The first quaternary vanadium niobium compounds containing triangular Nb-3 clusters corresponding to the general formula, AVNb(3)Cl(11) (A = K, Rb, Cs, TI), have been prepared in sealed quartz tubes from stoichiometric amounts of ACl (A = K, Rb, Cs), or TI metal, VCl3, Nb powder, and NbCl5 heated at 740 degreesC. The compounds crystallize in the orthorhombic space group Pnma (No. 62). The crystal structures of the Rb and TI members were determined by single-crystal X-ray diffraction techniques. Crystal data: a = 12.771(3) Angstrom, b = 6.811(2) Angstrom, c = 17.183(3) Angstrom, V = 1494.6(1) Angstrom(3), and Z = 4 for A = Rb; and a = 12.698(5) Angstrom, b = 6.798(3) Angstrom, c = 17.145(10) Angstrom, V = 1480.0(13) Angstrom(3), and Z = 4 for A = TI. The crystal structure of AVNb(3)Cl(11) consists of triangular Nb3Cl13 clusters (Nb-Nb = 2.826 Angstrom) connected to each other via four outer ligands to form infinite chains along the b-axis. The chains are connected by vanadium atoms located in an octahedral environment to form puckered sheets. The A(+) counterions are located between adjacent sheets and coordinate to twelve chlorine ligands in anticubeoctahedral geometry. Electronic structure calculations show bonding orbitals similar to those in Nb3Cl8. Magnetic susceptibility measurements show paramagnetic Curie Weiss behavior.