Electronic Structure and Bonding in Neutral and Dianionic Boradiphospholes: R ' BC2P2R2 (R=H, tBu, R '=H, Ph)

Usharani, Dandamudi and Podnska, Anne and Nixon, John F and Jemmis, Eluvathingal D (2009) Electronic Structure and Bonding in Neutral and Dianionic Boradiphospholes: R ' BC2P2R2 (R=H, tBu, R '=H, Ph). In: Chemistry - A European Journal, 159 (34). pp. 8429-8442.

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Abstract

Classical and non-classical isomers of both neutral and dianionic BC2P2H3 species, which are isolobal to Cp+ and Cp-, are studied at both B3LYP/6-311++G(d,p) and G3B3 levels of theory. The global minimum structure given by B3LYP/6-311+ + G(d,p) for BC2P2H3 is based on a vinylcyclopropenyl-type structure, whereas BC2P2H32- has a planar aromatic cyclopentadienyl-ion-like structure. However, at the G3B3 level, there are three low-energy isomers for BC2P2H3: 1)tricyclopentane, 2) nido and 3) vinylcyclopropenyl-type structures, all within 1.7 kcal mol(-1) of each other. On the contrary, for the dianionic species the cyclic planar structure is still the minimum. In comparison to the isolobal Cp+ and HnCnP5-n+ isomers, BC2P2H3 shows a competition between pi-delocalised vinylcyclopropenyl- and cluster-type structures (nido and tricyclopentane). Substitution of H on C by tBu, and H on B by Ph, in BC2P2H3 increases the energy difference between the low-lying isomers, giving the lowest energy structure as a tricyclopentane type. Similar substitution in BC2P2H32- merely favours different positional isomers of the cyclic planar geometry, as observed in 1) isoelectronic neutral heterodiphospholes EtBu2C2P2 (E=S, Se, Te), 2) monoanionic heterophospholyl rings EtBu2C2P2 (E=P-, As-, Sb-) and 3) polyphospholyl rings anions tBu(5-n)C(n)P(5-n) (n=0-5). The principal factors that affect the stability of three-, four-, and five-membered ring and acyclic geometrical and positional isomers of neutral and dianionic BC2P2H3 isomers appear to be: 1) relative bond strengths, 2) availability of electrons for the empty 2p boron orbital and 3) steric effects of the tBu groups in the HBC(2)P(2)tBu(2) systems.

Item Type:	Journal Article
Publication:	Chemistry - A European Journal
Publisher:	John Wiley and Sons
Additional Information:	Copyright of this article belongs to John Wiley and Sons.
Keywords:	boradiphosphole • cyclopentadienyl anion • cyclopentadienyl cation • electronic structure • isolobal relationship
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	08 Mar 2010 09:05
Last Modified:	19 Sep 2010 05:56
URI:	http://eprints.iisc.ac.in/id/eprint/26010

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