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Magnetic measurements either in the solid or in the liquid phases indicate that complexes 3a and 3b have low-spin ground states ( S = 1/2). Complex 4a shows clearly a compressed geometry, but for complex 4b, two polymorphs were characterized, exhibiting molecules with different Co−O (THF) bond lengths, one of them being compatible with an elongated form. All the compounds have been characterized by X-ray diffraction, with 3a and 3b showing axially compressed trigonal bipyramidal geometry (with the PMe 3 ligand lying on the equatorial plane), whereas complexes 4a and 4b exhibit distorted square pyramidal geometries with the THF molecule occupying the axial position.
![fivem coords fivem coords](https://i.ytimg.com/vi/mgrswXTNWAc/maxresdefault.jpg)
80−90%) by the reaction of CoCl 2(THF) 1.5 with the corresponding iminopyrrolyl Na salt. The synthesis of the new bis-iminopyrrolyl five-coordinate Co(II) complexes (R = H 4a Me 4b) were carried out in high yields (ca. The synthesis of 3b in THF was unfruitful because of the kinetic competition of the solvent, giving rise to mixtures of 1f and its coordinated THF adduct 4b. A third route was tested, involving the addition of excesses of PMe 3 to the complexes (R = H 1e Me 1f), which was only successful for the synthesis of 3a, in lower yields (ca. 80−90%), using THF and diethyl ether as solvents, respectively, by (a) treatment of CoCl 2(PMe 3) 2 with the corresponding iminopyrrolyl Na salts ( Ie or If) or (b) reaction of anhydrous CoCl 2 and PMe 3 with Ie or If. The new bis-iminopyrrolyl five-coordinate Co(II) complexes (R = H 3a Me 3b) were synthesized in high yields (ca.