Copper complexes tridentate ligands

The cationic aqua complexes prepared from traws-chelating tridentate ligand, R,R-DBFOX/Ph, and various transition metal(II) perchlorates induce absolute enantio-selectivity in the Diels-Alder reactions of cyclopentadiene with 3-alkenoyl-2-oxazoli-dinone dienophiles. Unlike other bisoxazoline type complex catalysts [38, 43-54], the J ,J -DBFOX/Ph complex of Ni(C104)2-6H20, which has an octahedral structure with three aqua ligands, is isolable and can be stored in air for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. 

Substituted terpyridine, 4,4, 4"-tris(5-nonyl)-2,2 <5, 2"-terpyridine (tNtpy), is a planar tridentate ligand that was successfully used in homogeneous ATRP of methyl acrylate and styrene [79]. Polymerization of both monomers was controlled and the resulting polymers had relatively low polydispersities (MJMn < 1.2). Similarly to PMDETA, the typical ligand to copper halide ratio used in the polymerization was 1 1. Terpyridine and its derivatives are expected to form tetra-coordinated complexes with copper in which the fourth coordination sphere is occupied by a monodentate ligand (Br-, Cl , solvent, monomer, etc.). Although,... 

In a similar investigation of the tautomeric tridentate ligand 2 -hydroxyphenylazo-2-naphthol (5.65 in Scheme 5.17), the first and second acidic dissociation constants (pKa) related to the two hydroxy groups in the parent structure (X = H) were found to be 11.0 and 13.75 respectively. On introduction of an electron-withdrawing substituent (X) the first dissociation constant decreased from 11.0 to 10.55 (X = Cl) or 7.67 (X = N02). The stability constants (log K1 1) of the derived 1 1 complexes were dependent on the metal ion introduced [46], being particularly high for nickel(n) at 19.6 and copper(II) at 23.3. 

The cationic aqua complexes of the C2-symmetric trans-chelating tridentate ligand 447 proved also highly effective chiral catalysts. The complexes involving the metal(II) perchlorates of iron, cobalt, nickel, copper and zinc produced the main endo adduct of cyclopentadiene and N - aery loy 1-1,3 -oxazo I i din -2 -one with very high ee values281. 

Figure 19 Some pentadentate Schiff bases (a) which act as bis-tridentate ligands in copper(ll) complexes (b) pentadentate...

The initial reactions of this type were used to produce copper(II) complexes of salicylaldimines, where additional coordination support is provided by the phenolic oxygen atoms (equation l).10 11 Similar use can be made of pyridine-2-carbaldehyde in the formation of imine chelates. For example, the combination of pyridine-2-carbaldehyde and 2-aminobenzenethiol in the presence of metal ions yields tridentate complexes (Scheme l).12 If the reaction is carried out in the absence of the metal ion, the benzothiazolidine (1) is isolated. Thus the metal ion is essential for the formation of the imine product in this case. Metal complexes of the related tridentate ligands (2),13 (3),14 (4)li and (5)16 can be prepared similarly. 

A novel peroxocopper complex with -coordination is formed when copper(II) perchlorate is reacted with the tridentate ligand 4-methyl-2,6-bis(pyrrol-idinomethyl)phenol (HL) in methanol solution, in the presence of air, triethyl-amine base, and 3,5-di-teri-butylcatechol [142], The four copper(II) ions in [Cu4L2(02)(0Me)2(C104)] (32) form a near-planar rectangle, with alternate methoxo (Cu... Cu = 3.03 A) and phenolato (Cu... Cu = 2.99 A) bridging ligands. 

B(C2H5)2The tridentate ligand [HB pz-3,5-(CH3)2 2(SCgH4-4-CH3)]" was synthesized intentionally from ArSH and K[H2B pz-3,5-(CH3)2 2]- It was converted to L MSR complexes (M = Cu or Co SR = 0-ethylcysteine,p-nitrobenzenethiolate or pentafluorophenylthiolate). These compounds were studied as synthetic approximations of the proposed active sites in the blue copper proteins (plastocyanin, azurin)... 

The 1,3,5-triketones are potentially dinegative, tridentate ligands and the well-developed JT-system of the dianion gives to the ligands a preference for a planar configuration, thus precluding tridentate coordination to one metal ion. For example, copper(ll) and heptane-2,4,6-trione give mononuclear (132) and dinuclear complexes (133) ". ... 

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