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X-Ray crystallographic analysis of bis[ 8-(phenylselanyl)naphthyl] diselenide 1 reveals that the four selenium atoms in 1 align almost linearly with the angles of the adjacent three Se atoms 176.9 and 170.3", respectively; the linear bond was shown to be a four-centre six-electron (4cde) bond by MO calculations.

An anthracene cyclic hexamer was synthesized by the coupling reaction as a macrocyclic hydrocarbon host. This disk-shaped host included a C guest in 1:1 ratio to form a Saturn-type supramolecular complex in solution and in crystals. X-ray analysis unambiguously revealed that the guest molecule was accommodated in the middle of the host cavity with several CH⋅⋅⋅π contacts. The association constant K determined by NMR titration measurements was 2.3×10 L mol at 298 K in toluene. The structural features and the role of CH⋅⋅⋅π interactions are discussed with the aid of DFT calculations.

The X-ray crystallographic analysis of bis[8-(phenylselanyl)naphthyl]-1,1‘-diselenide (1) and 1-(methylselanyl)-8-(phenylselanyl)naphthalene (2) showed that the four selenium atoms in 1 aligned linearly, while the Se−C(Me) and Se−C(Ph) bond in 2 declined by about 50° and 40° from the naphthyl plane, respectively. Ab initio molecular orbital calculations were performed on the models of 1 and 2, model a (HbHc 2Se···Ha 1Se3SeHa···4SeHbHc) and model b (HaHb 1Se···2SeHa ‘Hb ‘), respectively, with the 6-311++G(3df,2pd) basis sets at the HF and MP2 levels, and the calculations reproduced well the observed structures and revealed the nature of the bonds constructed by the selenium atoms containing nonbonded interactions. The bond with four linearly aligned selenium atoms in model a can be analyzed with the 4c-6e model constructed with the nonbonded interaction between the two p-type lone pairs on the outside selenium atoms and the σ*(Se−Se) orbital of the inside Se−Se bond, which results in charge transfer from the outside Se atoms to the inside Se atoms. The nonbonded interaction between the two p-type lone pairs at the Se atoms in model b is analyzed as a π-type 2c-4e bond. The bent structure in Hb-1Se···2Se−Hb ‘ was demonstrated to be the result of the requirement to avoid the severe exchange repulsion between the filled p-type lone pairs at the two selenium atoms. The calculations on the other models, PhSeH···HSeSeH···HSePh and PhSeH···HSeMe, with the 6-311+G(d,p) basis sets at the DFT (B3LYP) level showed that the π-orbitals of the phenyl groups of the former interacted effectively with the 4c-6e orbitals but the π-orbitals of the latter did little with the 2c-4e orbitals due to the orthogonality of the two systems.

To distinguish between dissociation of a B-N coordination bond by S N 1-and S N 2-type mechanisms, two series of 1,3,2-dioxaborolanes (boronates) and BEt 2 (borane) complexes carrying a 2,6-bis((dimethylamino)methyl)phenyl group as a third substituent were synthesized by the reaction of the corresponding organolithium compound with an appropriate boron reagent. In the solid state, the boronate complex exhibits a structure in which only one NMe 2 group is coordinated to a tetracoordinated boron atom according to the X-ray analysis and the solid-state NMR. In solution there is a rapid exchange between the coordinated and uncoordinated amine ligands. The barriers to B-N dissociation in the boronate and borane complexes are lower by >3.4 and 6.6 kcal/mol than in the corresponding monoamino complexes, respectively, which is due to electronic assistance in an S N 2-type mechanism. This observation is supported by ab initio calculations for the system of NH 3 and BH 3 . The dynamic process observed in the boronate complex with 4,4-diphenyl substituents is also discussed.

