Heterometallic compounds

Gleizes, A. N. 2000. MOCVD of chalcogenides, pnictides, heterometallic compounds from single-source molecule precursors. Chem. Vap. Deposition 6 155-173. 

Ferrocenyl-containing zinc complexes 64 and 65 were analyzed by El mass spectrome-try57"58 For 64, the intact M+ has been recorded at 70 eV gj mass spectra for the other heterometallic compounds, such as Zn F. containing mixed-valence Mn Fjy[n( 7... 

Figure 4.48 Imidazole-based species used as ligands in Au/Ag heterometallic compounds.

The chemistry of these heterometallic compounds based on the M—O—motif covers main-group elements, transition metals, and lanthanides. The generation of the M—O—motif (21) requires the successful s)mtheses and stabilization of well-defined hydroxides. A considerable effort has been ongoing to stabilize terminal hydroxides of main-group and transition metals (22). Recently, a number of well-defined hydroxides of main-group and transition metals 1-11 (Chart 1) have been made (23-35) by careful hydrolysis of suitable precursors. Some of these hydroxides were used as building blocks to synthesize heterometallic complexes with M—O—backbones by reaction with catalyti-cally active transition metal complex precursors. 

The s)mthesis of a new transition metal precursor chemically fixed to main-group organometallic cocatalysts is an important subject—pointing the way toward heterometallic compounds with unusual properties and... 

This section covers some other heterometallic rare earth oxides, including Al, Ti, Zr, Sn, Mo, W, Mn, Fe, Co, Ni, and Cu complex oxides, while certain well-known oxysalts, Y-Ba-Cu-O, for example, will not be specifically discussed. For these heterometallic compounds, due to their relatively complex compositions, it is usually difficult to obtain phase-pure products, especially when some dopant ions are added. At elevated temperatures, some of these oxides undergo phase transitions, which may significantly change their physical and chemical properties such as thermal expansion coefficient and ionic conductivity. And for fhose oxides with variable metal valencies, different nonstoichiometric compositions may also result in distinct functionalities in magnetism and catalysis. 

Many studies have focused on the rich redox and magnetic behaviors of PB materials (45 9), as well as on the synthesis and characterization of PB analogues. Synthetic studies have produced a vast number of new materials that include binary (homometallic) and ternary (heterometallic) compounds, as well as compounds that incorporate additional organic ligands. Structurally, these PB analogues range from discrete compounds (50-53) to extended, 3D frameworks. A more comprehensive review of PB is beyond the scope of this chapter. 

Scheme 1. A classification scheme to describe the overall dimensionality and local uranyl geometry in U(VI) containing CPs and MOFs. The superscripts describe the uranium coordination geometry whereas the subscripts refer to any second metal centers present, as in heterometallic compounds.

Thus, the methodology to synthesize heterometallic compounds mainly depends on both the nature of the elements and the ligand(s) employed. 

Finally, elemental analysis results may pose difficulties in arriving at the correct composition of tin(II) heterometallic compounds due to changes in metal-ligand ratio. However, with the help of X-ray structural analysis, the CHN results may prove fruitful to prove the stoichiometry of the heterometallic species. 

Cages within this class are less common than the former class. There are four Mn cages within the group and a heterometallic compound involving cobalt. 

Scheme 1. A classification scheme to describe the overall dimensionality and local Ln geometry in CPs and MOFs. The superscripts describe the lanthanide coordination geometry, whereas the subscripts refer to any additional metal centers present, as in heterometallic compounds. D = overall dimensionality of compound a = building unit dimensionality of /-block metal b = number of centers in zero-dimensional building unit of first metal c = building unit dimensionality of d-block metal (if present) d = number of centers in zero-dimensional building unit of second metal center. This labeling scheme is represented in the tables for all referenced compounds.

Theoreticians are invited to develop new approaches to account for the redox behavior of polynuclear heterometallic compounds. 

CL-substituted metal alkoxide derivatives can, in principle, also be obtained by ligand exchange reactions between different metal complexes. For example, reaction of Y(0CH2CH20Me)3 with Cu(acac)2 resulted in a variety of species, from which Y3(0CH2CH20Me)s(acac)4 was isolated." Depending on the combination of metal complexes, heterometallic compounds may also be formed in such reactions." ... 

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