Size control of monodisperse palladium nanoparticles with sizes ranging from 1.7 to 3.5 nm was accomplished using thioethers as stabilizing ligands, in a one-step procedure. Modulation of the reaction temperature, reaction time, solvent, and carbon chain length of the thioether provided control over the nanoparticle size and size distribution. The resulting Pd nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). 1 H NMR spectroscopy provided insight into the thioether-Pd nanoparticle surface interaction. To demonstrate the catalytic activity of the thioether-stabilized Pd nanoparticles, hydrogenation reactions were carried out using the as-synthesized Pd nanoparticles. We observed a trend in the reactivity of the nanoparticles with respect to their size, however, recovery of the nanoparticles following subsequent reactions was rather challenging. Immobilization of the Pd nanoparticles onto commercial SiO 2 resulted in rapid and efficient catalysis, successful recovery of the Pd nanoparticles, and furthermore, the nanoparticles could be used up to 8 times with no measurable decrease in catalytic activity. This work demonstrates the utility of thioether ligands for the synthesis of monodisperse Pd nanoparticles that are efficient catalysts for various organic transformations.

A new class of diphosphine PNP pincer ligand, 2,5-bis(diphenylphosphinomethyl)pyrrole 2, was synthesized by the reaction between Ph2PH and 2,5-bis(dimethylaminomethyl)pyrrole in 90% yield. The analogous reaction of Ph2PH with 1,9-bis(dimethylaminomethyl)diphenyldipyrrolylmethane readily afforded a PNNP type diphosphine ligand, 1,9-bis(diphenylphosphinomethyl)diphenyldipyrrolylmethane 5 in 92% yield. These phosphine compounds were oxidized with H2O2 and S8 to give the corresponding phosphoryl and thiophosphoryl compounds 6-9 in very good yields. The reaction of the PNP pincer ligand 2 with [PdCl2(PhCN)2] in the presence of Et3N afforded the mononuclear Pd(II) complex, [PdCl{C4H2N-2,5-(CH2PPh2)2-κ(3)PNP}] 10 in 87% yield. Conversely, treatment of 2 with [PdCl2(PhCN)2] in the absence of Et3N gave the dinuclear Pd(II) complex [Pd2Cl4{μ-C4H3N-2,5-(CH2PPh2)2-κ(2)PP}2], the structure which is proposed based on the spectroscopic data. When 2 was treated with Pd(0) precursor [Pd2(dba)3]·CHCl3 the dinuclear Pd(I) complex [Pd2{μ-C4H2N-2,5-(CH2PPh2)2-κ(2)PN,κ(1)P}2], 12, was obtained in 23% yield. The formation of complex 12 is solvent dependent, which transforms into complex 10 in CDCl3 as studied by variable temperature (1)H and (31)P NMR methods. Treatment of 2 with [Ni(OAc)2]·4H2O gave the mononuclear Ni(II) pincer complex [Ni(OAc){C4H2N-2,5-(CH2PPh2)2-κ(3)PNP}], 13, which upon treatment with an excess of LiCl or LiBr or KI afforded the respective halide ion substituted Ni(II) complexes, [NiX{C4H2N-2,5-(CH2PPh2)2-κ(3)PNP}] (X = Cl, Br, and I), 14-16, in very good yields. The structures of 5, 2,5-bis(diphenylphosphorylmethyl)pyrrole 6, 10, 12, and 14-16 were determined by the single crystal X-ray diffraction method. In the structure of 12, two short contacts between the diagonally positioned Pd and P atoms are observed. To understand these weak interactions, density functional theory (DFT) calculations were done and an interaction MO diagram is presented.

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Transamination reactions of [{(Me3Si)2N}2Sm(thf)2] with the dianion of either 1,1‐di‐(α‐pyrrolyl)cyclohexane or diphenyl dipyrromethane led to the octanuclear complex shown in the picture and the hexanuclear complex [{[Ph2C(α‐C4H3N)2]Sm}6(thf)3], respectively. Both clusters possess flat macrocyclic structures and react with dinitrogen to afford the corresponding isostructural tetranuclear dinitrogen complexes.

Reduction of trivalent samarium complexes obtained via reaction of SmCl3(THF)3 with the disodium salt of the dipyrrolide dianion [R2C(H3C4N)2]2- (R = Ph, 1/2 −(CH2)5−) were carried out with sodium in THF and under nitrogen. The two reactions respectively yielded the tetranuclear divalent hydride {Na(THF)6}{([Ph2C(C4H3N)2]Sm)4(H)(THF)2} (1) and the tetranuclear dinitrogen complex {[(CH2)5C(C4H3N)2]Sm}4(THF)2(μ-N2)[Na(THF)]2·2THF (2). Transmetalation of [(Me3Si)N]2Sm(THF)2 with 1,1-dipyrrolylcyclohexane afforded the dinitrogen complex {[(CH2)5C(C4H3N)2]Sm}4(μ-N2)·0.5THF (3). Despite the different oxidation states of 2 and 3 and the presence/absence of alkali-metal cation the two complexes display the same N−N distance.