Heterolytic dihydrogen activation by B(C 6 F 5 ) 3 and carbonyl compounds

Transcription

1 Heterolytic dihydrogen activation by B(C 6 5 ) 3 and carbonyl compounds Markus Lindqvist, Nina Sarnela, Victor Sumerin, Konstantin Chernichenko, Markku Leskelä and Timo Repo* epartment of Chemistry, Laboratory of Inorganic Chemistry, P.. Box 55, IN-00014, University of Helsinki, inland. ax: +358 (9) ; Tel: +358 (9) ; timo.repo@helsinki. Experimental details: All experiments were performed using dual-manifold gas-inlet/vacuum line or in a glove box (MBraun Unilab) under argon atmosphere. H 2 was purchased from AGA Ab and passed through a column of molecular sieves prior to use. All reagents were purchased from Sigma-Aldrich or Strem and purified by conventional methods. Solvents were dried according to published procedures and distilled under argon atmosphere. NMR experiments were performed on a Varian Mercury 300 MHz spectrometer. HRMS (ESI-T) mass spectra were recorded on Bruker micrt mass spectrometer. General procedure: A solution of B(C 6 5 ) 3 (51.2 mg, mmol) and carbonyl compound ( mmol) in 1 ml of toluene, toluene-d 8 or C 2 Cl 2 was placed in a 25 ml vacuum-dried Schlenk tube equipped with a stirring bar, a teflon stopcock and a glass stopper (sealed with Glindemann sealing rings). The reaction mixture was freeze-thaw degassed and refilled with H 2 or 2 (2 atm) and then stirred at (temperature of oil bath) for 48 h. The solution was transferred to a NMR tube and analyzed. Before analyzing product 3, it was exposed to moisture and heated at 60 C in order to release it from its adducts with decomposition products of B(C 6 5 ) 3. Toluene was evaporated at reduced pressure. The residue was dissolved in CCl 3 and investigated by 1 H-NMR. Reported yields determined by NMR-spectroscopy. The 1 H, 13 C and 19 NMR spectroscopic data of the products and adducts were identical to values reported in literature. Benzyl alcohol 1 (3): 1 H NMR (300MHz, CCl 3 ) δ (m, 5H), 4.62 (s, 2H). (4-Methylphenyl)diphenylmethane 2 (6a): 1 H NMR (300MHz, CCl 3 ) δ (m, 14H), 5.50 (s, 1H), 2.31 (s, 3H). (2-Methylphenyl)diphenylmethane 2 (6b): 1 H NMR (300MHz, CCl 3 ) δ (m, 14H), 5.66 (s, 1H), 2.20 (s, 3H). Toluene 3 (9): 1 H NMR (300MHz, C 2 Cl 2 ) δ (m, 5H), 2.34 (s, 3H). iphenylmethane 4 (10): 1 H NMR (300MHz, CCl 3 ) δ (m, 10H), 3.97 (s, 2H). 1 A. R. Jagdale, A. S. Paraskar and A. Sudalai, Synthesis, 2008, J-Y. Yu and R. Kuwano, rg. Lett., 2008, 10, G. R. ulmer, A. J. M. Miller, N. H. Sherden, H. E. Gottlieb, A. Nudelman, B. M. Stoltz, J. E. Bercaw and K. I. Goldberg, rganometallics, 2010, 29, E. Alacid and C. Nájera, rg. Lett.,2008, 10, 5011.

2 PhCH 2 a) PhCH PhCH b) PhCH PhCH 2 C 6 H 5 PhCH 2 H Toluene-d a) Reference 1 H-NMR spectrum of benzyl alcohol in CCl 3. b) Hydrogenation of benzaldehyde in toluene-d 8 ( 1 H-NMR, CCl 3, after aqueous work-up).

3 CCl 3 CPh 2 (p-tolyl) Toluene 2 (2 atm) + 9 : 1 CPh 2 (o-tolyl) c) toluene C 6 5 toluene (o/p-tolyl)chph 2 and C 3 Benzophenone benzophenone CHPh 2 (p-tolyl-d 7 ) Toluene-d : 1 C 3 d) C 6 H 5 CHPh 2 (o-tolyl-d 7 ) Toluene-d 8 residual peak c) Reaction of benzophenone-b(c 6 5 ) 3 with deuterium ( 2 H-NMR, Toluene). d) Reaction benzophenone-b(c 6 5 ) 3 with H 2 ( 1 H-NMR, Toluene-d 8 ).

