Heterobinuclear complexes synthesis

As mentioned above, in the heterobinuclear preparations the presence of both mono- and homobi-nuclear V02+ complexes was detected 897 two alternative explanations were suggested (i) any HC1 present in the CHCI3 used for recrystallizing could strip the metals from the ligand and allow subsequent incorporation of V02+ into the outer compartment (ii) during the synthesis, the mechanism depicted in Scheme 23 could take place. These observations suggest that in solutions of the heterobinuclear complexes, several species are probably present and the product isolated is a function of the insolubility of the individual species. 

The macrocyclic Schiff base 5,9,14,18-tetramethyl-l,4,10,13-tetraazacyclo-octadeca-5,8,14,17-tetraene-7,16-dione (I) (H4daen) can serve as a precursor to the formation of either mononuclear macrocyclic complexes or mononuclear acyclic complexes, depending on the reaction conditions. The mononuclear complexes may then be used in the synthesis of homo- or heterobinuclear complexes. The synthetic procedures described have been extended to include Schiff bases derived from a range of symmetrical and nonsymmetrical tri-... 

In 1987 we published the first review on the magnetism of heteropoly-metallic systems (3). This article was largely devoted to the mechanism of the interaction in heterobinuclear complexes. The field of heteropoly-metallic compounds was covered up to the first attempts to obtain molecular-based magnets. The very last sentence of this article was One may anticipate that in a few years another review will be necessary, and that its main emphasis will be on systems of higher nuclearity and extended systems with subtle spin orders. In the present case, our prediction was quite correct, which is not so frequent in science. The field of heterobimetallic systems has developed tremendously since 1987, particularly in relation to the synthesis of molecular-based magnets. It is now timely to write a second review concerning this topic. 

The best precursors are obtained using the sol-gel technique for they require lower calcination temperatures, allow better microstructural and compositional control plus the flexibility to produce a variety of shapes. Chandler et al. (1993) have reviewed the chemical aspects of solution routes to produce mixed oxides. The thermal decomposition of heterobinuclear complexes reported by Skaribas et al. (1991) leads to the production of perovskite oxides. More recently, Moreau et al. (1996) synthesized binuclear complexes of La-Ni, La-Co and La—Cu. Upon calcination at 973 K, the former two complexes yielded LaNiC>3 and LaCoC>3 perovskites while the latter yielded La2CuC>4. The main limitation in this and related methods is the complicated synthesis of the binuclear complexes that makes their application for large scale processing very unlikely. 

In this paper we shall concentrate on the synthesis and properties of bis-macrocyclic ligands with special attention to the preparation of homo- and heterobinuclear complexes. 

Jain, V. K. In Synthesis, Reactivity and Redistribution Reactions of Homo- and Heterobinuclear Palladium(II) and Platinum(II) Complexes. Adv. Organomet. Proceedings Indo-Sov. Symp. Organomet. Chem., 1st. ed. Jain, D. V. S., Ed. Indian Natl. Sci. Acad New Delhi, India 1989, 143-162. 

Costes J. P. and Fernandez Garcia M. I., Synthesis and characterization of homobinuclear and heterobinuclear imidazalate-bridged complexes, Inorg. Chim. Acta, 173 (1990) pp.247-254. 

The synthesis of homo- (Ti-Ti) and heterobinuclear (Ti-Zr) complexes linked by 1,2-G2H4 linker groups as shown in Scheme 316 has been reported. The molecular structures of the dimethylamido derivatives have been determined by X-ray diffraction methods. In the presence of binuclear borate activators, the methyl complexes produce long-chain branched polyethylene and polystyrene in homopolymerization reactions and ethylene-styrene co-polymers. The polymerization behavior differs from that obtained with the mononuclear compound (3-ethylindenylSiMe2-NBiOTiMea (Scheme 3 1 7).762"764... 

Thioalkyne titanium derivatives with functionalized Cp rings (C5H4R1)(G5H4R2)Ti(SG=CR)2 (R = Ph, Buc, R1 = R2 = SiMe3 R = Buc, R1 = SiMe3, R2 = PPh2 R = Buc, R = R2 = PPh2) have been prepared and used as precursors for the synthesis of heterobinuclear Ti-M (M = Mo, Pd, Pt) complexes with different coordination modes (Scheme 732). The crystal structures of some of these complexes have been reported.1840... 

It is against this background that we have developed in our laboratories a very simple one-step procedure which allows the synthesis, usually in acceptable yields, of a wide variety of and M -dppm-CO mono- and (more usually) binuclear complexes directly from metal salts. The procedure has been extendi with considerable success to the one-step synthesis of certain heterobinuclear systems and also some phosphido-bridged complexes of Co and Np. While this study has so far been largely concerned with Co and systems, preliminary work has been carried out with Rh , Pd and Fe . Some of the work described herein has been reported in preliminary communications but a complete overview of all aspects of the investigations carried out so far is given here in order that the very broad applicability of the procedure can be fully appreciated. 

Scheme 5.7 Synthesis of Group 1/Group 2 heterobinuclear NHC complexes 50.

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