Reactivity of [2,6-Bis((dimethylamino)methyl)phenyl]gold(I), an unusual Intermolecularly Stabilised Bis(amino)aryl-Gold(I) Dimer, towards Alkyl Halides : X-ray Crystal Structures of its Iodomethane and Methylene Diiodide Adducts

Abstract

Novel [2,6-bis((dimethylamino)methyl)phenyl]gold(I) dimer (4) was prepared in 60% yield from [AuCl(tht)] (tht = tetrahydrothiophene) and [2,6-bis((dimethylamino)methyl)phenyl]lithium. Compound 4 is a rare example of a dimeric organogold(I) species involving intermolecular gold(I)-N(sp3) coordination. Variable-temperature NMR points to the formation of a 10-membered ring and provides evidence for the occurrence of a boat-chair ring conformation equilibrium. Reaction of 4 with MeI affords the unexpected heteroaurate(I) [Au(C6H3{CH2NMe3}2-2,6)I]I (5) by Me transfer to the nitrogen atom of the ortho amino ligand. The molecular structure of 5 was elucidated by means of X-ray analysis. Conversely, the reaction of 4 with CH2I2 afforded the organogold(III) complex [Au(C6H3{CH2NMe2}-2-{CH2N(Me)2CH2}-6)I]I (6), containing a methylene fragment bridging a Au(III) center and a quaternary N center, as confirmed by a single-crystal X-ray diffraction study. A mechanistic pathway involving prior coordination of the alkyl halide to gold(I) followed by oxidative addition and alkyl transfer is proposed to account for the formation of both 5 and 6.