Rotation of coordinated cyanoolefins in their adducts with some rhodium(I) isocyanide complexes

Barrier to the intramolecular rearrangement of tetrakis(isocyano)(tetracyanoethylene)cobalt(I) and -rhodium(I) complexes

“…1 Recently, we prepared the [Rh(RNC)4(TCNE)]C104 type complexes (R = organic group, TCNE = tetracyanoethylene) whose NMR spectra show two nonequivalent isocyanide signals with equal intensity at low temperatures, while they coalesce at elevated temperatures.2 This result has been interpreted in terms of TCNE rotation around the coordination bond coupled with the Berry pseudorotation as shown in Figure l. 2 It is of interest to compare quantitatively the barrier of this rearrangement with those of the complexes exhibiting the Berry pseudorotation alone. This paper reports activation parameters of the rearrangement of the [M(RNC)4(TCNE)]X type complexes (M = Co(I), Rh(I); R = Z-C4H9, CFI3, 4-CH30C6H4; X = C104, PF6, BPh4; but not all combinations) on the basis of the line-shape analysis of NMR spectra.…”