I assume your confusion comes from failing to distinguish two different words spelled to.
The examples in your question aren't exceptions. They contain the preposition to:
The key [ to being more productive ] is ...
I look forward [ to seeing you ].
He admitted [ to taking the money ].
Scientists are closer [ to being able to ... ].
seven steps [ to reaching your goals ]
In each case, the -ing form of the verb is what is traditionally called a gerund. When the verb is in its gerund form, the clause as a whole functions very much like a noun phrase.
Each of the bracketed phrases is a preposition phrase.
This should be distinguished from the infinitive marker to:
I want [ to eat as many sandwiches as possible ].
I'd like [ to visit New York ].
In each of these examples, the bracketed portion is a to-infinitival clause.
The word to in these examples marks the clause as infinitive; the -ing form is not possible here.