The object of the present invention is to provide a
metal catalyst which allows the production of a ring-opened
polymer available from a
heterocyclic compound, having primary terminal heteroatomic groups (terminal hydroxyl groups, in particular) in a ratio exceeding 75%. The above object can be attained by using a
metal catalyst comprising a ligand and a
metal atom for ring-opening
polymerization of heterocyclic compounds in which, of all maximum angles (D) meeting the following definition, the smallest maximum angle (Dm) is not larger than 60 degrees; The maximum angle (D) is the largest angle between an imaginary line (X) and an imaginary line (Y) of all the angles which can be assumed in a
metal catalyst comprising a ligand and a metal atom, said imaginary line (X) means a line perpendicular to an imaginary plane (P) including the respective centers of 3 coordinating atoms among those directly coordinating the metal atom (M) and not substitutable by a reaction substrate (S) and passing through the center of the metal atom, said imaginary line (Y) means a line linking the center of a non-coordinating atom in the ligand and the center of the metal atom, and said maximum angle (D) exists in a number equal to the number of non-coordinating atoms, that is, the number of imaginary lines (Y).