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.

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.

In the salt (C8H20N)[ReBr(C7H2Br3O2)(CO)3], the bromidotricarbonyl(tribromotropolonato)rhenate(I) anion interacts with adjacent anions through intermolecular bromido–bromido interactions [3.2675 (5)–3.4962 (4) Å]. The ReI atom shows octahedral coordination. The crystal structure also involves C—H...O and C—H...Br interactions.

Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.009 Å; R factor = 0.033; wR factor = 0.079; data-to-parameter ratio = 17.4.

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.