On–off allosteric control of a bifunctional catalyst

A Pt(II) weak-link tweezer and a sulfonate regulator switch a squaramide–amine co-catalyst fully on or off in situ.

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What architecture enables reversible allosteric switching here?

A heteroligated Pt(II) weak-link tweezer with hemilabile P,S ligands.

Which two functions are switched together?

HBD electrophile activation and Lewis-base nucleophile activation.

How does the semi-open sulfonate complex bind DMA?

It shows no observable recognition of the substrate.

What Ka does closed complex 2 show for DMA?

About 75 558 M−1.

What Ka does free ligand 6 show for DMA?

About 11 336 M−1.

What model reaction was used to time catalysis?

Michael addition of nitroethane to β-nitrostyrene.

What TOF does fully closed 2 achieve?

2.69 × 10−4 s−1 with nearly quantitative conversion.

Does embedding the catalyst in the WLA help?

Yes: incorporation into the WLA architecture improves catalytic activity versus free ligand.

How is switching described?

Highly reversible on–off switching that extends to disparate organic transformations.

Which NMR nuclei report the two phosphines in SO 1?

31P{1H}: 7.60 ppm (JP–Pt = 3172 Hz) and 41.84 ppm (JP–Pt = 3504 Hz).

How do you toggle FC 2 and SO 1?

Introduce and then abstract Cl−.