Tetranuclear cores, shapes

Figure 7. Divergent synthetic strategy to obtain polynuclear metal complexes of dendrimer shape. - ° Each deprotected compound of the dive ent synthetic approach can be used as a core in convergent synthetic processes. Some of these routes starting from a tetranuclear core are illustrated in Figure 8.

H.-B. Song, Q.-M. Wang, Z.-Z. Zhang andT. C. W. Mak, A novel luminescent cop-per(I) complex containing an acetylenediide-bridged, butterfly-shaped tetranuclear core. Chem. Commun., 1658-59 (2001). 

Examples of tetranuclear adamantane-shaped complexes (Type Iff) are [Mn4 06(bpea)4]" + and its corresponding one-electron rednced species, while cnbane cores (Type TV) are fonnd in [Mn2 Mn2 04(02PPh2)6] and its one-electron rednced species. A large family of tetrannclear clnsters is... 

Fig. 1. Shapes of tetranuclear cores (a) tetrahedron, (b) square, (c) rhombus.

The crystal structure of the tetranuclear complex is assembled from one [La(H2Ll)]+ and two [La(N03)2] cations, molecule [La(HLl)], and one NO3 and two bridging [/t3-OH] anions. The [La(N03)2] species are themselves bridged by the two [/ts-OH] groups and the alkoxide site (Figure 7, left). The tetranuclear core forms a rare scoop-like motif (Figure 7, right) as opposed to other more frequently observed tetranuclear cluster core structures, such as distorted cubane, tetrahedron, butterfly, or square-shaped assemblies. 

The crystal structures of several of the tri- and tetranuclear cluster complexes 19-21 were determined. Two typical examples are shown in Figs. 10 and 11. The molecular Co3(/ 3-alkyne) cores of 19 and 20 are quite similar to that of 15a. The complexes 21 have a butterfly-shaped framework of four metal atoms, which is symmetrically bridged by the cycloalkyne. Due to their multiple metal coordination, the carbon-carbon bonds are comparatively long, about 1.40 A in the trinuclear and 1.46 - 1.50 A in the tetranuclear complexes. There appears to be no sig-... 

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