An oscillating C22? unit inside a copper rectangleElectronic supplementary information (ESI) available: NMR spectra and computational details. See http://www.rsc.org/suppdata/cc/b3/b301842c/

Abstract

[Cu4(mu-dppm)4(mu4-eta1,eta2-C[triple bond]C-)]2+ has been shown by 31P and 1H NMR studies to undergo two fluxional processes in solution, the oscillation of the C[triple bond]C2- unit inside the copper rectangle and the flipping of the diphosphines, and this has been supported by DFT(B3LYP) calculations.