Synthesis and Structural Characterization of closo-exo, exo-nido, and pseudocloso Group 1 Carborane Compounds of the C₂B₁₀ System

Abstract

Treatment of 1,2-(C6H5CH2)2-1,2-C2B10H10 with excess Na or K metal in THF at room temperature gave closo-exo-[(C6H5CH2)2C2B10H10]Na2(THF)4 (1) or [closo-exo-{(C6H5CH2)2C2B10H10}K2(THF)2(O2C4H8)0.5] n (2) in good yield after recrystallization from a THF solution or a THF/dioxane solution, respectively. Dissolution of 2 in a THF solution of 18-crown-6 ether afforded an exo-nido-{K(18-crown-6)}{[(C6H5CH2)2C2B10H10]K(18-crown-6)} (3). An equimolar reaction between 1,2-(C6H5CH2)2-1,2-C2B10H10 and K metal or 1,2-(C6H5CH2)2-1,2-C2B10H10 and [(C6H5CH2)2C2B10H10]K2 in THF at room temperature in the presence of 18-crown-6 ether generated two monoanion carborane compounds, [(THF)2K(18-crown-6)][nido-(C6H5CH2)2C2B10H11] (4) and {(THF)K(18-crown-6)}{1-(C6H5CH2)-2-(C6H5CH)-1,2-C2B10H10} (5), respectively. All of these complexes have been fully characterized by various spectroscopic data, elemental analyses, and X-ray diffraction studies. Compounds 1 − 3 represent the first structurally characterized examples of group 1 salts of carborane dianions of the C2B10 system.

An unprecedented bonding mode for potassium within a PCP-pincer palladium hydride–K-Selectride® complex

“…At the center of this K 2 H 2 unit is the crystallographically-imposed inversion center. Related K 2 H 2 units with bridging hydrides have been seen previously in metal-borohydride structural chemistry; however, unlike our case, these previous examples contain K + ions that are coordinated to multiple, usually chelating, electron donors [31][32][33][34].…”

Crystal Structures of the Carborane Dianions [1,4‐(PhCB10H10C)2C6H4]2− and [1,4‐(PhCB10H10C)2C6F4]2− and the Stabilizing Role of the para‐Phenylene Unit on 2 n+3 Skeletal Electron Clusters

“…The bridges become more quinoid-like with the bond between the aryl ring and the cluster shortened by 0.08–0.09 Å. While this bond shortening agrees with an increased bond order, it is quite small when compared to carborane anions with substantial exo -multiple bond character 6. 12 The geometrical parameters of the ═C 6 H 4 ═ ring in [ 3 ] 2− resemble the phenylene units in the experimentally determined geometries of para -quinodimethane analogues, disilaquinodimethane 6 and diboraquinodimethane 7 (Scheme 3).…”

“…Electron-counting rules dictate that these closo -clusters are held together by 2  n +2 skeletal electrons (SE) where n represents the number of skeletal atoms 5. Addition of two electrons to closo -carboranes by reduction with alkali metals leads to more open nido geometries with a 2  n +4 skeletal electron count 6. 7 While closo - and nido -carboranes are widely known, little is reported8, 9 on carboranes with odd numbers of skeletal electrons and no crystallographic studies are published on carborane radical anions from 12-vertex carboranes.…”

New synthetic and structural studies on nitroso-ortho-carboranes RCB10H10CNO and bis(ortho-carboranyl)amines (RCB10H10C)2NH (R=Ph or Me)

“…Figure 4 shows the environment surrounding the amide anion in the salt, including the cation and diglyme molecule. The potassium cation effectively caps a triangular face of one of the two cages (a face remote from the two cage carbon atoms) in a manner common in potassium-18-crown-6 salts of carborane anions [21]. The diglyme molecule, with its central oxygen atom O(2) disordered over two sites in the crystal structure, is coordinated through its outer oxygen atoms to two cations.…”