T-Shaped Palladium and Platinum {MNO} Nitrosyl Complexes.

The synthesis and characterization of a homologous series of T-shaped {MNO} nitrosyl complexes of the form [M(PR)(NO)] (M = Pd, Pt; R = Bu, Ad) are reported. These diamagnetic nitrosyls are obtained from monovalent or zerovalent precursors by treatment with NO and NO, respectively, and are notable for distinctly bent M-NO angles of ∼123° in the solid state. Adoption of this coordination mode in solution is also supported by the analysis of isotopically enriched samples by N NMR spectroscopy.

Stability and C-H Bond Activation Reactions of Palladium(I) and Platinum(I) Metalloradicals: Carbon-to-Metal H-Atom Transfer and an Organometallic Radical Rebound Mechanism.

One-electron oxidation of palladium(0) and platinum(0) bis(phosphine) complexes enables isolation of a homologous series of linear d metalloradicals of the form [M(PR)] (M = Pd, Pt; R = Bu, Ad), which are stable in 1,2-difluorobenzene (DFB) solution for >1 day at room temperature when partnered with the weakly coordinating [BAr] (Ar = 3,5-(CF)CH) counterion. The metalloradicals exhibit reduced stability in THF, decreasing in the order palladium(I) > platinum(I) and PAd > PBu, especially in the case of [Pt(PBu)], which is converted into a 1:1 mixture of the platinum(II) complexes [Pt(PBuCMeCH)(PBu)] and [Pt(PBu)H] upon dissolution at room temperature. Cyclometalation of [Pt(PBu)] can also be induced by reaction with the 2,4,6-tri-butylphenoxyl radical in DFB, and a common radical rebound mechanism involving carbon-to-metal H-atom transfer and formation of an intermediate platinum(III) hydride complex, [Pt(PBuCMeCH)H(PBu)], has been substantiated by computational analysis.

Heterolytic carbon-iodine bond cleavage by a palladium(I) metalloradical.

The well-defined Pd(I) metalloradical [Pd(PBu)] reacts with aryl and alkyl iodides at room temperature, yielding [Pd(PBu)(μ-I)] and phosphonium salts. Pd(II) aryl/alkyl derivates, reflecting net radical oxidative addition of the substrate to the metalloradical, are generated during the reaction and two examples have been isolated and crystallographically characterised.

Oxidative Cross-Coupling of Boron and Antimony Nucleophiles via Palladium(I).

The use of an isolatable, monomeric Pd(I) complex as a catalyst for the oxidative cross-coupling of aryl-antimony and aryl-boron nucleophiles is reported. This reaction tolerates a wide variety of substrates, with >20:1 selectivity for cross-coupled products. This strategy offers a new approach to achieving the selective cross-coupling of nucleophiles.