Molybdenum is an essential trace element for virtually all life forms. It functions as a co-factor
for a number of enzymes that catalyse important chemical transformations in the global
carbon, nitrogen, and sulphur cycles. Thus, molybdenum-dependent enzymes are not only
required for human health, but also for the health of our ecosystem. Molybdenum and its
compounds are also very important in catalysis and in medicine, so it is not surprising that its
biological and coordination chemistry remain very active areas of research. The enormous
chemistry of molybdenum, much of which remains untapped, was investigated over many
years by two icons: Edward I Stiefel and A Geoffrey Sykes. Ed and Geoff, as they were
affectionately called by many of their friends and research students, are being honoured for
their contributions to research on molybdenum with this textbook.