Amineboranes for Hydrogen Storage

Transcription

1 Amineboranes for ydrogen Storage Michael einekey University of Washington UW Karen Goldberg Melanie C. Denney Vincent Pons Travis ebden Denise Mery Brandon Dietrich UNC Maurice Brookhart Inigo Göttker-Schnetmann Barcelona Augusti Lledos, Jose Lluch PNNL Tom Autrey, John Linehan Crystallography: Antonio DiPasquale, Arnie Rheingold (UCSD) Tom Koetzle, Paula Piccoli, Art Schultz (Argonne). 1

2 M M M dihydrogen elongated dihydrogen dihydride 2

3 What do we mean by Structure? A set of bond distances and bond angles Generally, a static concept For stable molecules, structure is usually independent of temperature 3

4 Does structure depend upon mass? pm D D pm 4

5 5

6 M M M dihydrogen elongated dihydrogen dihydride 6

7 Characterization of 2 Complexes by 1 NMR ydride resonances at high field Deuterium: nuclear spin I = 1 observation of a 1:1:1 triplet in the 1 spectrum 25 z < J D < 35 z (D gas: J D = 43 z) L n M D d- = J D 7

8 D. M. einekey, V. Pons et. al. J. Am. Chem. Soc. 2004, 126,,

9 + N N Os O C=O 3 C N N Ph 2 P Ru PPh P P Os Cl P P + Ph Br 2 PR 3 Re PR 3 Br NO Cl 2 PiPr 3 Os PiPr 3 Cl N C Ph Ph N SiMe 3 N Me 3 P Mo N PMe 3 2 SiMe 3 Cl 2 PiPr 3 Os N Nb SiMe 3 PMe 2 Ph 2 + Me 2 P 2 2+ PiPr 3 PMe 2 SiMe 3 Chem. Soc. Rev. 2004, 33,

10 W. T. Klooster,, T. F. Koetzle,, G. Jia,, T. P. Fong, R.. Morris and A. Albinati, J. Am. Chem. Soc. 1994, 116,

11 11

12 12

13 J D (z) T (K) J. K. Law,. Mellows and D. M. einekey J. Am. Chem. Soc. 2001, 123,,

14 Theory Lledos et. al. J. Am. Chem. Soc. 1997, 119,

15 1 NMR spectrum (hydride region) of a sample partially labeled with D and T 15

16 16

17 r X (Å) T (K) X distances derived from J D, J T and J DT Law, J. K.; Mellows,.; einekey,, D. M. J. Am. Chem. Soc. 2002, 124,,

18 (pincer)()2 complexes are active alkane dehydrogenation catalysts.* PR 2 PR 2 Structure? In Silico: d- = 1.66 Å Niu and all, J.Am. Chem. Soc. 1999, 121, *e.g. Jensen et al. Chem. Comm.1999, 2443; Goldman et al. J. Am. Chem. Soc. 2002, 124, 11404; Brookhart et al. J. Am. Chem. Soc. 2004, 126, 1804; Jensen et al. Inorg. Chim. Acta. 2004, 357,

19 Most active catalyst for alkane dehydrogenation: (POCOP)() 2 19

20 + D D + + D 2 D + D 20

21 D J D = 7.5 z(pentane); T dependent J D = zero! (C 2 Cl 2 ) sol D D 21

22 President's ydrogen Fuel Initiative The ydrogen Fuel Initiative aims to reverse America's growing dependence on foreign oil by developing the technology needed for commercially viable hydrogen-powered fuel cells. With a new national commitment, our scientists and engineers will overcome obstacles to taking these cars from laboratory to showroom so that the first car driven by a child born today could be powered by hydrogen, and pollution-free.. President Bush, State of the Union Address, January 28, 2003 One obstacle is hydrogen storage what is needed? Appropriate thermodynamics, igh storage capacity (igh gravimetric and volumetric densities), Fast kinetics, Long lifetime, Effective heat transfer, igh mechanical strength and durability,safe 22

23 Ammonia Borane as a 2 Storage Material DOE Storage Targets Target wt% usable Vol. density (kg 2.m -3 ) Storage Potential of Ammonia Borane 2 Released 1 2 Wt% Vol. density Product [ 2 NB 2 ] n [NB] n [NB] n Appropriate Thermodynamics Gas phase calculations predict ammonia borane dehydrogenation is near thermoneutral.* Important for reversibility. *Dixon, D. A.; Gutowski, M. J. Phys. Chem. A 2005, 109,

