Patent ID: 7820862

Claim:
A ligand represented by following general formula I: wherein each of R 1 and R 2 independently represents 0 to 5 substituent groups; X represents P, As or N; m represents an integer of 0 to 7; n represents an integer of 0 to 3; and each of A 1 to A 4 independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a benzoyl group, an acetyl group, a nitro group, a trifluoroacetyl group, a trifluoromethyl group, an alkoxy group represented by —OR a (R a represents a linear or branched alkyl group having 1 to 4 carbon atoms), an amino group represented by —NR b R c (each of R b and R c independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms), a linear or branched alkyl group having 1 to 4 carbon atoms, a hydroxyl group or a ring formed of A 2 and A 3 .