Heterobimetallic compounds

In contrast to homobimettJlic compounds, heterobimetallic compounds with M-M bonds (where M and M are different group 10 metals) are far less developed. In the last decade, a few of these compounds were synthesized and representatives are summarized in the following section. 

Pt-Pd compounds represent the vast majority of the family of Group 10 heterobimetallic compounds with metal-metal bonds. 

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A heterobimetallic compound containing a Cp2Tilv unit linked via diphenylphosphinoacetate to a silver(I) center has been isolated, [TiCp2 /r-OCOCH2PPh2)2AgCl].7 In the complex... 

M Shibasaki, H. Sasai, T. Arai, Asymmetric Catalysis with Heterobimetallic Compounds, Angew. Chem Int. Ed Engl 1997, 36,1236-1256. 

In the solid state, both 46 and 47 exist as bent monomeric sandwich complexes with ring centroid-lead-ring centroid angles of 152.2° in 46 and 144.2° in 47. Interestingly, if the reaction between PbCl2 and [Li(dme)2][/Bu2G2P3] is carried out in tmen rather than DME, the product formed is not a homoleptic plumbylene but rather the novel heterobimetallic compound 48.73... 

The complex [ ((Me3Si)2N)4K2Mg2(O2) ] obtained from KBu, Mg Bui and (Si-Me3)2NH is similar to the related heterobimetallic compounds [ (Me3Si)N 4Li2M-in that it... 

In addition to the heterometallic species involving group 1 and group 2 metals there is also an example featuring two alkahne earth elements in the heterobimetallic compound which has a puckered (MgNCaN) ring... 

Ethynylruthenocene acetylides, preparation, 6, 642 ETL, see Electron-transporting layer ET reactions, see Electron-transfer reactions Europium complexes with arenes, 4, 118-119 Cp2Ln compounds, 4, 27 CpLnX2 compounds, 4, 29-30 Cp2M compounds, 4, 63 cyclooctatetraenyl compounds, 4, 122-123 heterobimetallic compounds without direct M—M bonds,... 

Most of the knowledge about aluminate and alkylaluminum coordination stems from X-ray crystallographic studies. The basic idea of this section is to compile a rare-earth metal aluminate library categorizing this meanwhile comprehensive class of heterobimetallic compounds. Main classification criteria are the type of homo- and heterobridging aluminate ligand (tetra-, tri-, di-, and mono alkylaluminum complexes), the type of co-ligand (cyclopen-tadienyl, carboxylate, alkoxide, siloxide, amide), and the Ln center oxidation state. In addition, related Ln/Al heterobimetallic alkoxide complexes ( non-alkylaluminum complexes) are surveyed. Emphasis is not put on wordy structure discussions but on the different coordination modes (charts) and important structural parameters in tabular form. An arbitrary collection of molecular structure drawings complements this structural report. 

Figure 18-A-4 Structure of some polar unsupported heterobimetallic compounds, M = Ti, Zr, and Hf and M = Fe and Ru.

Some of these oxygen-bridged heterobimetallic compounds were found highly active as catalysts in ethylene polymerization. Tables 1-3 represent the results of ethylene polymerization experiments. All polymerization reactions were carried out under extremely mild conditions at room temperature and at ambient pressure. The data of Tables 1-3 show that the highest activities (activities of the order of 10 g-(mol of catalyst) h ) in ethylene polymerization were observed for the complexes of the type [LAlMe(g-0)MRCp2] (12a, 13, and 15, Scheme 9) (27,45). These catalysts exhibited activities in ethylene polymerization two orders... 

Shibasaki, M. Sasai, H. Asymmetric Catalysis Using Heterobimetallic Compounds, Adv. Asym. Synth., Vol. 3, Hassner, A., Ed., JAI Press, Stamford, CT, 1998. 

Ferrocenyl and ferrocenyl thiolate derivatives of the metals are heterobimetallic compounds, one component of which is iron. In principle, complex fragments of different metals may be combined with a ferrocene unit, as in the trimetallic l,T-ferrocenylene dithiolate, Cp(NO)2Cr-[S(fc)S]-W(CO)3Cp. Another versatile method to synthesize heterobimetallic complexes makes use of chelating ligands such as l,l -bis(diphenylphosphinyl) ferrocene, fc(PPh2)2 (see Chapter 1), and 1,1 -bis(methylchalcogenyl) ferrocene, fc(EMe)2 (E = S, Se), (Sect. 5.4). 

Several molecular structures, including those of T1(I) nitrate," " iodate," " borate," germ-anate," sulfate, " phosphates, arsenate, chromate," and selenate," have been reported. Heterobimetallic compounds with Tl-0 interactions have been reported. Their metal-thallium bonding and their photophysical properties are of particular interest. 

Ethyl rhenlumpentacarbonyl has been reacted with various metal hydrides in acetonitrile 158). The observed products were heterobimetallic compounds, although a solvated rheniumtetracarbonyl acyl complex was detected [Eq. (47)]. If the metal hydride is in excess, the rate-determining step is formation of the propionyl complex. The reaction was subsequently found to be first order in both the propionyl complex and the metal hydride. The second-order rate constants were measured and were found to be the reverse of the order of the acidities of the transition metal hydrides, which implies that the hydrides react as nucleophiles with the propionyl complex. In a separate experiment, [Re(COEt)(CO)j] was found to react with [Re(H)(CO)j] only after carbonyl dissociation, implying that the metal and not the acyl carbonyl is the site of nucleophilic attack by transition metal hydrides on acyl complexes. 

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