Structural Properties and Dynamics of Five-Coordinate Nickel(II)−π-Allyl Complexes Containing Monodentate Phosphorus Ligands

The novel ionic pentacoordinate NiII−π-allyl complexes [(η3-C3H5)Ni(PMe3)3]Y (1a−d) and [(η3-C3H5)Ni{P(OMe)3}3]Y (2a−d) (Y = SO3CF3 (a), PF6 (b), Br (c), I (d)) have been synthesized and investigated by DSC, solid-state NMR, and X-ray single-crystal and powder diffractometry. Apart from 1a, all complexes are polymorphic. The PMe3 complexes 1b−d undergo monoclinic-monoclinic phase transitions. The solid-state structures of 1a and 1b-II are rigid at low temperature but fluxional at ambient temperature, whereas those of 1c-II and 1d-II are almost rigid, while somewhat faster dynamics occur for 1c-I and 1d-I. Similarly, the structures of 2c-II and 2d-II are fully or almost fully rigid at ambient temperature. The properties of the P(OMe)3-ligated OTf and PF6 salts 2a,b are completely different. 2a crystallizes in the triclinic phase 2a-II, which transforms at −21 °C into the highly mobile, plastically crystalline mesophase 2a-I with a cubic primitive cell. 2b crystallizes from solution in the monoclinic phase ...