title: Covalent hypercoordination: can carbon bind five methyl ligands?
abstract: C(CH3)5(+) is the first reported example of a five-coordinate carbon atom bound only to separate (that is, monodentate) carbon ligands. This species illustrate the limits of carbon bonding, exhibiting Lewis-violating "electron-deficient bonds" between the hypercoordinate carbon and its methyl groups. Though not kinetically persistent under standard laboratory conditions, its dissociation activation barriers may permit C(CH3)5(+) fleeting existence near 0 K.
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar Street, Athens GA, 30602-2525 (USA) http://schleyer.chem.uga.edu.
authors.forename: William C
authors.initials: WC
authors.lastname: McKee
authors.forename: Jay
authors.initials: J
authors.lastname: Agarwal
authors.forename: Henry F
authors.initials: HF
authors.lastname: Schaefer
authors.forename: Paul von R
authors.initials: Pv
authors.lastname: Schleyer
keywords: 3-center 2-electron bonds; carbonium ions; hypercoordinate carbons; hypercoordination; σ-allyl bonding