Metalated Phosphandiides and Arsandiides

Another method to prepare mixed Li/Al derivatives has been developed by ligand-exchange reactions, starting from the AI4N4 cube 39 and LiPHR (R = cyclohexyl) (68). Thus, the outcome of the latter is the rhombododecahedral Li4Al4Pe cluster 40, which bears exohedral THF donor ligands at the lithium centers (Eq. 23) (68). 

The same strategy as for the synthesis of 40 has been employed for the preparation of the Li/Sn-mixed cluster 41. Thus, replacement of the imido groups in [Sn(NtBu)]4 with LiPHR (R = cyclohexyl) in the molar ratio of 4 6 yielded the metallacyclic cage complex 41, which has a rhombododecahedral Li4Sn4Pe core (Eq. 24) (69). The clusters 40 and 41 are isostructural, since the MeAl fragments in 40 have been replaced by the isoelectronic Sn(II) centers. 

Replacement of the NMe2 groups in Sb(NMe2)3 by phosphandiide ligands has been achieved by the reaction shown in Eq. (25) (70). Interestingly, all of the HNMe2 produced by this reaction coordinates to the Li ions in 42, which leads to a rhombododecahedral Li6Sb2Pe skeleton. 

The first Ca/Sn-mixed phosphandiide cluster 43 has been prepared by reaction of the calcium phosphanide 44 with Sn[N(SiMe3)2l2 in THF 

The presence of both ionic and covalent backbones in the clusters 37, 38, 40, 41, 42, and 43 has raised the question whether the structures of the andiides remain intact in solution. This is undoubtly 

The ion-triple 37 crystallizes in the orthorhombic space group P2i2i2i. The dianion in 37 is remarkable, since the hydridic H atoms are evidently better donors toward Li ions than the As centers, and the DME molecule functions rather surprisingly as a monodentate ligand (Fig. 29) (07). The Al-As distances are unremarkable and in the range of other chair-shaped ARAS3 frameworks (03). 

---