General Strategy for the Synthesis of Rigid Weak-Link Approach Platinum(II) Complexes: Tweezers, Triple-Layer Complexes, and Macrocycles

Air-stable, heteroligated
platinum­(II) weak-link approach (WLA) tweezer and triple-layer complexes
that possess P,X–Aryl hemilabile ligands (P^ = Ph2PCH2CH2–, X = chalcoethers or amines)
have been synthesized via the halide-induced ligand rearrangement
(HILR) reaction, using a one-pot, partial chloride-abstraction method.
The approach is general and works with a variety of phosphine-based
hemilabile ligands; when a P,S–Ph ligand is used as the relatively
strongly chelating ligand, heteroligated complexes are formed cleanly
when an ether- (P,O–Ph), amine- (P,N–Ph2),
or fluorinated thioether-based (P,S–C6F4H) hemilabile ligand is used as the weakly chelating counterpart.
The HILR reaction has also been used to synthesize bisplatinum­(II)
macrocycles free of oligomeric material without having to resort to
the high-dilution conditions typical for macrocycle synthesis. This
approach is complementary to the traditional WLA to the synthesis
of macrocyclic complexes which typically proceeds via fully closed,
chloride-free intermediates. The structures of the complexes may be
toggled between semiopen (with only one chelating ligand) and fully
closed (with both ligands chelating) via the abstraction and addition
of chloride.