A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

Abstract

A series of computational studies have been undertaken to investigate the electronic structures and bonding schemes for six hetero-substituted borane cages, all of which have been presented in the literature as potential hypho structures. The six species are hypho-7,8-[C2B6H13](-) (1a), hypho-7,8-[CSB6H11](-) (1b), hypho-7,8-[S2B6H9](-) (1c), hypho-7,8-[NSB6H11] (1d), exo-7-Me-hypho-7,8-[NCB6H12] (1e), and endo-7-Me-hypho-7,8-[NCB6H12] (1f) and the so-called mno rule has been applied to each of them. As no structural data are known for the carbathia-, azathia-, and dithiahexaboranes, we have also applied the ab initio/GIAO/NMR structural tool for 1b-1d, with 1c having been prepared for this purpose. We conclude that an mno count of 10 means that 1a, 1b, 1d, 1e, and 1f should be termed pseudo-nido or pseudo-hypho. Only 1c can be considered to be correctly termed hypho-7,8-[S2B6H9](-).

A systematic examination of classical and multi-center bonding in heteroborane clusters

“…In the first step, the IBO method was validated on a series of organic and inorganic compounds with well described either covalent or multicenter bonding: ethane, elemental white phosphorus P 4 and hydrogen disulfide (containing classical, 2c2e bonding), trimethylaluminium dimer, 6 diborane, 12 and tetra-tert-butyltetrabora-tetrahedrane. 20 In the second step, we used the IBO method to investigate the nature of bonding in a series of experimentally known heteroboranes containing only up to third-row elements, specifically: closo-1-CB 11 H 12 À , 21 closo-1,2-C 2 B 10 H 12 , 22 closo-1,7-C 2 B 10 H 12 , 22 closo-1-NB 11 H 12 , 23 closo-1,2-P 2 B 10 H 10 , 24 closo-1,7-P 2 B 10 H 10 , 25 closo-1-SB 11 H 11 , 26 closo-2-CB 10 H 11 À , 27 closo-2,3- 28 closo-1-CB 9 H 10 À , 29 closo-1,2-C 2 B 8 H 10 , 30 closo-1,6-C 2 B 8 H 10 , 31 closo-1,10-C 2 B 8 H 10 , 32 closo-1-NB 9 H 10 , 33 54 The numbering of the studied cages is shown in Fig. 1.…”

“…In the first step, the IBO method was validated on a series of organic and inorganic compounds with well described either covalent or multicenter bonding: ethane, elemental white phosphorus P 4 and hydrogen disulfide (containing classical, 2c2e bonding), trimethylaluminium dimer, 6 diborane, 12 , 17 closo-B 6 H 6 2À , 18 closo-B 5 H 5 2À , 19 and tetra-tert-butyltetrabora-tetrahedrane. 20 In the second step, we used the IBO method to investigate the nature of bonding in a series of experimentally known heteroboranes containing only up to third-row elements, specifically: closo-1-CB 11 H 54 Because of the hypho vs. nido conflict present, the classification of such compounds as hypho should be treated with caution. 54 The numbering of the studied cages is shown in Fig.…”

“…20 In the second step, we used the IBO method to investigate the nature of bonding in a series of experimentally known heteroboranes containing only up to third-row elements, specifically: closo-1-CB 11 H 54 Because of the hypho vs. nido conflict present, the classification of such compounds as hypho should be treated with caution. 54 The numbering of the studied cages is shown in Fig. 1.…”

Anion‐Guided Stepwise Assembly of High‐Nuclearity Lanthanide Hydroxide Clusters

“…This situation is similar to the well-established hierarchical structural series of polyhedral boranes. [16] With such an analogy, we sought the next members in order, namely the arachano-and nidostructures toward {Er 60 }. The appropriately disposed anions in the structure of Er 34 portend the formation of such intermediates on way to Er 60 .…”

“…To this end, we demonstrate in this work how a giant cluster may be produced by a rational and stepwise assembly guided by judiciously chosen mixed-anion templates. The synthetic target-an Er III -histidine complex of the formula [Er 60 (μ 6 -CO 3 ) 8 (μ 4 -I) 7 (μ 2 -NO 3 ) 12 (μ 3 -OH) 96 (His) 24 (H 2 O) 36 ](ClO 4 ) 5 I 4 (NO 3 ) 16 •35 H 2 O (Er 60 , His = deprotonated L-histidine)-fea-tures a 60-metal core motif reported previously by us and others (Figure 3a); [13] the truncated octahedral structure, or that of a sodalite cage, features 24 vertex-sharing {Er 4 } units (Figure 3b) organized into 6 square faces of {Er 12 } (Figure 3c, gold) and 8 hexagonal faces of {Er 18 } (Figure 3c, blue). We succeeded in the preparation and structural determination of three intermediates, namely Er 12 , Er 34 , and Er 48 , leading eventually to the targeted Er 60 .…”