Synthesis, structures and reactivity of cobalt(II) complexes supported by N,N,N′,N″-tetradentate N′-substituted bis((1H-pyrazol-1-yl)methyl)amine

Synthesis, structures, and catalytic efficiency in ring opening polymerization of rac-lactide with tridentate vs. bidentate cobalt(ii), zinc(ii), and cadmium(ii) complexes containing N-substituted N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)amine ligands

“… 68 The M–N pyrazole bond distances in [L B CoCl 2 ] and [L B ZnCl 2 ] have values of 2.037 and 2.054 Å, respectively; notably, these geometric parameters are in good agreement with the accepted values. 66 Similarly, the M–Cl and M–Br bond distances of these complexes are comparable to the bond lengths reported for structurally related Zn( ii ) compounds. 66 Furthermore, the N pyrazole –M–N pyrazole bond angles had values of 110.22(6)° for [L B CoCl 2 ] and 109.00(5)° for [L B ZnCl 2 ], whereas the values for the Cl terminal –M–Cl terminal bond angles lie in the 102.67(5)°–112.42(4)° range.…”

“…68 The M-N pyrazole bond distances in [L B CoCl 2 ] and [L B ZnCl 2 ] have values of 2.037 and 2.054Å, respectively; notably, these geometric parameters are in good agreement with the accepted values. 66 Similarly, the M-Cl and M-Br bond distances of these complexes are comparable to the bond lengths reported for structurally related Zn(II) compounds. 66 Contrarily, the ORTEP diagram of [L B CdBr 2 ] illustrates that this complex has two crystal structures in one unit cell.…”

“…66 Similarly, the M-Cl and M-Br bond distances of these complexes are comparable to the bond lengths reported for structurally related Zn(II) compounds. 66 Contrarily, the ORTEP diagram of [L B CdBr 2 ] illustrates that this complex has two crystal structures in one unit cell. These crystal structures are depicted in Fig.…”

“…bonds appeared at the expected wavenumbers, based on literature data. 50,51,66 Additionally, the C-O bond stretching appeared in the 1110-1230 cm À1 wavenumber range, in the case of [L B MX 2 ] (M ¼ Zn(II) or Co(II), with X ¼ Cl; M ¼ Cd(II), with X ¼ Br). The absorption bands assigned to the stretching of the (C]N) pyrazole bond shied to higher wavenumbers in the FTIR spectra of [L n MX 2 ] complexes with respect to the corresponding (free) ligands, which suggests the possibility of a back-donation and the involvement of the nitrogen atoms of pyrazolyl or/and amine moieties in metal bonding.…”

Diverse coordination geometry of cobalt (II), zinc (II), and cadmium (II) complexes comprising N,N‐bis(1H‐pyrazol‐1‐yl)methyl)amines derivatives: Synthesis, structures, and ring opening polymerization of rac‐lactide

“…[69][70][71] The obtained M (II) centers and were obtained in the tridentate coordination mode with the nitrogen atoms of the amine and pyrazolyl moieties, thus forming two five-membered chelate rings (Figures 1 and 5). [52,69,71] The M-N pyrazole bond distances are 2.009(1) and 2.014( 1 The geometric indexes of the tetra-coordinated complexes can be represented by the τ 4 value. The τ 4 value of an ideal square planar geometry is zero whereas that of an ideal tetrahedron geometry is one.…”