Nucleophilic addition reactions on the electron-deficient cluster dication [H4Ru4(C6H6)4]2+: synthesis and structural characterisation of the water-soluble cluster cations [H3Ru4(C6H6)4(CO)]+ and [H3Ru4(C6H6)4(OH)]2+

Abstract

The electron-deficient (58e) cluster cation [H₄Ru₄(C₆H₆)₄]²⁺  1 was found to react in aqueous solution with simple nucleophiles to give electron-precise (60e) clusters. With carbon monoxide, the cluster cation [H₃Ru₄(C₆H₆)₄(CO)]⁺  3 is formed. The reaction with water needs NaN₃ as catalyst and yields the cluster dication [H₃Ru₄(C₆H₆)₄(OH)]²⁺  4a; the reaction with alcohols leads to the analogous clusters [H₃Ru₄(C₆H₆)₄(OR)]²⁺ (R = Me: 4b, R = Et: 4c, R = PhCH₂: 4d, R = Ph: 4e, R = 4-EtC₆H₄: 4f). The single-crystal X-ray structure analyses of the chloride salts of 3 and 4a reveal a tetrahedral Ru₄ metal core. Each ruthenium atom is coordinated by a η⁶-benzene ligand, while the carbonyl or hydroxo ligands are found as μ₃ capping ligands over a triangular face of the Ru₄ tetrahedron.