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-m Tol)(CO) 3 (HOCH3)], fac-[Re (Sal-p Tol)(CO) 3 (HOCH3)], fac-
[Re (Sal-Ph)(CO) 3 (HOCH3)], and fac-[Re (Sal-Ph)(CO) 3 (Py)](Sal-m Tol= 2-(m …
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-m Tol)(CO) 3 (HOCH3)], fac-[Re (Sal-p Tol)(CO) 3 (HOCH3)], fac-
[Re (Sal-Ph)(CO) 3 (HOCH3)], and fac-[Re (Sal-Ph)(CO) 3 (Py)](Sal-m Tol= 2-(m …
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.
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