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Keywords:

  • Alkali metals;
  • Ladder polymers;
  • Magnesium;
  • Zinc;
  • Chalcogens

Abstract

The complexes [Na{HC(PPh2S)2}] (Na3a), [Na{HC(PPh2Se)2}] (Na3b), [K{HC(PPh2S)2}] (K3a), [K{HC(PPh2Se)2}] (K3b), [Mg{HC(PPh2S)2}2] (Mg(3a)2), [Mg{HC(PPh2Se)2}2] (Mg(3b)2), and [Zn{HC(PPh2S)2}2] [Zn(3a)2] have been prepared in good yields (69–92 %) by treatment of the neutral ligands H2C(PPh2E)2 (1a, E = S; 1b, E = Se) with [Na{N(SiMe3)2}] (Na3a), NaNH2 (Na3b), [K{N(SiMe3)2}] (K3a and K3b), [Mg{N(SiMe3)2}2] [Mg(3a)2 and Mg(3b)2], or Me2Zn [Zn(3a)2] as base in THF/toluene. These compounds were characterized in solution by multinuclear (1H, 13C, 31P, and 77Se) NMR spectroscopy and the X-ray structures of K3a, K3b, Mg(3a)2, Mg(3b)2, and Zn(3a)2 were determined. In the solid state, the E,E′-chelated ligands in K3a and K3b also engage in potassium–chalcogen interactions with adjacent molecules to form one-dimensional ladder structures. With K3a, both sulfur atoms of the ligand are involved in chelation leading to four-membered K2S2 rings, whereas only one selenium atom is tricoordinated in K3b; significant potassium···aryl interactions are also observed in both structures. In the homoleptic magnesium complexes Mg(3a)2 and Mg(3b)2, the E,E′ chelation by the methanide ligands is supplemented by weak, unequal Mg···C interactions [2.781(10) and 3.199(7) Å for Mg(3a)2; 3.331(8) and 3.217(7) Å for Mg(3b)2]. The zinc complex Zn(3a)2 is isostructural with the previously reported selenium analogue Zn(3b)2. The X-ray structures of the S,S-chelated complex [(TMEDA)Li3a] as well as new polymorphs of 1a and 1b are also reported.