How do I know when to you "to + V-ing" in English?
The following sentences are completely correct, could someone explain how grammatically correct? Or there are exceptions? For example, why not use "I look forward to see you" and "he admitted to take his money" instead?
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!
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.
