The synthesis of a sterically encumbered β-diketone ligand (^Aracac) substituted with 2,6-(2,4,6-Me₃C₆H₂)₂C₆H₃ is described. Coordination complexes of the type M(^Aracac)₂Cl(solv) (M = Ti, V, Cr; solv = THF, CH₃CN) were prepared by the reaction of ^Aracac with MCl₃ (M = V, Cr) or with TiCl₄ to generate Ti(^Aracac)₂Cl₂, followed by reduction. These complexes show a trend of alternating the cis/trans geometric preference with increasing dⁿ electron count (n = 0, 1, 2, 3), which is rationalized in part by the unusual ability of β-diketonates to behave as either a weak π donor or a π acceptor in the cis and trans geometries, respectively. In this way, the bis-β-diketonate platform can accommodate the varying electronic demands of the coordinated metal ion. These results demonstrate the ability to limit the coordination of β-diketonates on metal complexes for the first time, providing a chemically robust and coordinatively versatile platform for mechanistic investigations, metal functionalization, and improved catalyst design.

中文翻译：

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庞大的β-二酮，使新的Lewis酸性配体平台成为可能

描述了被2,6-（2,4,6-Me ₃ C ₆ H ₂）₂ C ₆ H ₃取代的位阻性β-二酮配体（^Ar acac）的合成。通过^Ar acac与MCl ₃（M = V，Cr）反应制得M（^Ar acac）₂ Cl（solv）（M = Ti，V，Cr; solv = THF，CH ₃ CN）型配位化合物或用TiCl ₄生成Ti（^Ar acac）₂ Cl ₂，然后减少。这些络合物显示出随着d ⁿ电子数量的增加（n = 0、1、2、3）交替出现顺/反几何偏好的趋势，这在一定程度上是由于β-二酮的异常能力表现得很弱。顺式和反式几何结构中的π供体或π受体。这样，双-β-二酮酸酯平台可以适应配位金属离子的各种电子需求。这些结果首次证明了限制β-二酮酸酯在金属络合物上的配位的能力，为机理研究，金属功能化和改进的催化剂设计提供了化学上坚固且具有协调性的多功能平台。