Hydride ions do not form 1:1 complexes with onium ions because the Brønsted basic, nucleophilic, reducing hydride ion will initiate a proton abstraction reaction.
A reaction always occurs, rather than forming a Lewis acid/base complex so the idea of a charge on a complex is not applicable.
If the onium ion has a proton ‘ligands’ the onium ion will act as a Brønsted acid and donate a proton to the hydride ion to form H2:
H3O+ + H– H2 + H2O:
If the onium ion has alkyl ligands (such as a trialkyl oxonium ion or a tetraalkyl ammonium ion) a nucleophilic substitution will occur in which electropositive nucleophilic hydride ion reduces one of the onium ion ligands to the corresponding alkane:
The concept of congeneric series is not so useful with onium ion/s-HOMO Lewis acid/base interactions.