Butene-l was polymerized using novel mono-(eta(5)-pentamethylcyclopentadienyl) tribenzyloxy titanium[Cp*Ti(OBz)(3)] complexes activated with three types of modified methylaluminoxanes (mMAO) containing different amounts of residual trimethylaluminum (TMA). The oxidation states of titanium in different Cp*Ti(OBz)(3) and mMAO catalytic systems were determined by redox titration method. The influences of various oxidation state of titanium active species on butene-1 polymerization were investigated. It is found that Ti(IV) active species is in favour of producing polybutene-1. The polymer obtained at 0 degrees C and 30 degrees C with melting temperature was shown by C-13-NMR and DSC characterizations to comprise of multiple blocks of isotactic and atactic segments. C-13-NMR analyses of polybutene-1 implies that chain propagation of butene-l involves primarily head-to-tail 1,2-insertions, with involving negligible proportion of head-to-head and tail-to-tail 2,1-misinsertions. There is a remarkable decrease in 2,1-misinsertions with decreasing temperature of polymerization.