Di-, Tri-, Tetra-, and Hexanuclear Copper(II) Mono-organophosphates: Structure and Nuclearity Dependence on the Choice of Phosphorus Substituents and Auxiliary N-Donor Ligands

Abstract

Reactions of 2,6-dimethylphenyl phosphate (dmppH(2)) and 2,6-diisopropylphenyl phosphate (dippH(2)) with copper(II) precursors have been investigated in the presence of auxiliary N-donor ligands, and new structural types of copper phosphates have been isolated. Copper acetate reacts with dmppH(2) in the presence of either 3,5-di-tert-butyl pyrazole (dbpz) or 3,5-dimethyl pyrazole (dmpz), leading to the isolation of tetrameric complex [Cu(dmpp)(dbpz)](4) 1 and hexanuclear cage complex [Cu(6)(PO(4))(dmpp)(3)(OAc)(3)(dmpz)(9)] 2, respectively. Whereas compound 1 is a cubane-shaped cluster whose Cu(4)O(12)P(4) core resembles the double-4-ring (D4R) zeolite SBU, compound 2 is a novel hexanuclear copper complex with an unprecedented structure in metal phosphate chemistry. Use of bulkier dippH(2) in the above reactions, however, yielded metal-free acid-base complexes [(dippH)(dbpz)(dbpzH)] 3 and [(dippH)(dmpz)(dmpzH)] 4, respectively. The reactions carried out between copper acetate and dmppH(2) or dippH(2) in the presence of chelating ligand 1,10-phenanthroline produced structurally similar dimeric copper phosphates [Cu(phen)(dmpp)(CH(3)OH)](2).2CH(3)OH 5 and [Cu(phen)(dipp)(CH(3)OH)](2).2CH(3)OH 6 with a S4R SBU core. Changing the copper source to [Cu(2)(bpy)(2)(OAc)(OH)(H(2)O)].2ClO(4) and carrying out reactions both with dippH(2) and with dmppH(2) result in the formation of trinuclear copper phosphates [Cu(3)(bpy)(3)(dmpp)(2)(CH(3)OH)(3)].2ClO(4).2CH(3)OH 7 and [Cu(3)(bpy)(3)(dipp)(2)(CH(3)OH)(3)].2ClO(4).2CH(3)OH 8. The three copper ions in 7 and 8 are held together by two bridging phosphate ligands to produce a tricyclic derivative whose core resembles the 4=1 SBU of zeolites. Compounds 1-8 have been characterized by elemental analysis and IR, absorption, emission, and EPR spectroscopic techniques. The crystal structures of compounds 1, 2, 4, 5, 6, and 8 have also been established by single-crystal X-ray diffraction studies.