Paired interacting orbitals (PIO) analysis of electronic structures of copper(I) complexes with hydrotris(pyrazolyl)borate ligands

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• 作者：Akinobu Shiga ; Kiyoshi Fujisawa
• 关键词：Paired interaction orbitals (PIO) analysis ; Copper complex ; Carbon monoxide ; Back donation ; Phosphine
• 刊名：Journal of Molecular Structure: THEOCHEM
• 出版年：2009
• 出版时间：15 November 2009
• 年：2009
• 卷：913
• 期：1-3
• 页码：173-178
• 全文大小：539 K

文摘

The influence of the hydrotris(pyrazolyl)borate (tpzb) ligand substituents on the electron delocalization of the copper(I) center with carbon monoxide and triphenylphosphine, i.e. the copper(I) carbonyl complexes, [Cu{HB(3,5-iPr₂pz)₃}(CO)] (1), [Cu{HB(3,5-Me₂pz)₃}(CO)] (2), [Cu{HB(pz)₃}(CO)] (3), [Cu{HB(3-CF₃-5-Mepz)₃}(CO)] (4), and the copper(I) triphenylphosphine complexes [Cu{HB(3,5-iPr₂pz)₃}(PPh₃)] (5), [Cu{HB(3-CF₃-5-Mepz)₃}(PPh₃)] (6), are studied by using paired interacting orbitals (PIO) analysis. Carbon monoxide is a weak σ-donor and strong π-acceptor ligand. The Cu(I)–CO interaction is entirely dominated by π back bonding between the two degenerate π* orbitals of carbon monoxide and two t₂ type d orbitals of copper(I) ion. This interaction is clearly expressed by two PIOs, PIO-2 and PIO-3, and the strength of this π-acceptability is estimated by the summation of their overlap populations (ΣOP). On the other hand, triphenylphosphine is a strong σ-donor ligand. The Cu(I)–P interaction is dominated by donation from the P atom to the copper(I) ion and expressed by PIO-1, and the strength of this donative interaction (σ-donationability) is estimated by the overlap population of PIO-1. These results are consistent with experimental data of the CO stretching frequencies by IR spectroscopy and of ¹³C chemical shifts of ¹³CO and the broadness of the ³¹P signals of PPh₃ by ¹³C and ³¹P NMR spectroscopy.