Diverse C−C Bond-Forming Reactions of Bis(carbene)platinum(II) Complexes

The platinum(0) complex Pt(PPh_3)_4 catalyzes coupling of the carbene ligands of (CO)_5Cr{C(OMe)(p-MeOC_6H_4)} (1). The stable bis(carbene)platinum(II) complexes Cl_2Pt{C(OMe)(Me)}_2 (3), Br_2Pt{C(OMe)(Me)}_2 (4), and Cl_2Pt{C(O^iPr)(Me)}_2 (5) can be induced to undergo C–C coupling reactions by several means. Reduction of 3–5 to platinum(0) with cobaltocene results in formation of internal olefins, (E/Z)-2,3-dimethoxybut-2-ene (6) or (E/Z)-2,3-diisopropoxybut-2-ene (7). Reaction of 3–5 with PPh3 yields terminal olefins, 2,3-dimethoxybut-1-ene (13) or 2,3-diisopropoxybut-1-ene (15), along with Cl_2Pt(PPh_3)_2 (12) or Br_2Pt(PPh_3)_2 (14). In contrast, addition of pyridine to 3–5 does not effect C–C coupling; instead, the acyl complexes cis-Cl(py)Pt(COMe){C(OMe)(Me)} (8), cis-Br(py)Pt(COMe){C(OMe)(Me)} (9), and cis-Cl(py)Pt(COMe){C(O^iPr)(Me)} (10) are obtained, with concomitant formation of alkyl halide. Possible mechanistic pathways for C–C bond formation are discussed, as well as explanations for the different reactivities observed for pyridine and PPh_3

Investigations into Asymmetric Post-Metallocene Group 4 Complexes for the Synthesis of Highly Regioirregular Polypropylene

A series of asymmetric post-metallocene group 4 complexes based on a modular anilide(pyridine)phenoxide framework have been synthesized and tested for propylene polymerization activity. These complexes, upon activation with methylaluminoxane (MAO), produce highly regioirregular and stereoirregular polypropylene with moderate to good activities. Surprisingly, modification of the anilide R-group substituent from 1-phenethyl to benzyl or adamantyl did not significantly change the polymer microstructure as determined by ^(13)C NMR spectroscopy. Although polymer molecular weights and polydispersities vary with propylene pressure, temperature, and activator, regio- and stereoirregularity were also found to be relatively insensitive to these variables. When the polymerization is conducted at 70 °C under dihydrogen, partial decomposition to a highly active catalyst that produces an isotactic microstructure occurs; the undecomposed catalyst continues to produce highly regioirregular and stereoirregular polypropylene under these conditions

Highly regioirregular polypropylene from asymmetric group 4 anilide(pyridine)phenoxide complexes

Group 4 complexes containing an anilide(pyridine)phenoxide ligand and activated with methylaluminoxane (MAO) catalyze the formation of highly regioirregular polypropylene

Diverse C–C Bond-Forming Reactions of Bis(carbene)platinum(II) Complexes

The platinum(0) complex Pt­(PPh₃)₄ catalyzes coupling of the carbene ligands of (CO)₅Cr­{C­(OMe)­(<i>p-</i>MeOC₆H₄)} (<b>1</b>). The stable bis­(carbene)­platinum­(II) complexes Cl₂Pt­{C­(OMe)­(Me)}₂ (<b>3</b>), Br₂Pt­{C­(OMe)­(Me)}₂ (<b>4</b>), and Cl₂Pt­{C­(O^<i>i</i>Pr)­(Me)}₂ (<b>5</b>) can be induced to undergo C–C coupling reactions by several means. Reduction of <b>3</b>–<b>5</b> to platinum(0) with cobaltocene results in formation of internal olefins, (<i>E/Z</i>)-2,3-dimethoxybut-2-ene (<b>6</b>) or (<i>E/Z</i>)-2,3-diisopropoxybut-2-ene (<b>7</b>). Reaction of <b>3</b>–<b>5</b> with PPh₃ yields terminal olefins, 2,3-dimethoxybut-1-ene (<b>13</b>) or 2,3-diisopropoxybut-1-ene (<b>15</b>), along with Cl₂Pt­(PPh₃)₂ (<b>12</b>) or Br₂Pt­(PPh₃)₂ (<b>14</b>). In contrast, addition of pyridine to <b>3</b>–<b>5</b> does not effect C–C coupling; instead, the acyl complexes <i>cis</i>-Cl­(py)­Pt­(COMe)­{C­(OMe)­(Me)} (<b>8</b>), <i>cis</i>-Br­(py)­Pt­(COMe)­{C­(OMe)­(Me)} (<b>9</b>), and <i>cis</i>-Cl­(py)­Pt­(COMe)­{C­(O^<i>i</i>Pr)­(Me)} (<b>10</b>) are obtained, with concomitant formation of alkyl halide. Possible mechanistic pathways for C–C bond formation are discussed, as well as explanations for the different reactivities observed for pyridine and PPh₃

New precatalysts for olefin polymerization having LX2 pincer ligands

Post metallocene zirconium and titanium catalysts with tridentate bis(phenolate)-donor (donor = pyridine, furan, and thiophene) "LX2" pincer ligands have been investigated as propylene and ethylene polymn. catalysts. Analogous Ti, Zr, Ta, and lanthanide complexes with pincer ligands having thiophenolate, anilide, and phospha-anilide X type ligands, as well as those having Nheterocyclic carbene L type donors have been prepd., and their performance as catalysts for olefin polymns. has been explored

Investigations into Asymmetric Post-Metallocene Group 4 Complexes for the Synthesis of Highly Regioirregular Polypropylene

A series of asymmetric post-metallocene group 4 complexes based on a modular anilide­(pyridine)­phenoxide framework have been synthesized and tested for propylene polymerization activity. These complexes, upon activation with methylaluminoxane (MAO), produce highly regioirregular and stereoirregular polypropylene with moderate to good activities. Surprisingly, modification of the anilide R-group substituent from 1-phenethyl to benzyl or adamantyl did not significantly change the polymer microstructure as determined by ¹³C NMR spectroscopy. Although polymer molecular weights and polydispersities vary with propylene pressure, temperature, and activator, regio- and stereoirregularity were also found to be relatively insensitive to these variables. When the polymerization is conducted at 70 °C under dihydrogen, partial decomposition to a highly active catalyst that produces an isotactic microstructure occurs; the undecomposed catalyst continues to produce highly regioirregular and stereoirregular polypropylene under these conditions

Synthetic Access to Atomically Dispersed Metals in Metal–Organic Frameworks via a Combined Atomic-Layer-Deposition-in-MOF and Metal-Exchange Approach

The combination (AIM-ME) of atomic layer deposition in metal–organic frameworks (MOFs) and metal exchange (ME) is introduced as a technique to install dispersed metal atoms into the mesoporous MOF, NU-1000. Zn-AIM, which contains four Zn atoms per Zr₆ node, has been synthesized through AIM and further characterized through density functional calculations to provide insight into the possible structure. Zn-AIM was then subjected to modification via transmetalation to yield uniform porous materials that present nonstructural Cu, Co, or Ni atoms