Syntheses, Structures and Vibrational Spectroscopy Studies of Copper(I) Perchlorate : Benzonitrile Adducts (1 : n) of n = 2, 3, 4, 5 Stoichiometry

Abstract

Abstract Syntheses and room-temperature single crystal X-ray structure determinations are recorded for an array of complexes formed between copper(I) perchlorate and benzonitrile of CuClO4 : PhCN (1:n) stoichiometry. Copper(I) perchlorate crystallized from neat benzonitrile solution yields a 1:5 CuClO4 : PhCN adduct, shown by the X-ray study to be of the form [Cu(NCPh)4](ClO4). PhCN, and, on recrystallization from dichloromethane, the 1:4 adduct, shown to be [Cu(NCPh)4](ClO4), the copper(I) atom in both the n = 4,5 adducts being in a quasi-tetrahedral four-coordinate environment, < Cu−N > 1.99 Å . Heating of either of the above materials under vacuum to 70 - 80◦ or 85 - 90 ◦C (Care!) yields 1:3 and 1:2 adducts respectively which may be crystallized from dichloromethane. The 1:3 adduct is shown to be of the form [(PhCN)3Cu(OClO3)], the CuN3 array quasi-trigonal planar (Σ N-Cu-N 358.0 ◦; Cu-N 1.906(4)-1.958(4), <> 1.93 Å ), with a long unidentate perchlorate oxygen approach (Cu. . .O 2.404(4) Å). The 1:2 adduct comprises a pair of quasi-linear [(PhCN)Cu(NCPh)] moieties (Cu-N 1.884(6), 1.866(5) Å ; N-Cu-N 158.6(3)◦] linked about an inversion centre by a pair of oxygen atoms from centrosymmetrically related perchlorate groups, so that a weakly bound fourmembered Cu(μ-O)2Cu central ring is obtained (Cu. . .O 2.445(4), 2.502(6) Å ). The structural data provide a basis for a comprehensive vibrational spectroscopic study across the whole array. These spectra show features that can be attributed to the structural changes that are observed with the change in the number of benzonitrile molecules in the compounds. The vibrational spectra of the acetonitrile complex [Cu(NCMe)4](ClO4) have also been recorded and used to assist in the assignment of the spectra of the various stoichiometries of the benzonitrile compounds.