Copolymerization of ethylene with isoprene (IP) catalyzed by 1,4-dithabutanediyl-linked bis(phenolato) titanium complexes 1 and 2 and methylaluminoxane (MAO) produced exclusively ethylene-IP copolymers with good activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with IP content similar to 60%. The copolymer microstructure was fully elucidated by C-13-NMR spectroscopy of the copolymers with various IP content revealing a strong tendency to the alternating microstructure. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4200-4206, 2010