Ligand survey results in identification of PNP pincer complexes of iridium as long-lived and chemoselective catalysts for dehydrogenative borylation of terminal alkynes

A new, highly active Ir catalyst for dehydrogenative borylation of terminal alkynes (DHBTA) has been identified.


S2
III. X-ray Structural Determination Details. S6 IV. Synthesis and Screening of Potential Catalysts for DHBTA. S11 A. Synthesis of Ligands S11 B. Ligand Screening of DHBTA S19

V. Synthesis of (PNP)Ir Complexes & Examination of Their Performance in
DHBTA.
Mass spectrometric analyses were carried out by the Texas A&M University Laboratory for S4 Biological Mass Spectrometry (LBMS). Elemental analyses were performed by CALI Labs, Inc.
Note: In 13 C NMR spectra of alkynylboronates and vinylidenes, quaternary carbon atoms attached to boron were usually not observed due to low intensity.

II. Computational Details.
All computations were carried out with the Gaussian09 program. 16 All of the geometries were fully optimized by M06 17 functional. The Stuttgart basis set and the associated effective core potential (ECP) was used for Ir atom, and an all-electron 6-311G(d,p) basis set was used for the other atoms. The harmonic vibrational frequency calculations were performed to ensure that a minimum was obtained. The energies reported here are Gibbs free energies in the gas phase at 298.15 K and 1 atm unless noted otherwise.

S6
III. X-ray Structural Determination Details.

X-Ray data collection, solution, and refinement for 10-Ir-HBpin (CCDC 1015119). A
Leica MZ 75 microscope was used to identify a suitable yellow block with very well defined faces with dimensions (max, intermediate, and min) 0.65 mm x 0.55 mm x 0.30 mm from a representative sample of crystals of the same habit. The crystal mounted on a nylon loop was then placed in a cold nitrogen stream (Oxford) maintained at 110 K. A BRUKER GADDS X-ray (three-circle) diffractometer was employed for crystal screening, unit cell determination, and data collection. The goniometer was controlled using the FRAMBO software, v.4.1.05. 18 The sample was optically centered with the aid of a video camera such that no translations were observed as the crystal was rotated through all positions. The detector was set at 5.0 cm from the crystal sample. The X-ray radiation employed was generated from a Cu sealed X-ray tube (K = 1.5418 Å with a potential of 40 kV and a current of 40 mA) fitted with a graphite monochromator in the parallel mode (175 mm collimator with 0.5 mm pinholes). 180 data frames were taken at widths of 0.5. These reflections were used to determine the unit cell using Cell_Now. 19 The unit cell was verified by examination of the h k l overlays on several frames of data. No super-cell or erroneous reflections were observed. After careful examination of the unit cell, an extended data collection procedure (26 sets) was initiated using omega and phi scans.
Integrated intensity information for each reflection was obtained by reduction of the data frames with APEX2. 20 The integration method employed a three dimensional profiling algorithm and all data were corrected for Lorentz and polarization factors, as well as for crystal decay effects.
Finally the data was merged and scaled to produce a suitable data set. SADABS 21 was employed to correct the data for absorption effects. Systematic reflection conditions and statistical tests indicated the space group P21/c. A solution was obtained readily using SHELXTL (SHELXS). 22

S7
Hydrogen atoms were placed in idealized positions and were refined using riding model. All non-hydrogen atoms were refined with anisotropic thermal parameters. The hydride on iridium was assigned from a Q peak near the expected position and refined. The presence of Ir-H is also indicated both by 1 H NMR spectroscopic data. The structure was refined (weighted least squares refinement on F 2 ) to convergence. 22 20 An absorption correction was applied using SADABS. 21 The space group was determined on the basis of systematic absences and intensity statistics and the structure was solved by direct methods and refined by full-matrix least squares on F 2 . The structure was solved in the monoclinic P21/c space group using XS 22 (incorporated in SHELXTL). All non-hydrogen atoms were refined with anisotropic thermal parameters. All hydrogen atoms were placed in idealized positions and refined using riding model. The structure was refined (weighted least squares refinement on F 2 ) and the final least-squares refinement converged.  18 The sample was optically centered with the aid of a video camera such that no translations were observed as the crystal was rotated through all positions. The detector was set at 5.0 cm from the crystal sample. The X-ray radiation employed was generated from a Cu sealed X-ray tube (K = 1.5418 Å with a potential of 40 kV and a current of 40 mA) fitted with a graphite monochromator in the parallel mode (175 mm collimator with 0.5 mm pinholes). 180 data frames were taken at widths of 0.5. These reflections were used to determine the unit cell using Cell_Now. 19 The unit cell was verified by examination of the h k l overlays on several frames of data. No super-cell or erroneous reflections were observed. After careful examination of the unit cell, an extended data collection procedure (26 sets) was initiated using omega and phi scans.
Integrated intensity information for each reflection was obtained by reduction of the data frames with APEX2. 20 The integration method employed a three dimensional profiling algorithm and all data were corrected for Lorentz and polarization factors, as well as for crystal decay effects.
Finally the data was merged and scaled to produce a suitable data set. SADABS 21 was employed to correct the data for absorption effects. Systematic reflection conditions and statistical tests indicated the space group P-1. A solution was obtained readily (Z' = 2; Z = 4) using SHELXTL (SHELXS). 22 Hydrogen atoms were placed in idealized positions and were refined using riding model. All non-hydrogen atoms were refined with anisotropic thermal parameters. Elongated thermal ellipsoids on (O1-O2-C36 to C41) group suggested disorder which was modeled successfully between two positions. Restraints and constraints were used to keep the bond distances, angles, and the thermal ellipsoids meaningful. 25 The structure was refined (weighted S9 least squares refinement on F 2 ) to convergence. 22 18 The sample was optically centered with the aid of a video camera such that no translations were observed as the crystal was rotated through all positions. The detector was set at 5.0 cm from the crystal sample. The X-ray radiation employed was generated from a Cu sealed X-ray tube (K = 1.5418 Å with a potential of 40 kV and a current of 40 mA) fitted with a graphite monochromator in the parallel mode (175 mm collimator with 0.5 mm pinholes). 180 data frames were taken at widths of 0.5. These reflections were used to determine the unit cell using Cell_Now. 19 The unit cell was verified by examination of the h k l overlays on several frames of data. No super-cell or erroneous reflections were observed. After careful examination of the unit cell, a standard data collection procedure (9 sets) was initiated using omega and phi scans.
Integrated intensity information for each reflection was obtained by reduction of the data frames with APEX2. 20 The integration method employed a three dimensional profiling algorithm and all data were corrected for Lorentz and polarization factors, as well as for crystal decay effects.
Finally the data was merged and scaled to produce a suitable data set. SADABS 21 was employed S10 to correct the data for absorption effects. Systematic reflection conditions and statistical tests indicated the space group P21/n. A solution was obtained readily using SHELXTL (SHELXS). 22 A molecule of fluorobenzene was found solvated. Hydrogen atoms were placed in idealized positions and were refined using riding model. All non-hydrogen atoms were refined with anisotropic thermal parameters. Thermal ellipsoids indicated fluorobenzene and CF3 groups were disordered. While the latter disorder was successfully modeled the former could be only modeled only with strong restraints / constraints. The structure was refined (weighted least squares refinement on F 2 ) to convergence. 22 3.75 mmol) was then added to the solution with 2 mL toluene to assist in transfer. The flask was taken outside the glovebox and heated at 115 °C for 3 d. After allowing the mixture to cool to ambient temperature, 0.5 mL of H2O was added and then the volatiles were removed in vacuo.
The volatiles of the eluate were removed in vacuo to give a yellow oil. Its 1 H NMR spectroscopic analysis indicated >98% purity. Yield: 339 mg (46%). 1

