Rhenium Dihydrogen Complexes with Isonitrile Coligands: Novel Displacement of Chloride by Hydrogen
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- 作者：D. M. Heinekey ; Mark H. Voges ; and David M. Barnhart
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：November 6, 1996
- 年：1996
- 卷：118
- 期：44
- 页码：10792 - 10802
- 全文大小：473K
- 年卷期：v.118,no.44(November 6, 1996)
- ISSN：1520-5126
文摘
The syntheses, properties, and characterization ofseveral new complexes,Re(CNtBu)3(PCy3)2H(1a),Re(CNtBu)3(PR3)2Cl[R = Cy, Ph (2a, 2b)], the 17-electron[Re(CNtBu)3(PCy3)2Cl]+(3a), the dihydrogen complex,[Re(CNtBu)3(PR3)2(H2)]+[R = Cy, Ph (4a, 4b)], the coordinativelyunsaturated[Re(CNtBu)3(PCy3)2]+(5a), and[Re(CNtBu)4(PCy3)2]+(6a) are reported. In addition, spectroscopic evidencefor the dinitrogen complex[Re(CNtBu)3(PCy3)2(N2)]+and the dihydrogen complex[Re(CNtBu)5(H2)]+is presented. Thermodynamic parameters have beenobtained for the equilibrium system,Re(CNtBu)3(PCy3)2Cl(2a) + H2 
[Re(CNtBu)3(PCy3)2(H2)]Cl(4a). 1H and31P{1H} NMR studies(CD2Cl2) over the temperature range286-316 K afford values of 
H
= -18.0 ± 0.7kcal/mol, S = -44 ± 2 eu, andG298 = -4.8 ± 1.3 kcal/mol for thisequilibrium. The complexes 4a and 4barecharacterized as dihydrogen complexes. TheirJHD (R = Cy, 30.3 Hz; R = Ph, 30.9 Hz) andT1(min) values of 8 ms(300 MHz) are consistent with H-H distances of ca. 0.80Å.[Re(CNtBu)5(HD)]+is also characterized as a dihydrogencomplex based on a JHD of 33.4 Hz. Thiscomplex could not be isolated at room temperature, even withnon-coordinating counteranions, due to the lability of the H2ligand.[Re(PMe3)5HD]+ showsno H-D coupling and ischaracterized as a dihydride complex. The unsaturated complex[Re(CNtBu)3(PCy3)2]+(5a) is found to undergo adynamic isonitrile rearrangement on the NMR time scale.1H NMR spin saturation transfer studies over atemperaturerange of 254-297 K afford the activation parametersH
= 11.4 ± 0.8 kcal/mol,S = -17.6 ± 1.6 eu, andG298 = 16.6 ± 1.2kcal/mol. The molecular structures of 2a and3a have been determined by X-raycrystallography.2a shows an unusually long Re-Cl bond distance of2.596(2) Å.
[Re(CNtBu)3(PCy3)2(H2)]Cl(4a). 1H and31P{1H} NMR studies(CD2Cl2) over the temperature range286-316 K afford values of H = -18.0 ± 0.7kcal/mol, S = -44 ± 2 eu, andG298 = -4.8 ± 1.3 kcal/mol for thisequilibrium. The complexes 4a and 4barecharacterized as dihydrogen complexes. TheirJHD (R = Cy, 30.3 Hz; R = Ph, 30.9 Hz) andT1(min) values of 8 ms(300 MHz) are consistent with H-H distances of ca. 0.80Å.[Re(CNtBu)5(HD)]+is also characterized as a dihydrogencomplex based on a JHD of 33.4 Hz. Thiscomplex could not be isolated at room temperature, even withnon-coordinating counteranions, due to the lability of the H2ligand.[Re(PMe3)5HD]+ showsno H-D coupling and ischaracterized as a dihydride complex. The unsaturated complex[Re(CNtBu)3(PCy3)2]+(5a) is found to undergo adynamic isonitrile rearrangement on the NMR time scale.1H NMR spin saturation transfer studies over atemperaturerange of 254-297 K afford the activation parametersH = 11.4 ± 0.8 kcal/mol,S = -17.6 ± 1.6 eu, andG298 = 16.6 ± 1.2kcal/mol. The molecular structures of 2a and3a have been determined by X-raycrystallography.2a shows an unusually long Re-Cl bond distance of2.596(2) Å.