Slide 1

NMR beyond ordinary undergraduate experiences: Routine measurements with heteronuclear, heterogeneous, and paramagnetic samples Patrick J. Desrochers, Richard M. Tarkka Department of Chemistry University of Central Arkansas Conway, 72035 Am. chem. Soc. Natl. Mtg. March 2011, CHED 26 Slide 2 About UCA Chemistry Department undergraduate-only department 15 tenured/t-track faculty 3 5 undergraduate researchers Instrumentation JEOL ECX 300 MHz FT NSF CCLI, 2002 award 1 H, 13 C, and 2-D expts (organic, etc.) on-site facilitates faculty/student training Slide 3 Hetero-atoms, pivotal signals 11 B: scorpionate chelates 31 P: phosphine chelates Heterogeneous resin samples, routine spectra 13 C { 1 H} but other J exists Paramagnetic samples: accessible, predictable Slide 4 H 1 C 13 It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail. A. Maslow Psychology of Science 1966 Slide 5 D F Se P C B V Pt Co Rh H Low Freq. probe range: 30 MHz to 120 MHz Slide 6 -50-40-30-20-100 11 B (ppm) Monitoring scorpionate formation N N B H N N N N H H H J B-H ~ 90 Hz KBH 4 KTp* N N H 3 H 2 210 o C 5-6 1999 Slide 7 Monitoring scorpionate formation KBH 4 KTp* N N H 3 H 2 210 o C 5-6 11 B (ppm) Et 2 O wash acetone wash Pz* Pz* B Pz* H H Pz* B Pz* H Slide 8 Monitoring scorpionate formation by ~MW~ KBH 4 KTp* N N H 3 H 2 ~MW~ 5-6 11 B (ppm) 180 o C, 5 min 200 o C, 10 min DMSO acetone Slide 9 Pivotal-donor heteroatom: phosphine ligands 90 CHCl 3 10 MeOH dppeNiCl 2 MeOH CysEt Ni P PS NH 2 Ph Ph Ph Ph OEt O + Cl 31 P (ppm) 0.1 M H 3 PO 4 (aq) capillary Cys CysEt J P-P = 47 Hz Desrochers, P. J.; Duong, D.; Marshall, A. S.; Lelievre, S. A.; Hong, B.; Brown, J. R.; Tarkka, R. M.; Manion, J. M.; Holman, G.; Merkert, J. W.; Vicic, D. A. Inorg. Chem. 2007, 46, 92219233. Slide 10 31 P ppm -80 o C -60 -40 -20 0 22Pivotal-donor trans cis Slide 11 Hetero-atoms, pivotal signals 11 B: scorpionate chelates 31 P: phosphine chelates Heterogeneous resin samples, routine spectra 13 C { 1 H} but other J exists Paramagnetic samples: accessible, predictable Slide 12 H B N N N het N het N N N N B N N H K N N N N N B N N H K Thought: NO Reaction N N N H = -7.6 ( 11 B ppm) Supported-scorpionates: early progress = -4.6 ( 11 B ppm) +Bzt, -Pz* DMF, 70 o C, 2h Slide 13 N N N NH O PEG H a b c d,e f,g Previously reported IR (ATR) MAS 1 H NMR Katritzky, A. R.; Pastor, A.; Voronkov, M.; Tymoshenko, D. J. Comb. Chem. 2001, 3, 167-170. Desrochers; Besel; Corken; Evanov; Hamilton; Nutt; Tarkka Inorg. Chem. 2011, 50, 19311941. Supported-scorpionates: almost there Slide 14 Scorpionate supported Desrochers; Besel; Corken; Evanov; Hamilton; Nutt; Tarkka Inorg. Chem. 2011, 50, 19311941. Slide 15 Hetero-atoms, pivotal signals 11 B: scorpionate chelates 31 P: phosphine chelates Heterogeneous resin samples, routine spectra 13 C { 1 H} but other J exists Paramagnetic samples: accessible, predictable Slide 16 Ni P PS NH 2 Ph Ph Ph Ph OEt O + Cl Routine 13 C { 1 H} spectra, but J C-P persists d (11.3 Hz) d of d (16.0, 31.9 Hz) d (9.1 Hz) d of d (11.8, 32.6 Hz) Desrochers, P. J.; Duong, D.; Marshall, A. S.; Lelievre, S. A.; Hong, B.; Brown, J. R.; Tarkka, R. M.; Manion, J. M.; Holman, G.; Merkert, J. W.; Vicic, D. A. Inorg. Chem. 2007, 46, 92219233. Slide 17 KTp R 13 C (ppm) Routine 13 C { 1 H} spectra, but J C-Rh persists [Rh(CO) 2 ( -Cl)] 2 Tp R Rh(CO) 2 THF -CH3-CH3 Tp R ring C Rh-CO Slide 18 13 C (ppm) N N B N N H N N N CO Rh CO N N B N N N N H CO Rh CO [Rh(CO) 2 ( -Cl)] 2 103 Rh-C (100 %, I = ) J C-Rh = 60 70 Hz Slide 19 Hetero-atoms, pivotal signals 11 B: scorpionate chelates 31 P: phosphine chelates Heterogeneous resin samples, routine spectra 13 C { 1 H} but other J exists Paramagnetic samples: accessible, predictable Slide 20 Tp*Ni I Tp*NiBrTp*NiCl Tp*Ni(NCMe) 3 + 11 B (ppm) Tp*Ni I Tp*NiBr Tp*Ni(NCMe) 3 + Tp*ZnX(Tp*) 2 Zn -40-30-20-1001020 (Tp*) 2 Ni Sensitivity of 11 B to paramagnetic Ni-X geometry Tp*NiNO 3 (Tp*) 2 M Tp*M(N-donor) 3 + Tp*MX N N N N B NN H MX N N N N BNNH M N-R N-R N-R Slide 21 Tp*NiBr + 3NCMe Tp*Ni(NCMe) 3 + Br 39 o C 33 27 21 15 9 3 -3 -9 Tp*NiBr Tp*Ni(NCMe) 3 X 11 B (ppm) Sensitivity gives T-dep. equilibrium measurements Slide 22 Tp*MBH 4 diamagnetic samples N N N N BNNH Zn H H H B H Slide 23 N N N N BNNH Ni H H H BH Tp*MBH 4 paramagnetic samples Slide 24 NMR more than just 1 H, 13 C Conclusions Slide 25 Routine 31 P, 11 B, 77 Se, 19 F, 195 Pt, 59 Co possible Can work with protio (even mixed) solvents Paramagnetic systems accessible Conclusions Slide 26 Acknowledgements Josh Brown, PhD Brian Besel Phillip Cook Davis Duong, MD Jared EvanovTristan Philips Ariel Marshall Kristin Thorvilson Chris Sutton Dr. Chip Detmer (JEOL) UCA Research Council NMR more than just 1 H, 13 C Routine 31 P, 11 B, 77 Se, 19 F, 195 Pt, 59 Co possible Can work with protio (even mixed) solvents Paramagnetic systems accessible NMR complements other characterizations On-site instrumentation essential Conclusions infrared (B-H) M H H H B H M H H H BH Slide 27 Extra slides Slide 28 P N P S N S P P N P S N S P P N P S N S P SP1 P N P S N S P TBP2 retain P S -Ni-S p -d OR P N P S N S P SP2 P S P S N P N TBP1 break P S -Ni-S p -d P S Ni S SP = square pyramid TBP = trigonal bipyramid Desrochers, P. J.; Duong, D.; Marshall, A. S.; Lelievre, S. A.; Hong, B.; Brown, J. R.; Tarkka, R. M.; Manion, J. M.; Holman, G.; Merkert, J. W.; Vicic, D. A. Inorg. Chem. 2007, 46, 92219233. Pivotal-donor: characterizes scrambling Slide 29 Ru P PN N Cl Cl Ru P ClN N Cl P Advanced inorganic experiments cistrans Ru(dppb)(phen)Cl 2 31 P H 3 N-BH 3 11 B pH dep. H n PO 4 m- : buffers, alkal. phosphatase 31 P 19 % H (w/w) BO n m- (aq) + 3H 2 (g) M 2+ Kalidindi, S. B.; Indirani, M.; Jagirdar, B. J. Inorg. Chem. 2008, 47, 7424 7429 Queiroz, S. L.; de Araujo, M. P.; Batista, A. A.; MacFarlane, K. S.; James, B. R. J. Chem. Ed. 2001, 78, 87. Slide 