Intermetallic bonds in metallophilic mercuraazametallamacrocycles of synthetic design

Abstract

22-Membered mercuraazametallamacrocycles 6, 7, and 12 have been synthesized by dipodal condensation (2+2) of bis(o-formylphenyl)mercury (11) and 1,2-disubstituted amines. Reduction of macrocycle 6 with sodium borohydride afforded novel 11-membered mercuraazametallamacrocycle 13. Macrocycle 6, when treated with [Cu(CH₃CN)₄]ClO₄ and Cu(OCOCH₃)₂/NH₄PF₆, formed orange-colored CuI complexes 14 ([6·Cu]ClO₄) and 15 ([6·Cu]PF₆), respectively, whereas red-colored complex 16 ([12·Cu]ClO₄) was obtained from the reaction of 12 with [Cu(CH₃CN)₄]ClO₄. Similarly, complexes 17 ([6·Ag]ClO₄) and 18 ([6·Ag]PF₆) were synthesized by the reaction of 6 with the corresponding silver salts. The reaction of 6 with Hg(OCOCH₃)₂/NH₄PF₆ led to the formation of hydroxo-bridged complex 19. The reaction of macrocycle 7 with Pd(C₆H₅CN)₂Cl₂ gave access to novel complex 9a. The macrocycles and the complexes have been characterized by elemental analysis, NMR (¹H, ¹³C, ¹⁹⁹Hg), fluorescence spectroscopy, and cyclic voltammetry. The molecular structures of organomercury precursors Hg{1-C₆H₄-2-(CH₂OH)}₂ (10) and Hg{1-C₆H₄-2-(CHO)}₂ (11) and macrocycles 6, 7, and 12 show almost linear geometry around mercury; however, 13 shows a bent structure, i.e., significant deviation of the C-Hg-C angle from linearity. 22-Membered mercuraazametallamacrocycles 6, 7, and 12 are stabilized by secondary Hg···N intramolecular interaction and have an "hour-glass"-like conformation. The molecular structures of 14, 17, and 9a showed metallophilic interactions. The metal ions (CuI and AgI) are coordinated not only to the four nitrogens but also to two mercury atoms, forming a distorted octahedral geometry around the metal ions.