Electron-poor clusters

Other electron-poor clusters include the 44-electron Pt3(CO)3(PPh3)4 and the 42-electron species Pd3(CO)3(PPh3)3 and [Re3Cl12p. For the 44-electron system, the 18-electron rule predicts two double bonds within the M3 triangle and for the 42-electron complexes, three double bonds. The structures of the platinum and palladium complexes are unknown, but the Re-Re distances of 2.47-2.49 A in the anion [Re l ]3- are regarded (20) as short and consistent with a formal bond order of two. 

Another contribution is represented by an investigation of a cubic thallium cluster phase of the Bergmann type Na13(TlA.Cdi A.)27 (0.24 < x <0.33) (Li and Corbett 2004). For this phase too the body centred cubic structure (space group Im 3, a = 1587-1599 pm) may be described in terms of multiple endo-hedral concentric shells of atoms around the cell positions 0, 0, 0, and 14,14,14. The subsequent shells in every unit are an icosahedron (formed by mixed Cd-Tl atoms), a pentagonal dodecahedron (20 Na atoms), a larger icosahedron (12 Cd atoms) these are surrounded by a truncated icosahedron (60 mixed Cd-Tl atoms) and then by a 24 vertices Na polyhedron. Every atom in the last two shells is shared with those of like shells in adjacent units. A view of the unit cell is shown in Fig. 4.38. According to Li and Corbett (2004), it may be described as an electron-poor Zintl phase. A systematic description of condensed metal clusters was reported by Simon (1981). 

The Nb3 binary halides with seven electrons available for metal-metal bonding within the triangle are electron poor clusters. A simplified MO scheme suggests that the HOMO and LUMO possess metal d character.645 One unpaired electron is expected to be present. The existence of a low-lying metal cluster orbital is also indicated by the electronic spectra. 

Trinuclear clusters play an important role in the chemistry of molybdenum and tungsten. Deep red, isostructural clusters containing both [M03O4F9]3- (148, 149) and [W304F9]5 (149-151) are later additions to this family of simplest types of cluster species. Their basic structures conform to the fii-type of trinuclear electron-poor transition-metal clusters where the metals are in a distorted octahedral environment. 

Clusters from Organoboranes and Electron-poor Metal Complexes... 

Electron-poor and electron-rich cube clusters 798... 

Electron-Poor (Hypoelectronic) Metal Carbonyl Clusters... 

The availability of d orbitals on transition metal vertices leads to the possibility ofelectron-poor or hypoelectronic transition metal clusters with n vertices having less than 2 -I- 2 apparent, skeletal electrons. Such electron-poor clusters form deltahedra containing tetrahedral chambers, i.e., deltahedra with one or more vertices of degree 3 (Figure 9). The simplest examples of such deltahedra are the capped tetrahedra, of which the trigonal bipyramid (i.e., the monocapped tetrahedron) with five vertices is the smallest. The capped tetrahedra consist of a series of fused tetrahedral chambers with faces in common. An example of a cluster based on a bicapped tetrahedron is... 

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