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Download fileActivation of Rhenium(I) Toward Substitution in fac-[Re(N,O′-Bid)(CO)3(HOCH3)] by Schiff-Base Bidentate Ligands (N,O′-Bid)
dataset
posted on 2016-02-19, 02:12 authored by Alice Brink, Hendrik G. Visser, Andreas RoodtA 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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