X-ray structure and bonding of 1-phenylethynyl-2-phenyl-1,2-dicarbadodecaborane(12), [1-(PhCC)-2-Ph-1,2-C2B10H10], a model alkyne complex containing a rich variety of carbon-carbon bond types

Sulfur, tin and gold derivatives of 1-(2′-pyridyl)-ortho-carborane, 1-R-2-X-1,2-C2B10H10(R = 2′-pyridyl, X = SH, SnMe3or AuPPh3)

“…21 The crystal The π orbital overlap between phenyl group and tangential cluster orbitals has been invoked to explain the cage C-C lengthening in aryl-ortho-carborane derivatives. 24,25 This was further explored by ab initio RHF/6-31G* and MP2/6-31G* calculational studies on 1-phenylortho-carborane and other aryl-carboranes in order to probe the orientational preferences of aryl groups attached to the carbon atoms of ortho-carborane. 26,27 These calculations have indicated that, although the overall energy of an aryl-carborane may vary only slightly with the aryl group orientation, the latter does have a perceptible influence on the C(1)-C(2) bond distance, which is greatest when the aryl group is aligned perpendicular to the aryl C-C(1)-C(2) plane.…”

Exo-π-bonding to an ortho-carborane hypercarbon atom: systematic icosahedral cage distortions reflected in the structures of the fluoro-, hydroxy- and amino-carboranes, 1-X-2-Ph-1,2-C2B10H10 (X = F, OH or NH2) and related anions

“…In 2-phenyl-ortho-carborane itself, PhCb o H (Fig 1(a), R = Ph, X = H), the hypercoordinated carbon ('hypercarbon' 6 ) atom C1 forms a single bond to the exohydrogen atom and bonds of lower order to the five neighbouring cage atoms (one carbon, four borons). As the order of the exo-C-X bond increases from one to two, we 3 shall show how the bond to the neighbouring cage carbon atom is particularly affected, 4,8 When the aryl planes are roughly perpendicular to the ipsoC-C1-C2 plane (as preferred sterically in diaryl derivatives) the skeletal C1-C2 distance is longer than for other ring orientations. Involvement in exo C1-Cipso dative -bonding from the aryl -system reduces the capacity of the appropriate tangential p AO on C1 for C1-C2 skeletal -bonding ( Fig.…”

“…Derivatives of phenyl-ortho-carborane were used in order to label the second carbon atom with a group whose influence was already understood; without such a label, CH/BH disorder problems can make X-ray structure determination difficult. Here, our work on PhCb o X systems (some aspects of which have appeared in preliminary accounts [1][2][3][4][5] ) is intended to provide a definitive account of the systematically more pronounced cage distortions that occur near the cage carbon atom C1 as exo C1-X -bonding builds up. In 2-phenyl-ortho-carborane itself, PhCb o H (Fig 1(a), R = Ph, X = H), the hypercoordinated carbon ('hypercarbon' 6 ) atom C1 forms a single bond to the exohydrogen atom and bonds of lower order to the five neighbouring cage atoms (one carbon, four borons).…”

“…in Hawthorne's studies 9,10 PhCH is linked to C1 by an exo C=C double bond (Fig 1(a), R = PhCH 2 , X = PhCH . [12][13][14][15][16][17] Welch carried out systematic studies of aryl-ortho-carboranes bearing substituents of varied bulk 4 on the second carbon atom, enabling him to document both the steric and subtle electronic effects on the cage C1-C2 distance. 12,13,14,15 Teixidor and Viñas, in extensive studies 16 on thiolato (RSCb o R') and phosphino (R 2 PCb o R') derivatives of orthocarborane, found the cage C1-C2 distances varied in a manner they attributed to steric and electronic factors and, more recently, 17 to exo C-X -bonding effects such as we advocate below.…”

Preparative and structural studies on sulfur-linked carborane icosahedra: 2-Phenyl-ortho-carboranyl-sulfur systems (2-Ph-1,2-C2B10H10)2X (X=S, S2 or SO), and ortho-carboran-di-yl systems (1,2-C2B10H10Y)2 (Y=S or SO)

“…A perpendicular orientation minimises non-bonding repulsions with the other substituent on C(12), and maximises the opportunity for dative π-bonding from the π-system of the phenyl group to the carborane cage. 16,17 The cage carbon-carbon distance, C(1)-C(2), of ortho carborane is the cage edge link known to be most sensitive to the presence of π-bonding substituents on the cage hypercarbon atoms. 11,18,19 Its length increases as exo π-bonding increases.…”