can the salt be substituted?
Yes
Rhodocene
Substitutions on the cyclopentadienyl rings of rhodocenes and rhodocenium salts produce compounds of higher stability
what is rhodocene? aA chemical compound with the formula [Rh(CH)]. for what purpose is it used? In radiotherapy for small tumours.
wiki:18239255
Rhodocene [SEP] Penta-substituted cyclopentadienyl ligands
The body of knowledge concerning compounds with penta-substituted cyclopentadienyl ligands is extensive, with organometallic complexes of the pentamethylcyclopentadienyl and pentaphenylcyclopentadienyl ligands being well-known. Substitutions on the cyclopentadienyl rings of rhodocenes and rhodocenium salts produce compounds of higher stability as they allow for the increased delocalisation of positive charge or electron density and also provide steric hindrance against other species approaching the metal centre. Various mono- and di-substituted rhodocenium species are known, but substantial stabilisation is not achieved without greater substitutions. Known highly substituted rhodocenium salts include decamethylrhodocenium hexafluorophosphate [(η-CMe)Rh]PF, decaisopropylrhodocenium hexafluorophosphate [(η-CPr)Rh]PF, and octaphenylrhodocenium hexafluorophosphate [(η-CPhH)Rh]PF. Decamethylrhodocenium tetrafluoroborate can be synthesised from the tris(acetone) complex [(η-CMe)Rh(MeCO)](BF) by reaction with pentamethylcyclopentadiene, and the analogous iridium synthesis is also known.