1. OSU-05 TA 101 The Structure of Ethynylferrocene using Microwave Spectroscopy. Ranga Subramanian, Chandana Karunatilaka, Kristen Keck and Stephen Kukolich Department of Chemistry University of Arizona, Tucson 85721

2. OSU-05 TA 102 Ethynylferrocene C 12 H 10 Fe  ETHFE  Singly-Substituted Ferrocene (#6)  Asymmetric top.I a ≠ I b ≠ I c  Has a & b dipole mom. PROPERTIES  Three Fe isotopes. 56 Fe(~92%), 54 Fe(~5.8%), 57 Fe(~2.1%)  C s symmety - a-b mirror plane

3. OSU-05 TA 103 - Previous work Spectroscopic studies [ 57 Fe-NMR / 13 C-NMR]. No previous gas-phase structural data ! Motivation: Important precursor for Polymeric ferrocenyl compounds. Organic conductors / Opto-electronics X-ray diffraction studies. Electrochemical studies.

4. OSU-05 TA 104 EXPERIMENTAL DETAILS - ETHFE used without further purification. - Heated both ETHFE & DETHFE  60 0 C - Spectra of 56 Fe, 54 Fe, 57 Fe, 13 C & DETHFE 56 Fe  4 – 12 GHz range. - DETHFE Modified synthesis of ferrocenyl propyne  (using D 2 O) -The ETFE was treated with 1.6M n-butyllithium (Li n Bu) in hexane, (Li replaced the acidic H on acetylene) and then with D 2 O, (D replaced H) and the product sublimed G.Doisneau, G. Balavoine, T. Fillebeen-Khan; J.Organomet.Chem, 425, 113, 1992.

5. OSU-05 TA 105 MEASURED LINES- No. of transitions IsotopomerDipole 39ETH 56 Fea & b 11ETH 54 Fea & b 5 eachETH 57 Fe & 4 - 13 C’s a 24DETH 56 Fea & b

6. OSU-05 TA 106 Fourier Transformed spectrum of the 4 13  3 12 transition for ETHFE. Frequencies in kHz relative to 6141730.0 kHz. - The spectrum is an average of five shots. J’ = 4 13  J = 3 12

7. OSU-05 TA 107 RESULTS FROM FITTING THE TRANSITION FREQUENCIES - Spectral fits using SPFIT ¥ least-squares fitting program with a standard rigid-rotor Hamiltonian. - 12 C / 1 H / 56 Fe  Used 5 adjustable parameters [ A, B, C,  J,  K ]. ¥ H.M.Pickett, J.Mol.Spec: 1991, 148, 371-377. - DETHFE  4 adjustable parameters [ A, B, C,  J]. - 54 Fe / 57 Fe / 13 C  3 adjustable parameters [A, B, C ].

8. OSU-05 TA 108 Spectral parameters obtained for the different isotopomers of ETHFE and DETHFE. (in MHz) a Fixed

9. OSU-05 TA 109 Structure Determination (least squares fit) - Altogether 24 rotational constants  Four parameters. P(1) = r(Fe-Cp) P(2) = r(C-C) of Cp ring P(3) = angle(Ethynyl group & Cp plane) i.e. (tilt – angle) P(4) = r(C-H) of Ethynyl group. r(C-H) of Cp / r(C1-C1’) & r(C1’-C2’)  Fixed at DFT values. - Fit deviation  0.02 MHz. - Initial geometry  From DFT (B3PW91) calculations.

10. OSU-05 TA 1010 Structural Fit results - C 1 & C 6 are eclipsed  Consistent with DFT -Ethynyl group  pointing away from the plane of Cp ring & away from the Fe atom. - “Tilt angle – 2.74(1)°” - r(Fe-Cp) = 1.647(4) Å - r(C 2 ’-H et ) = 1.053(2) Å - r(C 1 -H et ) = 3.691(2) Å

11. OSU-05 TA 0911 Structural parameters obtained for the ETHFE complex.

12. OSU-05 TA 1012 Comparison of structural parameters ParameterX-rayDFTThis workFree acetylene r (C 2 ’ – H et ) / Å0.7731.0741.05(1)1.058 ParameterX-rayKraitchmanStructure Fit Avg: r (Fe-C) / Å2.02.048(6)2.049(5) r (Fe-H et ) / Å4.95.09(8)5.16(2)

13. OSU-05 TA 1013 - Comparing 3 singly-substituted ferrocenes - - Two Cp rings are eclipsed  Consistent with DFT. ( E staggered – E Eclipsed ) = 3 kJ / mol (ETHFE) MoleculeTilt angle / deg: Chloroferrocene 2.7(6)  Dimethyl- ferrocene 2.66(2)  ETHFE (X-ray) 1.7  ETHFE (This work) 2.74(1)  “Drooping away from Fe”

14. OSU-05 TA 1014 The Structural parameters of different ferrocene compounds of the type, (C5H4-X)Fe(C5H4-Y). Relationship between r(Fe-Cp) to the Inductive Hammett Parameter ( I ) NameXYr (C-C) / År (Fe –Cp) / Å  I Chloroferrocene я ClH1.433(2)1.610(5)0.47 Bromoferrocene я BrH1.433(1)1.630(2)0.44 Methylferrocene я CH 3 H1.4289(2)1.6528(3)-0.04 Dimethylferrocene я CH 3 1.434(5)1.670(2)-0.08 ETHFE * CΞCHH1.4315(6)1.6464(1)0.21 Ferrocene † HH1.440(2)1.661(2)0.00 Я Kukolich et. Al. * Present work, † A.Haaland and J.E.Nilsson; Acta. Chem. Scan. 23, 2653, 1968.  Electron Diffraction studies

15. Linear correlation between the gas-phase structural parameter r(Fe-Cp) and the Inductive Hammett parameter  I.  I r(Fe-Cp) / Å Gas-phase r (Fe-Cp) of Ferrocene. = 1.659 Å Electron Diffraction value for Å Ferrocene  1.661(2) Å

16. OSU-05 TA 1016 Acknowledgements We thank Prof. Robin Polt, University of Arizona, for useful suggestions during the synthesis of the deuterated Ethynylferrocene. N$F - This material is based upon work supported by the National Science Foundation under Grant No. CHE-0304969. This support from the National Science Foundation is gratefully acknowledged Department of Chemistry, University of Arizona.