Search

The characteristic of the triple bonding between gallium (Ga) atoms was determined through a theoretical analysis of a gallyne complex's model electronic structure and related molecules. The existence of the triple bond was doubted since the bond length was shorter than known Ga-Ga single bonds. It was observed that bent structures of model molecules contained triple bonds composed of two dative and a pi bond although the dative bonds in the molecules were weak. The nature of the chemical bond was determined mainly by the electronic structure and not by the molecular geometry.

Ab initio quantum mechanical techniques were employed in the study of M2(GaH)3 (M = Li,Na,K) compounds, which are models for the newly synthesized class of Ga3 three-membered -ring cyclogallene compounds. The experimental (X-ray) structures were in close agreement with theory. While Na2(GaH)3 has C3 symmetry, the remaining two compounds are C3h symmetric. The parent neutral three-membered-ring structure (GaH)3 is not stable as the imaginary vibrational frequencies of (GaH)3 lead to Ga-Ga bond breaking.

The first anionic N-heterocyclic dicarbene containing both normal (C2) and abnormal carbene (C4) centers in the same five-membered imidazole ring (III) is prepared by lithiation of the imidazole monocarbene. The dicarbene nature is shown by the formation of the group 13 Lewis acid adducts.

Potassium graphite reduction of L:Ga(Mes)[Cl.sub.2] [L: = :C[{(i-Pr)NC[(Me)}.sub.2], Mes = 2,4,6-[Me.sub.3][c.sub.6][H.sub.2]] in hexane has produced the organogallium dimer L:(Mes)(Cl)Ga-Ga(Cl)(Mes):L. Potassium reduction of L:Ga(Mes)[Cl.sub.2] in toluene has produced the neutral aromatic [Ga.sub.6] octahedron L:Ga[[Ga.sub.4][Mes.sub.4]]Ga:L.

The syntheses, structures and computations of N-heterocyclic carbene (NHC, L:) stabilized [P.sub.2] molecules are described. These compounds have displayed a unique bis-phosphinidene structure, containing two phosphinidene units, each with two lone pairs of electrons, bridged by a phosphorus-phosphorus single bond.

The conformational variations of neutral diborenes in the solid state are described. The polymorphic structures of diborene are attributed to a combination of inter alia, packing effects in the crystal, crystallizing-solvent polarity and intramolecular ligand steric effects.

The synthesis and molecular structure of the first isoelectronic gallepin are described along with its nature of bonding and aromaticity. This compound has displayed the aromatic 6[pi]-electron structure.

The synthesis and characterization of the first stable neutral diborene compound with double boron-boron (B=B) bond are presented.

The redox chemistry of the first stable anionic dithiolene radical 1Ṗ was investigated by both reactivity and cyclic voltammetry studies. While one-electron reduction of 1Ṗ by Cp2Co or KC8 affords the corresponding dithiolate dimers 2 and 3, respectively, one-electron oxidation of 1Ṗ by Ph3C+BF4− (or O2) conveniently gives 4, the neutral dithiolene dimer. [ABSTRACT FROM AUTHOR]

The synthesis of all possible stable chiral pseudotetrahedral polyhalocubanes and estimation of their parity violating energy differences together with selected parity violating vibrational frequency shifts are presented. The absolute values of the parity violating energy differences in the chiral polyhalocubanes are approximately one to two orders of magnitude smaller than those predicted for the related chiral polyhalomethanes.

The synthesis and molecular structure of the second compound with a ZN-Zn bond, RZn-ZnR (R=[{2,6-Pr(super i)(sub 2)C6H3)N(Me)C}(sub 2)CH]), is reported. The NLMO/NPA Zn-Zn bond order of 0.87 and the electron occupancy of the Zn-Zn bonding orbital of 1.9542 are supportive of the intriguing Zn-Zn single bond.

The synthesis and the molecular structure of metallocene-complexed dibismuthene, Cp(sub 2)Zr(BiR)(sub 2) [Cp = C(sub 5)H(sub 5); R = C(sub 6)H(sub 3)-2,6-Mes(sub 2)] is reported. This dark reddish/brown compound that is air- and moisture sensitive, is prepared by sodium metal reduction of Cp(sub 2)ZrCl(sub 2) with RBiCl(sub 2)(super 5).

The synthesis, characterization, chromatographic enatioseparation, and stereochemical analysis of pseudotetrahedral polyhaloadamantanes is described. The power of combining experiment and theory in assigning absolute configurations even for molecules without chromophors and with very small values for the optical rotation at a set wavelength is demonstrated.

(Li(THF)*12-crown-4)((PhC=CPhPhC=CpH)2Ga), which was isolated from the reaction of 1,4-dilithiotetraphenylbutadiene with gallium chloride in the presence of 12-crown-4/THF was synthesized and its molecular structure investigated. The anion is the first example of a spirogallane, a bicyclic organometallic compound with a tetrahedral gallium atom in both rings. The metal is surrounded by a distorted environment, with the two five-membered rings formed by the two tetraphenylbutadiene units and the gallium atom completely planar and orthogonal to each other.

The synthesis and molecular structure of Na2[Mes*2C6H3-Ga(equivalent to)Ga-C6H3Mes*2] (Mes* = 2,4,6-i-Pr3C6H2) are described. Na2[Mes*2C6H3-Ga(equivalent to)Ga-C6H3Mes*2] was found to have a Ga-Ga bond distance of 2.319(3) angstrom, the shortest ever recorded. This short Ga-ga bond, along with the novel two-coordinate status of the gallium atoms and the overall sterically crowded geometry, affirms that Na2[Mess*2C6H3-Ga(equivalent to)Ga-C6H3Mes*2] is the first example of a Ga(equivalent to)Ga triple bond. These also consequently confirm that the compound is the first group 13 metal engaging in triple bond formation, the first Ga(equivalent to)Ga gallyne.

The study reports the synthesis and molecular structure of Na2({Mes2C6H3}-Ga)3, isolated from the sodium metal reduction of (Mes2C6H3)-GaCl2 in diethyl ether. Na2({Mes2C6H3}Ga)3 shows aromatic characteristics, thus constituting a rare example of metalloaromaticity, as well as demonstrating planarity in the ring system.

Reaction of carbene-stabilized disilicon L: Si=Si:L (L: = :C{N(2,6-Pri2C6H3)CH}2, 1) with BH3 · THF results in facile cleavage of the silicon-silicon double bond and the formation of two quite different "push-pull" stabilized products with borane-and carbene-coordinated silylene moieties: 2, containing a parent silylene (:SiH2); and 3, containing a unique three-membered cyclosilylene. [ABSTRACT FROM AUTHOR]