Showing papers by "Richard F. Jordan published in 2017"
TL;DR: Metal-organic framework nodes can be directly transformed into novel single-site solid organometallic catalysts without homogeneous analogs for polymerization reactions.
Abstract: We report the stepwise and quantitative transformation of the Zr6(μ3-O)4(μ3-OH)4(HCO2)6 nodes in Zr-BTC (MOF-808) to the [Zr6(μ3-O)4(μ3-OH)4Cl12]6– nodes in ZrCl2-BTC, and then to the organometallic [Zr6(μ3-O)4(μ3-OLi)4R12]6– nodes in ZrR2-BTC (R = CH2SiMe3 or Me). Activation of ZrCl2-BTC with MMAO-12 generates ZrMe-BTC, which is an efficient catalyst for ethylene polymerization. ZrMe-BTC displays unusual electronic and steric properties compared to homogeneous Zr catalysts, possesses multimetallic active sites, and produces high-molecular-weight linear polyethylene. Metal–organic framework nodes can thus be directly transformed into novel single-site solid organometallic catalysts without homogeneous analogs for polymerization reactions.
95 citations
TL;DR: Results provide strong evidence that the -CHF2 and -CH2 F chain ends in E/VF copolymer generated by (phosphinoarenesulfonate)PdR catalysts form by β-F elimination of Pd(β-F-alkyl) species, VF or E insertion of the resulting (PO) PdF species, and subsequent chain growth.
Abstract: The discrete (phosphinoarenesulfonate)Pd fluoride complex (POBp,OMe )PdF(lutidine), where POBp,OMe =(2-MeOC6 H4 )(2-{2,6-(MeO)2 C6 H3 }C6 H4 )(2-SO3 -5-MeC6 H3 )P, inserts vinyl fluoride (VF) to form (POBp,OMe )PdCH2 CHF2 (lutidine) and inserts multiple ethylene (E) units to generate polyethylene that contains -CH2 F chain ends. These results provide strong evidence that the -CHF2 and -CH2 F chain ends in E/VF copolymer generated by (phosphinoarenesulfonate)PdR catalysts form by β-F elimination of Pd(β-F-alkyl) species, VF or E insertion of the resulting (PO)PdF species, and subsequent chain growth. These results also imply that β-F elimination is not an important catalyst deactivation reaction in this system.
54 citations
TL;DR: In this paper, the synthesis and coordination chemistry of the (1R,2S,5R)-menthyl-substituted N,N′-diaryl-α-diimine ligands was described.
38 citations
TL;DR: Using two-dimensional electronic spectroscopy, it is found that both limiting the relative rotation of chromophores and tuning the energy difference between the two electronic transitions in the dimer to match a vibrational mode of the lower-energy monomer are necessary to enhance the observed quantum-beating signals.
Abstract: In multidimensional spectroscopy, dynamics of coherences between excited states report on the interactions between electronic states and their environment. The prolonged coherence lifetimes revealed through beating signals in the spectra of some systems may result from vibronic coupling between nearly degenerate excited states, and recent observations confirm the existence of such coupling in both model systems and photosynthetic complexes. Understanding the origin of beating signals in the spectra of photosynthetic complexes has been given considerable attention; however, strategies to generate them in artificial systems that would allow us to test the hypotheses in detail are still lacking. Here we demonstrate control over the presence of quantum-beating signals by packing structurally flexible synthetic heterodimers on single-walled carbon nanotubes, and thereby restrict the motions of chromophores. Using two-dimensional electronic spectroscopy, we find that both limiting the relative rotation of chromophores and tuning the energy difference between the two electronic transitions in the dimer to match a vibrational mode of the lower-energy monomer are necessary to enhance the observed quantum-beating signals.
37 citations
TL;DR: In this article, a series of (N,N′-diaryl-α-diimine) Pd catalysts that contain secondary amide (CONHMe) or tertiary amide (−CONMe2) substituents on the N-aryl rings were reported.
30 citations
TL;DR: In this article, the binding of B(C6F5)3 to PdMeL (L = pyridine or lutidine) or {(PPO)PdMe}2 ethylene polymerization catalysts that contain phosphine-arenephosphinate or PHN-paraphosphonate ligands significantly increases the catalyst activity and the molecular weight of the polyethylene (PE) product.
24 citations
TL;DR: In this paper, the synthesis of the phosphine-cyclopentanesulfonate pro-ligands Li/K[2-PPh2-cyclopentane sulfonate] and H[2b] was described.
21 citations
TL;DR: Computational studies reveal that heterolytic activation by this nickel μ-sulfide complex can be generalized to other H-E bonds, and complexes 1 and 2 react in a similar manner with pinacolborane to produce {(IPr)Ni}2(μ-SH)(μ-SBPin) (3), showing that heterophosphorus-based nickel-Sulfide complexes can be universal.
Abstract: Kinetic and DFT computational studies reveal that the reaction of {(IPr)Ni(μ-S)}2 (1, IPr = 1,3-bis(2,6-diisopropyl-phenyl)imidazolin-2-ylidene) with dihydrogen to produce {(IPr)Ni(μ-SH)}2 (2) proceeds by rate-limiting heterolytic addition of H2 across a Ni–S bond of intact dinuclear 1, followed by cis/trans isomerization at Ni and subsequent H migration from Ni to S, to produce the bis-hydrosulfide product 2. Complex 1 reacts in a similar manner with pinacolborane to produce {(IPr)Ni}2(μ-SH)(μ-SBPin) (3), showing that heterolytic activation by this nickel μ-sulfide complex can be generalized to other H–E bonds.
13 citations
29 Jun 2017
TL;DR: The autoxidation reactions of 2-acyl-2,3-dihydroquinazolin-4(1H)-ones 4a and 5a and 2,2′-bis(dihYDroquinzolinone) 6a lead to diverse products with good selectivity, depending on the structure of the substrate.
Abstract: The autoxidation reactions of 2-acyl-2,3-dihydroquinazolin-4(1H)-ones 4a and 5a and 2,2′-bis(dihydroquinazolinone) 6a are described. These reactions generate aminyl radicals that undergo β-C–C cleavage, and subsequent reactions of the resulting C-based radicals with O2 lead to diverse products with good selectivity, depending on the structure of the substrate. Oxidation of 4a, in which the 2-acyl group is part of a cyclic acenaphthenone unit, yields a heterocyclic C-hydroperoxylaminal via 1,2-acyl migration. Oxidation of 5a, which contains a 2-acetyl group, yields peracetic acid and a quinazolinone product. Oxidation of 6a forms a bis(quinazolinone) by net dehydrogenation.
4 citations