Question

I write a letter to call him coming

Answer 1

I wrote a letter 【asking him to come】

asking him to come 是分词短语作后置定语修饰 a letter 的.

如果说成

I wrote a letter,asking him to come.

（加逗号,意思一样,此时,分词短语作状语表伴随行为）

不可以说：

I wrote a letter to ask him coming

要说：

I wrote a letter to ask him to come （不定式to ask him to come 作目的状语）

ask sb to do sth 要求某人做什么

ask 后面的复合宾语中不可以用doing sth 作宾补,OK?!