Magnesium clusters dimers

Reviews covering the chemistry of group 2 metal complexes with phosphorus-stabilized carbanions,279 and of molecular clusters of magnesium dimetallated primary phosphanes, are available.2 u Magnesium phosphanes remain rare compounds.281 Lithiation of bromide 98 with BuLi in the presence of tmeda in pentane produces a lithium phosphine dimer subsequent treatment with MgCl2 in EtzO gives the phosphane 99 in 69% overall yield (Equation (19)). The centrosymmetric 99 has Mg-C = 2.217 A Mg-P = 2.77 A (av.).282... 

Figure 8. Ribbon diagram showing the FPpoI dimer structure complexed with DNA as reported by Stoddard (PDB lA 73). One monomer has residue numbers and shows Asnl 19, His 98, and the magnesium-water cluster(40).

The correlation effects which influence the ground-state properties of metals are quite local. Therefore, the question can arise, whether it is really necessary to embed the clusters for the correlation calculation. Could we not take the correlation part from free fragments of the metals, i.e. the two-body part from dimers, the three-body parts from trimers and so on. Still the long range HF part of the ground-state properties would be calculated in the periodic system. In order to answer this question, the correlation contributions extracted from free and embedded fragments of the hep structure of magnesium have been compared. 

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