group and/or silylene group, R3 and R4 each are a hydrogen atom or a C1 -C18 hydrocarbon group, R5, R7, R9, R10, R11, R12, R13 and R14 each are a hydrogen atom or a C1 -C18 hydrocarbon group and may be bonded to each other through a hydrocarbon group to form a cyclic hydrocarbon group.