zinc complex についてググったら、
以下の文章が書いてありました。
参考にならないかな？
あと、配位化学の本とかにはなんてかいてあるのだろうか？

The most common structure of zinc complexes is tetrahedral
which is clearly connected with the fact that the octet rule
is obeyed in these cases. Nevertheless, octahedral complexes
comparable to those of the transition elements are not rare.
Zn2+ is a class A acceptor in the classification of Ahrland,
Chatt and Davies,[17] and so forms stronger complexes with
the first-row donor atoms oxygen or nitrogen than with
second-row sulfur or phosphorus. In terms of HSAB
theory Zn2+ is a hard acid.