REACTIONS OF CuX (X = SCN AND CN) WITH 2-BENZOYLPYRIDINE. SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF [9-OXO-INDOLO[1,2-a] PYRIDINIUM] DITHIOCYANATOCUPRATE(I) AND POLYMERIC μ-CYANO(2-BENZOYLPYRIDINE) COPPER(I)

Abstract

When a mixture of excess CuSCN and 2-benzoylpyridine (2-Bzpy) stands in an ethanolic medium for about ten days in contact with air, the intramolecular oxidative cyclization of 2-Bzpy occurs with formation of the ionic compound 9-oxo-indolo1,2-a]pyridinium]⁺ Cu(SCN)₂]^? (1). In contrast, interaction of CuCN and 2-Bzpy in ethanol leads to formation of the polymer Cu(CN)(2-Bzpy)]_n (2). The reaction of Cu(II) and 2-Bzpy in presence of excess SCN^? in ethanol affords (1) and the green monomer Cu(SCN)₂(2-Bzpy)₂] (4). These complexes, along with the 1:1 CuSCN complex of 2-Bzpy (3) are studied by IR, Raman and electronic spectroscopic methods and X-ray structural analysis of (1) and (2). Crystals of (1) are monoclinic, space group P2₁/n (No. 14), with a = 5.887(1), b = 36.142(7), c = 7.083(1) Å, B = 109.56(1)°, Z = 4, and R_F = 0.033 for 2487 observed MoKα data, (2) monoclinic, space group P2₁/c (No. 14), a = 14.393(3), b = 8.881(2), c = 9.287(2) Å, B = 103.80(3)°, Z = 4, and R_F = 0.036 for 2030 observed MoKα data. The structure of (1) consists of a packing of 9-oxo-indolo 1,2-a]pyridinium]⁺ cations and Cu(SCN)₂]^? anions. Puckered layers are formed by the Cu(SCN)₂]^? component with four-coordinate Cu(I) and one tridentate μ(N,S,S)-thiocyanato ligand. Complex (2) features distorted tetrahedral Cu(I) geometry, formed by a bidentate chelating 2-Bzpy and linear C- and N-bonded bidentate cyano groups, which link adjacent copper centers to form zigzag chains extending along the c axis. Complexes (1) and (2) do not fluoresce at room temperature.