Modification of C−F bonds with main-group catalysts has typically employed electron-deficient Lewis superacids in high oxidation states, and the challenges of preparing and handling such species have prevented broader adoption of metal-free reduction protocols. Here, we show that a hemilabile ligand coordinated to an easily accessed P(III) center imparts air stability without sacrificing the ability to activate C−F bonds. Catalytic C−C coupling of benzyl fluorides with allylsilanes was achieved using a P(III) complex under benchtop conditions. This application of coordination chemistry principles to main-group Lewis acids reveals a new strategy for controlling catalysis.

Phosphinoboration of diazobenzene with Ph2PBR′2 cleanly affords products of the form Ph2P(PhNNPh)BR′2 (2: R′2=catechol, cat; 4: R′2=phenanthrenediol, quin) and shows evidence of Ph2P(PhNNPh)Bpin 7 (pin: pinacol). The mechanism of these reactions was probed computationally and shown to proceed via intermediates involving a diazobenzene‐adduct of the boron center of the PB reagent. The resulting PNNB species 2 and 4 are shown to be frustrated Lewis pairs (FLPs). Despite the presence of weakly Lewis acidic boron centers, these species react with diazobenzene. Additionally, the FLP reactivity of 2 was further probed with 4‐phenyl‐1,2,4‐triazole‐3,5‐dione, 1,10‐phenanthroline‐5,6‐dione, and benzyl azide to give unique five‐, six‐, and eight‐membered heterocyclic rings. Thus, phosphinoboration provides a new avenue to FLPs in which donor and acceptor sites are linked by nitrogen atoms.

NOTES 1785 described by Mustafa el oí.1 the same product 9-phenyI-9,10-dihydro-10-oximino-9-hydroxyphenanthrene (II), is obtained according to the following scheme:The identity of the phenyllithium product and the phenylmagnesium bromide product is again verified by melting point and mixture melting point experiment, as well as by ultraviolet spectrum, X-(mju) 254, Cm«i 23990, " ( µ) 288, em" 8535, Xm»i (m^) 324,