[NbAs₈]³⁻, a Novel Type of Complex and an Unexpected One‐Dimensional Chain Structure: [Rb{NbAs₈}]²⁻

Abstract

which would be in agreement with the (irregular) increase in the differences A6=16(x)-6(x+ 1)1 in the series [P7 -x A~x ] 3 ~ with increasing x. It is also possible, however, that this heteroanion is unstable and decomposes into As: -and, for example, [P2Ass]37, because incorporation of the small P atom into the large As, cage is unfavorable. The "P-NMR spectra of solutions of mixtures of the pure compounds Rb3P7 and Rb3As, exhibit, even after several weeks, only the signal of P;-, so that no exchange between P:-and As:-occurs in solution.The intensities of the 3'P-NMR signals-after correction with respect to the number of P atoms involved in the heteroanion-indicate a preference for the groups [P6AsI3and [P,As,]'-, but none for [P4As3I3-, as would have been expected based on the concept of topological charge stabilization. With increasing content of arsenic, the valence tautomerism becomes slower, as shown by the increasing halfwidths of the signals. The question remains open, therefore, whether As:-also has a fluxional structure in solution.

[V@Ge8As4]3−and [Nb@Ge8As6]3−: encapsulation of electron-poor transition metal atoms

“…6b Combining two different main group elements within the cluster shell recently opened up a new direction, as the systems are free to adjust their charge by isolobal substitution of formal (E 14 ) 2À or (E 14 ) À by (E 15 ) AE0 . 8 According to X-ray structure analyses, ‡ both cluster anions exhibit non-deltahedral topologies (Fig. 7 In the present case, formal Ge À besides As atoms served to compensate for the high charge of an interstitial group 5 metal ion M 5+ , forming the first endohedral clusters comprising these extremely hard cations of electron-poor transition metals V and Nb.…”

“…4 In conclusion, it was shown that electron-poor V and Nb atoms can be accommodated within endohedral clusters [V@Ge 8 As 4 ] 3À and [Nb@Ge 8 As 6 ] 3À , the first members of an M-Ge-As cluster family. 4 In conclusion, it was shown that electron-poor V and Nb atoms can be accommodated within endohedral clusters [V@Ge 8 As 4 ] 3À and [Nb@Ge 8 As 6 ] 3À , the first members of an M-Ge-As cluster family.…”

“…Exclusions have been species with interstitial lanthanide ions, 2a,3c,d,5 [Cp 5 Ti 4 Sn 15 ], 6a and species detected via mass spectrometry, like [V@Si 16 ] + . 8 As 6 ]ÁtolÁen (2, 22%) were obtained by extraction of solid mixtures K-Ge-As-V or K-Ge-As-Nb (with about 3 atom% of the group 5 metal according to EDX measurements) with ethane-1,2-diamine (en)/[2.2.2]crypt; the quoted solids were obtained by fusing equimolar amounts of K, Ge and As with about 0.1 equivalents of V in a silica glass ampoule, or by simply fusing K, Ge, and As in an Nb ampoule, respectively. This way, many new topologies have been observed that were not accessible with only one of the main group elements involved.…”

“…ESI-MS(À) spectra (measured: top versus calculated: bottom) of [K([2.2.2]crypt)][V@Ge 8 As 4 ] À (m/z = 1348.23; top) and [Nb@Ge8 As 6 ] À (m/z = 1123.81; bottom). The isotopic patterns are well reproduced by simulations, and all measured m/z values agree with the simulated ones within deviations of less than 0.003 m/z.…”

Aromaticity and Antiaromaticity in Zintl Clusters

“…However, von Schnering et al. suggested an additional π‐donation from the [As 8 ] 8− unit to the central metal, which leads to the stable 18‐electron complexes . The S 8 ‐like [Pn 8 ] 8− rings are not planar, and, hence, are not considered as aromatic.…”