Step 1: Recall the correct grammatical structure.
The correct construction is:
\[
\text{too + adjective + to + base form of verb}
\]
Example:
\[
\text{too difficult to solve}
\]
Step 2: Apply the rule to the given sentence.
Incorrect part:
\[
\text{for tolerating}
\]
Correct form:
\[
\text{to tolerate}
\]
So, the correct sentence should be:
\[
\text{For Seema, Mohan is too important to tolerate any delay.}
\]
Step 3: Check the given options.
At tolerating — incorrect preposition.
With tolerating — incorrect construction.
To tolerating — incorrect verb form.
To tolerate — correct infinitive form.
Hence, the correct answer is
\[
\boxed{\text{To tolerate}}
\]