1. Microwave Spectroscopic Investigations of the C—H…  Containing Complexes CH 2 F 2 …Propyne and CH 2 ClF…Propyne Rebecca A. Peebles, Sean A. Peebles, Cori L. Christenholz, Yasser J. Dhahir, Anthony A. Ernst Department of Chemistry, Eastern Illinois University, Charleston, IL 61920

2. C—H…  Interactions

3. Propyne Complexes New considerations New considerations – Two inequivalent C—H bond donors in propyne – Internal rotation

4. Possible Structures Gaussian 03: MP2/6-311++G(2d,2p)

5. Experimental CH 2 F 2 …Propyne CH 2 F 2 …Propyne – Scanned on 480 MHz CP-FTMW – Sample: ~1.8% each CH 2 F 2 and propyne in He/Ne pressurized to 5.2 bar in 1 L tank – delivered to nozzle at ~2 bar – 2000 gas and microwave pulses per frequency step – Isotopes on cavity FTMW Enriched: CH 3 CCD (98% D, CDN Isotopes) Enriched: CH 3 CCD (98% D, CDN Isotopes) All four carbons in natural abundance All four carbons in natural abundance

6. J = 3 - 2 J = 4 - 3 J = 5 - 4 J = 6 - 5 AABS: Z. Kisiel, L. Pszczolkowski, I. R. Medvedev, M. Winnewisser, F.C.De Lucia, C. E. Herbst, J.Mol.Spectrosc., 233, (2005), 231. PROSPE Web SITE: Z.Kisiel, in: J. Demaison, et al. (Eds.), Spectroscopy from Space, Kluwer Academic Publishers, Dordrecht, 2001, pp.91-106.

7. Spectroscopic Constants propyne P bb 1.59 u Å 2 CH 2 F 2 P aa 46.01 u Å 2 CH 2 F 2 P bb 8.63 u Å 2 CH 2 F 2 P cc 1.66 u Å 2 Structure I: 1.59 + 46.01 = 47.60 u Å 2 Structure II: 1.59 + 1.65 = 3.24 u Å 2 I II

8. CH 2 F 2 -Propyne Structure r0 rs rer0 rs rer0 rs rer0 rs re 3.497(1) Å 3.480(2) Å 3.388 Å 85.56(9)°85.84(23)°84.7° 89.61(4)°85.0° 1.060(2) Å 1.060(1) Å 1.2073(10) Å 1.212(5) Å 1.4596(10) Å 1.452(5) Å Lit. r s J. L. Duncan, et al., J. Mol. Spectrosc. 46 (1973) 232. 3.170(1) Å 3.097 Å 3.109(4) Å 2.875 Å r0 rer0 rer0 rer0 re

9. Dipole moment a b 1.97 D 0.7804 D  a = 1.568(2) D  a = 1.434 D  b = 0.587(2) D  b = 0.656 D  tot = 1.674(1) D  tot = 1.577 D measuredprojectedmonomers QSTARK: Kisiel, et al., Chem. Phys. Lett., 325, (2000), 523.

10. Next Step – CH 2 ClF…Propyne

12. Experimental CH 2 ClF…Propyne CH 2 ClF…Propyne – ~1.7% of each component in He/Ne, delivered at 1.5 – 2.5 atm – Original scan on CP-FTMW – a few very weak candidate lines – Checked these on cavity FTMW – identified a few transitions – Further cavity FTMW searching led to assignment – Very weak transitions – seem to get weaker and weaker – Only 35 Cl and 37 Cl assigned

14. Spectroscopic Constants Chlorine atom coordinates (Å) Ab initio: a = 1.5246 b = 0.9575c = 0.0287 Kraitchman: a = ±1.6106(9) b = ±0.9235(16)c = ±0.051(30)

15. Comparison of Alkyne Complexes Cl F Fitted: R( ≡ … C) = 3.706(4) Å  (C– ≡ … C) = 71.1(16) °  (Cl–C … ≡ ) = 88.3(5) ° 80.0(16)° 3.122(46) Å 148.7(7)° 2.724(7) Å 3.293(40) Å 2.670(8) Å 153.2(5)° 81.6(14)° Fitted: R( ≡ … C) = 3.683(7) Å  (C– ≡ … C) = 73.9(14) °  (Br–C … ≡ ) = 91.7(4) ° 3.207(22) Å 101.0(1)° 3.236(6) Å Fitted: R( ≡ … C) = 3.605(4) Å  (C– ≡ … C) = 73.9(9)°  (Cl–C … ≡ ) = 91.9(3)° 2.84(6) Å 94.9(3)° 3.363(14) Å Fitted: R( ≡ … C) = 3.625(9) Å  (C– ≡ … C) = 70.2(28)°  (F–C … ≡ ) = 80.0(8)° Fitted: R( ≡ … C) = 3.497(1) Å  (C– ≡ … C) = 85.56(9)°  (F–C … ≡ ) = 89.61(4)° 3.109(4) Å 3.170(1) Å 98.2(5)° To be determined?

16. What’s Next? Complexes with aromatic  systems – Next talk! Including benzene…HCCH

17. Acknowledgements Ashley Elliott, Dan Obenchain Ashley Elliott, Dan Obenchain Current Peebles group: Anu Akmeemana, Ashley Anderton, Cori Christenholz, Rachel Dorris, Nate Ulrich Current Peebles group: Anu Akmeemana, Ashley Anderton, Cori Christenholz, Rachel Dorris, Nate Ulrich NSF grants: RUI-0809387, RUI-1214070 NSF grants: RUI-0809387, RUI-1214070