An EPR study of the intramolecular dynamics in o-semiquinonic nickel complexes with a diphosphorous pincer ligandElectronic supplementary information (ESI) available: synthetic procedures. See http://www.rsc.org/suppdata/cc/b3/b308701h/

Abstract

Square pyramidal o-semiquinonic nickel complexes with 2,6-bis(diphenylphosphinomethyl)phenyl have a flexible coordination sphere and exist in solution as the mixture of tautomers rapidly, according to EPR time scale, interconverting at room temperature.

o-Semiquinonato and o-iminosemiquinonato rhodium complexes. EPR study of the reactions in coordination sphere of rhodium

“…Using of previous experience [1][2][3][4] The EPR spectrum of reaction mixture of complex 5 and dppbiphen is doublet of triplets of multiplets: g i = 2.0012, a i (P) = 7.53 G, a i (P/Rh) ffi 1.8/1.65 G, a i (4H) ffi 0.59 G. Only two coupling constants can be unambiguously attributed: a i (P) = 7.53 G and a i (4H) ffi 0.59 G. Coupling constants 1.8 and 1.65 G are close one to another and it is impossible to attribute each of them to rhodium or to the second phosphorus. Different coupling constants on the phosphorous atoms indicate their different positions: one occupies planar position and the other one -axial.…”

“…o-Semiquinones and o-iminosemiquinones were successfully used as spin labels for investigation of reactions [1,2] and dynamic processes [3,4] occurring in the coordination sphere of metals. One of the mostly interesting our papers was dedicated to carbonyl-osemiquinonato complexes of rhodium [2].…”

EPR study of intramolecular dynamics in o-semiquinonic nickel complexes with PCP-pincer ligand in solution

“…7 Combination of the pincer skeleton and o-semiquinone on nickel atom allowed us to observe inner-sphere dynamics consisting of pendulum (or swing) oscillations of one ligand relative to the other one. 8 This motion is responsible for migration of vacant site and this was not mentioned in literature before. The present report develops this research by increasing the number of semiquinonic ligands in order to investigate the effect of ring substituents in o-semiquinone on inner-sphere dynamics and spin-density distribution.…”

o-Semiquinonic PCP-pincer nickel complexes with alkyl substituents: versatile coordination sphere dynamics

“…1 Previously we have reported a number of spin-labeled osemiquinonic nickel complexes with diphenylphosphine pincer ligands. 2 An unusual structural isomerisation of these complexes via unique "swing" oscillation has been reported (Scheme 1). 2 Scheme 1 Structural isomerism of o-semiquinonic PCP-pincer nickel complexes.…”