Reactions of Zr, ZrCl4, and MnCl2 in welded Ta containers at 800 OC produce the title phase in major amounts. A comparable electronic and structural configuration is also found with interstitial boron, but not in isostructural compounds with other interstitial or alkali metal atoms. The crystal structure of Cs-3(ZrCl5) [Zr-6(Mn)Cl-12]Cl-6/2 was established by single-crystal diffraction (R (3) over bar c, Z = 6, a = 12.8924 (1) Angstrom, c = 35.187 (6) Angstrom, R/R(w) = 1.9/2.3% for 920 data to 2 theta = 60 degrees). The structure contains a three-dimensional array of 18-electron Zr-6(Mn)Cl-12 clusters interbridged by 6/2 Cl-a-a atoms at zirconium vertices. This represents a sixth independent structure type for M(6)X(15) bridged cluster networks. The structure derives from a ReO3-like primitive lattice of the cubic Nb6F15 structure with linear bridges that has been given a "trigonal twist" about [111] to form a rhombohedral (tilted) perovskite arrangement with the novel ZrCl5- at the body center. This new D-3h, anion does not share halogen with the rest of the structure and appears to be stabilized by a particularly good fit within the network. A double ccp cluster arrangement along c(H) provides for a coherent intercluster bridging arrangement. The cesium cations necessitated by the anionic network and by the CsZrCl5 component are bound in well-suited 12-coordinate sites among the chlorines.