4 Toluene + (o/p-tolyl)chph 2 9 : 1 Benzophenone e) CHPh 2 (o-tolyl) CHPh 2 (o-tolyl) (p-ch 3 C 6 H 4 )CHPh 2 (o-ch 3 C 6 H 4 )CHPh (o/p-tolyl-d 7 )CHPh 2 C 3 Toluene-d 8 + C 3 Benzophenone f) CHPh 2 (p-tolyl-d 7 ) CHPh 2 (o-tolyl-d 7 ) 9 : e) Hydrogenation of benzophenone in toluene ( 1 H-NMR, CCl 3, after evaporation of all volatiles). f) Hydrogenation of benzophenone in toluene-d 8 ( 1 H-NMR, CCl 3, after evaporation of all volatiles).

5 PhCH 3 H C 2 Cl 2 C 2 Cl 2 residual peak Benzaldehyde PhCH 3 g) g) Hydrogenation of benzaldehyde in C 2 Cl 2 ( 1 H-NMR, C 2 Cl 2 ).

6 Ph 2 CH 2 CHPh 2 h) Benzophenone Ph 2 CH 2 C 2 Cl 2 Ph 2 CH 2 i) h) Reference 1 H-NMR spectrum of diphenylmethane in CCl 3. i) Hydrogenation of benzophenone in C 2 Cl 2 ( 1 H-NMR, CCl 3, after evaporation of all volatiles)

7 iphenylmethanol and tris(pentafluorophenyl)borane give products of dismutation instantly upon mixing in CCl 3. Tris(pentafluorophenyl)borane (25 mg, 5 mmol) was dissolved in CCl 3 ( ml) and diphenylmethanol was added (9 mg, mmol) and analyzed by NMR-spectroscopy. 2 + H 2 -B(C 6 5 ) 3 Ph2C iphenylmethanol and B(C 6 5 ) 3 1:1 in CCl 3 soon after mixing ( 1 H-NMR, CCl 3 ) Ph2C CH2Ph2 Ph2C ppm Ph2C ( 1 H-NMR, CCl 3 ) Ph2C CH2Ph2 iphenylmethanol and B(C 6 5 ) 3 1:1 in CCl 3 after 12 h CH2Ph2 CH2Ph2 Ph2C ppm

8 B Benzyl alcohol compound with tris(pentafluorophenyl)borane (1:1) Tris(pentafluorophenyl)borane (51 mg, mmol) was dissolved in CCl 3 ( ml) and benzyl alcohol was added (1 mg, mmol) and analyzed by NMRspectroscopy. Evaporation of the solution gave white solid. This was recrystallized from hexane (1 ml) to give. Storage in solution or heating during recrystallization promote formation of B(C 6 5 ) 3 -H 2 adduct evidently due to dehydration of benzyl alcohol. 1 H NMR (300 MHz, CHLRRM-) δ, ppm: 4.93 (s, 2 H), 6.32 (m, 1 H) (m, 2 H), (m, 3 H) 13 C NMR (75.43 MHz, CHLRRM-) δ, ppm: (s), (s), (s), 130 (s), (s), (dm, J=230 Hz), (dm, J=250 Hz), (dm, J=240 Hz), 19 NMR ( MHz, CHLRRM-) δ, ppm: (d, J=20 Hz, 6), (s, 3), (m, 6). 10 B NMR (53.70 MHz, CHLRRM-) δ, ppm: 9.25 (br. s.) ESI-MS-neg: [C 25 H 7 B 15 ] -, calc.: , found.:

9 B ( 1 H-NMR, CCl 3 ) Chloroform-d B ( 13 C-NMR, CCl 3 ) Chloroform-d

10 ( 19 -NMR, CCl 3 ) B ( 10 B-NMR, CCl 3 ) B