Copolymerization of Ethylene with Acrylate Monomers by Amide-Functionalized α‑Diimine Pd Catalysts

We report the ethylene homopolymerization and ethylene/methyl-acrylate (MA) and ethylene/acrylic-acid (AA) copolymerization behavior of a series of (<i>N,N</i>′-diaryl-α-diimine)­Pd catalysts that contain secondary amide (−CONHMe) or tertiary amide (−CONMe₂) substituents on the N-aryl rings, including the “first-generation” catalysts {(2,6-^<i>i</i>Pr₂-Ph)­NCMeCMeN­(2-CONHMe-6-^<i>i</i>Pr-Ph)}­PdMeCl (<b>1a</b>,<b>a</b>′) and {(2,6-^<i>i</i>Pr₂-Ph)­NCMeCMeN­(2-CONMe₂-6-^<i>i</i>Pr-Ph)}­PdMeCl (<b>1b</b>,<b>b</b>′) and the “second-generation” catalysts [{2,6-(CHPh₂)₂-4-Me-Ph}­NCMeCMeN­(2-CONHMe-6-^<i>i</i>Pr-Ph)]­PdMeCl (<b>1d</b>,<b>d</b>′) and [{2,6-(CHPh₂)₂-4-Me-Ph}­NCMeCMeN­(2-CONMe₂-6-^<i>i</i>Pr-Ph)]­PdMeCl (<b>1e</b>,<b>e</b>′). Activation of <b>1d</b>,<b>d</b>′ and <b>1e</b>,<b>e</b>′ by NaB­{3,5-(CF₃)₂C₆H₃}₄ generates active ethylene polymerization catalysts that produce highly branched (77–81 br/1000 C) polyethylenes with number-average molecular weights (<i>M</i>_ns) in the range 26–60 kDa. The replacement of two isopropyl units in <b>1a</b>,<b>a</b>′ and <b>1b</b>,<b>b</b>′ with benzhydryl groups in <b>1d</b>,<b>d</b>′ and <b>1e</b>,<b>e</b>′ leads to a significant improvement in ethylene homopolymerization performance. The secondary amide-functionalized catalyst <b>1d</b>,<b>d</b>′ incorporates ca. twice as much MA and ca. three times as much AA as the ^<i>i</i>Pr-substituted catalyst [{2,6-(CHPh₂)₂-4-Me-Ph}­NCMeCMeN­(2,6-^<i>i</i>Pr₂-Ph)]­PdMeCl (<b>1f</b>,<b>f</b>′) in copolymerization with ethylene. The reactions of <b>1a</b>,<b>a</b>′ and <b>1b</b>,<b>b</b>′ with metal salts that contain weakly coordinating anions lead to extrusion of CH₄ and the formation of [{(μ-κ²-<i>N,N</i>′,κ-<i>O</i>-α-diimine)­Pd}₂(μ-CH₂)]²⁺ complexes, in which the amide carbonyl O atoms coordinate to Pd centers

Transformation of Metal–Organic Framework Secondary Building Units into Hexanuclear Zr-Alkyl Catalysts for Ethylene Polymerization

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