Synthesis, Spectroscopy, and Electrochemistry of Ternary Copper(II) Complexes with 2,2-Diphenyl-4,4,6,6-tetrakis(3,5-dimethylpyrazolyl)cyclotriphosphazene and Nitrogenous Bases. X-ray Structures of N3P3Ph2(3,5-Me2Pz)4•Cu(ClO4)2•2H2O and N3P3Ph2(3,5-Me2Pz)4•Cu(ClO4)2-2ImH

Abstract

The reaction of 2,2-diphenyl-4,4,6,6-tetrakis(3,5-dimethylpyrazolyl)cyclotriphosphazene, N3P3Ph2(3,5-Me2Pz)4 (TPCTP), with copper(II) perchlorate hexahydrate affords a mononuclear coordination complex, TPCTP-Cu- (ClO4)2•2H2O (1). This, on treatment with nitrogenous bases such as pyridine, imidazole, 2,2′-bipyridine, and 1,10-phenanthroline in appropriate proportions, yields the ternary complexes TPCTP•Cu(ClO4)•nL (2, L = Py (n = 2); 3, L = ImH (n = 2); 4, L = Bipy (n = 1); 5, L = Phen (n = 1)). Optical absorption and EPR spectra of these complexes indicate a distorted tetragonal geometry around copper in all the compounds. The structures of TPCTP•Cu(ClO4)2-2H2O (1) and TPCTP•Cu(ClO4)•2ImH (3) were determined by X-ray crystallography. Crystals of 1 were monoclinic, with the space group P21/a and with a = 18.401(4) Å, b = 19.927(4) Å, c = 11.875(20) Å, β = 90.696(15)°, V = 4354(15) Å3, and Z = 4. The copper atom is coordinated by two nongeminal pyrazolyl pyridinic nitrogens, two water molecules, cyclophosphazene skeletal nitrogen, and a perchlorate anion in an elongated octahedral geometry. Crystals of compound 3 were also monoclinic, with the space group P21/n and with a = 12.121(7) Å, b = 21.110(2) Å, c = 19.464(5) Å, β = 101.39(3)°, V= 4882(3) Å3, and Z = 4. Copper assumes a distorted square pyramidal geometry with the basal plane comprised of two pyrazolyl nitrogens and two imidazolyl nitrogens and the apical position being occupied by the cyclophosphazene ring nitrogen. The cyclophosphazene ring nitrogen–copper binding appears to be σ -bonding interaction, as evidenced by the lengthening of the P–N bonds that flank the coordination site. Cyclic voltammetric studies have also been carried out on complexes 1–5. The six-coordinate complex 1 exhibits redox potentials 0.3 V higher than the fivecoordinate square pyramidal complexes. © 1994, American Chemical Society. All rights reserved.