Mass-Analyzed Threshold Ionization Spectroscopy Yttrium-Assisted C-H and C-C Bond Activation of Ethylene (C2H4) Probed by Mass-Analyzed Threshold Ionization Spectroscopy Jong Hyun Kim, Dong-Sheng Yang June 23th 2016 International Symposium on Molecular Spectroscopy Champaign-Urbana, Illinois

Introduction Metal activation of hydrocarbons plays an important role in organic synthesis and catalysis Understanding of metal mediated C-H & C-C activation helps to figure out the reaction mechanisms of metal-hydrocarbon reactions Few spectroscopic studies, little information about the structures and electronic states of the intermediates and products.

La + Ethylene  La(C2H2) + La(C4H6) Background La + Ethylene  La(C2H2) + La(C4H6) La([Xe]5d16s2) vs. Y([Kr]4d15s2) Similar electron configurations, but different promotion energies What about Yttrium + Ethylene reaction? Similar or different? La La C2V CS Kumari, Sudesh. 2014. Electron and ion spectroscopy of metal hydrocarbon complexes. Ph.D. dissertation, University of Kentucky

Wiley-McLaren Time-of-Flight Mass Spec. Experimental Setup Wiley-McLaren Time-of-Flight Mass Spec. MCP Detector Electric Field (200 V/cm) Extraction Can Pulse Valve GV He Pulse Field Ionization 240 V/cm UV 42800 – 46000 cm-1 (0.45 – 0.15 mJ/pulse) 532 nm < 2.0 mJ/pulse Diffusion Pump Turbo Pump Reaction Chamber Spectroscopy Chamber

TOF Mass Spectrum of La vs. Y + Ethylene Kumari, Sudesh, 2014. Electron and Ion Spectroscopy of Metal Hydrocarbon Complexes. Ph.D. dissertation, University of Kentucky

PIE Curve of Y(C2H2) Due to the Y atomic transition

Experimental and Simulated Spectra 45679 / 45586 536 / 530 ~ 45 576 / 565 830 / 821 576+830/ 1386 Experimental 1A1  2A1 250 K 25 cm-1 FWHM 1A1  2A1 5 K 25 cm-1 FWHM

AIE and Vibrational Frequencies (cm-1) Y(C2H2), C2v isomer MATI BPW91 AIE: 1A1 ¬ 2A1 45679 45586 Assignment n 𝟑 + 830 821 n 𝟒 + 576 565

Geometries (C2V) Neutral Cation Y Y 2A1 1A1 2.208 2.159 1.355 1.355 C-C : 1.54 C=C : 1.34 Unit: Å 2A1 Kumari, Sudesh, 2014. Electron and Ion Spectroscopy of Metal Hydrocarbon Complexes. Ph.D. dissertation, University of Kentucky

TOF Mass Spectrum of La vs. Y + Ethylene Kumari, Sudesh, 2014. Electron and Ion Spectroscopy of Metal Hydrocarbon Complexes. Ph.D. dissertation, University of Kentucky

PIE Curve of Y(C2H4) Due to the Y atomic transition

Experimental and Simulated Spectra 45603 / 45681 ~ 77 444 / 452 784 / 833 X 610 / 659 (330): A1  A2  A2 = A1 totally symmetric A1  A2 = A2 444 + 784 Experimental 1A1  2A1 250 K 25 cm-1 FWHM 1A1  2A1 5 K 25 cm-1 FWHM

AIE and Vibrational Frequencies (cm-1) Y(C2H4), C2v isomer MATI BPW91 AIE: 1A1 ¬ 2A1 45603 45681 Assignment n 𝟒 + 784 833 n 𝟓 + 444 452 Not Measured (610) n 𝟖 + 330 (659)

Geometries (C2V) Neutral Cation Y Y 2A1 1A1 La(C2H4): Not detected 2.264 2.214 1.526 1.521 2A1 1A1 C-C : 1.54 C=C : 1.34 Unit: Å

TOF Mass Spectrum of La vs. Y + Ethylene

PIE Curve of Y(C4H6) Thermally excited

Experimental and Simulated Spectra 43475 / 43014 308 / 280 352 / 328 392 / 387 ~26 424 / 422 504 / 524 424+352 Experimental 1A’  2A’ 200 K 25 cm-1 FWHM 1A’  2A’ 5 K 25 cm-1 FWHM

