Heteropolymetalates

Kahn, O. (1987) Magnetism of the heteropolymetallic systems, Struct. Bonding, 68, 89-167. 

LLB, KHMDS (0.9 equiv to LLB) and H20 (1 equiv to LLB), which presumably forms a heteropolymetallic complex (LLB-ID, was found to be a superior catalyst for the direct catalytic asymmetric aldol reaction giving 49 in 89 % yield and 79 % ee (using 8 mol% of LLB). We employed this method to generate KOH in situ because of its insolubility in THE The use of KO-t-Bu instead of KHMDS gave a similar result, indicating that HMDS dose not play a key role. Interestingly, further addition of H20 (1 equiv with respect to LLB) resulted in the formation of 49 in 83 % yield and higher ee. The powder obtained from the cata-... 

This newly developed heteropolymetallic catalyst system (LLB-ID was applied to a variety of direct cat-... 

The carbonylmetallate anions are extremely useful organometallic reagents, particularly for the syntheses of heteropolymetallic clusters.3,4,7 However, they have rarely been isolated in the solid state and their solutions are obtained either by reduction of their dimers or by reaction of NaCsHs with the parent metal carbonyls,2 and immediately used. The first method is not very economical since the dimers are usually themselves obtained from the metallate anions. The second method has been improved as detailed below to allow the easy isolation of the pure Na[M(CO)3(//s-CsH5)] (M = Cr, Mo, W) solids as DME solvates.4 The nonsolvated Na[M(CO)3(f/5-C5H5)] salts can... 

Trost et al. [11] reported another impressive example of bimetallic catalysts in which a Zn-Zn homobimetallic complex (17, Scheme 7) serves as an effective catalyst for direct aldol reactions [11-13]. The proposed structure of the catalyst was verified by mass spectrometry and the best ratio of Et2Zn and the ligand. The chemical yield was moderate in the reaction of methyl ketones (1) (Scheme 7, top) [11,12], but a highly atom-economic system was achieved when a-hydroxylated ketones (10) were used as a substrate (Scheme 7, bottom) [13]. Excellent diastereo- and enantioselectivity were obtained under mild conditions. In contrast to the case of Shibasaki s heteropolymetallic catalyst, syn-1,2-diols (syn-11) were obtained as the major diastereomers. 

This system has been chosen just to pinpoint the variety of systems and of spin coupling schemes available in heteropolymetallic systems. 

The synthesis of heteropolymetallic d-f complexes is well documented and understood because the two metal ions display highly different stereochemical preferences. Valence... 

We have prepared a variety of new Schiff base bis crown ether ligands (98-100) that contain alkali and transition metal coordinating sites via the condensation of two or three equivalents of 4-formyl-benzo-15-crown-5 with an appropriate di- or triamine (Scheme 18). Homometallic copper(I), silver(I), and heteropolymetallic copper(I)-sodium, silver-(I)-sodium, and potassium complexes have been isolated. The singlecrystal X-ray structure of the [Cu(57)K](PF6)2 complex (100) is shown... 

Scarcia V, Furlani A, Longato B, Corain B, Pilloni G (1988) Heteropolymetallic complexes of 1, l -bis(diphenylphosphino)ferrocene (dppf). IV. Solvolytic behavior and cytostatic properties towards the KB cell-line of dppf and 1, 2-bis(diphenylphosphino)ethane cis complexes of platinum(II) and palladium(II). Inorg Chim Acta 153 67-70... 

Examples of other interesting additions (225) across the Rh=Rh bond include complexes of S02 (96 ) (225,230,231), selenium (97 ) (225,232), tellurium (225), sulfur (225,233), and AuCl [from AuCl(CO)] (225,230). The latter reaction results in a Rh2Au triangle and is just one of a large number of heteropolymetallic cluster complexes built up from 4 and 5 (see below). 

Feng J.-H., Li X.-J., Jing F.-Y., Pei F.-K., Synthesis, characterization, stability and relaxation behaviors of rare earth heteropolymetalates, Acta Chim. Sinica, 58 (2000) pp. 423 (in Chinese). 

Lanthanides Containing Multifunctional Heterobimetallic and Heteropolymetallic Asymmetric Catalysis... 

---