Formation and mixed-valent behaviour of a substituted tetraferrocenylstannane.

A tetrasubstituted tetraferrocenylstannane is formed from 1-bromoferrocene-1'-carboxylic acid methyl ester and copper bronze. The molecular structure is almost perfectly tetrahedral with FeFe distances of around 6 A. In solution two sequential one-electron processes and one two-electron process are indicative of mixed-valent intermediates. Intermetallic interactions have been probed by preparative oxidation, paramagnetic NMR spectroscopy, Mössbauer spectroscopy, UV/Vis/NIR spectroscopy and DFT calculations.