Robin Haunschild

π‐Bonding in Complexes of Benzannulated Biscarbenes, ‐germylenes, and ‐stannylenes: An Experimental and Theoretical Study

Benzannulated bisstannylenes, exhibiting a CH(2)C(CH(3))(2)CH(2) linking unit and CH(2)tBu (1) or CH(2)CH(2)CH(2)NMe(2) (2) N-substituents, and their molybdenum tetacarbonyl complexes 3 and 4 have been prepared. The complexes 3 and 4 exhibit remarkably short Mo-E bond lengths compared to the related biscarbene and bisgermylene complexes. The experimentally determined bonding parameters of the molybdenum bisstannylene complexes are discussed based on DFT calculations.

The Dewar–Chatt–Duncanson model reversed — Bonding analysis of group-10 complexes [(PMe3)2M–EX3] (M = Ni, Pd, Pt; E = B, Al, Ga, In, Tl; X = H, F, Cl, Br, I)

Quantum chemical calculations using BP86 with TZ2P basis sets were carried out to elucidate the structures and the bond–bond dissociation energies of the donor–acceptor complexes [(PMe3)2M–EX3] wit...

Tetrahedranes. A theoretical study of singlet E4H4 molecules (E = C–Pb and B–Tl)

Quantum chemical calculations using DFT (B3LYP) and ab initio (CCSD(T)) methods have been carried out to elucidate the E4H4 singlet potential energy hypersurface for the group-13 and group-14 elements. The results show that there are numerous E4H4 energy minima for the compounds of group-13 and group-14 elements. This holds particularly for the heavier atoms. The classical Td tetrahedron structure is energetically more favourable for the group-13 compounds E4H4 where the tetrahedron isomers are energy minima for all elements E except for thallium. The tetrahedranes Al4H4 1Al and Ga4H4 1Ga are the global energy minima on the singlet PES while 1B is slightly less stable than the singly hydrogen-bridged planar form 12B which has a rhombic B4 core. The lowest-lying energy minima for In4H4 and Tl4H4 are tetrahedranes where the E4 core is face-bridged by the hydrogen atoms. The classical Td tetrahedron structure of the group-14 elements is only for carbon and silicon an energy minimum at B3LYP/def2-TZVPP. The latter form of Si4H4 is a second-order saddle point at BP86/def2-TZVPP and MP2/def2-TZVPP. The global energy minimum form for C4H4 is the vinylideneacetylene isomer 27C which is −63.7 kcal/mol lower in energy than the tetrahedrane. The most stable isomers of Si4H4 and Ge4H4 at CCSD(T)/def2-QZVPP//B3LYP/def2-TZVPP//B3LYP/def2-TZVPP are the singly hydrogen edge-bridged tetrahedrane structures 18E, which are more than 40 kcal/mol lower in energy than the classical tetrahedrane. The B3LYP/def2-TZVPP calculations predict that tetrahedrane structure with edge-bridging hydrogen atoms 3Ge is slightly more stable than 18Ge. The former isomer is calculated as the global energy minimum on the singlet PES of Sn4H4 and Pb4H4.

Theoretical Study of Ethylene Addition to O=W(=CH2)(CH3)2

Quantum chemical calculations using density functional theory at the B3LYP level of theory were carried out to investigate the reaction pathways for the addition of ethylene to WO(CH3)2(CH2) (W1). The results are compared to those of previous theoretical studies of the ethylene addition to OsO3(CH2) (Os1) and ReO2(CH3)(CH2) (Re1). The theoretically predicted reactions pathways exhibit significant differences. The energetically most favourable reaction of the tungsten system W1 is the [2+2]W,C addition across theW=C double bond yielding the metallacyclobutane W3a which then rearranges to the slightly more stable isomer W3b. The [2+2]Re,C addition of the rhenium compound yielding the metallacyclobutane Re3a has the lowest activation barrier for the ethylene addition to the rhenium system, but the reaction is endothermic while the exothermic formation of the more stable isomer Re3b has a much higher activation barrier. The [3+2]C,O addition Os1+C2H4→Os2 is the thermodynamically most favorable reaction of the osmium compound.