Synthesis and Characterization of the Double Salts [Pt(bzq)(CNR)2][Pt(bzq)(CN)2] with Significant Pt路路路Pt and 蟺路路路蟺 Interactions. Mechanistic Insights into the Ligand Exchange Pr

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• 作者：Juan Forni茅s ; Sara Fuertes ; Carmen Larraz ; Antonio Mart铆n ; Violeta Sicilia ; Athanassios C. Tsipis
• 刊名：Organometallics
• 出版年：2012
• 出版时间：April 9, 2012
• 年：2012
• 卷：31
• 期：7
• 页码：2729-2740
• 全文大小：533K
• 年卷期：v.31,no.7(April 9, 2012)
• ISSN：1520-6041

文摘

Double complex salts (DCSs) of stoichiometry [Pt(bzq)(CNR)₂][Pt(bzq)(CN)₂] (bzq = 7,8-benzoquinolinate; R = tert-butyl (1), 2,6-dimethylphenyl (2), 2-naphtyl (3)) have been prepared by a metathesis reaction between [Pt(bzq)(CNR)₂]ClO₄ and [K(H₂O)][Pt(bzq)(CN)₂] in a 1:1 molar ratio under controlled temperature conditions (range: 鈭?0 to 0 掳C). Compounds 1鈥?b>3 have been isolated as air-stable and strongly colored solids [purple (1), orange (2), red-purple (3)]. The X-ray structure of 2 shows that it consists of ionic pairs in which the cationic and anionic square-planar Pt(II) complexes are almost parallel to each other and are connected by Pt鈥揚t (3.1557(4) 脜) and 蟺路路路蟺 (3.41鈥?.79 脜) interactions. Energy decomposition analysis calculations on DCSs 1鈥?b>3 showed relatively strong ionic-pair interactions (estimated interaction energies of 鈭?9.1, 鈭?10.0, and 鈭?08.6 kcal/mol), which are dominated by electrostatic interactions with small contributions from dispersion (蟺路路路蟺) and covalent (Pt路路路Pt) bonding interactions involving the 5d and 6p atomic orbitals of the Pt centers. Compounds 1鈥?b>3 undergo a thermal (165 掳C, 24 h) irreversible ligand rearrangement process in the solid state and also in solution at temperatures above 0 掳C to give the neutral complexes [Pt(bzq)(CN)(CNR)] as a mixture of two possible isomers (SP-4-2 and SP-4-3). The mechanism of this process has been thoroughly explored by combined NMR and DFT studies. DFT calculations on 1鈥?b>3 show that the existing Pt路路路Pt interactions block the associative attack of the Pt(II) centers by the coordinated cyanide and/or isocyanide ligands. Moreover, they support a significant transfer of electron density from the anionic to the cationic component (0.20鈥?.32 |e|), which renders the isocyanide ligand dissociation more feasible than that in the 鈥渇ree-standing鈥?cationic [Pt(bzq)(CNR)₂]⁺ components as well as the dissociation of the CN^{鈥?/sup> in trans position to the C_bzq in the anionic [Pt(bzq)(CN)₂]鈭?/sup> component. Therefore, the first step in the ligand rearrangement pathway is the dissociation of the isocyanide in trans position to the C_bzq, yielding the [(RNC)(bzq)(渭₂-畏1,畏1-CN)Pt路路路Pt(bzq)(CN)] intermediates. The rate-limiting step corresponds to the transformation of these intermediates to the neutral [Pt(bzq)(CN)(CNR)] complexes following a synchronous mechanism involving rupture of the Pt鈥揚t and formation of the Pt鈥揅N bonds through transition states formulated as [(RNC)(bzq)Pt(渭₂-畏1,畏1-CN)Pt(bzq)(CN)].}