Diimine type ligand

Correia SG, Marques MM, Ascenso JR, Ribeiro AFG, Gomes PT, Dias AR, Blais M, Rausch MD, Chien JCW (1999) Polymerization with TMA-protected polar vinyl comonomers. II. Catalyzed by nickel complexes containing a-diimine-type ligands. J Polym Sci A Polym Chem 37 2471... 

The trans-cis photoisomerization of the stilbene-type ligand in the Re(I) diimine complexes has been reported (55). 

Dinuclear complexes of the type (CAN)2Rh(LAL/LAL)Rh(CAN)2 can be prepared according to the following reaction sequence, where (L A L/L A L) are diimin bridging ligands of the bipyrimidine-type ... 

A number of dinuclear cobalt dioxygen complexes with polyamine type ligands (pyen, pydien, amp) have been reported to undergo oxidative dehydrogenation in water at 35 [5,17,23,24]. These reactions are base catalyzed and lead to the formation of mono- and diimines in which the C=N bonds are conjugated with an aromatic ring. In addition to UV and IR evidence, the monoimine intermediate has been detected via hydrolysis to the aldehyde. The proposed reaction paths are shown for the pydien system in Scheme 1. 

A large amount of work has been published on Re complexes of the general type [(L)Re(CO)3(a-diimine)] +. These complexes exhibit Re —> (diimine) MLCT emission at room temperature in solution and the emission energy can be tuned by variation of the diimine, ancillary ligand, L, and solvent. Several reviews have appeared that discuss the luminescence behavior of these complexes. " Recently, detailed temperature-dependent luminescence measurements have been made on several methylated phenanthroline (w-phen) complexes of the type [ClRe(CO)3( i-phen)] the emission from the complexes was comprised of components from the MLCT and m-phen localized tt-tt states. Emission from this class of chromophores has been plied recently to immunoassays based on luminescence polarization of Re diimine complexes and the development of unique luminescent arylethynylene polymers. ... 

A considerable amount of work has focused on understanding die photophysical behavior of the halo analogue complexes ReX(CO)3(diimine). These complexes, where the diimine is a bipyridine- or a phenanthroline-type ligand, show... 

There are more examples of a second type in which the chirality of the metal center is the result of the coordination of polydentate ligands. The easiest case is that of octahedral complexes with at least two achiral bidentate ligands coordinated to the metal ion. The prototype complex with chirality exclusively at the metal site is the octahedral tris-diimine ruthenium complex [Ru(diimine)3 with diimine = bipyridine or phenanthroline. As shown in Fig. 2 such a complex can exist in two enantiomeric forms named A and A [6,7]. The bidentate ligands are achiral and the stereoisomery results from the hehcal chirality of the coordination and the propeller shape of the complex. The absolute configuration is related to the handness of the hehx formed by the hgands when rotated... 

The formation of diimine systems by Schiff -base-type condensation of suitable aldehydes and primary amines has been widely applied. Those reported are mostly strong field systems and their relevance to the spin crossover field is generally in systems of the kind [Fe(diimine)2(NCS)2]. The effect of the incorporation of substituents likely to hinder coordination has been studied. Robinson and Busch noted a fundamental difference at room temperature in the electronic properties of the [Fe N6]2+ derivatives of 2-pyridi-nalmethylhydrazone and 2-pyridinal-dimethylhydrazone, those of the former being low spin and those of the latter high spin [49]. The temperature-dependence of the magnetism of the latter complex was not reported but may well be of interest. However, spin crossover [Fe(diimine)3]2+ systems have been characterised for systems where the incorporation of appropriate substituents has reduced the ligand field. 

What specific properties of these complexes have allowed isolation of five-coordinate Pt(IV), in the form of the trimethyl complex and the dihy-dridosilyl complexes These two types of complexes are significantly different, and their stability is apparently due to different factors. Comparing the trimethyl complex in Scheme 21(A) with the related but six-coordinate complexes of a similarly bulky oc-diimine ligand (98), shown in Scheme 23, is instructive. In Scheme 23A, triflate is clearly coordinated, exhibiting an O-Pt distance of 2.276(3) A (98), which is typical for Pt-coordinated triflate (108). This triflate complex A in Scheme 23 was obtained from dry tetrahydrofuran. The aqua complex cation B, also structurally characterized, was obtained from acetone containing trace water. An equilibrium between coordinated triflate and coordinated water, very likely via a common five-coordinate intermediate, was indicated by NMR spectroscopy (98). 

Ni(II) by strong oxidants, such as OH, Br and (SCN), produced by pulse radiolysis and flash photolysis. Rate constants are 10 M" s for oxidation by OH and Brf and = 10 M s for (SCN)f Ref. 259. The most popular means of production in both aqueous and nonaqueous solution is electrolytic, jjjg ligands which stabilize Ni(III) are cyanide, deprotonated peptides, amines and aminocarboxylates, a-diimines and tetraaza macrocycles, including porphyrins. Low spin d Ni(III) resembles low spin Co(II). The kinetics of the following types of reactions have been studied ... 

Substitution reactions of hexadentate diimine complexes of iron(II) are generally slow, thanks to the combination of the strongly binding diimine groups and the chelate effect, even when the ligand contains only two diimine units of the less strongly bonding py—CH=N— type k2(OH)... 

Yttrium bis(alkyl) and bis(amido) complexes of the type [LY(CH2SiMe3)2] bearing N,0-multidentate ligands (L), such as p-diimines, displayed high activity for the ROP of L-lactide at room temperature (100% conversion in most experiments in THF within 2-60 min). In this case, an influence of the ligand framework and the geometry of the alkyl(amido) species (single site or double site) on the catalytic activity have been reported [106]. 

Oxidases, types, 40 122 Oxidation, see also Coordinated diimine ligands... 

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