Dinuclear metal complex

Reactions of clusters with mononuclear or dinuclear metal complexes frequently provide a method of expanding the metal core nuclearity under controlled conditions. The majority of medium- and high-nuclearity homometallic clusters has been prepared from lower-nuclearity cluster precursors by thermolyses ("heat-it-and-hope ) reactions. This is less true of the heterometallic clusters in this... 

Oxidative-addition reactions have been widely studied with bridged dinuclear metal complexes [1,2,5, 32]. Earlier work with the ylides and sulfur bonded ligands... 

A large number of mono- and dinuclear metal complexes of the ligands H2L19 and H2L23 has been synthesized and characterized within the last five years. Selected examples originating from this work will now be presented and discussed. 

Fig. 1. The common binding modes of dioxygen as a ligand in mononuclear and dinuclear metal complexes.

O. (2004) Synthetic metallonucleases for RNA cleavage. Curr. Opin. Chem. Biol., 8, 192. (e) Molenveld, P., Engbersen, J.F.J. and Reinhoudt, D.N. (2000) Dinuclear metallophosphodiesterase models application of calix[4]arenes as molecular scaffold. Chem. Soc. Rev., 29, 75. (f) Kimura, E. (2000) Dimetallic hydrolases and their models. Curr. Opin. Chem. Biol., 4,207. (g) Williams, N.H., Takasaki, B. and Chin, J. (1999) Structure and nuclease activity of simple dinuclear metal complexes quantitative dissection of the role of metal ions. Acc. Chem. Res., 32, 485. (h) Hegg, E.L. and Burstyn, J.N. (1998) Toward the development of metal-based synthetic nucleases and peptidases a rationale and progress report in applying the principles of coordination chemistry. Coord. Chem. Rev., 173, 133. 

As previously observed with hexadentate Schiff bases, potentially heptadentate ligands easily form dinuclear metal complexes. This is the case with trisalicylidenetriethylenetetramine, shown in Figure 21b, which gives methoxo145 and hydroxo146 dinuclear Fe111 complexes. 

Numerous dinucleating macrocyclic and macrobicyclic ligands have been synthesized, in particular by the versatile amine + carbonyl — imine reaction they form dinuclear metal complexes as well as cascade complexes with bridging groups [2.58-2.63, 3.24-3.27, 4.1-4.4], for instance in dicobalt complexes that are oxygen carriers [3.26]. 

Molecular hysteresis results when the interconversion between the states does not follow the same pathway on sweeping the external stimulus or field in one or the opposite directions [8.240a, 8.241]. A hysteresis loop has, for instance, been described for the electrochemical interconversion of redox states in a dinuclear metal complex it involves the switching between two different binding sites [8.240b]. Spin... 

BALCH Novel Reactions of Dinuclear Metal Complexes... 

Several dinuclear metal complexes with the ligand system 53 as bridging unit are now known, where steric constraints are much less pronounced and where fold angles are much greater or nearly 180°. These complexes belong to the structure types 60-63, where the metal fragments reside in fraws-configuration, i.e. on different sides of the... 

Table 13.2. Experimentally determined and calculated metal-metal distances for dinuclear metal complexes (see Fig. 13.6)[244 245].

A dinuclear metal complex, 76, in a more rigid framework, which forces two manganese centers into close proximity within a single macrocycle (Figure 33), also evolves 02 from H20 [163a,164],... 

Giuffrida, G. and Campagna, S. (1994) Influence of peripheral ligands on the metal-metal interaction in dinuclear metal complexes with V-heterocyclic bridging ligands, Coord. Chem. Rev. 135/136, 517-531. 

By reaction of cobalt(II) aquacation with triphos and HSR [R = H, He) different dinuclear metal complexes are formed with formulae [(triphosJCoIp-SR Cottriphos)] + and [(triphos)Co(u-S)2 Co[triphos)]0 +. These dinuclear complexes contain from 32 to 34 valence electrons. Those with 34 electrons present antiferromagnetic behavior. These properties are explained in terms of a molecular orbital treatment of the type suggested by Hoffmann and Burdett for unpuckered dinuclear metal complexes. 

Imae, T., Y. Ikeda, M. Iida, N. Koine, and S. Kaizaki. 1998. Self-organization of a dinuclear metal complex in lyotropic liquid crystal Ribbonlike supramolecular assemblies. Langmuir 14 5631-5635. 

O. Picazo et al., Bonding properties related with chiral discrimination in dinuclear metal complexes of group 10. Eur. J. Inorg. Chem. 2, 324-332 (2007)... 

Fig. 2.1.4. Bis(2,2 -bipyridine)-substituted BINOL 10 and its dimeric and trimeric dinuclear metal complex.

In this case, the best results were obtained by precipitating the dinuclear metal complexes as the PF6 salts. Elemental analysis suggests, as already indicated above, that the products are isolated as sodium salts such as Na3[Ru(dcb)2(bpt)]-3H20 for the mononuclear precursor and Na3[Ru(dcb)2(bpt)0s(bpy)2](PF6)2-3H20 for the Ru-Os dyad. The number of sodium atoms incorporated is, however, not always the same but appears to depend on the manner in which the materials are precipitated. Nevertheless, the uncertainty in the composition of the compounds in the solid state does not affect the measurements, since in all cases the protonation state of the compounds in solution is controlled by the pH of the solutions. 

Floris B, Donzello MP, Ercolani C (2003) Single-atom bridged dinuclear metal complexes with emphasis on phthalocyanine systems. In Kadish KM, Smith KM, Guilard R (eds) The porphyrin handbook, vol 18. Academic Press, San Diego, p 1... 

Figure 6.13 Joint Lewis acid activation and nudeophile activation with dinuclear metal complexes.

Phosphates bridge dinuclear metal centers in the active sites of some phosphoes-terases [1-3]. Dinuclear metal complexes should be able to provide double Lewis acid activation for hydrolyzing phosphates. To quantify double Lewis acid activation for cleaving phosphate diesters, we studied the reaction of 24 (Figure 6.16), which has... 

DINUCLEAR METAL COMPLEXES WITH BRIDGING M—H—SI INTERACTIONS... 

The distinction between between mono- and dinuclear metal complexes is only a formal one in terms of bonding (consider one substituent at silicon the second metal atom instead of an organic group, halide, or hydride substituent). The structural and spectroscopic features related to the three-center bond should therefore be more or less the same as previously discussed. 

Apart from the dinuclear metal complexes 17-19 there are also some mononuclear metal compounds for which the occurrence of M—H—Si three-center bonds appears possible, judging from currently available data. The first complex in this category, 20, was obtained by Jetz and Graham among other products by reaction of trichlorosilane with Cp2(OC)4Fe2 (65). 

---