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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >The surprising lability of bis(2,2':6',2'-terpyridine)- chromium(III) complexes
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The surprising lability of bis(2,2':6',2'-terpyridine)- chromium(III) complexes

机译：双（2,2'：6'，2“-三吡啶）-铬（III）配合物的惊人的不稳定性

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The complex [Cr(tpy)(O_3SCF_3)_3] (tpy = 2,2':6',2"-terpyridine) is readily made from [Cr(tpy)Cl_3] and is a convenient precursor to [Cr(tpy)_2][PF_6]_3 and to [Cr(tpy)(4'-(4-tolyl)tpy)][PF_6]_3 and [Cr(tpy)(5,5"-Me_2tpy)][PF_6]_3 (4'-(4-tolyl)tpy = 4'-(4-tolyl)-2,2':6',2"-terpyridine; 5,5"-Me_2tpy = 5,5"-dimethyl-2,2':6',2"-terpyridine); these are the first examples of heteroleptic bis(tpy) chromium(III) complexes. The single crystal structures of 2{[Cr(tpy)_2][PF_6]_3}?5MeCN, [Cr(tpy)(4'-(4-tolyl)tpy)][PF_6]_3?3MeCN and [Cr(tpy)(5,5"-Me_2tpy)]- [PF_6]_3?3MeCN have been determined. Each cation contains the expected octahedral {Cr(tpy)_2}~(3+) unit; in all three structures, the need to accommodate three anions per cation and the solvent molecules prevents the formation of a grid-like array of cations that is typical of many lattices containing {M(tpy)_2}~(2+) motifs. Three reversible electrochemical processes are observed for [Cr(tpy)(4'-(4-tolyl)tpy)][PF_6]_3 and [Cr(tpy)(5,5"-Me_2tpy)][PF_6]_3, consistent with those documented for [Cr(tpy)_2]~(3+). At pH 6.36, aqueous solutions of [Cr(tpy)_2][PF_6]_3 are stable for at least two months. However, contrary to the expectations of the d3 Cr~(3+) ion being a kinetically inert metal centre, the tpy ligands in [Cr(tpy)_2]~(3+) are labile in the presence of base; absorption and ~1H NMR spectroscopies have been used to monitor the effects of adding NaOH to aqueous and CD_3OD solutions, respectively, of the homo- and heteroleptic complexes. Ligand dissociation is also observed when [Bu4N]F is added to CD_3OD solutions of the complexes, but in aqueous solution, [Cr(tpy)_2][PF_6]_3 is stable in the presence of fluoride ion.
机译：络合物[Cr（tpy）（O_3SCF_3）_3]（tpy = 2,2'：6'，2“-叔吡啶）易于由[Cr（tpy）Cl_3]制成，并且是[Cr（tpy）的便利前体_2] [PF_6] _3和[Cr（tpy）（4'-（4-tolyl）tpy）] [PF_6] _3和[Cr（tpy）（5,5“ -Me_2tpy）] [PF_6] _3（4 '-（4-甲苯基）tpy = 4'-（4-甲苯基-2,2'：6'，2“-叔吡啶; 5,5” -Me_2tpy = 5,5“-二甲基-2,2'： 6'，2“-吡啶）;这些是杂合双（tpy）铬（III）配合物的第一个实例。 2 {[Cr（tpy）_2] [PF_6] _3}？5MeCN，[Cr（tpy）（4'-（4-tolyl）tpy）] [PF_6] _3？3MeCN和[Cr（tpy） ）（5,5“ -Me_2tpy）]-[PF_6] _3？3MeCN已确定。每个阳离子均包含预期的八面体{Cr（tpy）_2}〜（3+）单元;在所有三个结构中，需要容纳每个阳离子含有三个阴离子，溶剂分子阻止形成许多{M（tpy）_2}〜（2+）主题的典型格子状阳离子的阵列。观察到[Cr（ tpy）（4'-（4-tolyl）tpy）] [PF_6] _3和[Cr（tpy）（5,5“ -Me_2tpy）] [PF_6] _3，与为[Cr（tpy）_2]记录的一致〜（3+）。在pH 6.36时，[Cr（tpy）_2] [PF_6] _3的水溶液稳定至少两个月。但是，与d3 Cr〜（3+）离子为动力学惰性金属中心的预期相反，[Cr（tpy）_2]〜（3+）中的tpy配体在碱的存在下不稳定。吸收光谱和〜1H NMR光谱学已用于监测分别向均配和杂配配合物的水溶液和CD_3OD溶液中添加NaOH的效果。当将[Bu4N] F添加到配合物的CD_3OD溶液中时，也观察到配体解离，但是在水溶液中，[Cr（tpy）_2] [PF_6] _3在氟离子存在下是稳定的。

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