Iron-catalysed Suzuki coupling? A cautionary tale

In our hands, Fe(II) or (III) pyridine complexes show no activity in Suzuki biaryl cross-coupling reactions, except in one irreproducible instance when complete conversion was observed. A comparison with palladium acetate under the same conditions showed that complete conversion can be obtained in a S:C ratio of 1,000,000:1 and therefore extreme caution must be exercised to prevent 'false-positives' arising from trace Pd-contaminants. (C) 2009 Elsevier Ltd. All rights reserved.