Flexibility is Key: Synthesis of a Tripyridylamine (TPA) Congener with a Phosphorus Apical Donor and Coordination to Cobalt(II)

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• 作者：Zachary Thammavongsy ; Juliet F. Khosrowabadi Kotyk ; Charlene Tsay ; Jenny Y. Yang
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：December 7, 2015
• 年：2015
• 卷：54
• 期：23
• 页码：11505-11510
• 全文大小：357K
• ISSN：1520-510X

文摘

Tripyridylamine (TPA), a tetradentate ligand that forms 5-membered chelate rings upon metal coordination, has demonstrated significant utility in synthetic inorganic chemistry. An analogue with a phosphorus apical donor is a desirable target for tuning electronic structure and enhancing reactivity. However, this congener has been synthetically elusive. Prior attempts have resulted in tridentate coordination to transition metal ions due to a lack of ligand flexibility. Herein, we report the successful synthesis of tris(2-pyridylmethyl)proazaphosphatrane (TPAP), a more accommodating tripyridyl ligand containing an apical phosphorus donor. The TPAP ligand forms 6-membered chelate rings upon coordination and binds in the desired tetradentate fashion to a Co(II) ion. Structural studies elucidate the importance of ligand flexibility in tripodal ligands featuring phosphorus donors. Cyclic voltammetry, UV鈥搗is, and solution magnetic susceptibility experiments of [Co(TPAP)(CH₃CN)]²⁺ are also reported and compared to [Co(TPA)(CH₃CN)]²⁺. Notably, magnetic susceptibility measurements of [Co(TPAP)(CH₃CN)]²⁺ indicate a low spin electronic configuration, in contrast to [Co(TPA)(CH₃CN)]²⁺, which is high spin.