title: Why are the {Cu4N4} rings in copper(I) phosphinimide clusters [Cu{μ-N = PR3}]4 (R = NMe3 or Ph) planar?
abstract: The copper phosphinimide complexes [Cu{μ-N[double bond, length as m-dash]PR3}]4 (1, R = NMe2 and 2, R = Ph) were obtained in good yields from the reactions of Cu[Mes] (Mes = mesityl, C6H2Me3-2,4,6) with the corresponding iminophosphoranes, HNPR3. The molecular structures of 1 and 2 reveal the presence of planar eight-membered {Cu4N4} rings which contrasts with the saddle-shaped {M4N4} rings found in related metal phosphinimide complexes. According to computations, there is negligible aromaticity in the planar {Cu4N4} rings in 1 and 2 and the saddle shape observed in related {M4N4} rings is due to steric factors.
authors.affiliation: Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. M.G.Davidson@bath.ac.uk A.L.Johnson@bath.ac.uk.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Robinson
authors.forename: Richard D
authors.initials: RD
authors.lastname: Price
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Davidson
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fox
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Johnson