Synthesis of Functionalized Hydrazines: Facile Homogeneous (N‐Heterocyclic Carbene)‐Palladium(0)‐Catalyzed Diboration and Silaboration of Azobenzenes

Abstract The bis(N‐heterocyclic carbene)(diphenylacetylene)palladium complex [Pd(ITMe)2(PhC≡CPh)] (ITMe=1,3,4,5‐tetramethylimidazol‐2‐ylidene) acts as a highly active pre‐catalyst in the diboration and silaboration of azobenzenes to synthesize a series of novel functionalized hydrazines. The reactions proceed using commercially available diboranes and silaboranes under mild reaction conditions.


In toluene
In an ampoule, azobenzene (0.101 g, 0.55 mmol), bis(pinacalato)diboron (0.109 g, 0.43 mmol) and 1 (0.001 g, 2.06 µmol) were dissolved in toluene (2 ml). The resulting reaction mixture was stirred at ambient temperature under an N2 atmosphere for 2 h. At this stage the reaction mixture was filtered via cannula and the filtrates volatiles were removed in vacuo. The resulting crude solid was re-crystallized in hexane (3 x 5 ml), which resulted in isolation of an off white powder. Yield: 0.119 g, 63%. 1

Hydrolysis of 2 to form 1,2-diphenylhydrazine
atmosphere. The volatiles were removed in vacuo and the product extracted with hexane (2 x

X-ray Crystallography Data
The crystal data of 2 was collected on a BRUKER X8-APEX II diffractometer with a CCD area detector and multi-layer mirror monochromated MoKa radiation. The structure was solved using intrinsic phasing method (SHELXT [4] ), refined with the SHELXL program, [5] and expanded using Fourier techniques. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included in structure factors calculations. All hydrogen atoms were assigned to idealised geometric positions. Single crystal X-ray diffraction data for 4, 9 and 11 were collected at the University of Sussex on an Agilent Technologies Xcalibur Gemini Ultra diffractometer (λCuKα = 1.54184) equipped with a Eos CCD area detector. The data were collected at 173 K using an Oxford Cryosystems Cobra low temperature device. Data were processed using CrysAlisPro, and the unit cell parameters were refined against all data. Semi empirical absorption corrections were carried out using the MULTI-SCAN program. [6] The structures were solved by using an intrinsic phasing method (SHELXT [4] ), and refined F0 by full matrix least squares refinement using SHELXL-2013, [7] within OLEX2. [8] All nonhydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were added at calculated positions and refined using riding models with isotropic displacement parameters based on the equivalent isotropic displacement parameter (Ueq) of the parent atoms.
The cif files for 2, 4, 9 and 11 have been deposited with the CCDC and have been given the deposition numbers 1501645, 1501646, 1501647 and 1501648 respectively.

S42
Crystal Structure Information for 2