Trimetallic species

Although stable and neutral bimetallic complexes were obtained from the dicat-ionic fragments and 129 or 130 there was the possibility that reactions with two molar equivalents of a metal-ligand monocation should give rise to trimetallic species. However, reactions of 130 with sources of the cations M (CO)3 (M = Mn, Re), namely [Mn(NCMe)3(CO)3][PF6] and [ReBr(THF)2(CO)3], yielded as products [N(PPh3)2][l,3,6- M (CO)3 -3,6-(p-H)2-l,l,l-(CO)3-2-Ph-c/ow-l,2-ReCBgHT] [M = Mn (156), Re (157)], respectively (Chart 27). ° In these molecules, the exo-polyhedral M (CO)3 moiety is almost certainly bonded to the cluster via two non-equivalent B-H M interactions with an Re-M bond completing... 

Addition of excess allylzinc bromide to the conjugated enynol 297 chemoselectively affected the triple bond and afforded a mixture of monoaddition and bis-addition products. The formation of di- and trimetallic species was unambiguously ascertained by deuteriolysis (equation 137)171. 

The Group IB metal site preferences in heteronuclear cluster compound allow coinage metal exchange reactions between clusters and mononuclear complexes to be used as a high yield synthetic route to novel trimetallic species containing two different Group IB metals. These reactions are discussed in detail in Section II,D,2. 

Some insights into the details of dithiolene-transfer reactions are provided by a study of the reaction of CpCo(S2C6H4) with Mo(CO)3 sources [e.g., Mo-(CO)3(py)3/BF3 py = pyridine]. The product is the trimetallic species Mo(CO)2[CpCo(S2C6H4)]2 (Fig. 16) (206). Structurally elated complexes have been prepared from [Ni(S2Q.,H4)2 and sources of CpRu+ (207). 

Lithiation of the tripodal triamines 9, 10, and 11 with wBuLi yields the corresponding trilithium triamides (Fig. 2). The metallation itself is a highly cooperative process in which the trimetallated species is already generated upon addition of only a fraction of the required amount of BuLi. This is thought to be due to the kinetic and thermodynamic stability of the adamantoid triamide, which is able to adopt a more compact structure than the partially metallated species [6],... 

A series of stable Pt-Hg compounds is obtained from reactions of [Pt(PPh3)3] with HgR2 (R = CeHnCls-n n = 0-3), and reaction with further [Pt(C2H4)(PPh3)2] gives linear trimetallic species ... 

Table 9. Redox potentials (V) and peak-to-peak separation (in millivolts) for the one-electron oxidation and reduction of sulfur-capped trimetallic species...

The related addition reaction of allylzinc bromide to alkynil zinc reagents in refluxing THF leads to a mixture of vinylic 1,1-organo- e/H-dimetallic species and. g e/H-trimetallic species, which respectively result from single and double additions (equation 51). The presence of a Lewis basic (see Lewis Acids Bases) group suitably placed for intramolecular (see Lntramolecular) chelation, and bearing a secondary substituent, avoids the formation of double addition products and allows the reaction to take place in mild conditions (equation 52). 

Figure 7. The molecular structure of [Cu2Ru4(//3-H)2 (/t-dppf )(CO)i2] (5), showing the capped trigonal bipyramidal skeletal geometry. The structure of the analogous silver-containing cluster [Ag2Ru4(/ ,-H)2(/(-dppf) CO)i2l (6) is thought to be very similar and that of the closely related trimetallic species [AuCuRu4 (/(3-H)2(/t-dppf )(CO)i2l (9) is also very similar, except that there is a gold atom in the site of Cu(2), rather than a copper atom (reprinted by permission of Elsevier Science Ltd. from ref. 38).

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