No. The initialization syntax for Dictionary<TKey,TValue> is C# syntax candy. Powershell has its own initializer syntax support for System.Collections.HashTable (@{}):
$drivers = @{"nitrous"="vx"; "directx"="vd"; "openGL"="vo"};
For [probably] nearly all cases it will work just as well as Dictionary<TKey,TValue>. If you really need Dictionary<TKey,TValue> for some reason, you could make a function that takes a HashTable and iterates through the keys and values to add them to a new Dictionary<TKey,TValue>.
The C# initializer syntax isn’t exactly “direct” anyway. The compiler generates calls to Add() from it.