The reactivity of the bis-isocyanide complex, Pd(CNArDipp2)2 (Dipp = 2,6-(i-Pr)2C6H3), towards small molecule substrates is discussed. Addition of two equivalents of nitrosobenzene (PhNO) to Pd(CNArDipp2)2 generated the divalent,diamagnetic complex Pd(k1-N-PhNO)2(CNArDipp2)2. Broken symmetry calculations and magnetic susceptibility measurements have confirmed the singlet diradical character of this compound, in which a one-electron reduction of each coordinated PhNO unit is observed, resulting in N-O bond lengthening. Several Pd(CNArDipp2)2-nitroso derivatives were prepared which illustrate variations in electronic structure and in the degree of N-O bond reduction. Additionally, Pd(CNArDipp2)2 was investigatedas a catalyst precursor for Suzuki-Miyaura cross-coupling reactions. 1 mol% of Pd(CNArDipp2)2 catalyzed the cross-coupling of aryl bromides with arylboronic acids under mild conditions to produce various biaryls in high yields. In these transformations, monoligated Pd(0) is presumably the catalytically active species and kinetic studies have demonstrated that the oxidative addition of 2-bromomesitylene to Pd(CNArDipp2)2 proceeds by a dissociative mechanism.

Synthetic, structural, and mechanistic studies on low-coordinate palladium-isocyanide complexes

241st National Meeting (2011)

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