30 Routine 13 C { 1 H} spectra, but J C-P persists P 3 10 13 90 4 (J C-P,Hz) + P 3 10 13 90 4 (J C-P,Hz) Desrochers; Besel; Corken; Evanov; Hamilton; Nutt; Tarkka Inorg. Chem. 2011, 50, 19311941. Slide 31 Experiments from Advanced Inorganic Lab 31 P { 1 H} cis and trans Ru(dppb)(phen)Cl 2 1)P a key donor atom, 31 P utility 2) 1 H decoupled 59 Co, 195 Pt 1)20,000 ppm 59 Co range 2) 195 Pt routine spectroscopy NH 3 BH 3 opportunities for 11 B and 1 H on the same molecule phosphate buffers: pH dependent 31 P 51 V ( I = 7 / 2 ) and 63,65 Cu ( I = 3 / 2 ) from EPR days Slide 32 Ambidentate triphos ligand square planar coordination predominates P scrambling at room temperature Bianchini, C., Meli, A.; Orlandini, A.; Sacconi, L. J. Organometallic Chem. 1981, 209, 219. Kandiah, M.; McGrady, G. S.; Decken, A.; Sirsch, P. Inorg. Chem. 2005, 44, 8650-8652. Ni Ph 2 P Ph 2 P Cl Cl PPh 2 Ni Ph 2 P Ph 2 P Cl Cl PPh 2 Slide 33 Ni Ph 2 P Ph 2 P NH 2 S P Ph 2 PF 6 O O 2 PPh 2 O PPh 2 -80 o C 22 o C after O 2 exposure air free samples 1:1 integration with PF 6 - ppm Slide 34 -80 o C -60 -40 -20 0 22 acetone-d 6 Slide 35 Protonation without Ni-S scission H+H+ H+ 1.9 ppm vs 1 M H 3 PO 4 (aq) capillary 0.1 M aqueous phosphate buffers 2.6 3.4 4.4 5.6 6.3 6.5 pH = 7.6 Ni P PS NH 2 Ph Ph Ph Ph CO 2 Ni P PS NH 2 Ph Ph Ph Ph CO 2 Slide 36 Ni Ph 2 P Ph 2 P NH 2 S P Ph 2 PF 6 O O 2 Pendant phosphorus reactions stop scrambling Pt Ph 2 P Ph 2 P S S P Ph 2 Pt Ph 2 P Ph 2 P S S P Ph 2 Colton, R.; Tedesco, V. Inorg. Chim. Acta 1992, 202, 95100. S S S C S OPr S C S NEt 2 S P(OEt) 2 S s Slide 37 Scrambling common in Ni-triphos systems Bianchini, C.; Mealli, C.; Meli, A.; Scapacci, G. Organometallics 1983, 2, 1413. Slide 38 NH 3 flow Tp*NiBr on silica Tp*Ni(NH 3 ) 3 Br on silica Slide 39 Ni P PS NH 2 Ph Ph Ph Ph C OCH 2 CH 3 O + at pH 10 J P-C 33.9 ppm Routine 13 C spectra Slide 40 + Chatt, J.; Hart, F. A.; Watson, H. R. J. Chem. Soc. 1962, 2537 Soft phosphorus-rich environments encourage reduction. PPh 2 Ni P Ph 2 Ph 2 P H 3 C II PPh 2 Ni P Ph 2 Ph 2 P H 3 C I-I- I 2 I Slide 41 NaBH 4,MeOH O2O2 PPh 2 Ni PPh 2 Ph 2 P H 3 C NH 2 S PPh 2 Ni PPh 2 Ph 2 P H 3 C NH 2 S III Reversible reduction silent 31 P NMR + Slide 42 ppm vs 1 M H 3 PO 4 (aq)* * -50 o C -30 -10 0 23 comparable to results in THF Kandiah, M.; McGrady, G. S.; Decken, A.; Sirsch, P. Inorg. Chem. 2005, 44, 8650-8652. in CH 2 Cl 2 Slide 43 P n Ni II SRP n Ni II SR H + pK a = 3-4 H+H+ Protonation, a first step in hydrogen production pK a = 7.1 2+ Ni P P P SEt Ph Ph Ph Ph Ph H Clegg, W.; Henderson, R. A. Inorg. Chem. 2002, 41, 1128. H-SEt pK a = 10.6 H 2 N S CO 2 H H H pK a = 8.3 pK a = 1.7 pK a = 10.8 + Slide 44 2H + + 2e H 2 (g) Soft phosphorus-rich environments encourage reduction. P n Ni II SRP n Ni II SR H + pK a = 3-4 H+H+ P n Ni I SR H + e - Slide 45 N N N N B NN H Ni X N N N N BNNH Ni N-donor N-donor N-donor Tp*NiX + 3N-donor Tp*Ni(N-donor) 3 + X