The new compounds Zn3Pt9B4, Ga2.7Ir9B5, and Ga3Pt9B4 were prepared by reaction of the elements at 1373 K. Their crystal structures were determined by means of single crystal X-ray methods. In the case of Zn3Pt9B4, powder neutron diffraction was applied in addition. Zn3Pt9B4 [hexagonal, P[unk]2m; a = 911.11(6) pm; c = 286.00(3) pm; Z = 1; 491 reflexions; 20 parameters; R = 0.023] and Ga2.7Ir9B5 [hexagonal, P[unk]2m; a = 904.65(9) pm; c = 287.03(2) pm; Z = 1; 412 reflexions; 20 parameters; R = 0.039] crystallize with a new structure. Trigonal transition metal prisms partly centered by boron atoms are arranged to form channels with pentagonal cross sections containing rows of zink and gallium atoms respectively. In the structure of Zn3Pt9B4 one of the boron sites has an occupation parameter of 0.5. Ordering of the vacancies in Ga3Pt9B4 [hexagonal, P[unk]2c; a = 875.03(1) pm; c = 637.42(1) pm; Z = 2; 991 reflexions; 26 parameters; R = 0.052] results in a variant of the structure with doubled lattice constant c and a zig-zag chain of gallium atoms within the channel.