Synthesis and structure of even-electron paramagnetic chromium(II) complexes

Article abstract of DOI:10.1021/om00011a042

In an effort to develop the coordination chemistry of Cr(II), we have prepared the starting chloro-bridged dimer {[(Ph₂PCH₂SiMe₂)₂N]Cr} ₂(μ-Cl)₂ by reaction of the lithium salt LiN-(SiMe₂CH₂PPh₂)₂ with CrCl₂·-THF. Subsequent replacement of the remaining chloride leads to the formation of mononuclear organochromium complexes of the general formula CrR-[N(SiMe₂CH₂PPh₂)₂] (R = Me, CH₂Ph, C₅H₅). The methyl and benzyl complexes display nearly planar geometries around each Cr(II) and both show high-spin (spin-only) d⁴ configurations; the solid-state structure of the benzyl derivative shows that the benzyl ligand is bound in an η² fashion. The cyclopentadienyl derivative is low spin (two unpaired electrons) and shows a geometry with the tridentate ligand in a distorted facial orientation and the cyclopentadienyl unit η⁵-bound. Semiempirical ZINDO restricted open-shell Hartree-Fock studies confirm the stabilities of the various spin states of the isolated complexes.