about which we complained/which we complained about

[Vladv1]

The original sentence "They canceled the event without telling us, about which we complained".
Does the version "They canceled the event without telling us, which we complained about" sound ok? I made up the examples.

 

[emsr2d2]

The original sentence is "They canceled the event without telling us, about which we complained".
Does the version "They canceled the event without telling us, which we complained about" sound ok OK? I made up the examples.

Yes, it does.
Note my corrections above. Remember that at the start of a sentence you can write "OK" or "Okay. Anywhere else in a sentence, you can write "OK" or "okay". However, "ok" is always wrong.

 

[Annabel Lee]

The original sentence "They canceled the event without telling us, about which we complained".
Does the version "They canceled the event without telling us, which we complained about" sound ok? I made up the examples.

Neither sentence sounds OK to me. Sentential "which" doesn't normally function as the object of a preposition.

It works better as subject:

They cancelled the event without telling us, which offended us so much that we complained.

 

[5jj]

Sentential "which" doesn't normally function as the object of a preposition.

It works for this speaker of BrE.

 

[BobK]

... but rather than use a senential which and leave the reader with the job of working out what abstraction it applies to, I'd prefer to specify whst the complaint is about, possibly in a new sentence: 'We complained about their lack of professionalism/thoughtlessness...(or whatever).