Chlorine nuclear quadrupole resonance in some chloro complexes of divalent copper

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 Cu2Cl62- 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.