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NMR beyond ordinary undergraduate experiences: Routine measurements with heteronuclear, heterogeneous, and paramagnetic samples Patrick J. Desrochers,

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Presentation on theme: "NMR beyond ordinary undergraduate experiences: Routine measurements with heteronuclear, heterogeneous, and paramagnetic samples Patrick J. Desrochers,"— Presentation transcript:

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, Am. chem. Soc. Natl. Mtg. March 2011, CHED 26

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

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

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

5 D F Se P C B V Pt Co Rh H Low Freq. probe range: 30 MHz to 120 MHz

6  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 o C 5-6 © 1999

7 Monitoring scorpionate formation KBH 4 KTp* N N H 3 H o C 5-6  11 B (ppm) Et 2 O wash acetone wash Pz* Pz* B Pz* H H Pz* B Pz* H

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

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, 9221–9233.

10  31 P ppm -80 o C Pivotal-donor trans cis

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

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

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, Desrochers; Besel; Corken; Evanov; Hamilton; Nutt; Tarkka Inorg. Chem. 2011, 50, 1931–1941. Supported-scorpionates: almost there

14 Scorpionate supported Desrochers; Besel; Corken; Evanov; Hamilton; Nutt; Tarkka Inorg. Chem. 2011, 50, 1931–1941.

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

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, 9221–9233.

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

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)] Rh-C (100 %, I = ½) J C-Rh = 60 – 70 Hz

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

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 (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

21 Tp*NiBr + 3NCMe Tp*Ni(NCMe) 3 + Br  39 o C  Tp*NiBr  Tp*Ni(NCMe) 3 X  11 B (ppm) Sensitivity gives T-dep. equilibrium measurements

22 Tp*MBH 4 diamagnetic samples N N N N BNNH Zn H H H B H

23 N N N N BNNH Ni H H H BH Tp*MBH 4 paramagnetic samples

24 NMR more than just 1 H, 13 C Conclusions

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

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

27 Extra slides

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, 9221–9233. Pivotal-donor: characterizes scrambling

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.

30 Routine 13 C { 1 H} spectra, but J C-P persists P (J C-P,Hz) + P (J C-P,Hz) Desrochers; Besel; Corken; Evanov; Hamilton; Nutt; Tarkka Inorg. Chem. 2011, 50, 1931–1941.

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

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, Ni Ph 2 P Ph 2 P Cl Cl PPh 2 Ni Ph 2 P Ph 2 P Cl Cl PPh 2

33 Ni Ph 2 P Ph 2 P NH 2 S P Ph 2 PF 6 O O 2 PPh 2 O PPh o C 22 o C after O 2 exposure air free samples 1:1 integration with PF 6 - ppm

34 -80 o C acetone-d 6

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 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

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, 95−100. S S S C S OPr S C S NEt 2 S P(OEt) 2 S s

37 Scrambling common in Ni-triphos systems Bianchini, C.; Mealli, C.; Meli, A.; Scapacci, G. Organometallics 1983, 2, 141−3.

38 NH 3 flow Tp*NiBr on silica Tp*Ni(NH 3 ) 3 Br on silica

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

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- ½ I 2 I

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 +

42 ppm vs 1 M H 3 PO 4 (aq)* * -50 o C comparable to results in THF Kandiah, M.; McGrady, G. S.; Decken, A.; Sirsch, P. Inorg. Chem. 2005, 44, in CH 2 Cl 2

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 = Ni P P P SEt Ph Ph Ph Ph Ph H Clegg, W.; Henderson, R. A. Inorg. Chem. 2002, 41, 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 =

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 -

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 


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