Diimine complex synthesis

Synthesis, photophysical, and electrochemical properties of dinuclear Cd(II) diimine complexes with bridging chalcogenolate ligands were described [91]. 

Also, Yam and Cheung [62] have carried out the synthesis of a series of novel polynuclear mercury(II) diimine complexes with bridging chalcogenate ligands and studied their luminescence and electrochemical properties. 

The synthesis of metal-coordinated 1-azirines and the reactions of azirines induced by metals have opened a new area in the chemistry of this small ring heterocycle. Many of the reactions encountered bear resemblance to previously discussed thermally and photo-chemically induced reactions of 1-azirines. The reaction of a series of diiron enneacarbonyls in benzene results in coupling and insertion to give diimine complexes and ureadiiron complexes as well as pyrroles and ketones (76CC191). A mechanism for the formation of these products which involves initial 1,3-bond cleavage and generation of a nitrene-iron carbonyl complex as an intermediate was proposed. 

Also other active metal complexes (i.e., several Co SchifF base [232] and Mn diimine complexes [233]) have been supported in this way. The high dispersion of the complexes in the cages of the molecular sieves allows to study the redox properties of mononuclear complexes that are imstable in solution [234]. The increased stability of the obtained materials, the easier handling of heterogeneous catalysts and the high yields achieved make these supramolecular systems a very promising candidate for further catalyst development in fine chemical synthesis. 

Shavaleev NM, Davies ES, Adams H et al (2008) Platinum(II) diimine complexes with catecholate ligands bearing imide electron-acceptor groups Synthesis, crystal structures (spectre) electrochemical and EPR studies, and electronic structure. Inorg Chem 47 1532-1547... 

Schmid, M., Eberhardt, R., Klinga, M et aL (2001) New C y- and chiral C2-symmetric olefin polymerization catalysts based on nickel(II) and palladium(II) diimine complexes bearing 2,6-diphenyl aniline, moieties Synthesis, structural characterization, and first insight into polymerization poperties. Organometallics, 20,2321 2330. 

Zhang, Y.W. and Ye, Z.B. (2008a) Homogeneous polyhedral oligomeric silsesquioxane (POSS)-suppdiimine complex and synthesis of polyethylenes end-tethered with a POSS nanoparticle via ethylene living polymerization. Chemical Communications, 1178-1180. 

Bazan and coworkers recently described the synthesis and olefin polymerization behavior of a nickel a-keto-p-diimine complex. At 0°C, aaivation of 117 (Figure 29) with MAO in the presence of 1-hexene furnished rtPH possessing Mn= 157000gmol" and My,/M =1.2. Over the coirrse of 120 min, molecular weights of the polymers obtained from the polymerization were observed to increase while polydispersities remained narrow. Microstmctural analysis of the polymer by C NMR spectroscopy revealed mainly butyl (81.9%) and methyl (12.0%) branches signatures arising from 2,1-rnsertions were not detected. 

An interesting extrapolation of this synthesis deals with the preparation of the bispyridinium salt 62 from 1,2-phthalic dicarboxaldehyde and its subsequent reaction with primary amines (92BSB509).Tlie expected diimines 63 readily cyclize so that 2-aryl-l-arylimino-2,3-dihydro-l//-isoindoles 64 can be isolated in excellent yields (90-95%). Contrary to the reactions performed by employing the dialdehyde and amines directly, the syntheses involving the azinium salts do not produce those typical dark-colored complex mixtures of products (77JOC4217 85JHC449) (Scheme 20). 

There are very few examples of asymmetric synthesis using optically pure ions as chiral-inducing agents for the control of the configuration at the metal center. Chiral anions for such an apphcation have recently been reviewed by Lacour [19]. For example, the chiral enantiomerically pure Trisphat anion was successfully used for the stereoselective synthesis of tris-diimine-Fe(ll) complex, made configurationally stable because of the presence of a tetradentate bis(l,10-phenanthroline) ligand (Fig. 9) [29]. Excellent diastereoselectivity (>20 1) was demonstrated as a consequence of the preferred homochiral association of the anion and the iron(ll) complex and evidence for a thermodynamic control of the selectivity was obtained. The two diastereoisomers can be efficiently separated by ion-pair chromatography on silica gel plates with excellent yields. 

