Chemistry of Triple‐Decker Sandwich Complexes Containing Four‐Membered Open B2E2 Rings (E = S or Se)

Building upon our earlier studies on cobaltaheteroboranes, we explored the chemistry with heavier group 9 metals. Reaction of [Cp*M(μ-Cl)Clx]2 (Cp* = ɳ-C5Me5; M = Co, x = 0; M = Rh or Ir, x = 1) with [LiBH4·THF] followed by thermolysis with excess of chalcogen powders (S or Se) afforded dimetallaheteroboranes nido[(Cp*M)2B2H2E2], 1-4 (1: E = S, 2: E = Se, M = Co; 3-4: E = Se, M = Rh and Ir) in moderate to good yields. The solid state X-ray structures of these compounds show open-cage triple decker clusters. Attempts to isolate the Te analogue was failed, however, in case of cobalt, we have isolated an 11 sep nido-[(Cp*Co)2B5H5Te2], 5. The X-ray structure of 5 shows mono-capped square antiprism geometry having two Te atoms in the core. In order to close the central four-membered B2E2 open ring of nido-1 and nido-2, we have performed the reaction with [Ru3(CO)12] that led to the formation of closo-[(Cp*Co){μ-η:η-B2H2E2M}M{μ-Ru(CO)4}], 6-7 (6: E = S, 7: E = Se; M = Ru(CO)2). In contrast, the reactions of nido-2 and nido-3 with [Fe2(CO)9] resulted heterometallic clusters nido[(Cp*M)Fe(CO)3B2H2Se2], 8-9 (8: M = Co; 9: M = Rh), [(Cp*Co)Fe3(CO)8Se2], 10 and [(Cp*Co)Fe2(CO)7Se], 11. As nido-8 also contains a four-membered open ring B2Se2, we treated this with [Ru3(CO)12] that yielded closo-[(Cp*Co){μ-η:η-B2H2Se2M}M{μFe(CO)4}], 12 (M = Ru(CO)2), analogous to that of 7. In addition, we have analyzed the divergence in reactivity of nido-[(Cp*M)2B2H2E2], 2-4 with the help of density functional theory (DFT) calculations.