Described herein are precursors and methods of forming dielectric films. In one aspect, there is provided a silicon precursor having the following formula I: wherein R1 is independently selected from hydrogen, a linear or branched C1 to C6 alkyl, a linear or branched C2 to C6 alkenyl, a linear or branched C2 to C6 alkynyl, a C1 to C6 alkoxy, a C1 to C6 dialkylamino and an electron withdrawing group and n is a number selected from 0, 1, 2, 3, 4, and 5; and R2 is independently selected from hydrogen, a linear or branched C1 to C6 alkyl, a linear or branched C2 to C6 alkenyl, a linear or branched C2 to C6 alkynyl, a C1 to C6 alkoxy, a C1 to C6 dialkylamino, a C6 to C10 aryl, a linear or branched C1 to C6 fluorinated alkyl, and a C4 to C10 cyclic alkyl group.