Lead electron-deficient cluster

When it comes to metal-rich compounds of the alkaline earth and alkali metals with their pronounced valence electron deficiencies it is no surprise that both principles play a dominant role. In addition, there is no capability for bonding of a ligand shell around the cluster cores. The discrete and condensed clusters of group 1 and 2 metals therefore are bare, a fact which leads to extended inter-cluster bonding and results in electronic delocalization and metallic properties for all known compounds. 

Incidentally, the B6 octahedron (Longuet and Roberts, 1955) and B12 cuboocta-hedron (Lipscomb and Britton, 1960) are also found to be two-electron deficient. This electron deficiency of the clusters leads to dramatically different physical properties for trivalent and divalent metal borides as illustrated for example in the next section on the dodecaborides. More on the bonding requirements in the higher borides will be discussed in later sections. 

There are a limited number of structures reported for Fe—Pb complexes and these are recorded in Tables 16-18. For a series of iron carbonyl lead clusters, the Fe—Pb bond lengths vary from 2.624 A for an electron-deficient three-coordinate planar Pb cluster [FefCO jjPbl to 2.828 A for a tetrahedral bridging anionic Pb cluster... 

The electron deficiency of small particles has been discussed by Boudart,33 and Sachtler.34 XPS measurements of the high electron binding energies in small Pt particles indicate that they are highly electron-deficient. In addition to this intrinsic character, there are strong interactions between metal particles and positively charged Lewis sites leading to the polarisation of Pt clusters to form local stable Pt Al(0)3 entities.35... 

We described boratiranes and boriranes with one boron substituent at each ring carbon atom. The geometrical distortions found experimentally in the X-ray structures as well as by model computations can be understood in terms of variably strong hyperconjugation between a(C-B) bonds and the formally empty p-orbitals of more or less electron deficient boron atoms. Two electron reduction of an oxatriborabicyclohexane leads to ex-treme distortion of the bicyclic to a cluster structure by formation of a 3c,2e-BBB-bond. 

The reactions of [Ru3(GO)io(/x-dppm)] with secondary phosphines R2PH (R = Bu, 1-Ad) lead to the formation of the electron-deficient metal cluster complexes Ru3(/x-GO)(GO)4(/X3-H)(/x-H)(/x-PR2)2(M-dppm) (132 R Bu 133 R= 1-Ad) in good yields. The related reaction of the starting dppm complex with the less bulky phosphine Gy2PH gives the electronically saturated complex Ru3(GO)6(M-H)2(//-PGy2)2(M"dppm) 134. All reactions proceed via the isolated intermediates, Ru3(GO)9(R2PH)(/x-dppm). ... 

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