Fast, base-promoted protodeboronation of polyfluoroaryl and heteroaryl boronic acids complicates their use in Suzuki-Miyaura coupling (SMC) because a base is generally required for catalysis. We report a "cationic" SMC method using a PAd-Pd catalyst that proceeds at rt in the absence of a base or metal mediator. A wide range of sensitive boronic acids, particularly polyfluoroaryl substrates that are poorly compatible with classic SMC conditions, undergo clean coupling. Stoichiometric experiments implicate the intermediacy of organopalladium cations, which supports a long-postulated cationic pathway for transmetalation in SMC.

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An attempt at transferring the imide of (dadi)TiNAd (2NAd, dadi 2− , dadia product that features four new C−C bonds to two new carbons. Mechanistic evaluation of its formation led to oxidative addition studies of SnX 4 (X = Cl, Br, I) and RX to (dadi)Ti(THF) (1-THF, dadi 4− ), in which the oxidation occurs at the dadi ligand. Products include (dadi)TiX 2 (2-X 2 , X = Cl, Br, I) and the imine-triamide (R-ita)TiX (5-RX, R = Me, Bn; X = Cl, Br; Rita = [{−CH 2 N(1,2-C 6 H 4 )N(2,6-i Pr 2 -C 6 H 3 )}{CRN(1,2-C 6 H 4 )N(2,6-i Pr 2 -C 6 H 3 )}]). Studies of the RX additions, including implementation of radical clocks, pointed toward concerted process(es). Rearrangements of 2-X 2 and 2NAd revealed a new tridentate benzimidazole diamide chelate (bida) structurally characterized in (bida)TiCl 2 (4-Cl 2 ) and (bida)TiNAd (OPMe 2 Ph) (6). The nature of various products suggests that the (dadi n )Ti core can act as a nucleophile (n = 4), electrophile (n = 2), or as a radical center (n = 3) under certain conditions.

The development of an air-stable iron(III)-based precatalyst for the Suzuki−Miyaura cross-coupling reaction of alkyl halides and unactivated aryl boronic esters is reported. Despite benefits to cost and toxicity, the proclivity of iron(II)-based complexes to undergo deactivation via oxidation or hydrolysis is a limiting factor for their widespread use in cross-coupling reactions compared to palladium-based or nickel-based complexes. The new octahedral iron(III) complex demonstrates long-term stability on the benchtop as assessed by a combination of 1 H NMR spectroscopy, Mossbauer spectroscopy, and its sustained catalytic activity after exposure to air. The improved stability of the iron-based catalyst facilitates an improved protocol in which Suzuki−Miyaura cross-coupling reactions of valuable substrates can be assembled without the use of a glovebox and access a diverse scope of products similar to reactions assembled in the glovebox with iron(II)-based catalysts.

Dilithium amides have been developed as a bespoke and general ligand for iron-catalyzed Kumada−Tamao−Corriu cross-coupling reactions, their design taking inspiration from previous mechanistic and structural studies. They allow for the cross-coupling of alkyl Grignard reagents with sp 2 -hybridized electrophiles as well as aryl Grignard reagents with sp 3 -hybridized electrophiles. This represents a rare example of a single ironcatalyzed system effective across diverse coupling reactions without significant modification of the catalytic protocol, as well as remaining operationally simple.