The thermodynamic stability of P8, A CBS-Q study

✍ Scribed by Michael K. Denk; Azardokht Hezarkhani

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 88 KB
• Volume: 16
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/hc.20119

✦ Synopsis

Abstract

The thermodynamic stabilities of P~2~, P~4~, and three P~8~ cage structure were investigated through high‐precision CBS‐Q calculations. The CBS‐Q values for the bond energy of P~2~ (ΔE~o~: +115.7 kcal mol^−1^) and the formation of P~4~ from P~2~ (Δ E~o~:‐56.6 kcal mol^−1^) were in excellent agreement with the experimental values (E~o~: +117 and ‐56.4 kcal mol^−1^ respectively). Among the P~8~ cages, the cubane structure was the least stable (Δ E~o~ +37 kcal vs. 2×P~4~). The most stable P~8~ isomer adopts a cuneane structure resembling S~4~N~4~, and is more stable than white phosphorus at T = 0 K (Δ E~o~ −3.3 kcal mol^−1^), but still unstable under standard conditions for entropic reasons (Δ G^o^ of +8.1 kcal mol^−1^ vs. 2×P~4~). The CBS‐Q energies represent significant revisions (6–20 kcal mol^−1^) of previous computational predictions obtained by high‐level single method calculations. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:453–457, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20119