Improved Synthesis of Dinuclear [M(μ-X)(η5-Cp*)X]2 Precursors for Half-Sandwich Complexes (M=Rh or Ir; X=Br or I)

Abstract

The long-known dinuclear complexes of the general formula [M(μ-X)(η⁵-Cp*)X]₂ (1–4; M=Rh or Ir, X=Br or I; HCp*=pentamethylcyclopentadiene) represent important intermediates for the preparation of biologically (e. g., anticancer or antimicrobial) and catalytically active half-sandwich rhodium(III) and iridium(III) complexes. Here we report the optimized rapid microwave-assisted syntheses of the mentioned dinuclear synthons 1–4. With respect to their following synthetic utilization, we examined their antiproliferative activity in the representative human cancer cell lines, where they did not show any relevant cytotoxicity. However, the iridium complexes 3 and 4 exhibited considerable catalytic activity in a model transfer hydrogenation of acetophenone using propan-2-ol as the hydrogen source. The obtained comprehensive data sets can be useful in the evaluation of the ligand effects in complexes prepared from 1–4 and used in e. g. bioinorganic and catalytic applications.