Can a linear metal–metal bonded array of tetravanadium be stabilized between two dicyclopenta[a,e]pentalene ligands? A theoretical investigation

Abstract

The 14-p cross-linked annulene dicyclopenta[a,e]pentalene (dcpp) is suggested for the first time to function as a sandwich ligand. According to density functional theory (DFT) calculations, upon being sandwiched between two dcpp ligands, the tetravanadium chain, without the support of auxiliary ligands, has two unpaired electrons and has a tendency for deformation to gain extra stability through multicenter bondings in the ground state. The one-electron ligand chlorine can lead to two types of structures, one with two chlorine atoms connecting to the two central vanadium atoms and the other one with two chlorine atoms connecting to the two terminal vanadium atoms, both of which are energetically more favorable in the triplet state. In the carbonyl end-capping complex, the tetravanadium is stable as a linear metal-metal bonded array with alternating single and double bonds and all electrons paired for bonding, although a triplet state conformer exists with two extra carbonyl ligands bound to the two central vanadium atoms which is more energy favorable by 15.1 kcal mol À1 .Bonding features within the tetravanadium moiety were obtained based on electron density analyses.We hope these discussions are helpful for the design of new extended metal atom chain (EMAC) systems and for the pursuit of effective catalysts based on the dcpp sandwich complexes. Fig. 1 Structures of dcpp and Pn 2 V 2 .

Pentaleno[1,2-a:4,5′]diacenaphthylenes: Uniquely Stabilized Pentalene Derivatives

“…The smallest oligoquinane is pentalene 1 (Figure ), a structural unit that is unstable except for sterically protected derivatives, when used as a ligand for metal complexes, or when annulated to other aromatic rings. − While the native pentalene is known to readily dimerize above −140 °C, , a growing list of aryl-fused pentalenes − (e.g., 2 ) are known to be quite stable owing to the delocalization of the pentalene double bonds into the adjoined aromatic subunits. Many of these materials have been successfully incorporated as active components in organic field effect transistors (OFETs). ,,, Larger oligoquinane derivatives have been studied theoretically − and are physically known, yet are very rare. Two separate groups − have reported the synthesis of tetraquinane derivatives ( 3 and 4 ) that employ sterically bulky groups to access structures that are fleeting in solution and in the solid state.…”