C–H
bond activation at cationic [(η
5
-C
5
Me
5
)Ir(PMe
2
Ar′)] centers is described,
where PMe
2
Ar′ are the terphenyl phosphine ligands
PMe
2
Ar
Xyl
2
and PMe
2
Ar
Dipp
2
. Different pathways are defined for the conversion
of the five-coordinate complexes [(η
5
-C
5
Me
5
)IrCl(PMe
2
Ar′)]
+
,
2(Xyl)
+
and
2(Dipp)
+
, into
the corresponding pseudoallyls
3(Xyl)
+
and
3(Dipp)
+
. In the absence of an external Brønsted
base, electrophilic, remote ζ C–H activation takes place,
for which the participation of dicationic species, [(η
5
-C
5
Me
5
)Ir(PMe
2
Ar′)]
2+
, is proposed. When NEt
3
is present, the PMe
2
Ar
Dipp
2
system is shown to proceed via
4(Dipp)
+
as an intermediate en route to the thermodynamic,
isomeric product
3(Dipp)
+
. This complex interconversion
involves a non-innocent C
5
Me
5
ligand, which
participates in C–H and C–C bond formation and cleavage.
Remarkably, the conversion of
4(Dipp)
+
to
3(Dipp)
+
also proceeds in the solid state.