Palladium(II), Ruthenium(II), and Ruthenium(III) Complexes of 23-Thiaazuliporphyrin: The Case of Coordination-Induced Contraction

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• 作者：Michał J. Białek ; Lechosław Latos-Grażyński
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：February 15, 2016
• 年：2016
• 卷：55
• 期：4
• 页码：1758-1769
• 全文大小：735K
• ISSN：1520-510X

文摘

5,10,15,20-Tetraaryl-23-thiaazuliporphyrin (SAz) was synthesized starting from nonfunctionalized azulene using a “1 + 3” method to be applied as a monoanionic macrocyclic ligand that provides a peculiar [CNSN] coordination cavity. An insertion of palladium(II) afforded the cationic [Pd^II(SAz)]⁺, which readily undergoes the seven-membered ring contraction to form palladium(II) 23-thiabenzocarbaporphyrin [Pd(SBzC)] providing the first example of metal azuliporphyrinoid contraction. A reaction of SAz and a ruthenium source ([RuCl₂(CO)₃]₂, [RuCl₂(p-cymene)]₂, or [RuCl₂(cod)]) yielded ruthenium(II) 23-thiaazuliporphyrin [Ru^II(SAz)Cl(CO)]. As shown by X-ray crystallography the thiophene ring in [Ru(SAz)Cl(CO)] is sharply tilted out of the plane of the two pyrrole nitrogen and carbon atoms being bound to the ruthenium through the pyramidal sulfur in the η¹ fashion. In solution, as demonstrated by variable-temperature ¹H NMR investigations, [Ru(SAz)Cl(CO)] exists as an equilibrium mixture of two isomers that are differentiated by the direction of thiophene folding (toward or outward of the axial chloride ligand). Apart of [Ru^II(SAz)Cl(CO)], ruthenium(III) 23-thiaazuliporphyrin [Ru^III(SAz)Cl₂] was obtained when [RuCl₂(p-cymene)]₂ or [RuCl₂(cod)]_n were used for insertion. The most characteristic ¹H NMR features of paramagnetic [Ru(SAz)Cl₂] are negative isotropic shifts of resonances assigned to meso-aryl, azulene, and pyrrolic hydrogen atoms. The analysis of contact shifts and the parallel density functional theory calculations of spin density distribution documented that in [Ru(SAz)Cl₂] the metal ion acquires the d_xy²(d_xzd_yz)³ ground electronic state. This C_s symmetry complex has singly occupied d_xz or d_yz orbitals that are symmetrically unequivalent. The resulting two different spin density distributions, when merged, reflect the spectroscopic image with the very specific π-spin delocalization, also including the azulene moiety.