Metalation studies of 3- and 4-pyridyloxycyclophosphazenes: metallamacrocycles to coordination polymers

Abstract

Pyridyloxy cyclophosphazenes, spiro-N₃P₃(O₂C₁₂H₈)(O-C₅H₄N-3)₄ (L1), dispiro-N₃P₃(O₂C₁₂H₈)₂(O-C₅H₄N-3)₂ (L2) and dispiro-N₃P₃(O₂C₁₂H₈)₂(O-C₅H₄N-4)₂ (L3) were prepared and characterized. The crystal structure of L1 was determined which showed that the cyclophosphazene ring is planar. The reaction of L1 with anhydrous copper(II) chloride or silver nitrate afforded L₂M₄ metallamacrocycles [{L1}₂{ClCu(μ-Cl)₂CuCl}]₂·8CHCl₃ (3) and [{L1}₂{(DMF)_0.5(NO₃)_0.5Ag}₂{Ag(μ₂-(O)NO₂)(H₂O)}₂]{μ-[NO₃]}·CH₃OH (4) respectively. The molecular structure of 3 reveals that two CuCl₂ dimers are bridged to each other in a complex metallamacrocycle that involves four metal ions and two ligands. The molecular structure of 4 is similar to that of 3 except for the presence of weak argentophilic interactions between the two Ag(I) centers. Also, a nitrate anion, which is trapped in the centre of the tetrameric assembly, assists in holding two Ag(I) ions together and 4 serves as a single source precursor for silver nanoparticles. The reaction L1 with ZnCl₂ and Cd(NO₃)₂·4H₂O afforded the 1D-coordination polymers [{L1}{ZnCl₂}₂]_n·2nCH₃OH·2nH₂O (5) and [{L1}₂{Cd(CH₃OH)₂(NO₃)₂}₂{Cd(NO₃)₂(H₂O)}]_n·3nCH₃OH·3nH₂O (6) respectively. While in 5 the 20-membered macrocycles are inter-connected directly, in 6 they are bridged by a Cd(II) connector. The reaction of L2 with CoCl₂ afforded the 1D-coordination polymer [{L2}₂{CoCl₂}]_n·2nCHCl₃ (7) which also contains interconnected 20-membered metallamacrocycles. On the other hand, the reaction of L2 with CuCl₂ afforded [{L2}₂{ClCu(μ-Cl)}₂]_n·2nCHCl₃·nH₂O (8) which is a 1D-coordination polymer that contains {ClCu(μ-Cl)₂CuCl} units. The reaction of L3 with CuCl₂ and Cd(NO₃)₂·4H₂O afforded [{L3}₂{CuCl₂}]_n·nDMF (9) and [{L3}₂{Cd(NO₃)₂}]_n·nCHCl₃·nCH₂Cl₂·nH₂O (10) respectively. While 9 is a 2D-coordination polymer containing 48-membered metallamacrocycles, 10 is a 1D-coordination polymer containing interconnected 24-membered metallamacrocycles which possess spirocyclic cadmium ions as nodes.