The Cp*Nd(BH4)(2)(THF)(2)/n-butylethylmagnesium combination affords a controlled and syndioselective oligomerisation of styrene. Living oligostyrenes can be used as macromonomers for block copolymerisation, leading to the unprecedented synthesis of a (polystyrene)-block-(1,4-trans polyisoprene) copolymer. Reversible transinetallation between the neodynnium and the magnesium atom is further established with a transfer efficiency close to 100%. (c) 2007 Elsevier Ltd. All rights reserved.