Saturn‐like systems consisting of nanoscale rings and spheres are fascinating motifs in supramolecular chemistry. Several ring molecules are known to include spherical molecules at the center of the cavity via noncovalent attractive interactions. In this Minireview, we generalize the molecular design, the structural features, and the supramolecular chemistry of such “nano‐Saturns”, which consist of monocyclic rings and fullerene spheres (mainly C60), on the basis of previous experimental and theoretical studies. Ring molecules are classified into three types (loop, belt, and disk) according to their shapes and possible interactions. Whereas typical belt‐shaped rings tend to form tight complexes due to the wide contact area via π–π interactions, flat disk‐shaped rings generally form weak complexes due to the narrow contact area mainly via CH–π interactions. In spite of the small association energies, disk‐shaped rings are attractive because such rings can mimic the planet Saturn precisely as exemplified by an anthracene cyclic hexamer–C60 complex.

C 3 symmetric chiral trimethylsumanene was enantioselectively synthesized through Pd-catalyzed syn-selective cyclotrimerization of an enantiomerically pure iodonorbornenone, ring-opening/closing olefin metathesis, and oxidative aromatization where the sp 3 stereogenic center was transmitted to the bowl chirality. Chiral HPLC analysis/resolution of the derivatives were also achieved. Based on theoretical calculations, the columnar crystal packing structure of sumanene and trimethylsumanene was interpreted as due to attractive electrostatic or CH³ interaction. According to the experimental and theoretical studies, the bowl depth and inversion energy were found to increase on methylation for sumanene in contrast to corannulene. Dissimilarities of the effect of methylation on the bowl structure and inversion energy of sumanene and corannulene were ascribed to differences in steric repulsion. A double-well potential model was fitted to the bowl structureinversion energy correlation of substituted sumanenes, with a small deviation. The effects of various substituents on the sumanene structure and bowl-inversion energy were analyzed by density functional theory calculations, and it was shown that the bowl rigidity is controlled by a combination of electronic and steric effects of the substituents. The electron conductivity of trimethylsumanene was investigated by time-resolved microwave conductivity method, compared with that of sumanene.In the wake of the discovery of fullerene, the chemical and physical properties of buckybowls have attracted a great deal of interest because of their unique bowl-shaped ³-conjugated structure. 13 The science of buckybowls has grown as a result of the development of practical routes for the synthesis of compounds such as sumanene (1) 4 and corannulene (2) have also been studied. With this background knowledge, we studied five aspects of C 3 symmetric trimethylsumanene (3), as listed below. Direct Selective Synthesis of C 3 Symmetric Substituted Sumanenes. One of the major difficulties in studying the properties of sumanene (1) is that of selective synthesis of its derivatives. Because sumanene is C 3v symmetric, the selective synthesis of C 3 symmetric trisubstituted derivatives through functionalization at either methylene or benzene is difficult to achieve. Functionalization of the parent compound 1 results in mixtures of regioisomers, with the desired C 3 symmetric derivatives as minor products that are difficult to separate. 6c,6i Because of the importance of C 3 symmetric trisubstituted derivatives for studies on the physical properties of sumanene (1) and its derivatives or for further transformation into ³-conjugated derivatives, functionalized sumanenes have to be

The molecular structures of a set of intramolecular boron-amine complexes, 9-[2-(dialkylaminomethyl)phenyl]-9-borabicyclo[3.3.1]nonanes (alkyl = Me and Et) and 2-[2-(dimethylaminomethyl)phenyl]-4,4-diphenyl-1,3,2-dioxaborolane, were determined by the X-ray analyses. The boron atom has a tetrahedral geometry and the five-membered ring is puckered with the nitrogen atom out of the plane in every complex. The distances of the N–B coordination bonds, which are in the range of 1.74–1.77Å, are not always correlated to the barrier to dissociation of the N–B bonds. In order to correlate the molecular structures to the strength of the N–B coordination bonds, the tetrahedral character, which is calculated from bond angles at a boron atom, is proposed. The usefulness as well as the limitation of this parameter are discussed.