Single crystals of K4CuV5O15Cl were prepared by crystallization from t
he melt. The yellow brown crystals show tetragonal symmetry, space gro
up C-4(1)-P-4, a = 8.8690, c = 5.4196 Angstrom, Z = 1. K4CuV5O15Cl is
strongly related to KBaCuV2O7Cl and K2V3O8. V(1) shows V2O7 double tet
rahedra connected by square VO5 and CuO4Cl pyramids. The crystal struc
ture is discussed with respect to the related compounds.