Unprecedented Calcium Metalla‐macrocycle Having Phosphinoselenoic Amide and Diphenylphosphinate in the Coordination Sphere

Abstract

AbstractAn eight‐membered calcium metalla‐macrocycle of the composition [Ca{Ph2P(Se)N(Ar)}{Ph2P(O)O}(THF)2]2 (2) (Ar = 2, 6‐dimethylphenyl) can be isolated with a good yield by the reaction of neutral phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) and calcium bis(trimethylsilyl)amides [Ca{N(SiMe3)2}2(THF)2] in toluene followed by crystallization in air. The homoleptic calcium phosphinoselenoic amido complex of the composition [Ca{Ph2P(Se)N(Ar)}2(THF)2] (3) can also be obtained through two synthetic routes. In the first route, [Ca{N(SiMe3)2}2(THF)2] is treated with phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) at an ambient temperature followed by re‐crystallization in an inert atmosphere to give complex 3 of high purity. In the second route, a one‐pot reaction is carried out involving 1, calcium diiodide, CaI2, and potassium bis(trimethylsilyl)amide [K{N(SiMe3)2}] in toluene in an inert atmosphere. When complex 3 is treated with diphenylphosphinic acid in THF, compound 2 is also obtained with a good yield. Both complexes are confirmed using single‐crystal X‐ray diffraction analysis. The solid‐state structure of complex 2 reveals an eight‐membered macrocycle formed by two diphenylphosphinate groups and two calcium ions. In addition, a four‐membered calcium metallacycle around each calcium atom is formed by the phosphinoselenoic amido ligand through coordination between the nitrogen and selenium atoms. In complex 3, the calcium atom is coordinated by two phosphinoselenoic amido groups and a direct metal selenium bond is observed.