Pyridines ligand structure

Zhang et al. [49] prepared a chiral ruthenium complex coordinated by a pyridine-bis(imine) ligand (structure 43 in Scheme 21). 

Ghosh et al. [70] reviewed a few years ago the utihty of C2-symmetric chiral bis(oxazoline)-metal complexes for catalytic asymmetric synthesis, and they reserved an important place for Diels-Alder and related transformations. Bis(oxazoline) copper(II)triflate derivatives have been indeed described by Evans et al. as effective catalysts for the asymmetric Diels-Alder reaction [71]. The bis(oxazoline) Ugand 54 allowed the Diels-Alder transformation of two-point binding N-acylimide dienophiles with good yields, good diastereos-electivities (in favor of the endo diastereoisomer) and excellent ee values (up to 99%) [72]. These substrates represent the standard test for new catalysts development. To widen the use of Lewis acidic chiral Cu(ll) complexes, Evans et al. prepared and tested bis(oxazoHnyl)pyridine (PyBOx, structure 55, Scheme 26) as ligand [73]. 

Lippard characterized the structural effect of variation in the alkyl bridge length in tropocoro-nand complexes of zinc (80). Six complexes of ligands with bridge lengths from n = m = 3 to n = m = 6 were structurally characterized.702 The complexes had distorted tetrahedral-square planar geometries, with the exception of the m = n = 3 adduct which was five-coordinate with an additional pyridine ligand. 

From 2002 to 2007, Kubiak and Janczak [27-30] and Sun s [31] groups investigated various symmetrical MPcs with pyridine and its derivatives 4-CP and 4-MP as two axial ligands. Six complexes in this series with crystal structures are reported. The crystal structures of MnPc(Py)2 (M = Mg (4), Mn (5), Co (6) or Fe (7)) complexes with axial pyridine ligands are isostructural. Another two compounds [FenPc(4-CP)2] 2(4-CP) (8) and [RunPc(4-MP)2] -2CHC13 (9) have similar molecular structures to 4-7. The central metal ions in these complexes lie at the inversion centres thus, the molecules are centrosymmetric. In the six complexes, the central metal ion and the four Niso atoms of the Pc(2-) ligands lie on a strict plane. The... 

Other structural features that have acceleratory influences in the base hydrolysis of Co(III) systems are (i) the incorporation of a pyridine ligand in the coordination sphere and (ii) the incorporation of a flat secondary nitrogen donor system in the polyamine ligand skeleton (5) (structures C and D in Fig. 17). 

Some multinuclear chromium(III) complexes which contain pyridine ligands have been described. The amide (122 - FL,L) reacts with CrCl3-6H20 in pyridine solution containing Na2C03 to give the dimer [Cr2(HL)2(py)4]-2py, the structure of which is described in Section 35.4.2,11.519... 

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