Department of Chemistry, PO Box 339 and University of the Free State, 9300 Bloemfontein, Republic of South Africa.
Dalton Trans. 2013 Jun 28;42(24):8655-66. doi: 10.1039/c3dt50310k. Epub 2013 Apr 30.
An experimental and computational chemistry study of the reactivity of [Rh(β-diketonato)(CO)(P(OCH2)3CCH3)] complexes towards chemical and electrochemical oxidation shows that more electron withdrawing groups on the β-diketonato ligand reduce electron density on the rhodium atom to a larger extent than electron donating groups. This leads to a slower second-order oxidative addition rate, k1, and a higher electrochemical oxidation potential, E(pa)(Rh), linearly related by ln k1 = -11(1) E(pa)(Rh) - 2.3(5). The reactivity of these complexes can be predicted by their DFT calculated HOMO energies: E(HOMO) = -0.34(8)E(pa)(Rh) - 5.04(4) = 0.032(5) ln k1- 4.96(4). k1 of [Rh(β-diketonato)(CO)(P(OCH2)3CCH3)] complexes is slower than that of related [Rh(β-diketonato)(CO)(PPh3)] and [Rh(β-diketonato)(P(OPh)3)2] complexes due to the better π-acceptor ability of the CO-phosphite-rhodium combination than that of CO-PPh3-rhodium or di-phosphite-rhodium.
[Rh(β-二酮)(CO)(P(OCH2)3CCH3)] 配合物的反应性的实验和计算化学研究表明，β-二酮配体上的吸电子基团比供电子基团更能大大降低铑原子上的电子密度。这导致较慢的二级氧化加成速率 k1 和较高的电化学氧化电位 E(pa)(Rh)，它们之间呈线性关系 ln k1 = -11(1) E(pa)(Rh) - 2.3(5)。这些配合物的反应性可以通过它们的 DFT 计算的 HOMO 能量来预测：E(HOMO) = -0.34(8)E(pa)(Rh) - 5.04(4) = 0.032(5) ln k1- 4.96(4)。由于 CO-亚磷酸酯-铑的配合物的π-接受能力比 CO-PPh3-铑或二亚磷酸酯-铑的配合物更强，因此 [Rh(β-二酮)(CO)(P(OCH2)3CCH3)] 配合物的 k1 比相关的 [Rh(β-二酮)(CO)(PPh3)] 和 [Rh(β-二酮)(P(OPh)3)2] 配合物慢。
