Nitrogen carbon in planar pentacoordinate environments supported by BeH rings.

NBeH ( = 0-5) (0A-5A) species with a novel planar pentacoordinate nitrogen (ppN) were designed by the isoelectronic substitution of the C atom in planar pentacoordinate carbon (ppC) species CBeH ( = 0-5) with an N atom. The highly flexible H atoms found in ppC species CBeH and CBeH were fixed upon the nitrogen substitution, as mirrored by the non-flexible H atoms in their ppN analogues NBeH (2A) and NBeH (3A). Moreover, the N atom was found to fit the H-surrounded Be rings better than the C atom because the ppC species CBeH and CBeH adopted non-planar structures due to size-mismatch between the C atom and the H-surrounded Be ring, but their ppN analogues NBeH (4A) and NBeH (5A) adopted perfect planar structures.

Transition metal chemistry in synthetically viable alkaline earth complexes M(Cp) (M = Ca, Sr, Ba).

We predicted the stable alkaline earth complexes M(Cp)3- (M = Ca, Sr, Ba; Cp = cyclopentadienyl), where the M centers were in their stable +2 oxidation state and mimicked the bonding behaviour of transition metals by participating in bonding with the π orbitals of Cp ligands using their d orbitals.

Mechanism of nickel-catalyzed direct carbonyl-Heck coupling reaction: the crucial role of second-sphere interactions.

We present a detailed DFT mechanistic study on the first Ni-catalyzed direct carbonyl-Heck coupling of aryl triflates and aldehydes to afford ketones. The precatalyst Ni(COD)2 is activated with the phosphine (phos) ligand, followed by coordination of the substrate PhOTf, to form [Ni(phos)(PhOTf)] for intramolecular PhOTf to Ni(0) oxidative addition. The ensuing phenyl-Ni(ii) triflate complex substitutes benzaldehyde for triflate by an interchange mechanism, leaving the triflate anion in the second coordination sphere held by Coulomb attraction.

Influence of stepwise oxidation on the structure, stability, and properties of planar pentacoordinate carbon species CAl.

Computational design has played an important role in planar hyper-coordinate carbon (phC) chemistry. However, none of numerous computationally predicted phC species were subsequently successfully synthesized in the condensed phase, perhaps due to the frustrating issue of oxidation. In the present work, we studied the influence of stepwise oxidation on the structure, stability, and properties of phC species using the milestone planar pentacoordinate carbon (ppC) species CAl as an example.

Transition-Metal Chemistry of Alkaline-Earth Elements: The Trisbenzene Complexes M(Bz) (M=Sr, Ba).

We report the synthesis and spectroscopic identification of the trisbenzene complexes of strontium and barium M(Bz) (M=Sr, Ba) in low-temperature Ne matrix. Both complexes are characterized by a D symmetric structure involving three equivalent η -bound benzene ligands and a closed-shell singlet electronic ground state. The analysis of the electronic structure shows that the complexes exhibit metal-ligand bonds that are typical for transition metal compounds.

Computational design of species with ultrashort Be-Be distances using planar hexacoordinate carbon structures as the templates.

A current project in metal-metal bonding chemistry is to achieve ultrashort metal-metal distances (USMMDs, denoted by dM-M < 1.900 Å) between main group metal beryllium atoms. A valid way for achieving such USMMDs is the substitution of a carbon atom in a planar pentacoordinate environment with the isoelectronic Be2 moiety.

Stabilization of beryllium-containing planar pentacoordinate carbon species through attaching hydrogen atoms.

The diagonal relationship between beryllium and aluminum and the isoelectronic relationship between BeH unit and Al atom were utilized to design nine new planar and quasi-planar pentacoordinate carbon (ppC) species CAl Be H ( + = 5, = 0, ±1, = + - 1) (1a-9a) by attaching H atoms onto the Be atoms in CAlBe, CAlBe , CAlBe , and CAlBe . These ppC species are σ and π double aromatic. In comparison with their parents, these H-attached molecules are more stable electronically, as can be reflected by the more favourable alternative negative-positive-negative charge-arranging pattern and the less dispersed peripheral orbitals.

CBE (q = ±1): a family of "hyparene" analogues with a planar pentacoordinate carbon.

A CB3 moiety extracted from the building units of milestone "hyparenes" (families of species with a planar pentacoordinate carbon (ppC)) was found to be a more basic building block, which can be employed to design a family of "hyparene" analogues CB3E2q (q = ±1) also with a ppC. The majority of main group elements can feasibly serve as the E atom. Despite the number of valence electrons, the ppC atoms in the CB3E2q (q = ±1) species were involved in three delocalized σ orbitals and a delocalized π orbital, so the carbon atom obeys the octet rule.