The 12-ethynylmonocarba-closo-dodecaborate anion as a versatile ligand for Cu(I) alkyne and heterobimetallic Cu(I)/M(II) (M = Pd, Pt) alkynide complexes
The anionic monocarborane alkyne [12-(HC≡C)-CB11H11]– was employed as a ligand towards Cu(I) to form terminal alkyne complexes. Spectroscopic methods and X-ray crystallography allowed for a detailed structural analysis of complexes with nitrogen ligands, which are the first examples featuring carborane-C≡CH→metal π coordination. Addition of phosphines to compound 2 afforded homoleptic Cu(I) complexes [Cu(PR3)n]+ (4), in which case the carborane becomes a non-coordinating anion. Polymeric acetylide 5 was obtained in almost quantitative yield from 2 and proved to be a suitable precursor to heterobimetallic Cu(I)/M(II) (M = Pd, Pt) alkynide complexes with side-on and end-on coordination to the metal centers.