Synthesis, characterisation and molecular structures of the closo and pseudocloso heptamethylindenyl carbarhodaboranes 1-Ph-3-(η-C9Me7)-3,1,2-closo-RhC2B9H10and 1,2-Ph2-3-(η-C9Me7)-3,1,2-pseudocloso-RhC2B9H9. Experimental assignment of the11B NMR spectrum of a pseudocloso carbametallaborane
- 1 January 1996
- journal article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 3,p. 335-342
- https://doi.org/10.1039/dt9960000335
Abstract
The reaction between [{RhCl2(η-C9Me7)}2] and Tl2[7-Ph-8-R-7,8-nido-C2B9H9](R = H or Ph) in CH2Cl2 afforded the heptamethylindenyl carbarhodaboranes 1-Ph-3-(η-C9Me7)-3,1,2-RhC2B9H101 and 1,2-Ph2-3-(η-C9Me7)-3,1,2-RhC2B9H92, respectively, in good yields. The 11B NMR chemical shifts of 1 and 2 showed that they posses closo and pseudocloso structures, respectively. Compound 1 was found to be fluctional in solution at room temperature via rotation of the Ph substituent, but cooling below ca. 230 K arrested this process, presumably by locking the indenly ligand into its preferred cisoid conformation and preventing phenyl rotation. An X-ray diffraction study of a single crystal of 1 confirmed both the closo nature of the cage and the cisoid conformation, but additionally showed that, of two possible cisoid conformations, the one adopted places the cage phenyl substituent underneath the six-membered ring of the indenyl group. Compound 2 was also subjected to crystallographic analysis, which confirmed the pseudocloso nature of the cage. Again, the relative conformation of the two η-bonded ligands is cisoid. An 11B–11B COSY spectrum of compound 2, the first to be recorded from a pseudocloso species, allowed experimental assignment of the 11B chemical shifts which were in excellent agreement with those previously obtained theoretically.Keywords
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