Transition metal complexes supported by pincer ligands have many important applications. Here, the syntheses of five-coordinate PNP pincer-supported Fe complexes of the type (PNP)FeCl2 (PNP = HN{CH2CH2(PR2)}2, R = iPr ((iPr)PNP), tBu ((tBu)PNP), or cyclohexyl ((Cy)PNP)) are reported. In the solid state, ((iPr)PNP)FeCl2 was characterized in two different geometries by X-ray crystallography.
View Article and Find Full Text PDFThe preparation of a number of iron complexes supported by ligands of the type HN{CH2CH2(PR2)}2 [R = isopropyl (((i)Pr)PNP) or cyclohexyl ((Cy)PNP)] is reported. This is the first time this important bifunctional ligand has been coordinated to iron. The iron(II) complexes (((i)Pr)PNP)FeCl2(CO) (1a) and ((Cy)PNP)FeCl2(CO) (1b) were synthesized through the reaction of the appropriate free ligand and FeCl2 in the presence of CO.
View Article and Find Full Text PDFPd and Ni dimers supported by PSiP ligands in which two hypervalent five-coordinate Si atoms bridge the two metal centers are reported. Crystallographic characterization revealed a rare square-pyramidal geometry at Si and an unusual asymmetric M2 Si2 core (M=Pd or Ni). DFT calculations showed that the unusual structure of the core is also found in a model in which the phosphine and Si centers are not part of a pincer group, thus indicating that the observed geometry is not imposed by the PSiP ligand.
View Article and Find Full Text PDFNonplatinum metals are needed to perform cost-effective water reduction electrocatalysis to enable technological implementation of a proposed hydrogen economy. We describe electrocatalytic proton reduction and H(2) production by two organometallic nickel complexes with tridentate pincer ligands. The kinetics of H(2) production from voltammetry is consistent with an overall third order rate law: the reaction is second order in acid and first order in catalyst.
View Article and Find Full Text PDFThe Ni amide and hydroxide complexes [(PCP)Ni(NH(2))] (2; PCP=bis-2,6-di-tert-butylphosphinomethylbenzene) and [(PCP)Ni(OH)] (3) were prepared by treatment of [(PCP)NiCl] (1) with NaNH(2) or NaOH, respectively. The conditions for the formation of 3 from 1 and NaOH were harsh (2 weeks in THF at reflux) and a more facile synthetic route involved protonation of 2 with H(2)O, to generate 3 and ammonia. Similarly the basic amide in 2 was protonated with a variety of other weak acids to form the complexes [(PCP)Ni(2-Me-imidazole)] (4), [(PCP)Ni(dimethylmalonate)] (5), [(PCP)Ni(oxazole)] (6), and [(PCP)Ni(CCPh)] (7), respectively.
View Article and Find Full Text PDFThere is considerable interest in both catalysts for CO(2) conversion and understanding how CO(2) reacts with transition metal complexes. Here we develop a simple model for predicting the thermodynamic favorability of CO(2) insertion into Ir(III) hydrides. In general this reaction is unfavorable; however, we demonstrate that with a hydrogen bond donor in the secondary coordination sphere it is possible to isolate a formate product from this reaction.
View Article and Find Full Text PDFA family of palladium allyl complexes of the type bis(2-methylallyl)Pd(L) (L = PMe(3) (1), PEt(3) (2), PPh(3) (3) or NHC (4); NHC = 1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) have been prepared through the reaction of bis(2-methylallyl)Pd with the appropriate free ligand. Compounds 1-4 contain one η(1) and one η(3)-2-methylallyl ligand and 3 was characterized by X-ray crystallography. These complexes react rapidly with CO(2) at low temperature to form well defined unidentate palladium carboxylates of the type (η(3)-2-methylallyl)Pd(OC(O)C(4)H(7))(L) (L = PMe(3) (6), PEt(3) (7), PPh(3) (8) or NHC (9).
View Article and Find Full Text PDFChem Commun (Camb)
February 2011
The reactions of PCP supported Ni hydride, methyl and allyl species with CO(2) to generate Ni carboxylates are described. Computational studies suggest that all three reactions follow different pathways.
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