A compound of formula (I-A), R.sup.1 in each occurrence is selected from H, optionally substituted C.sub.1-12 alkyl and optionally substituted C.sub.6-20 aryl; R.sup.2 in each occurrence is selected from optionally substituted C.sub.1-12 alkyl and optionally substituted C.sub.6-20 aryl; p is 1 and q is 5 or pis 2 and q is 4; p+q=6; Y is an anion; and n is 1 or 2. The compounds of formula (I-A) may be used to catalyse reactions including arylation and alkylation at the carbon atom of a CH group in which the C atom is sp.sup.2-hybridised.

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