Chlorine nuclear quadrupole resonance in some chloro complexes of divalent copper

Abstract

Nuclear quadrupole resonance for the ³⁵Cl nucleus has been observed in some chloro complexes of divalent copper. Square-planar complexes each show two resonance lines, with the following frequencies (at 77°K): (CH₃NH₃)₂CuCl₄, 10.780, 12.157 MHz; (C₂H₅NH₃)2CuCl₄, 10.817, 12.074 MHz; (enH₂)CuCl₄, 10.271, 11.901 MHz; and (C₃H₇NH₃)₂CuCl₄ at 223°K, 11.290 and 11.781 MHz. NH₄CuCl₃, containing dimeric Cu₂Cl₆^2- units, has resonances, at 77°K, at 11.907, 11.993, and 12.448 MHz. The trigonal pyramidal anion in Co(NH₃)₆CuCl₅ has two resonances at 9.642 and 10.352 MHz at 77°K.     These results are compared with previous results for copper chloro complexes, and the implications of covalent bonding are discussed. In particular, it is suggested that the long-bond interaction between units in square-planar complexes amounts to 7-16% of the bonding interaction within the units.