24 Dehydrogenation of Ammonia Borane Thermal 3 NB 3 2 N 2 B B B 2N N 2 N B B N N B 2 B N2 B 2 borazine Wang, J. S.; Geanangel, R. A. Inorg. Chim. Acta 1988, 148, 185. Catalyzed 3 NB 3 [Rh] N B B N N B mol% catalyst hours at 45 ºC Jaska, C. A.; Manners, I. J. Am. Chem. Soc. 2004, 126,

25 A Better Catalyst Choice? [catalyst] n N 3 B 3 [N 2 B 2 ] n + n 2 TF, rt Amineboranes are isoelectronic with alkanes. (pincer)() 2 complexes are active alkane dehydrogenation catalysts.* (POCOP)() 2 *e.g. Jensen et al. Chem. Comm.1999, 2443; Goldman et al. J. Am. Chem. Soc. 2002, 124, 11404; Brookhart et al. J. Am. Chem. Soc. 2004, 126, 1804; Jensen et al. Inorg. Chim. Acta. 2004, 357,

26 Quantification of ydrogen [] n N 3 B 3 [N 2 B 2 ] n + n 2 TF, rt Equivalents of [] = 0.25 mol% 0.5 mol% 1.0 mol% Time (min) 26

27 Demonstration of 2 Release 27

28 Characterization of Solid Product n N 3 B 3 [N 2 B 2 ] n + n 2 [catalyst] TF, rt solid Solid state 11 B NMR. Infrared spectroscopy. Powder X-ray diffraction. Non-volatile product should not poison fuel cell. 2 B 2 N 2 N B 2 N 2 B 2 n = 5 2 N B 2 N 2 B 2 Böddeker, K. W.; et al. J. Am. Chem. Soc. 1966, 88,

29 Solid State 11 B NMR of [B 2 N 2 ] 5 29

30 IR of [B 2 N 2 ] Wavenumber cm Transmittance [%]

31 XRD of [ 2 NB 2 ] 5 31 d = 7.96 d = 4.33 d = 3.74 d = 3.00 d = 2.85 d = 2.17 d = 1.89 d = 1.66 d = 1.53 d = 1.43 d = 1.25

32 Comparison with Previous Best Catalyst [Rh(1,5-COD)(µ-Cl)] 2 * Catalyst Loading Temperature (ºC) 2 evolved (equiv.) Products Time 0.6 mol% 45 2 Borazine hr 0.5 mol% 25 1 [ 2 NB 2 ] n < 15 min At least 200 fold increase in reaction rate over previous best. *Manners et al. J. Am. Chem. Soc. 2003, 125,

33 Formation of Catalytically Dormant Species (POCOP) NB 3 [ 2 NB 2 ] TF, rt 1 NMR: ydride region O P t Bu 2 Ratio of 3 new signals: 1:1:1 5 min 1 hr + 4 nights + 3 NB hrs 33

34 Identification of Dormant Species Same compound is formed via B 3.TF TF Bond Length (Å) (1)-B(1) (1)-P(1) (1)-P(2) (1)-C(1) 2.185(9) (14) (14) 2.032(4) 34

35 Neutron Structure Bond Lengths (Å) 1-B1 2.37(3) 1-P1 1-P2 1-C (2) 2.31(2) 1.99(2) 1.61(4) 1.74(4) (POCOP)(B 3 )() 2 or (POCOP)(B 4 )() O P O t Bu 2 P t Bu 2 B 2 O P O t Bu 2 P t Bu 2 B 1-ctr 2.02(1) B1-1a 1.18(8) B1-1b 1.22(5) B1-1c 1.45(5) B *ctr is the center of the B1 1C bond IR: B- stretches at 2466(s), 2441(s), 2285(s) and 2219 cm -1 (m) and - at 1930 cm -1 (m) 35

36 NMR of (BD 4 )D Analogue B t Bu B B (B 4 )() 298 K (B 4 )() 240 K (BD 4 )(D) 298 K (BD 4 )(D) 200 K

37 O P O t Bu 2 P t Bu 2 B +B O P t Bu B 3-2 O P t Bu 2 O P O t Bu 2 P t Bu 2 DORMANT ACTIVE ACTIVE 31 P NMR Active form of catalyst can be regenerated with hydrogen! [](B 3 ) 2 [] 2 [] 4 start 5 atm 2 ; 2 hr Soln degassed 37

38 Dehydrogenation of Ammonia Borane (POCOP)() 2 5 N 3 B 3 [N 2 B 2 ] TF, rt Efficient catalyst discovered. Reaction proceeds under mild conditions. Non-volatile [N 2 B 2 ] 5 formed. Regeneration of active catalyst using hydrogen. 38

39 Reversibility? New (last week) solution calorimetry data from PNNL: N 3 B 3 1/5 (N 2 B 2 ) = -28 kj/mol 39

40 Acknowledgements DOE Center of Excellence For Chemical ydrogen Storage 40