Synthesis and structural characterization of 14-vertex germa-, stanna-, and plumba-carboranes

Abstract

This article reports the synthesis and structures of several 14-vertex germa-, stanna-, and plumba-carboranes of the MC2B11 system. The reaction of GeCl2·dioxane, SnCl2 or Pb(OAc)2 with [8,9-(CH2)3-8,9-C2B11H11][Na2] in THF gave, after recrystallization from bidentate ligands such as bipyridine, 4,4'-dimethyl-2,2'-bipyridine, phenantroline and 1,2-bis(diphenylphosphino)ethane (dppe), eight 14-vertex p-block metallacarboranes 2,3-(CH2)3-1-(2',2''-bipyridine)-1,2,3-GeC2B11H11 (1), 2,3-(CH2)3-1-(4',4''-dimethyl-bipyridine)-1,2,3-GeC2B11H11 (2), 2,3-(CH2)3-1-(1',10'-phenantroline)-1,2,3-GeC2B11H11 (3), 2,3-(CH2)3-1-(2',2''-bipyridine)-1,2,3-SnC2B11H11 (4), 2,3-(CH2)3-1-(4',4''-dimethyl-bipyridine)-1,2,3-SnC2B11H11 (5), 2,3-(CH2)3-1-(1',10'-phenantroline)-1,2,3-SnC2B11H11 (6), 2,3-(CH2)3-1-(dppe)-1,2,3-SnC2B11H11 (7) and 2,3-(CH2)3-1-(2',2''-bipyridine)-1,2,3-PbC2B11H11 (8) in high isolated yields. Single-crystal X-ray analyses reveal that they adopt a distorted-bicapped-hexagonal antiprism geometry, in which the p-block metal atom slips away from the above center of the C2B4 bonding face towards the boron side, leading to an η(4) bonding mode. The results suggest that [nido-8,9-(CH2)3-8,9-C2B11H11](2-) is a redox inactive species and a good π-ligand for transition metals and p-block elements.

Synthesis, Structure, and Reactivity of 13- and 14-Vertex Carboranes

“…Instead, it affords a structural isomer of CAd 14-vertex closo -carborane. On the other hand, both 13- and 14-vertex nido -carborane dianions are a class of useful synthons for the preparation of 14- and 15-vertex metallacarboranes via polyhedral expansion methodology. − Thus, 14-vertex closo -carboranes and 15-vertex metallacarboranes represent the largest carboranes and metallacarboranes known so far.…”

Reaction of N-heterocyclic carbenes with 13-vertex closo-carboranes: synthesis and structural characterization of zwitterionic salts of 13-vertex nido-carboranes

“…The chemical shifts of the unique B atoms bound to NHCs fell in the range −1.4-−3.8 ppm with J BH = 40-84 Hz, suggesting that this boron still binds to an exo-hydrogen atom. In addition, the proton coupled 11 B NMR spectra showed one singlet at 13.9 ppm in 5, 13.5 ppm in 6, 13.2 ppm in 7, 13.6 ppm in 8, 13.0 ppm in 11, and 11.5 ppm in 12 corresponding to the BPh vertex in these complexes.…”

“…We wondered whether such a salt is an intermediate for the formation of the final products 1-12. To this end, 11 9 it is suggested that the deprotonation of α-methylene in 13-vertex carboranes proceeds instantly after mixing with NHC to afford the imidazolium salt of carborane anion that is slowly converted to the final product 1.…”

“…2 A number of 13-and 14-vertex carboranes as well as their metal complexes have been prepared and structurally characterized. [3][4][5][6][7][8][9][10][11][12][13] They share some chemical properties with 12-vertex carboranes, and on the other hand they have their own unique features. For example, 13-vertex carborane 1,2-(CH 2 ) 3 -1,2-C 2 B 11 H 11 can undergo single-electron reduction to afford a stable carborane radical anion with [2n + 3] framework electrons, 14 which accepts additional electrons to give 13vertex nido-carborane dianions.…”