Novel asymmetric phosphine ligand

A phosphine-phosphorane compound represented by the general formula (1):

• 7
• wherein R1 represents hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms and a represents an integer of 1 to 4;
• R2, R3, R4, and R5 are the same or different, and each represents hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and each of R2 and R3, R3 and R4, and R4 and R5 may be together combined to form a ring which may contain one or more oxygen atoms;
• and R6 and R7 are the same or different, and each represents a linear or branched alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 7 carbon atoms, a perfluoroalkyl group, a phenyl group, a phenyl group having one or more substituents each selected from the group consisting of each an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms which is substituted by one or more halogen atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen atom), an aralkyl group having 7 to 12 carbon atoms, or a ring-substituted aralkyl group.