Intramolecular proton-hydride activation using the example of cobalt bis(dicarbollide) derivative [8-Et(HO)CHN-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)]

[Display omitted] •Pyrolysis of amide derivative of cobalt bis(dicarbollide) at 180–220 °C was studied.•8,9-Oxazole fused and 8,8′-N,O-bridged cobaltacarborane derivatives were prepared.•Pyrolysis of nitrilium derivative gives 8,8′-N,C-bridged bis(dicarbollide). Heating the propionamide derivative of cobalt bis(dicarbollide) [8-Et(HO)CHN-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)] at temperatures above 200 °C leads to the activation of the BH and OH (or NH) bonds through the corresponding dihydrogen bonds with the formation of 8,8′-N,O-bridged derivative [8,8′-μ-(NHC(Et)ON,O)-3,3′-Co(1,2-C2B9H10)2] and 8,9(12)-fused oxazole [8,9(12)-(NHC(Et)ON,O)-3,3′-Co(1,2-C2B9H9)(1′,2′-C2B9H11)], along with minor amount of 8,8′-N-bridged derivative [8,8′-μ-Et(HO)CN-3,3′-Co(1,2-C2B9H10)2]. However, the high-temperature reactions can be complicated by dehydration of the amide to the corresponding nitrilium derivative [8-EtCN-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)], followed by addition reaction of the BH group of the adjacent dicarbollide ligand to the activated −CN+- triple bond, which leads to the formation of 8,8′-N,C-bridged [8,8′-μ-(EtCHN-N,C)-3,3′-Co(1,2-C2B9H10)2] and 8,4′-N-bridged [8,4′-μ-EtCHN-3,3′-Co(1,2-C2B9H10)2] derivatives. Heating [8-Et(HO)CHN-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)] in boiling nitrobenzene gives amidine [8-PhNHC(Et)HN-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)] as the major reaction product.