Experimental and Simulated Spectra 43473 / 43014 422 / 422 350 / 328 502 / 524 400 / 387 310 / 280 492 / 498 798 / 794 ~ 26 422+422+350 422+422+502 350+350+422 422+502+502 422+350 422+502 102 10X Experimental 1A’  2A’ 200 K 25 cm-1 FWHM 1A’  2A’ 5 K 25 cm-1 FWHM

AIE and Vibrational Frequencies (cm-1) Y(C4H6), CS isomer MATI BPW91 AIE: 1A' ¬ 2A' 43473 43014 Assignment n 𝟏𝟏 + 502 524 n 𝟏𝟐 + 422 422 n 𝟏𝟑 + 350 328

Geometries (CS) Neutral Cation Y Y 4 4 2 3 2 3 2A’ 1A’ 1 1 2.329 2.394 2.549 2.479 1 4 1 4 122.68° 124.28° 1.456 2 1.454 3 2 3 1.397 1.402 2A’ 1A’ C-C : 1.54 C=C : 1.34 Unit: Å Kumari, Sudesh, 2014. Electron and Ion Spectroscopy of Metal Hydrocarbon Complexes. Ph.D. dissertation, University of Kentucky

Conclusions Y + ethylene reaction produced Y(C2H2), Y(C2H4), and Y(C4H6) via C-H activation and C-C coupling. Their structures, AIEs, electronic states, and vibrational modes were measured and investigated, respectively. Similar to La + ethylene reaction, except for one more product, Y(C2H4). This may be caused by different nd1(n+1)s2  nd2(n+1)s1 promotion energies.

Thank you Any Questions?

excited state: 5d2 6s1 2F 7011.909 cm-1 (20.048 kcal/mol) *La promotion energy:  ground state: 5d1 6s2 2D 0 cm-1 excited state: 5d2  6s1 2F 7011.909 cm-1 (20.048 kcal/mol) *Y promotion energy: ground state: 4d1 5s2 2D 0 cm-1 excited state: 4d2 5s1 2F 15326.83 cm-1 (43.821 kcal/mol) (1cm-1 = 0.002 859 11 kcal/mol) As we guessed, La has lower promotion energy than Y. Weisshaar, Bare Transition Metal Atoms in the Gas Phase: Reactions of M, M+, and M2+ with Hydrocarbons, Acc. Chem. Res. 26, 213 (1993)

Time-of-Flight Mass Spectrum of La + Ethylene

Time-of-Flight Mass Spectrum of Y + Ethylene

MATI Spectrum of Y(C4H6) 43475 308 352 392 ~26 424 504 424+352

Possible Structures? Y(C4H6) A big energy difference between the calculated and experimental IE Disagreement between the simulated and experimental spectra A large structural change upon ionization  B was considered as the most likely candidate Hewage, Dilrukshi C. 2015. Spectroscopic characterization of lanthanum-mediated hydrocarbon activation. Ph.D. dissertation, University of Kentucky

Possible Structures? Cs Electronic States Relative Energies (cm-1) Geometry optimization and frequency calculations were carried at BPW91/6-311++G** for C, H and LANL2DZ for Yttrium Electronic States Relative Energies (cm-1) 2A’ (neutral) 4A’’ (neutral) 10123 1A’ (ion) 43014 3A’’ (ion) 52670 IE (cm-1) 1A' ¬ 2A' IE (cm-1) 3A'' ¬ 4A'' 42547 IE (exp) = 43475 cm-1 3A’’  2A’, 52670 cm-1 (high energy) : omitted

Experimental and Simulated Spectra 43475 (0-0) Experimental 43014 1A’  2A’, 200 K, 25 cm-1 FWHM 42547 3A’’  4A’’, 200 K, 25 cm-1 FWHM 3A’’  2A’, 52670 cm-1 ( high energy) : omitted

Wiley-McLaren Time-of-Flight Mass Spec. Metal Atom reaction? Wiley-McLaren Time-of-Flight Mass Spec. MCP Detector Electric Field Electric Field (200 V/cm) Extraction Can HC Pulse Valve GV He Pulse Field Ionization 240 V/cm UV 42800 – 46000 cm-1 532 nm Diffusion Pump Turbo Pump Reaction Chamber Spectroscopy Chamber

Metal Atom reaction?

Metal Atom reaction?

Metal Atom reaction?

Metal Atom reaction?

Metal Atom reaction? (Pre-mixture gas)

Metal Atom reaction?