Who says you can't use "to" with "neglectful"? There is no such rule. Some prepositions clearly sound better than others, but in various contexts, who knows what preposition might work best? After "neglectful", neither "of" nor "to" stands out as an especially good choice. Here are some other reasonable possibilities: "He was neglectful towards Sally". (this would be my first pick) "He was neglectful with Sally". "He was neglectful about Sally". "He was neglectful by Sally". "He was neglectful near Sally". "He was neglectful over Sally". "He was neglectful apropos Sally". Instead of worrying whether a preposition is right or wrong, think about what each preposition means and whether that meaning is the one you want to convey.

The difference in preposition usage between oblivious and neglectful can be explained by their different meanings. Oblivious means "not aware of something." It can be followed by both of and to, but to is more common. For example, you could say "She was oblivious of the danger" or "She was oblivious to the danger." Neglectful means "failing to give proper care or attention." It can only be followed by of. For example, you could say "He was neglectful of his children" or "She was neglectful of her duties." The reason for this difference is that oblivious describes a state of mind, while neglectful describes an action. When you are oblivious of something, you are simply not aware of it. You may be unaware of the danger because you are not paying attention, or you may be unaware of the danger because you do not know about it. When you are neglectful of something, you are failing to give it proper care or attention. This implies that you are aware of the thing, but you are choosing to ignore it. Here are some examples of how oblivious and neglectful can be used in a sentence: The oblivious child ran into the street without looking. The neglectful parent did not feed their child for days. The oblivious driver crashed into the parked car. The neglectful teacher did not grade the students' papers.