The straightforward synthesis of the cationic, purely organometallic NiI-salt [Ni(cod)2]+[Al(ORF)4]– was realized through a reaction between Ni(cod)2 and Ag[Al(ORF)4]. Crystal structure, EPR, XANES and cyclic voltammetry confirmed the presence of a homoleptic NiI-olefin complex. Weak interactions between the metal centre, the ligands and the anion provide a good starting material for further cationic NiI-chemistry.
The recently published purely metallo-organic Ni salt [Ni(cod) ][Al(OR ) ] (1, cod=1,5-cyclooctadiene, R =C(CF ) ) provides a starting point for a new synthesis strategy leading to Ni phosphine complexes, replacing cod ligands by phosphines. Clearly visible colour changes indicate reactions within minutes, while quantum chemical calculations (PBE0-D3(BJ)/def2-TZVPP) approve exergonic reaction enthalpies in all performed ligand exchange reactions. Hence, [Ni(dppp) ][Al(OR ) ] (2, dppp=1,3-bis(diphenylphosphino)propane), [Ni(dppe) ][Al(OR ) ] (3, dppe=1,3-bis(diphenyl-phosphino)ethane), three-coordinate [Ni(PPh ) ][Al(OR ) ] (4) and a remarkable two-coordinate Ni phosphine complex [Ni(PtBu ) ][Al(OR ) ] (5) were characterised by single crystal X-ray structure analysis. EPR studies were performed, confirming a nickel d -configuration in complexes 2, 4 and 5. This result is supported by additional magnetization measurements of 4 and 5. Further investigations by cyclic voltammetry indicate relatively high oxidation potentials for these Ni compounds between 0.7 and 1.7 V versus Fc/Fc . Screening reactions with O and CO gave first insights on the reaction behaviour of the Ni phosphine complexes towards small molecules with formation of mixed phosphine-CO-Ni complexes and oxidation processes yielding new Ni and/or Ni derivatives. Moreover, 4 reacted with CH Cl at RT to give a dimeric Ni ylide complex (4 c). As CH Cl is a rather stable alkyl halide with relatively high C-Cl bond energies, 4 appears to be a suitable reagent for more general C-Cl bond activation reactions.
The straightforward synthesis of the cationic, purely organometallic NiI salt [Ni(cod)2]+[Al(ORF)4]− was realized through a reaction between [Ni(cod)2] and Ag[Al(ORF)4] (cod=1,5‐cyclooctadiene). Crystal‐structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic NiI olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic NiI complexes.
The NiI salt [Ni(cod)2]+[Al(ORF)4]– {RF = C(CF3)3} is the starting material for ligand exchange reactions with arenes (benzene, mesitylene and hexamethylbenzene) yielding cationic and purely organometallic 19 valence electron [Ni(cod)(arene)]+ complex salts. The reactions are accompanied by fast solution color changes from yellow to intensely green. Single crystal X‐ray structure analysis, EPR, UV/Vis and IR‐spectroscopic investigations confirm the formation of [Ni(cod)(C6Me6)][Al(ORF)4] (2) as well as [Ni(cod)(mes)][Al(ORF)4] (3, mes = mesitylene) with η6‐coordinated arenes and bidentate cod ligands. The reaction with benzene is plausible but remains less characterized. The energetics of these reactions were used to evaluate diverse DFT methods. 16 functionals with and without D3(BJ) dispersion correction failed to describe the reaction energetics correctly. However, correcting the basic reaction energies with a CCSD(T)/TZ→QZ approach and using further isodesmic reactions with inclusion of COSMO‐RS solvation gave reaction energetics in best agreement with all experimental observations.
The thermally unstable α-fluoroalcohol undecafluorocyclohexanol (c-C6F11OH) was prepared by addition of hydrogen fluoride to the corresponding ketone. c-C6F10(CF3)OH was obtained by protonation of its alkoxide [NMe4]+[C7F13O]-. Decafluorocyclohexane-1,1-diol (c-C6F10(OH)2) was prepared by acidic workup of the corresponding alkoxide [NMe4]+[C6F11O]- with sulfuric acid, which yielded (c-C6F10(OH)2) and fluorosulfonic acid. The structures of c-C6F10(CF3)OH·2H2O and of (c-C6F10(OH)2) were elucidated by single-crystal X-ray and gas-phase electron-diffraction studies.
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