Are there any examples of activating meta directors? I have heard about activating ortho-para directors. For example: methoxy group, hydroxy group, alkyl group, et cetera.

I have heard about deactivating ortho-para directors. For example: halogen substituents

I have heard about deactivating meta directors. For example: nitro, trifluromethyl group, carboxylic acid group, et cetera.



So, naturally, I have embarked on a quest to find Activating Meta directors.

I have found one potential candidate, which is dimethylphenylborane:



Boron possesses a vacant $\mathrm{p}_z$ orbital, which can interact with the $\pi$-cloud of the benzene ring.



Considering the fact that boron is treated as a metalloid, it will definitely be less electronegative than carbon, so the dimethylborane group should offer a good +I effect, which could possibly outweigh the -M effects.

Can anyone shed some light on this issue? Are there any other examples of activating meta directors?
Note: This requires an extremely high energy scenario to occur. 

This is another example that looks promising, it is essentially an ylide that has enough EWing power to meta direct while giving some density to the ring in another resonance structure. []

The phosphonium ylide derivative (phenylphosphonic acid) may provide the same effect if the hypervalent nature of nitrogen is challenged, or if this substance is unobtainable under any circumstances.