Synthesis of 8-H.
In an Ar-filled glovebox, S1 (1.00 g, 3.62 mmol) was dissolved in 20 mL Et2O in a 50 mL Schlenk flask. n-BuLi ( The reaction mixture was then stirred for 12 h and prior to being quenched with degassed H2O S16 (50 µL). The volatiles were then removed in vacuo and the resulting residue was dissolved in pentane and filtered through Celite. All volatiles were removed in vacuo to yield a white solid.
Its 1 H NMR spectroscopic analysis indicated 95% purity. Yield: 479 mg (85%). The material was further recrystallized from pentane prior to testing its catalytic reactivity in DHBTA. 1

14-Ir-COE
0% 3% 0% 6% a The conversion was determined by 1 H NMR by the ratio of integration of Ar-CH3 on A-0 to the internal standard. b 2% A-3 was observed. c 3% A-3 was observed. d 52% A-1 and 39% A-2 were observed. e 8% A-1 and 3% A-2 were observed. f 31% A-1 and 13% A-2 were observed.     1-H and A5-H, THF for A8-H), placed in the freezer and the 2 nd fraction was collected in the same manner.

A8-Bpin
Light brown solid, yield: 3.09 g (82%). 1  After allowing the mixture to cool to ambient temperature, the flask was taken into a glovebox. Attempt at making terminal alkyne derived complexes (2). 10-Ir-H2 (10 mg, 0.018 mmol) was dissolved in 0.5 mL C6D6 in a J. Young tube and followed by A1-H (11 µL, 0.087 mmol). After 10 min at RT, analysis by 31 P spectroscopy revealed 36% unknown at δ 37.5, 36%unknown at δ 30.4, 28% unknown at δ 28.3. Young tube was allowed to cool to ambient temperature and brought back into the glovebox. The solution was transferred to a 25 mL Schlenk flask with fluorobenzene to assist. All volatiles were removed in vacuo. The residue was redissolved in PhF/pentane, and the flask was then placed in a -35 °C freezer overnight. The next day, the solid was collected by decantation, washed with cold pentane, and dried under vacuum to produce a brick-red solid. The decanted solution was combined with the washings, and the volatiles were removed in vacuo. The residue was then redissolved in PhF/pentane, placed in the freezer and the second fraction was collected in the same manner. Its 1 H NMR spectroscopic analysis indicated >97% purity. Combined yield: 70 mg (51%). 1  Synthesis of 4-CF3C6H4C≡CBpin (A10-Bpin). The procedure was adapted from the previously reported synthesis. 1 In an Ar-filled glove box, 1-Ir-COE (14 mg, 0.020 mmol) and pinacolborane (580 µL, 4.00 mmol) were dissolved in 4 mL PhF in a 50 mL Schlenk flask. After stirring for 3 min at ambient temperature, 4-CF3C6H4C≡CH (A10-H, 326 µL, 2.00 mmol) in 3 mL PhF was then added dropwise over 5 min. Bubbles evolved immediately which indicated H2 generation. After all alkyne was added, the mixture was stirred for 5 min and then the volatiles were removed in vacuo. The residue was recrystallized in PhF/pentane in a -35 °C freezer. After overnight, the solution was decanted and the solid was washed with 1 mL pentane three times. The solid was dried in vacuo to yield offwhite crystals. Its 1 H NMR spectroscopic analysis indicated >98% purity. Yield: 441 mg (74%).