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

Reactions of 2,6-dimethylphenyl phosphate (dmppH2) and 2,6-diisopropylphenyl phosphate (dippH2) 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 dmppH2 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)]41 and hexanuclear cage complex [Cu6(PO4)(dmpp)3(OAc)3(dmpz)9] 2, respectively. Whereas compound 1 is a cubane-shaped cluster whose Cu4O12P4 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 dippH2 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 dmppH2 or dippH2 in the presence of chelating ligand 1,10-phenanthroline produced structurally similar dimeric copper phosphates [Cu(phen)(dmpp)(CH3OH)]2·2CH3OH 5 and [Cu(phen)(dipp)(CH3OH)]2·2CH3OH 6 with a S4R SBU core. Changing the copper source to [Cu2(bpy)2(OAc)(OH)(H2O)]·2ClO4 and carrying out reactions both with dippH2 and with dmppH2 result in the formation of trinuclear copper phosphates [Cu3(bpy)3(dmpp)2(CH3OH)3]·2ClO4·2CH3OH 7 and [Cu3(bpy)3(dipp)2(CH3OH)3]·2ClO4·2CH3OH 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. Structurally diverse, oligomeric copper arylphosphate complexes have been synthesized by varying the aryl substituent on the phosphate ester, the ancillary ligand, the organic substituents on the auxiliary ligands, and the source of the metal ion. The dimeric, tetrameric, and trimeric copper phosphates reported in this study serve as useful, suitable model compounds for the S4R, D4R, and 4=1 SBUs of zeolites, respectively, that incorporate transition-metal ions. [ABSTRACT FROM AUTHOR]