Crystal and molecular structure of (dioxygen){NN′-[2-(2′-pyridyl)ethyl]-ethylenebis(salicylideneiminato)}cobalt–acetonitrile (1/1)

Abstract

The title complex [Co(salpeen)(O2)]·MeCN crystallises in the monoclinic space group P21/c with the unit-cell parameters a= 9.563(2), b= 19.490(4), c= 12.770(3)A, β= 106.04(2)°, and Z= 4. The structure has been refined using 915 diffractometer-collected reflections having I > σI to give R 0.128 and R′ 0.089. The co-ordination sphere around the cobalt centre is approximately octahedral and the Schiff-base moiety is nearly planar. Dioxygen is co-ordinated in the end-on bent-bond mode and irresolvable disorder and high thermal motion result in an O–O separation of 1.06(3)A and a Co–[graphic omitted] angle of 134(4)°. In contrast to other Co–O2 structures where the axial base bisects the O–Co–N in-plane right angle, here the pyridyl plane is constrained to bisect the N–Co–N in-plane angle. Marked stereochemical changes accompany the co-ordination of dioxygen to [Co(salpeen)]. Structural evidence is accumulated to support a CoIII—O2-formulation.