Preparation of copper(I) binap-P₂N₂ complexes; crystal and molecular structure of [Cu(Binap-P₂N₂)Br]

The interaction of a racemic mixture of N,N′-bis[o-(diphenylphosphino)benzylidene-2,2′-diimino-1,1′-binaphthyl (Binap-P₂N₂) (I) with 1 equivalent of Cu(Ph₃P)₂Br and [Cu(CH₃CN)₄]PF₆ in CH₂Cl₂ gave Cu(Binap-P₂N₂)Br (II) and [Cu(Binap-P₂N₂)]PF₆ (III) in 60 and 74% yield, respectively. The structure of II was established by X-ray diffraction and can be described as distorted tetrahedral with the bromide ion and the two phosphino groups and one of the two imino groups of I coordinated to the copper. Variable temperature ³¹P {¹H} NMR study of II shows that the coordinated and the uncoordinated imino groups of the tridentate Binap-P₂N₂ ligand undergo a facile intramolecular exchange even at -55°C.