The EDA-NOCV analysis shows that the singlet 2-adamantylidene is a foiled-type carbene stabilized by the hyperconjugative interaction of one pair of the vicinal C-C σ-MOs with the empty p-orbital on the carbene carbon atom. The high proton affinity and hydride affinity indicate the ambiphilic nature of 2-adamantylidene.

Complexes with two and three coordinate chromium(i).

Crystallographic studies of the fluorinated tetraarylporphyrin 5,10,15,20‐tetrakis(2′,3′,5′,6′‐tetrafluoro‐N,N‐dimethyl‐4‐anilinyl)porphyrin and its metal complexes [MTF4DMAP; M = 2H·2H2O, 1; NiII·THF, 2; CuII·5H2O, 3; and ZnII·(THF)2, 4; THF = tetrahydrofuran] are reported. To analyse the weak intermolecular interactions, we have used a combination of energy decomposition analysis and Hirshfeld surface analysis, which allowed us to elucidate the nature of various close contacts. The energy decomposition analysis shows that dispersive interactions involving fluorine atoms significantly contribute to the stabilizing intermolecular interactions. Cooperative weak interactions such as C–F···H/C/F, C–H···π and H···H are responsible for the formation and stabilization of the supramolecular self assemblies.

Electronic structure of the six-membered N-heterocyclic carbene, silylene, germylene, and stannylene having an exocyclic double bond at the C3 carbon atom as well as the relative reactivity of the lone-pair on the divalent group 14 element and the exocyclic double bond have been studied at the BP86 level of theory with a TZVPP basis set. The geometrical parameters, NICS values, and NBO population analysis indicate that these molecules can be best described as the localized structure 1X(a), where a trans-butadiene (C1-C2-C3-C4) unit is connected with diaminocarbene (N1-X-N2) via N-atoms having a little contribution from the delocalized structure 1X(b). The proton affinity at X is higher than at C4 for 1C, and a reverse trend is observed for the heavier analogues. Hence, the lone pair on a heavier divalent Group 14 element is less reactive than the exocyclic double bond. This is consistent with the argument that, even though the parent six-membered carbene and its heavier analogues are nonaromatic in nature, the controlled and targeted protonation can lead to either the aromatic system 3X having a lone pair on X or the nonaromatic system 2X with readily polarizable C3-C4 π-bond. The energetics for the reaction with BH(3) and W(CO)(6) further suggest that both the lone pair of Group 14 element and the exocyclic double bond can act as Lewis basic positions, although the reaction at one of the Lewis basic positions in 1X does not considerably influence the reactivity at the other. The protonation and adduct formation with BH(3) and W(CO)(5) at X lead to nonaromatic systems whereas similar reactions at C4 lead to aromatic systems due to π-bond polarization at C3-C4. The degree of polarization of the C3-C4 π-bond is maximum in the protonated adduct and reduces in the complexes formed with BH(3) and W(CO)(5).

First examples of racemization of tetrahedral tetracoordinated centers via a planar transition state or an intermediate structure.