Reversal of Stability on Metalation of Pentagonal-Bipyramidal (1-MB6H7 2- , 1-M-2-CB5H7 1- , and 1-M-2,4-C2B4H7) and Icosahedral (1-MB11H12 2- , 1-M-2-CB10H12 1- , and 1-M-2,4-C2B9H12) Boranes (M = Al, Ga, In, and Tl): Energetics of Condensation and Relationship to Binuclear Metallocenes

• Published in: Journal of the American Chemical Society Vol. 128; no. 33; pp. 10915 - 10922
• Main Authors: Pathak, Biswarup, Pandian, Shanthi, Hosmane, Narayan, Jemmis, Eluvathingal D
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 23.08.2006
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Five membered ring; Condensation reaction; Stability; Ligand; Thermodynamic parameter; Density functional method; Metalation; Organic borane; Metal; Metallocene
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja061399f

The usual assumption of the extra stability of icosahedral boranes (2) over pentagonal-bipyramidal boranes (1) is reversed by substitution of a vertex by a group 13 metal. This preference is a result of the geometrical requirements for optimum overlap between the five-membered face of the ligand and the metal fragment. Isodesmic equations calculated at the B3LYP/LANL2DZ level indicate that the extra stability of 1-M-2,4-C2B4H7 varies from 14.44 kcal/mol (M = Al) to 15.30 kcal/mol (M = Tl). Similarly, M(2,4-C2B4H6)2 1- is more stable than M(2,4-C2B9H11)2 1- by 9.26 kcal/mol (M = Al) and by 6.75 kcal/mol (M = Tl). The preference for (MC2B4H6)2 over (MC2B9H11)2 at the same level is 30.54 kcal/mol (M = Al), 33.16 kcal/ mol (M = Ga) and 37.77 kcal/mol (M = In). The metal−metal bonding here is comparable to those in CpZn−ZnCp and H2M−MH2 (M= Al, Ga, and In).