04) × 10(-2), (4 ± 1) × 10(-3), 18 ± 4; fac-[Re(CO)(3)(Flav)(MeOH)] 7.2 ± 0.3, 3.17 ± 0.09, 2.5 ± 2. Activation parameters (ΔH(k1)(++), kJmol(-1); ΔS(k1)(), J K(-1) mol(-1)) from Eyring plots for entering nucleophiles as indicated are as follows: fac-[Re(CO)(3)(Phen)(MeOH)](+) iodide 70 ± 1, -35 ± 3; fac-[Re(CO)(3)(2,4-dPico)(MeOH)] bromide 80.8 ± 6, -8 ± 2; fac-[Re(CO)(3)(Flav)(MeOH)] bromide 52 ± 5, -52 ± 15. A dissociative interchange mechanism is proposed.

fac-Tricarbon-yl(pyridine-κN)(1,1,1-trifluoro-acetyl-acetonato-κO,O')rhenium(I)

In the title compound, [Re(C(5)H(4)F(3)O(2))(C(5)H(5)N)(CO)(3)], the Re(I) atom is six-coordinated owing to bonding by three carbonyl ligands arranged in a fac configuration, two O atoms from the bidentate 1,1,1-trifluoro-acetyl-acetonate ligand and an N atom from a pyridine ligand. In the crystal, the mol-ecules pack in layers, diagonally, in a head-to-tail fashion across the ab plane. These layers are stabilsed by inter-molecular C-H⋯O and C-H⋯F hydrogen bonds.