Exploring the Scope of Pyridyl- and Picolyl-Functionalized 1,2,3-Triazol-5-ylidenes in Bidentate Coordination to Ruthenium(II) Cymene Chloride Complexes

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• 作者：Aljo拧a Bolje ; Stephan Hohloch ; Damijana Urankar ; Andrej Pevec ; Martin Gazvoda ; Biprajit Sarkar ; Janez Ko拧mrlj
• 刊名：Organometallics
• 出版年：2014
• 出版时间：May 27, 2014
• 年：2014
• 卷：33
• 期：10
• 页码：2588-2598
• 全文大小：405K
• 年卷期：v.33,no.10(May 27, 2014)
• ISSN：1520-6041

文摘

1-(2-Pyridyl)-, 4-(2-pyridyl)-, 1-(2-picolyl)-, and 4-(2-picolyl)-functionalized 1,3,4-trisubstituted 1,2,3-triazolium salts (1A鈥?b>D, respectively) were investigated as N-heterocyclic carbene (trzNHC) precursors for bidentate coordination to ruthenium(II) through the C^NHC and N^pyridyl donors. In addition to the pyridyl and picolyl pendant groups, a variety of para-substituted phenyl rings were attached to the 1,2,3-triazolylidene via carbon or nitrogen atoms. The ruthenation was accomplished by metalation with Ag₂O to form intermediate silver carbene complexes and subsequent transmetalation with [Ru(畏⁶-p-cymene)Cl₂]₂. The cationic ruthenium complexes [Ru(畏⁶-p-cymene)(trzNHC)Cl]⁺ (3A鈥?b>C) were readily obtained with 1-(2-pyridyl)-, 4-(2-pyridyl)-, and 1-(2-picolyl)-1,2,3-triazolium salts (1A鈥?b>C) but not with the 4-picolyl analogue (1D). The bidentate coordination of the ligand precursors 1 was followed by multinuclear NMR spectroscopy, revealing significant changes in chemical shifts for triazole C-5, pyridine nitrogen atoms, and the neighboring 伪-proton (H-6^pyridyl) in ¹³C, ¹⁵N, and ¹H NMR spectra. The molecular composition of complexes 3A鈥?b>C was confirmed by elemental analysis and positive ion electrospray ionization (ESI+) mass spectra, the latter showing ions corresponding to [Ru(畏⁶-p-cymene)(trzNHC)Cl]⁺. The solid-state structures of the three representative complexes were confirmed by single-crystal X-ray analyses; all complexes displayed a typical piano-stool type configuration. Preliminary catalytic activity screening of 3A鈥?b>C in the oxidation of selected primary and secondary alcohols with tert-butyl hydroperoxide (TBHP) to give carbonyl compounds is also discussed.