C50
In Sir Harry Kroto's paper with David Walton, C50 was predicted to be decavalent. The addition of ten monovalent atoms, such as H or Cl, should result in a stable compound.
Paper
H W Kroto and D R M Walton, 'Stable derivatives of small fullerenes', 1993.
Abstract
Recent developments in experiment and theory have enhanced our understanding of fullerene stability and reactivity to the point where predictions may be made concerning the probable existence of specific fullerenes and their derivatives.
One approach, considered here for small fullerenes (C(n), n < 60) – which cannot have isomers in which all pentagons are isolated – invokes the concepts of localised surface stability domains and angle strain release.
Sir Harry Kroto's reflections
"'Stable derivatives of small fullerenes' was shown to be correct in this paper (PDF, 117KB) in which, oddly at the time it seemed to me, our paper was not referenced.
"As I was a bit miffed by not referencing our nice prediction, I wrote to the main author. He wrote back that they knew about our work, but there was not enough room to reference our paper!
"A colleague has since pointed out that an advisor is referenced on their manuscript who may have made the “helpful suggestion” that the paper should be shortened by deleting our reference."
Valence of D5h C50 fullerene
Z Xu, J Han, Z Zhu and W Zhang, 'Valence of D5h C50 fullerene' (PDF, 370KB), 2007.
Abstract
The energetic and electronic properties of D5h C50 before and after passivation by H or Cl are investigated using first-principle computational method of density functional theory with generalised gradient approximation and local density approximation functionals.
The results show that H or Cl addition can lead to energetic stabilisation. Additions also increase the highest occupied molecular orbit−lowest unoccupied molecular orbital (HOMO−LUMO) gaps of C50 fullerides and make them chemically more stable.
In the series of C50H2m (m = 0∼7), the Saturn-shaped D5h C50H10 has the largest HOMO−LUMO gap, which suggests that such a structure of C50H10 is a “magic-number” stable one of C50 adducts, and ten is a pseudovalence or effective valence of C50 fullerene pseudoatom.
This point also is supported by the energetic properties of C50H2m series such as binding energies, etc. A minimal energy reaction pathway is constructed to get C50H10 and C50H14. Some useful experience for determining the favourable addition sites was summarised. A simple steric method is developed to predict the effective valences of classical fullerenes.
Alternative paper
Dr J-H Chen, Dr Z-Y Gao, Q-H Weng, W-S Jiang, Q He, Dr H Liang, L-L Deng, S-L Xie, Dr H-Y Huang, Professor X Lu, Professor S-Y Xie, Professor K Shi, Professor R-B Huang and Professor L-S Zheng, 'Combustion synthesis and electrochemical properties of the small hydrofullerene C50H10', 2012.