Building upon our earlier studies of cobaltaheteroboranes, we explore the chemistry with heavier group 9 metals. Reaction of [Cp*M(μ-Cl)Cl x ] 2 (Cp* = η 5 -C 5 Me 5 ; M = Co, x = 0; M = Rh or Ir, x = 1) with [LiBH 4 ·THF], followed by thermolysis with an excess of chalcogen powders (S or Se), affords dimetallaheteroboranes nido-[(Cp*M) 2 B 2 H 2 E 2 ], 1-4 (1: E = S; 2: E = Se, M = Co; 3 and 4: E = Se, M = Rh and Ir, respectively) in moderate-to-good yields. The solid-state structures of these compounds show open-cage triple-decker clusters. Attempts to isolate the Te analogue have failed; however, in the case of cobalt, we have isolated an 11 skeletal-electron-pair nido-[(Cp*Co) 2 B 5 H 5 Te 2 ], 5. The X-ray diffraction structure of 5 shows monocapped square antiprismatic geometry, with two Te atoms in the core. To close the central four-membered B 2 E 2 open ring [a]