The synthesis and characterization of the bimetallic 2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato group 10 metal polymerization catalysts {[Ni(CH(3))](2)[1,8-(O)(2)C(10)H(4)-2,7-[CH=N(2,6-(i)Pr(2)C(6)H(3))](PMe(3))(2)} and {[Ni(1-naphthyl)](2)[1,8-(O)(2)C(10)H(4)-2,7-[CH=N(2,6-(i)Pr(2)C(6)H(3))](PPh(3))(2)} [FI(2)-Ni(2)(PR(3))(2)] are presented, along with the synthesis and characterization of the mononuclear analogues {Ni(CH(3))[3-(t)Bu-2-(O)C(6)H(3)CH=N(2,6-(i)Pr(2)C(6)H(3))](PMe)(3)} and {Ni(1-naphthyl)[3-(t)Bu-2-(O)C(6)H(3)CH=N(2,6-(i)Pr(2)C(6)H(3))](PPh)(3)} [FI-Ni (PR(3))]. Monometallic Ni catalysts were also prepared by functionalizing one ligation center of the bimetallic ligand with a trimethylsilyl group (TMS), yielding {Ni(CH(3))[1,8-(O)(TMSO)C(10)H(4)-2,7-[CH=N(2,6-(i)Pr(2)C(6)H(3))](PMe(3))} [TMS-FI(2)-Ni(PMe(3))]. The FI(2)-Ni(2) catalysts exhibit significant increases in ethylene homopolymerization activity versus the monometallic analogues, as well as increased branching and methyl branch selectivity, even in the absence of a Ni(cod)(2) cocatalyst. Increasing ethylene concentrations significantly suppress branching and alter branch morphology. FI(2)-Ni(2)-mediated copolymerizations with ethylene + polar-functionalized norbornenes exhibit a 4-fold increase in comonomer incorporation versus FI-Ni, yielding copolymers with up to 10% norbornene copolymer incorporation. FI(2)-Ni(2)-catalyzed copolymerizations with ethylene + methylacrylate or methyl methacrylate incorporate up to 11% acrylate comonomer, while the corresponding mononuclear FI-Ni catalysts incorporate negligible amounts. Furthermore, the FI(2)-Ni(2)-mediated polymerizations exhibit appreciable polar solvent tolerance, turning over in the presence of ethyl ether, acetone, and even water. The mechanism by which the present cooperative effects take place is investigated, as is the nature of the copolymer microstructures produced.

The synthesis and characterization of noVel bimetallic, neutrally charged dinickel 2,7-diimino-1,8-dioxynaphthalene polymerization catalysts is reported. Ethylene polymerizations as well as ethylene-co-norbornene copolymerizations display increased catalytic actiVity, methyl branch formation, and comonomer enchainment selectiVity Versus the monometallic analogues. Furthermore, these systems turn oVer in the absence of cocatalyst under mild conditions.The remarkable enchainment cooperativity effects displayed by single-site group 4 bimetallic olefin polymerization catalysts include significantly enhanced activity, chain branching, and comonomer enchainment selectivity. 1 Moreover, these effects roughly scale inversely with the intermetallic distance and are evident in both constrained geometry 1 and aryloxyiminato 2 group 4 catalysts (e.g., Ti 2 , FI 2 -Zr 2 , respectively). Since studies to date have focused exclusively on group 4 metals, the question arises as to whether such cooperativity effects are limited to early transition metals or might be more pervasive. To explore this issue, we focused on Ni(II) complexes, which are active olefin polymerization catalysts, 3 as exemplified by the Ni phenoxyiminates of Grubbs, which afford LDPEs having moderate molecular weights and 10-55 branches/1000 C atoms. 4 This general ligand architecture confers distinctive electronic, steric, and catalytic characteristics on the metal center, and we report here the synthesis of binuclear 2,7-diimino-1,8-dioxynaphthalene Ni(II) catalysts FI 2-Ni 2 -A and FI 2 -Ni 2 -B, in which rigid ligation enforces Ni · · · Ni distances as small as ∼3.1 Å, 5 and initial observations on ethylene polymerization and copolymerization characteristics. It will be seen that these catalysts exhibit non-negligible cooperativity effectssthe first reported for a group 10 metalsmanifested in enhanced polymerization activity, enhanced methyl chain branching, and enhanced comonomer incorporation under mild reaction conditions and not requiring a cocatalyst. 6The sodium salt of ligand FI 2 -H 2 2 was obtained by treating 2,7-di(2,6-diisopropylphenyl)imino-1,8-dihydroxynaphthalene 2 with NaH in THF. The bimetallic catalysts FI 2 -Ni 2 -A and FI 2 -Ni 2 -B were prepared as shown in Scheme 1 (for details, see Supporting Information). The imine protons in the Ni 2 FI 2 -A 1 H NMR spectrum exhibit a characteristic 4 J PH ≈ 9 Hz, corresponding to PMe 3 coordination trans to the ketimine Friedrich, S. K.; Younkin, T. R.; Li, R. T.; Grubbs, R. H.; Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149-3151. (5) Ni-Ni ) 3.09 Å in the crystal structure of a Ni2L2(OPMe3)2 thermolysis product (Rodriguez, B. A.; Delferro, M.; Marks, T. J., unpublished results). (6) For binuclear Ni(II) catalysts having less rigid ligation, longer intermetallic distances, and minimal cooperative polymerization effects, see: (a) Chen, Q.; Yu, J.; Huang, J. Organometallics 2007, 26, 617-625. (b) Hu, T.; Tang, L.; Li, X.; Li, Y.; Hu, N.

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Propionic acid (PA) is a short-chain fatty acid with wide industrial application including uses in pharmaceuticals, herbicides, cosmetics, and food preservatives. As a three-carbon building block, PA also has potential as a precursor for high-volume commodity chemicals such as propylene. Currently, most PA is manufactured through petrochemical routes, which can be tied to increasing prices and volatility due to difficulty in demand forecasting and feedstock availability. Herein described are research advancements to develop an industrially feasible, renewable route to PA. Seventeen Propionibacterium strains were screened using glucose and sucrose as the carbon source to identify the best platform strain. Propionibacterium acidipropionici ATCC 4875 was selected as the platform strain and subsequent fermentation optimization studies were performed to maximize productivity and yield. Fermentation productivity was improved three-fold to exceed 2 g/l/h by densifying the inoculum source. Byproduct levels, particularly lactic and succinic acid, were reduced by optimizing fermentor headspace pressure and shear. Following achievement of commercially viable productivities, the lab-grade medium components were replaced with industrial counterparts to further reduce fermentation costs. A pure enzymatically treated corn mash (ECM) medium improved the apparent PA yield to 0.6 g/g (PA produced/glucose consumed), but it came at the cost of reduced productivity. Supplementation of ECM with cyanocobalamin restored productivity to near lab-grade media levels. The optimized ECM recipe achieved a productivity of 0.5 g/l/h with an apparent PA yield of 0.60 g/g corresponding to a media cost <1 USD/kg of PA. These improvements significantly narrow the gap between the fermentation and incumbent petrochemical processes, which is estimated to have a manufacturing cost of 0.82 USD/kg in 2017.