Rhodri Ll. Thomas

Arene-perfluoroarene interactions in crystal engineering. Part 3. Single-crystal structures of 1 : 1 complexes of octafluoronaphthalene with fused-ring polyaromatic hydrocarbons

Molecular complexes of 1 : 1 stoichiometry of octafluoronaphthalene (OFN) with the polyaromatic hydrocarbons anthracene, phenanthrene, pyrene and triphenylene have been prepared, and their single-crystal X-ray structures determined at 120 K. All of the structures are composed of infinite stacks of alternating, almost parallel molecules of OFN and the hydrocarbons, in contrast to the herringbone or γ-type (flattened herringbone) packing of the pure components. It is clearly shown that the stacking motif does not require a close correlation between the molecular geometry of the arene and perfluoroarene species, but is stable over a wide range of differing sizes and shapes. Thus, the arene–perfluoroarene interaction is of general importance as a supramolecular synthon. The molecular geometries of the components are not affected by complexation, indicating the absence of charge transfer in the complexes. The role of close C–H···F–C and C–F···F–C intermolecular contacts between stacks is discussed. A re-determination of the single-crystal structure of triphenylene at 150 K is also reported, providing a more accurate comparison with that of the 1 : 1 OFN·triphenylene complex.

Arene-perfluoroarene interactions in crystal engineering: structural preferences in polyfluorinated tolans

The compounds 4-ROC6F4CCPh (4) where R = Me (a), Et (b), Prn (c), Pri (d), Bun (e), n-C5H11 (f), PhCH2 (g), PhCH2CH2 (h), 4-MeC6H4 (i), 4-EtC6H4 (j) and menthyl (k), have been prepared by reaction of C6F5CCPh (3) with ROH in the presence of KOH, and characterised by NMR (1H, 13C, 19F) and mass spectroscopy. The single-crystal structures of PhCCPh·C6F5CCC6F5 (1∶2), 3 and 4a,c,d,f,g,i have been determined by X-ray diffraction at 120–160 K, and that of 3 also calculated by an ab initio pseudo-potential DFT method. The tolan moiety is nearly planar in each molecule except 4a, which has a Ph/C6F5 dihedral angle of 25.8°. The R group adopts an out-of-plane orientation except in 4f, where the n-pentyl chain is nearly coplanar with the C6F5 group at the cost of severe distortion of the C(ar)–C(ar)–O angles (which differ by 13.5°). The structures of 1∶2, 3 (pseudo-isomorphous with 1∶2), 4a, 4g (disordered) and 4i contain stacks of alternating arene and perfluoroarene moieties; 4c and 4d form discrete centrosymmetric dimers with arene/perfluoroarene overlap, while 4f forms infinite stacks without such overlap. Differential thermal analysis and transmitted polarised light microscopy revealed no liquid-crystalline behaviour of 3 and 4.

Crystal engineering with p-substituted 4-ethynylbenzenes using the C–H⋯O supramolecular synthon

The crystal structures of several para-substituted ethynylbenzene derivatives; namely, 4-ethynylanisole (1), 4-ethynylmethylbenzoate (2), 4-ethynylbenzaldehyde (3), 4-ethynyl-2,3,5,6-tetrafluoroanisole (4), 4-ethynylthioanisole (5), and 4-ethynyltoluene (6) have been solved from X-ray diffraction data. In 1–4, the molecular packing consists of infinite chains of molecules, linked by intermolecular C–H⋯O hydrogen bonds. The structure of 5 contains weak bifurcated C–H⋯S and C–H⋯π (CC) interactions and that of 6, C–H⋯π(benzene) interactions.

A new crystalline form of 1-phenyl-1,2-dicarba-closo-dodecaborane(12)

A new polymorph of the title compound, C 8 H 16 B 10 , is reported. The carborane icosahedron is relatively undistorted, with the phenyl substituent twisted out of the C2-C1-C ring plane by 18.3(2)°, which is in good agreement with the conformation predicted by molecular-orbital calculations.

Haloaryl carboranes. I. 1,4-bis[2-phenyl-1,2-dicarba-closo-dodecaboran(12)-1-yl]-2,3,5,6- tetrafluorobenzene

The title molecule, C22H30B20F4, has a crystallographically imposed inversion centre. The twist angle (θ) of the phenyl ring is 15.6 (3)°, and that of the haloaryl ring is 3.7 (3)°, these low values are presumably a consequence of the mutual steric crowding of the rings. The Ccage-Ccage distance is 1.730 (3) A, in good agreement with that found in similar molecules.

Synthesis and characterisation of a semipseudoclosocarbaruthenaborane. Molecular structure of[1-(PhCC)-2-Ph-3-(cym)-3,1,2-semipseudocloso-RuC2B9H9](cym = p-cymene)

The closo carbaborane 1-(PhCC)-2-Ph-1,2-C 2 B 10 H 10 was readily decapitated to afford either [7-(PhCC)-8-Ph-7,8-C 2 B 9 H 10 ] - or [7-(PhCC)-8-Ph-7,8-C 2 B 9 H 9 ] 2 - . Reaction of the thallium(I) salt of the latter with [{RuCl 2 (cym)} 2 ] (cym = p-cymene) yielded the unique semipseudocloso carbaruthenaborane [1-(PhCC)-2-Ph-3-(cym)-3,1,2-RuC 2 B 9 H 9 ] characterised by multinuclear NMR spectroscopy (weighted average 11 B chemical shift +2.41 ppm) and by single-crystal X-ray diffraction [C(1)–C(2) 2.184(7), Ru(3)···B(6) 3.166(6) A]. The semipseudocloso shape thus appears to lie between closo and pseudocloso, although somewhat closer to the latter. Confirmation of the structure strongly supports the idea of a continuum of cluster structures from closo to pseudocloso, the position of a molecule on which may be controlled by steric effects.

Synthesis and molecular structure of dicarbaboryl ethenes and an unexpected dimetallated derivative

The first examples of molecules in which carbaborane clusters are linked via a simple CC double bond, and which constitute model compounds for boronated polydiacetylenes, are reported; double metallation of one of these molecules affords a unique closo–pseudocloso bis(carbametallaborane).

Rhodium catalysed dehydrogenative borylation of vinylarenes and 1,1-disubstituted alkenes without sacrificial hydrogenation-a route to 1,1-disubstituted vinylboronates

The complex trans-[Rh(Cl)(CO)(PPh3)2] (1) is an efficient catalyst precursor for the dehydrogenative borylation of alkenes without consumption of half the alkene substrate by hydrogenation, giving useful vinylboronate esters including 1,1-disubstituted derviatives that cannot be made by alkyne hydroboration.

1-Phenyl-3,3-bis(triethylphosphine)-1,2-dicarba-3-platina-closo-dodecaborane 0.5-dichloromethane solvate

The title compound, [Pt(C 8 H 15 B 9 )(C 6 H 15 P) 2 ].0.5CH 2 Cl 2 , crystallizes with two carbaplatinaborane molecules and one solvent molecule in the asymmetric unit. The conformation of the {Pt(PEt 3 ) 2 } fragment relative to the carbaborane ligand is practically the same in both crystallographically independent molecules and similar to that in 1-Ph-3,3-(PMe 2 Ph) 2 -3,1,2-PtC 2 B 9 H 10 .