Dianionic clusters

Salt elimination reactions proved to be very effective for the synthesis of closo-heteroborates with the heavy elements of this group. Todd and co-workers prepared for the first time the lead, tin and germanium cluster dianions [EBnHn]2 as shown in Scheme 3.3-5 [17]. 

Two M(PR3) groups can be introduced into a preformed cluster dianion. Equation (6) shows an example (27). 

In 1980, Albano et al. (32) showed that two Cu(NCMe) units could be incorporated into a mixed-metal cluster by treating a preformed cluster dianion with the complex [Cu(NCMe)4][BF4] ]Eq. (16)]. Other workers... 

C. Femoni, F. Kaswalder, M. C. Iapalucci, G. Longoni, and S. Zacchini, Infinite Molecular [Pt3n(CO)6n]2 Joo Conductor Wires by Self-Assembly of [Pt3n(CO)gn]2 (n = 5-8) Cluster Dianions Formally Resembling CO-Sheathed Three-Platinum Cables, Eur. J. Inorg. Chem. 2007, 1483-1486. 

Lawrence F. Dahl Platinum carbonyl cluster dianions ( tinker toy construction) with trigonal prismatic configuration... 

Salts of the cluster dianion with other cations may be isolated by use of the appropriate water soluble salt in place of Et4NBr. 

Figure 104 shows the molecular structure of the dicarbide cluster dianion [Co6Ni2(CO)16(C)2]2- [183]. 

Some uncertainty still exists on the exact formulation and structure of a series of redox-active giant heteronuclear clusters formulable as Os20M and/or Os18M3 (M = Hg, Au, Ag). Accordingly, the previously formulated cluster dianion [Os20Hg(C)2(CO)48]2 [195] has been now reassigned as... 

Yannouleas and Landman have theoretically considered the stability and decay channels of Au and Ag . They find that autodetachment dominates fission as the mode of decay at a finite temperature. Earlier they had studied sodium cluster dianions. These calculations show pronounced shell-effects in the second electron affinities illustrating the failure of the simple electrostatic model of charging a conducting sphere as depicted in Figure 1. However, the Coulomb barrier calculated with such simple assumptions probably is a reasonably good approximation. The importance of the Coulomb barrier in multiply charged anions is emphasized below. 

The bicapped octahedral octanuclear osmium cluster dianion [Osg(CO)22] can be prepared from the solid state pyrolysis of [Os3(CO)io(NCMe)2]. An X-ray analysis of the [N(PPh3)2j salt shows that the two Os(CO)3 caps occupy the 1 and 3 faces of the octahedron s as shown in Fig. 10, and the structure of the dianion is consistent with the electron count of 110 e and seven skeletal electron pairs. 

The cluster dianions [Co8C(CO)ig]- (Fig. 8a) and [NigC(CO)i6] provide rare examples of a first-row main-group atom occupying a square antiprismatic cluster cavity,and also illustrate the capacity of carbon to become eight-coordinate. However, on progressing to the heavier main-group elements such as Si, P, S and As we find a propensity for clusters based on the square-antiprism. 

The use of singly charged cations, i.e. [Ru(C5H5)(CH3CN)3]+, in reactions with cluster dianions, allows for the introduction of two organometallic units... 

Synthesis and structural characterization of Pt carbonyl clusters dianions... 

The tetranuclear cluster dianion [H2Ru4(CO)i2] has been reported to show excellent activity for the reduction of nitrobenzene to aniline by CO/H2 (120 °C, 20 Kg/cm (H2/CO = 19 1), in methanol) [41]. The IR spectrum of the catalytic solution at the end of the reactions showed the presence of the dianion. The clusters [HRu3(CO)h] and [H3Ru4(CO)i2] proved to be less effective [41]. Note that the very low CO pressure ( 1 atm) may avoid cluster decomposition to yield monomeric complexes. 

The face-capped octahedral cluster dianion [Os7(CO)2o] 290 forms in 70% yield from the reduction of Os7(CO)2i with Addition of Os(CNBu )(CO)4 to Os6(CO)is/Me3NO affords Os7(CO)2o(CNBu ) 291 in 25% yield. ... 

Osmium cluster dianions [Os]7(CO)36] 330 and [Os2o(CO)4o] 331 are formed in up to 10 and 20% yields, respectively, by vacuum pyrolysis of Os3(CO)io(NCMe)2 at temperatures above 260 °C. Complex 330 contains a close-packed arrangement of 16 metal atoms, with the additional Os breaking the otherwise threefold symmetry of the metal core. The two osmium atoms with metal connectivities of 8 and 9 have significantly shorter Os-Os bond distances (2.663 A), comparable to that of the bulk metal (2.6754A). The cluster is electron-precise, with 210 c.v.e. The electron-deficient complex 331 consists of a cubic close-packed arrangement of metal atoms, and has been characterized by IR spectroscopy in five oxidation states. 

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