Unexpected Photoisomerization of a Pincer-type Amido Ligand Leads to Facial Coordination at Pt(IV)

The divalent complex (BQA)PtMe undergoes oxidative addition with
MeI to afford the octahedral complex cis-(mer-BQA)PtMe2I {(BQA)-
= bis(8-quinolinyl)amide}. When this molecule is irradiated with
visible light, it isomerizes to (fac-BQA)PtMe2I, where the BQA ligand
adopts an unexpected facial coordination mode. The amide nitrogen
in this molecule is sp3 hybridized and can be easily quarternized
with HBF4, resulting in [H(fac-BQA)PtMe2I][BF4], with only minor
perturbation to the coordination sphere.