Isoprene polymerisation performed under microwave irradiation with [Nd(BH4)(3)(THF)(3)]/Mg(Bu)(2) and [Nd(BH4)(3)(THF)(3)]/Al(Et)(3) showed an enhancement in reactivity, with selectivity being only slightly modified. An explanation of the observed effect is proposed based on our current knowledge of the catalytic mechanism and by considering the alkylated complex as an ion pair. An analogy is proposed with the pseudoanionic polymerisation of oxygenated monomers. Finally, depolymerisation is observed under microwave irradiation at high temperature.