Is it permissible for me to lead women in prayer without the presence of their mahrams?

There is no harm in a man leading women in prayer without the presence of their mahrams, provided there is no fear of fitna (temptation/discord). However, it is better for him not to be alone with them, as a preventative measure against fitna, due to the Prophet's (peace and blessings be upon him) saying: "I have not left behind me any fitna more harmful to men than women."