Generally speaking, the only class of clematis that respond well to dividing are the heracleifolias. I wouldn't dare risk dividing any other class of clematis that I have. Taking cuttings is another matter although some clematis are easier to propagate than others. Jackmanii is a very common clematis and can easily be purchased. I would much rather pay the money to purchase one than to try to propogate one from cuttings however.