Clusters heteroleptic

Although most of the structurally characterized gold clusters are phosphine-based systems, in recent years some studies have focused on the synthesis of gold clusters with other stabilizers coexisting with phosphines such as thiols, arsines and boranes. Certain heteroleptic gold clusters stabilized with these ligands and arylphosphines in the same molecule have been structurally characterized. 

In earlier work, no molecular structural data were available on mononuclear M amides, but this has changed markedly in the last three (and particularly last two) decades. Another significant development has been the use of the title compounds, and especially the homoleptic dimethylamides M(NMe2)3, as reagents, or synthons for the preparation of bridging binuclear imides 7 (Section 10.3) or cluster imides (e.g. 3 7) (Section 10.4), or Bi[N(SiMe3)2]3 as a precursor for atomic layer deposition.Heteroleptic amidometal chlorides have featured as precursors to cationic metal(III) amides (Section 10.2.4). 

Pentanuclear complexes are represented by 2 major structural types closo- clusters with a (i5-0-ligand in the center (heteroleptic complexes) and by combinations of 2 [M2M ] triangular aggregates, having 1 common metal atom (heterometallic ones as this M central metal atom should have higher coordination number and be rather electropositive to permit the existence of such an aggregate). 

Novel, monomeric heteroleptic derivatives of divalent Ge 40 and divalent Sn 41 have been prepared and characterized by single crystal X-ray diffraction <19990M389>. Heteroatoms in these germylene and stannylene species are not formally part of a four-membered ring however, crystal structures point to the azametallacyclobutane structures formed due to the N —> M coordination. The heteroleptic nature of 40 and 41 gives rise to an interesting reactivity in their coupling with transition metal clusters. 

Treatment of a suspension of Nd(NHPh)3(KCl)3 with trimethylalumi-num in hexane yielded the heteroleptic heterobimetallic cluster [Nd[(//.2-Me)2A/Me2]2(M3-NPh)(M2-Me)AlMe 2 in low yield (Fig. 29). The formation of the cyclic byproduct (Me2AlNHPh)3 was proven by means of NMR spectroscopy and X-ray crystallography [217]. The molecular structure of the Nd2Al6 dimer revealed the presence of a doubly deprotonated imido ligand bridging each a neodymium center and two aluminum atoms. 

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