Reactivity of a Soft Indium‐Based Frustrated Lewis Pair Towards Alkynes

The geminal pyridine stabilized frustrated Lewis pair (FLP) t Bu 2 In(py)CH 2 P t Bu 2 ( 1 ·py) was reacted with various alkynes. 1 ·py does not react with PhC≡CH, however, it does with the unsymmetrically substituted PhC≡CSiMe 3 and p‐ Br‐C 6 H 4 C≡CSiMe 3 under reversible formation of adducts. Unexpectedly, 1 ·py reacted with the terminal alkyne phenylacetylene as a “hidden” In/C‐FLP, resulting in the formation of the neutral indium alkynyl t Bu 2 InCCPh and loss of MeP t Bu 2 . Compared to this finding, the reaction of tri( tert ‐butyl)indium with phenylacetylene was slow and resulted in formation of equal amounts of t Bu 2 InCCPh and cis ‐ tert ‐butylstyrene. The reaction of 1 ·py with dimethylacetylenedicarboxylate is different from those of typical hard FLP systems, and leads to an 1,2‐addition product to the C≡C triple bond instead of targeting the carbonyl function. The reaction with methylvinylketone results in the FLP‐typical formation of an 1,4‐addition product under formation of an indium–oxygen bond. For both adducts, the addition of a further equivalent of 1 ·py led to no further reaction. All obtained adducts were isolated and completely characterized via NMR spectroscopy and single crystal X‐ray diffraction analyses.