Preparation of Complexes Bearing N-Alkylated, Anionic or Protic CAACs Through Oxidative Addition of 2-Halogenoindole Derivatives.

CAAC precursors 2-chloro-3,3-dimethylindole 1 and 2-chloro-1-ethyl-3,3-dimethylindolium tetrafluoroborate 2BF4 have been prepared and oxidatively added to [M(PPh3 )4 ] (M=Pd, Pt). Salt 2BF4 reacts with [Pd(PPh3 )4 ] in toluene at 25 °C over 4 days to yield complex cis-[3]BF4 featuring an N-ethyl substituted CAAC, two cis-arranged phosphines and a chloro ligand. Compound trans-[3]BF4 was obtained from the same reaction at 80 °C over 1 day. Salt 2BF4 reacts with [Pt(PPh3 )4 ] to give cis-[4]BF4 . The neutral indole derivative 1 adds oxidatively to [Pt(PPh3 )4 ] to give trans-[5] featuring a CAAC ligand with an unsubstituted ring-nitrogen atom. This nitrogen atom has been protonated with py⋅HBF4 to give trans-[6]BF4 bearing a protic CAAC ligand. The PdII complex trans-[7]BF4 bearing a protic CAAC ligand was obtained in a one-pot reaction from 1 and [Pd(PPh3 )4 ] in the presence of py⋅HBF4 .

Synthesis of IrIII Hydrido Complexes by Oxidative Addition of Halogenated Theophylline and Adenine Derivatives.

The IrIII hydrido complexes [1] and [2] have been synthesized by the regioselective oxidative addition of the N7-H bond of 8-halogenotheophyllines to [IrCl(coe)2]2 in the presence of PPh3. The use of dppf in this reaction yielded the bimetallic IrIII/FeII hydrido complexes [3] and [4]. X-ray diffraction studies confirmed that complexes [1]-[4] feature a theophyllinato ligand coordinated to the metal center in the rarely observed, chelating fashion via the N7 and O1 atoms. In addition, 8-bromoadenine reacts with [IrCl(coe)2]2 in the presence of PPh3 to form the IrIII hydrido complex [5] which features one anionic 8-bromoadeninato and one neutral 8-bromoadenine ligand linked by an intramolecular hydrogen bond. Complex [5] was characterized by high-resolution mass spectrometry and an X-ray diffraction analysis but could not be analyzed by nuclear magnetic resonance spectroscopy because of its low solubility.

Formation, structural characterization, and reactions of a unique cyclotrimeric vicinal Lewis pair containing (C6F5)2P-Lewis base and (C6F5)BH-Lewis acid components.

The synthesis of the new vicinal frustrated Lewis pair 5 containing (C6F5)2P-Lewis base and (C6F5)BH-Lewis acid functionality is described. It forms a unique cyclotrimer (5)3 which was structurally characterized by X-ray crystallography and high-resolution solid-state NMR spectroscopy. The relevant NMR Hamiltonian parameters ((11)B and (31)P chemical shielding tensors, (11)B quadrupolar coupling tensors, and (31)P-(11)B spin-spin coupling constants) indicate significant intramolecular covalent BP interactions, consistent with results from density functional theory (DFT) calculations. In addition, the (11)B/(31)P and (31)P/(31)P three-spin geometries are accurately reproduced by suitable high-resolution hetero- and homonuclear dipolar NMR experiments. As predicted from the bonding character portrayed by the solid-state NMR results, the cyclotrimer (5)3 possesses only moderate catalytic activity. However, it undergoes an addition reaction with pyridine and hydroboration reactions with benzaldehyde and tert-butylacetylene. The products of the hydroboration reactions form stable adducts with pyridine.