Coordinated aqua vs methanol substitution kinetics in fac-Re(I) tricarbonyl tropolonato complexes.

Water-soluble fac-[Re(CO)(3)(L,L'-Bid)(X)] (L,L'-Bid = tropolonato, X = H(2)O, methanol) complexes have been synthesized, and the aqua and methanol substitution reactions were investigated in water (pH range 6.3-10.0) and methanol, respectively, and compared. Thiocyanate ions were used as monodentate entering ligand. The complexes were characterized by UV-vis, IR, and NMR spectroscopy. The crystal structures of the complexes [NEt(4)] fac-[Re(Trop)(CO)(3)(H(2)O)].NO(3).H(2)O (reactant) and fac-[Re(CO)(3)(Trop)(Py)], a substitution product, are reported. Overall it was found that the aqua substitution of fac-[Re(CO)(3)(Trop)(H(2)O)] is about 10 times faster than the methanol substitution reaction for fac-[Re(CO)(3)(Trop)(MeOH)], with forward and reverse rate and stability constants [k(1) (M(-1) s(-1)), k(-1) (s(-1)), K(1), (M(-1))] for thiocyanate as monodentate entering ligand as follows: fac-[Re(CO)(3)(Trop)(H(2)O)] = 2.54 ± 0.03, 0.0077 ± 0.0005, 330 ± 22/207 ± 14 and fac-[Re(CO)(3)(Trop)(MeOH)] = 0.268 ± 0.002, 0.0044 ± 0.0002, (61 ± 3)/(52 ± 4). The activation parameters [ΔH(‡)(k1) (kJ mol(-1)), ΔS(‡)(k1) (J K(-1) mol(-1))] for the aqua and methanol complex respectively are 56.1 ± 0.7, -49 ± 2 and 64 ± 1, -43 ± 5.

[Bis(pyridin-2-ylmeth-yl)amine-κ(3)N,N',N'']tricarbonyl-rhenium(I) bromide hemihydrate.

The title compound, fac-[Re(C(12)H(12)N(3))(CO)(3)]Br·0.5H(2)O, crystallizes with a cationic rhenium(I) unit, a bromide ion and half a water mol-ecule, situated on a twofold rotation axis, in the asymmetric unit. The Re(I) atom is facially surrounded by three carbonyl ligands and a tridentate bis-(pyridin-2-ylmeth-yl)amine ligand in a distorted octahedral environment. N-H⋯Br, O-H⋯Br, C-H⋯O and C-H⋯Br hydrogen bonds are present in the crystal structure and π-π stacking is also observed [centroid-centroid distances = 3.669 (1) Šand 4.054 (1) Å], giving rise to a three-dimentional network. The mol-ecules pack in a head-to-head fashion along the ac plane.

Bis[4-(4-bromophenylimino-κN)pent-2-en-2-olato-κO]copper(II).

In the title compound, [Cu(C(11)H(11)BrNO)(2)], the Cu(II) atom is in a distorted square-planar geometry, with the two bidentate ketimine ligands positioned in a trans geometry. Two inter-molecular C-H⋯O hydrogen bond inter-actions are present which link the mol-ecules in a zigzag manner along the a axis. The mol-ecules pack in layers along the diagonal of the bc plane.

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.

Mechanism for the formation of substituted manganese(V) cyanidonitrido complexes: crystallographic and kinetic study of the substitution reactions of trans-[MnN(H2O)(CN)4]2- with monodentate pyridine and bidentate pyridine-carboxylate ligands.

