posted on 2021-09-13, 13:04authored byJesse
E. Smith, Haifeng Yang, François P. Gabbaï
As part of our interest in the chemistry
of late transition metal
complexes bearing cationic antimony ligands, we have investigated
the reaction of ((o-(Ph2P)C6H4)3)SbClPtCl (1) with H2O2 and found that it affords [((o-(Ph2P)C6H4)2(o-Ph2PO)C6H4)SbPtCl]+ ([2–Cl]+), a monocationic complex with the
newly installed P=O moiety coordinated intramolecularly to the antimony
atom via a P=O → Sb dative bond. The Pt–Cl bond of this
complex is readily activated by addition of a ligand such as cyclohexyl
isocyanide. When carried out in the presence of AgBF4,
this reaction affords the dicationic complex [((o-(Ph2P)C6H4)2(o-Ph2PO)C6H4)SbPt(CNCy)]+ ([2–CNCy]2+). In addition
to structurally characterizing [2–Cl]+ and [2–CNCy]2+ as their chloride
and tetrafluoroborate salts, respectively, we have also studied the
reaction of [2–Cl]+ with AgBF4 in the presence of PhCCH as a substrate surrogate. When monitored
by 31P NMR spectroscopy in CDCl3, this reaction
shows the formation of a new species tentatively assigned to [((o-(Ph2P)C6H4)2(o-Ph2PO)C6H4)SbPt]2+ ([2]2+) stabilized by coordination
of the alkyne. This formulation is supported by the elevated carbophilic
reactivity of [2]2+, which readily catalyzes
the cyclization of 2-allyl-2-(2-propynyl)malonate. Altogether, these
results show that the accumulation of charge in such reactive complexes
can be facilitated by the intramolecular base-stabilization of the
dinuclear core.