Red moisture-sensitive crystals of Nb2Cl10(P4S10)(2) were obtained from a solution of P4S10 and Nb2Cl10 in CS2. Nb2Cl10(P4S10)(2) crystallises in the space group P (1) over bar with a = 9.577(2), b = 10.894(2), c = 11.477(2) angstrom, alpha = 71.40(1), beta = 68.14(1), gamma = 67.58(1)degrees; V = 1005.2(3) angstrom(3), Z = 2. In the crystal structure molecules of P4S10 and Nb2Cl10 are arranged similar to the packing of the ions in the CaF2 structure type. A comparison of the Raman spectrum of Nb2Cl10(P4S10)2 with spectra of the corresponding reactants indicates that no significant bonds are present between both components of the title compound. Therefore, Nb2Cl10(P4S10)(2) has to be considered as a co-crystal of the starting materials. Ta2Cl10(P4S10)(2) is isotypic with Nb2Cl10(P4S10)(2), the lattice constants are a = 9.643(3), b = 10.963(3), c = 11.572(4) angstrom; alpha = 71.54(2), beta = 68.11(2), gamma = 67.61(2)degrees.