Synthesis and crystal structure of new σ-bonded alkynylcobalt(III) complexes of 1,3-bis(diacetylmonoximeimino)propane

Abstract

σ-Alkynyl Costa complexes can be readily synthesized from the trans diiodo-1,3-bis(diacetylmonoximeimino)propanecobalt complex 1 and alkynyl Grignard reagents 2a–d. The conversions are carried out under daylight irradiation and give the cobalt acetylides 3a–d in high yields. This photosubstitution method can be used to synthesize σ-alkynylcobalt(III) complexes with various substituents. The crystal structure of trimethylsilylethynyliodo-1,3-bis(diacetylmonoximeimino)propanecobalt(III) ( 3a) has been established by an X-ray diffraction study. The reaction of complexes 3a–d with 4-tert-butylpyridine ( 4) in the presence of AgPF 6 gives positively charged complexes having the nitrogen base trans to the alkynyl ligand. Treatment of phenylethynyl-1,3-bis(diacetylmonoximeimino)propanecobalt(III) ( 3b) with I 2 gives quantitatively complex 1 and 1-iodo-2-phenylethyne ( 6).