title: The Synthesis, Characterization and Dehydrogenation of Sigma-Complexes of BN-Cyclohexanes.
abstract: The coordination chemistry of the 1,2-BN-cyclohexanes 2,2-R2 -1,2-B,N-C4 H10 (R2 =HH, MeH, Me2 ) with Ir and Rh metal fragments has been studied. This led to the solution (NMR spectroscopy) and solid-state (X-ray diffraction) characterization of [Ir(PCy3 )2 (H)2 (η(2) η(2) -H2 BNR2 C4 H8 )][BAr(F) 4 ] (NR2 =NH2 , NMeH) and [Rh(iPr2 PCH2 CH2 CH2 PiPr2 )(η(2) η(2) -H2 BNR2 C4 H8 )][BAr(F) 4 ] (NR2 =NH2 , NMeH, NMe2 ). For NR2 =NH2 subsequent metal-promoted, dehydrocoupling shows the eventual formation of the cyclic tricyclic borazine [BNC4 H8 ]3 , via amino-borane and, tentatively characterized using DFT/GIAO chemical shift calculations, cycloborazane intermediates. For NR2 =NMeH the final product is the cyclic amino-borane HBNMeC4 H8 . The mechanism of dehydrogenation of 2,2-H,Me-1,2-B,N-C4 H10 using the {Rh(iPr2 PCH2 CH2 CH2 PiPr2 )}(+) catalyst has been probed. Catalytic experiments indicate the rapid formation of a dimeric species, [Rh2 (iPr2 PCH2 CH2 CH2 PiPr2 )2 H5 ][BAr(F) 4 ]. Using the initial rate method starting from this dimer, a first-order relationship to [amine-borane], but half-order to [Rh] is established, which is suggested to be due to a rapid dimer-monomer equilibrium operating.
authors.affiliation: Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA (UK).
authors.forename: Amit
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Department of Chemistry, Boston College, Chestnut Hill, Massachusetts, 02467-3860 (USA).
authors.forename: Jacob S A
authors.initials: JS
authors.lastname: Ishibashi
authors.affiliation: Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA (UK).
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Hooper
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487-0336 (USA).
authors.forename: Tanya C
authors.initials: TC
authors.lastname: Mikulas
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487-0336 (USA).
authors.forename: David A
authors.initials: DA
authors.lastname: Dixon
authors.affiliation: Department of Chemistry, Boston College, Chestnut Hill, Massachusetts, 02467-3860 (USA). shihyuan.liu@bc.edu.
authors.forename: Shih-Yuan
authors.initials: SY
authors.lastname: Liu
authors.affiliation: Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA (UK). andrew.weller@chem.ox.ac.uk.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Weller
mesh_terms: D000588:Amines / Q000737:chemistry*; D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003510:Cyclohexanes / Q000138:chemical synthesis* / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012238:Rhodium / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction
chemical_list: D000588:Amines; D001896:Boron Compounds; D003510:Cyclohexanes; D008024:Ligands; D009942:Organometallic Compounds; D012238:Rhodium
keywords: amine-borane; catalysis; iridium; phosphine; rhodium