Why are the {Cu4N4} rings in copper(i) phosphinimide clusters [Cu{μ-N![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
PR3}]4 (R = NMe3 or Ph) planar?†‡
Mark A.
Fox 
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Abstract
The copper phosphinimide complexes [Cu{μ-NPR3}]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.
![Graphical abstract: Why are the {Cu4N4} rings in copper(i) phosphinimide clusters [Cu{μ-N [[double bond, length as m-dash]] PR3}]4 (R = NMe3 or Ph) planar?](/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=C5DT00255A&imageInfo.ImageIdentifier.Year=2015)
- This article is part of the themed collection: In memory of Professor Kenneth Wade
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![[double bond, length as m-dash]](https://www.rsc.org/images/entities/h2_char_e001.gif)
PR3}]4 (R = NMe3 or Ph) planar?
