Novel triarylphosphine or triarylarsine compound, alpha-olefin polymerization catalyst using the compound, ternary copolymer, and production process of alpha-olefin -((meth)acrylic acid)-based copolymer

A metal complex represented by the following formula (2):

• wherein Y is phosphorus or arsenic, Z is —SO3— or CO2—, each of R1 to R4 independently represents a hydrogen atom, a hydrocarbon group having a carbon number of 1 to 30, a halogen atom-substituted hydrocarbon group having a carbon number of 1 to 30, a heteroatom-containing hydrocarbon group having a carbon number of 1 to 30, an alkoxy group having a carbon number of 1 to 30, or an aryloxy group having a carbon number of 6 to 30, at least one of R1 to R4 is a substituent where the carbon directly bonded to the aromatic ring is single-bonded to two or more elements selected from the group consisting of C, O and N, each of R5 to R14 independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having a carbon number of 1 to 30, a halogen atom-substituted hydrocarbon group having a carbon number of 1 to 30, a heteroatom containing hydrocarbon group having a carbon number of 1 to 30, an alkoxy group having a carbon number of 1 to 30, an aryloxy group having a carbon number of 6 to 30, or a silyl group substituted with a hydrocarbon group having a carbon number of 1 to 30, M represents a metal atom selected from the group consisting of transition metals of Groups 8 to 10, A represents a hydrogen atom, a halogen atom, an alkyl group having a carbon number of 1 to 30, which may have a heteroatom, or an aryl group having a carbon number of 6 to 30, which may have a heteroatom, B represents an arbitrary ligand coordinated to M, and A and B may combine with each other to form a ring.

A ternary copolymer of an ethylene, an α-olefin having a carbon number of 3 to 10 and a (meth)acrylic acid or ester represented by CH2═C(R18)CO2(R19) wherein R18 is a hydrogen atom or an alkyl group having a carbon number of 1 to 10, and R19 is a hydrogen atom or an alkyl group having a carbon number of 1 to 30, which may contain a hydroxyl group, an alkoxy group or an epoxy group on an arbitrary position, the ternary copolymer satisfying the following requirements (a) and (b):

• (a) the ratio Mw/Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) satisfies the following relationship:
• 1.5≦Mw/Mn≦3
• (b) the melting point Tin (° C.), the α-olefin content [C] (mol %) and the polar group-containing vinyl monomer content [X] (mol %) satisfy the following relationship:
• 60≦Tm≦135−6.4×([C]+[X])
• wherein Tm is a peak temperature of a melting curve obtained by the measurement using a differential scanning calorimeter (DSC) and when a plurality of melting peaks are detected, Tm is the temperature of the maximum peak out of detected peaks.