4,4 '-Diamino-2,2 ',6,6 '-tetramethylbiphenyl

Each of the three independent mol­ecules of the title compound, C16H20N2, has near-perpendicular benzene rings and pyramidal N atoms. Hydrogen bonding in the structure is rather inefficient

Do the discrete dianions C2B9H112- exist? Characterisation of alkali metal salts of the 11-vertex nido dicarboranes, C2B9H112-, in solution

Detailed experimental solution-state NMR data are reported for the nine moisture-sensitive salts of M2C2B9H11 (M = Li, Na, K) 1–9 generated by deprotonation of 7,8-C2B9H13, 7,9-C2B9H12− and 2,9-C2B9H13 by butyllithium, sodium hydride and potassium hydride. Indicative of cation–anion interactions, the 11B, 13C and 1H chemical shifts depend on the identity of the cation and, to a lesser degree, the solvent. Computed NMR shifts generated from MP2-optimised geometries of C2B9H112−, LiC2B9H11− and NaC2B9H11− suggest that intimate ion-pair cluster anions MC2B9H11− are present in solutions of M2C2B9H11. As a test of the method of comparing experimental structures and chemical shifts with those from optimised geometries, the optimised geometries of the small carborane alkali metal salts M2C2B4H4(SiR3)2 (M = Li or Na, R = H or Me) were computed and shown to agree well with experimental structures

Electrochemical evidence for electronic interactions through the para-carborane skeleton in the novel tricluster [{Co2C2(SiMe3)(CO)4(dppm)}2(μ-CB10H10C)]

The electrochemical properties of the title compound reveal electronic interactions between two dicobalt-dicarbon clusters via a 1,12-para-carborane cage

Synthetic and structural studies on C-ethynyl- and C-bromo-carboranes.

A high-yield preparation of the C-monoethynyl para-carborane, 1-Me3SiC[triple bond, length as m-dash]C-1,12-C2B10H11, from C-monocopper para-carborane and 1-bromo-2-(trimethylsilyl)ethyne, BrC[triple bond, length as m-dash]CSiMe3 is reported. The low-yield preparation of 1,12-(Me3SiC[triple bond, length as m-dash]C)2-1,12-C2B10H10 from the C,C′-dicopper para-carborane derivative with 1-bromo-2-(trimethylsilyl)ethyne, BrC[triple bond, length as m-dash]CSiMe3, has been re-investigated and other products were identified including the C-monoethynyl-carborane 1-Me3SiC[triple bond, length as m-dash]C-1,12-C2B10H11 and two-cage assemblies generated from cage–cage couplings. The contrast in the yields of the monoethynyl and diethynyl products is due to the highly unfavourable coupling process between 1-RC[triple bond, length as m-dash]C-12-Cu-1,12-C2B10H10 and the bromoalkyne. The ethynyl group at the cage carbon C(1) strongly influences the chemical reactivity of the cage carbon at C(12)—the first example of the ‘antipodal effect’ affecting the syntheses of para-carborane derivatives. New two-step preparations of 1-ethynyl- and 1,12-bis(ethynyl)-para-carboranes have been developed using a more readily prepared bromoethyne, 1-bromo-3-methyl-1-butyn-3-ol, BrC[triple bond, length as m-dash]CCMe2OH. The molecular structures of the two C-monoethynyl-carboranes, 1-RC[triple bond, length as m-dash]C-1,12-C2B10H11 (R = H and Me3Si), were experimentally determined using gas-phase electron diffraction (GED). For R = H (RG = 0.053) a model with C5v symmetry refined to give a C[triple bond, length as m-dash]C bond distance of 1.233(5) Å. For R = Me3Si (RG = 0.048) a model with Cs symmetry refined to give a C[triple bond, length as m-dash]C bond distance of 1.227(5) Å. Molecular structures of 1,12-Br2-1,12-C2B10H10, 1-HC[triple bond, length as m-dash]C-12-Br-1,12-C2B10H10 and 1,12-(Me3SiC[triple bond, length as m-dash]C)2-1,12-C2B10H10 were determined by X-ray crystallography. Substituents at the cage carbon atoms on the C2B10 cage skeleton in 1-X-12-Y-1,12-C2B10H10 derivatives invariably lengthen the cage C–B bonds. However, the subtle substituent effects on the tropical B–B bond lengths in these compounds are more complex. The molecular structures of the ethynyl-ortho-carborane, 1-HC[triple bond, length as m-dash]C-1,2-C2B10H11 and the ethene, trans-Me3SiBrC[double bond, length as m-dash]CSiMe3Br are also reported

Crystal, Molecular and Electronic Structure of N,N'-diphenyl-N,N'-bis(2,4-dimethylphenyl)-(1,1'-biphenyl)-4,4'-diamine and the Corresponding Radical Cation

Oxidation of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD, 1a) and N,N'-diphenyl-N,N'-bis(2,4-dimethylphenyl)- (1,1'-biphenyl)-4,4'-diamine (1b) with SbCl5 affords the corresponding radical cations quantitatively. The crystal and molecular structure of 1b and [1b]SbCl6, the first tetraphenyl benzidene derivatives to be characterised crystallographically in both the neutral and radical cation states, reveal molecular parameters in agreement with the predictions made on the basis of DFT studies. Analysis of the NIR transition in the radical cations [1](+.) allows an estimate of the electronic coupling parameter V (1a(+.) 3200 cm(-1); 1b(+.) 3300 cm(-1)), the reorganisation energy lambda(1a(+.) 7500 cm(-1); 1b(+.) 7800 cm(-1)), and the linear coupling constant I (1a(+.) 3100 cm(-1); 1b(+.) 2700 cm(-1)) of the symmetric mode

Electronic interactions in bridged bis(cluster) assemblies - a comparison of para-CB10H10C, para-C6H4 and C-4 bridges

The electrochemical response of bis-Co2C2(CO)(4)(mu-dppm) complexes featuring bridging para-CB10H10C (5) and para-C6H4 (6) moieties are similar, each exhibiting two oxidations separated by ca. 100 mV, and two reductions separated by 80 mV, evidencing a degree of "electronic communication". A computational study of these systems and of the butadiyndiyl-bridged species (7) reveals an increasing contribution from the bridge pi-orbitals in the frontier MO's of the monocations 5(+) < 6(+) < 7(+). Thus, while similar conclusions about electronic interactions between the cluster-based redox probes through the cluster or organic bridges may be drawn from electrochemical studies, the mechanism by which these effects transmitted is subtly different in each case