The synthesis of [Ircp Cl(bpy-cd)]Cl, where bpy-cd is a /3-cyclo-dextrin attached at the 6 position to a bpy ligand, is detailed.138 The complexes [Ircp (diimine)X]+, X = C1, H, diimine = bpy, phen, are active catalysts for the light-driven water-gas-shift reaction.139 The hydride complexes luminesce at 77 K and room temperature, whereas the chloride complexes do not.140 The three-legged piano-stool arrangement of the ligands in [Ircp (bpy)Cl]+ and [Ircp (4,4 -COOFl-bpy)Cl]+ is confirmed by X-ray crystallography.141,142 Further mechanistic studies on the catalytic cycle shown in reaction Scheme 11 indicate that Cl- is substituted by CO and the rate-determining step involves loss of C02 and H+ to leave the Ir1 species, which readily binds Fl+ to yield the lrIH hydride species.143... 

The introduction of cyano groups in the 3-position of diketimiminate ligands greatly increased the crystallinity of their complexes (Figure 49, 95), due to the formation of one-dimensional coordination polymers. A new f3-oxo-<5-diimine ligand, in turn, allowed the synthesis of a bimetallic organozinc complex 96, by the same methods that had been used for the syntheses of the mononuclear species 92-94.154... 

As mentioned already, Curtis reported the first (Curtis, 1960) of a number of pioneering template reactions for macrocyclic systems which were published in the period 1960 to 1965. In the Curtis synthesis, a yellow crystalline product was observed to result from the reaction of [Ni(l,2-diaminoethane)3]2+ and dry acetone. This product was initially thought to be a bis-ligand complex of the diimine species (58). However, the stability of the product in the presence of boiling acid or alkali was... 

However, the practical, direct synthesis of functionalized linear polyolefins via coordination copolymerization olefins with polar monomers (CH2 = CHX) remains a challenging and industrially important goal. In the mid-1990s Brookhart et al. [25, 27] reported that cationic (a-diimine)palladium complexes with weakly coordinating anions catalyze the copolymerization of ethylene with alkylacrylates to afford hyperbranched copolymers with the acrylate functions located almost exclusively at the chain ends, via a chain-walking mechanism that has been meticulously studied and elucidated by Brookhart and his collaborators at DuPont [25, 27], Indeed, this seminal work demonstrated for the first time that the insertion of acrylate monomers into certain late transition metal alkyl species is a surprisingly facile process. It spawned almost a decade of intense research by several groups to understand and advance this new science and to attempt to exploit it commercially [30-33, 61]. 

The formation of circular or linear forms seems to depend on balances between kinetic and thermodynamic control iron(II)-poly-2,2 -diimine systems with their substitutionally inert metal centers provide useful systems for disentangling thermodynamic and kinetic contributions. The mechanism of formation of circular helicates is believed to entail a kinetically favored triple helicate intermediate. Self-assembly of chiral dinuclear binaphthol-linked iron(III) porphyrin complexes into extended polynuclear species takes place through the intermediacy of fi-oxo dimers. Predetermined //-oxo-di-iron-dimers may be used in this type of synthesis. 

The synthesis of hexadentate tris-diimine ligands, e.g., (75), has resulted in Fe " eomplexes whieh are very inert to substitution, especially when the ligand is tripodal, e.g., (76), even more so when it is eneapsulating. Such extremely inert complexes are partieularly valuable for studies of eleetron transfer or of solubilities and solvation. Fe complexes of several encapsulating tris-diimine ligands, for example the cage ligands (77), (78) and (79), show the expeeted extreme substitution inertness." ... 

Gibson described the synthesis of four-coordinate cationic aluminium alkyls 1 which were reported to be well-defined aluminium polymerization catalysts [12]. However, the polydispersities of the products obtained were high (2.9-6.3), showing that there is not a single well-defined active species. The experiments were carried out in metal autoclaves, and Fe and Co complexes of pyridine-diimine ligands are extremely active in ethene polymerization [34], so a transition-metal impurity does not seem an unreasonable explanation. 

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