Dissolution of [(CH(3))N](2)Na[MnN(CN)(5)]·H(2)O in water results in the rapid dissociation of the trans-CN(-) ligand to form trans-[MnN(H(2)O)(CN)(4)](2-)(aq), which reacts with monodentate pyridine ligands such as 3-methyl and 4-methyl pyridine to form the corresponding mono-substituted complexes, of which the molecular structures obtained from X-ray crystallography, trans-[MnN(3-pic)(CN)(4)](2-) and trans-[MnN(4-pic)(CN)(4)](2-), are reported. [MnN(H(2)O)(CN)(4)](2-)(aq) also reacts with bidentate nucleophiles such as pyridine-2-carboxylate (pico) and quinoline-2-carboxylate (quino), yielding the corresponding [MnN(η(2)-pico)(CN)(3)](2-) and [MnN(η(2)-quino)(CN)(3)](2-) complexes as determined by X-ray crystallography. The formation kinetics of pyridine-2-carboxylate and three different pyridine-2,x-dicarboxylate ligands (x = 3, 4, 5) are reported, and two consecutive reaction steps are proposed, defined as the formation of the [MnN(η(1)-pico)(CN)(4)](3-) and [MnN(η(2)-pico)(CN)(3)](3-) complexes, respectively. Only the second steps could be spectrophotometrically observed and kinetically investigated. The first reaction is attributed to the rapid aqua substitution of [MnN(H(2)O)(CN)(4)](2-), thermodynamically unfavored and too fast to observe by conventional rapid third generation stopped-flow techniques. The second, slower reaction is attributed to cyanido substitution, with overall formation rate constants (25 °C; k(1)'; M(-1) s(-1)) and corresponding activation parameters (ΔH(k1')(double dagger), kJ mol(-1), ΔS(k1')(double dagger), J K(-1) mol(-1)) for the following entering bidentate nucleophiles: pyridine-2-carboxylate: (1.15 ± 0.04) × 10(-3), 102 ± 1, and 48 ± 3; pyridine-2,3-dicarboxylate: (1.1 ± 0.1) × 10(-3), 93 ± 2, and 20 ± 4; pyridine-2,4-dicarboxylate (8.5 ± 0.5) × 10(-4), 123 ± 5, and 115 ± 14; pyridine-2,5-dicarboxylate: (1.08 ± 0.04) × 10(-3), 106 ± 1, and 60 ± 2. A dissociative activation for the cyanido substitution process is proposed.

Tetra-ethyl-ammonium bromidotricarbon-yl(tropolonato)rhenate(I).

In the title salt, (C(8)H(20)N)[ReBr(C(7)H(5)O(2))(CO)(3)], the Re(I) atom is octa-hedrally surrounded by three facially orientated carbonyl ligands, one bidendate tropolonate ligand and a bromide ligand. The small O-Re-O bite angle of 74.88 (12)° leads to a distortion of the octa-hedral coordination sphere. The bromide ligand and the axial carbonyl ligand are substitutionally disordered over two positions in a 0.922 (3):0.078 (3) ratio. An array of C-H⋯O and C-H⋯Br hydrogen-bonding inter-actions between the cations and neighbouring rhenate anions stabilizes the crystal packing.

[N,N-Bis(diphenyl-phosphino)propyl-amine-κP,P]bromidotricarbonyl-rhenium(I).

In the title compound, [ReBr(C(27)H(27)NP(2))(CO)(3)], the Re(I) atom is octa-hedrally surrounded by three carbonyl ligands in a facial arrangement, a bromide ligand and the P,P'-bidentate ligand Bis(diphenyl-phosphino)propyl-amine. The compound exhibits substitutional disorder of the bromide ligand and the axial carbonyl ligand, with almost 50% occupancy for both Br amd CO [0.538 (4) and 0.462 (4), respectively]. In addition, the propyl chain on the N atom of the bidentate ligand exhibits a 0.648 (9):0.352 (9) disorder. C-H⋯O and C-H⋯Br hydrogen bonding consolidates the crystal packing.

Aqua-tricarbon-yl(4-carboxy-pyridine-2-carboxyl-ato-κN,O)rhenium(I).

There are two mol-ecules with similar bond dimensions in the asymmetric unit of the title complex, [Re(C(7)H(4)NO(4))(CO)(3)(H(2)O)]. The metal centre is coordinated facially by three carbonyl groups, is chelated by a 4-carboxy-pyridine-2-carboxyl-ate ligand and is also coordinated by a water mol-ecule. O-H⋯O hydrogen bonds give rise to a three-dimensional network.

Aqua-tricarbon-yl(3,5,7-tribromo-tropolonato)rhenium(I) methanol solvate.

The title complex, [Re(C(7)H(2)Br(3)O(2))(CO)(3)(H(2)O)]·CH(3)OH, crystallized as a neutral Re(I) compound and one methanol solvent mol-ecule in the asymmetric unit. The metal centre is coordinated facially by three carbonyl groups. The bidentate tribromo-tropolanate ligand and a water mol-ecule complete the distorted octahedral coordination around the central metal. Inter-molecular Br⋯O [3.226 (5) Å] and Br⋯Br [3.590 (2) Å] contacts are observed between adjacent mol-ecules. These contacts, together with an array of O-H⋯O, O-H⋯Br and C-H⋯O hydrogen bonds, complete a three-dimensional polymeric network formed between the methanol solvent and the complex.