Polymorphism in the Crystal Structures of the Group 13 Trimethyls

详细信息    查看全文

• 作者：Roland Boese ; Anthony J. Downs ; Timothy M. Greene ; Alexander W. Hall ; Carole A. Morrison ; and Simon Parsons
• 刊名：Organometallics
• 出版年：2003
• 出版时间：June 9, 2003
• 年：2003
• 卷：22
• 期：12
• 页码：2450 - 2457
• 全文大小：224K
• 年卷期：v.22,no.12(June 9, 2003)
• ISSN：1520-6041

文摘

Crystal structures have been determined for trimethylboron, BMe₃, and for a newpolymorph of trimethylgallium, GaMe₃; in addition, the crystal structure of trimethylthallium,TlMe₃, has been redetermined. The BMe₃ crystal structure represents a new structural typefor the group 13 trimethyl derivatives in the solid state. In contrast to its heavier analogues,it consists of layers containing only very weakly interacting BMe₃ molecules. GaMe₃ formsa ladder-like pseudo-polymer via long gallium-to-methyl intermolecular interactions withGa···C distances in the range 3.096(3)-3.226(4) Å. This is compared with a recently reportedcrystal structure of a polymorph, which, like InMe₃ and TlMe₃, is characterized by theformation of pseudo-tetramers. The effects of crystallization and secondary interactions havebeen analyzed by comparison with related crystallographic, gas-phase electron diffraction,and spectroscopic studies of these and other trimethyl derivatives of the group 13 elements.The energetic differences between polymorphs of BMe₃, GaMe₃, and InMe₃ have been exploredby plane wave DFT calculations. The energy differences between the BMe₃-like layeredstructure and the InMe₃-like pseudo-tetrameric structure are calculated to be -1.7, +3.6,and +10.4 kJ mol^-1 for BMe₃, GaMe₃, and InMe₃, respectively.