A New Approach to the Synthesis of Nanocrystalline Cobalt Boride in the Course of the Thermal Decomposition of Cobalt Complexes [Co(DMF) 6 ] 2+ with Boron Cluster Anions.

In the course of the study, nanocrystalline cobalt monoboride was prepared by thermal decomposition of precursors [Co(DMF) 6 ][An], where [An] = [B 12 H 12 ] 2- ( 1 ), [ trans -B 20 H 18 ] 2- ( 2 ) or [B 10 Cl 10 ] 2- ( 3 ) in an argon atmosphere. Three new salt-like compounds 1 - 3 were prepared when Co(NO 3 ) 2 was allowed to react with (Et 3 NH) 2 [An]. Compound 1 is new; the structures of compounds 2 and 3 have been previously reported. Samples 1 - 3 were annealed at 900 °C in argon to form samples 1a - 3a , which were characterized by single crystal XRD for 1 and powder XRD for 1-3 . Powder XRD on the products showed the formation of BN and CoB for 1a in a 1:1 ratio; 2a gave a higher CoB:BN ratio but an overall decreased crystallinity. For 3a , only CoB was found. IR spectra of samples 1a - 3a as well as X-ray spectral fluorescence analysis for 3a confirmed these results. The nanoparticular character of the decomposition products 1a - 3a was shown using TEM; quite small particle sizes of about 10-15 nm and a quite normal size distribution were found for 1a and 2 a, while the decomposition of 3 gave large particles with 200-350 nm and a broad distribution.