70th International Symposium on Molecular Spectroscopy, University of Illinois, Champaign-Urbana, 22-26 June 2015 Formation of Complexes CyclopropaneMCl (M = Ag or Cu) and their Characterization by Broadband Rotational Spectroscopy Daniel Zaleski,a John Mullaney,a Nicholas Walkera and Anthony Legonb aSchool of Chemistry, University of Newcastle bSchool of Chemistry, University of Bristol Background: Involvement of π electrons in hydrogen-bond interactions → Rules for angular geometry in hydrogen-bonded complexes π-electrons in ethene Hydrogen bond to electrons A. C. Legon, P. D. Aldrich and W. H. Flygare, J. Chem. Phys., 75, 625-30, (1981). π-electrons in ethyne Hydrogen bond to electrons P. D. Aldrich, A. C. Legon and W. H. Flygare, J. Chem. Phys., 75, 2126-34, (1981) Background: Involvement of π electrons in halogen-bond interactions → Rules for angular geometry in halogen-bonded complexes π-electrons in ethene Halogen bond to electrons H.I. Bloemink, J.H. Holloway and A.C. Legon, Chem. Phys. Letters, 250, 567-575, (1996). π-electrons in ethyne Halogen bond to electrons K. Hinds, J.H. Holloway and A.C. Legon, J. Chem. Soc. Faraday Trans., 92, 1291-1296, (1996). More recent background: Systematic investigations of complexes of Lewis bases with CuX and AgX S. L. Stephens, D. M. Bittner, V. A. Mikhailov, W. Mizukami, D. P. Tew, N. R. Walker and A. C. Legon, Inorg. Chem., 53, 10722-10730, (2014). S. L. Stephens, D. P. Tew, V. A. Mikhailov, N. R. Walker and A. C. Legon, J. Chem. Phys., 135, 024315, (2011). CuCl and AgCl also undergo non-covalent interactions with π system of ethene, but note distortion of ethene. Angular geometries of C2H4HCl, C2H4ClF and C2H4Cu Cl and C2H4AgCl are isomorphic More recent background: Systematic investigations of complexes of Lewis bases with CuCl and AgCl S. L. Stephens, D. M. Bittner, V. A. Mikhailov, W. Mizukami, D. P. Tew, N. R. Walker and A. C. Legon, Inorg. Chem., 53, 10722-10730, (2014). S. L. Stephens, W Mizukami, D. P. Tew, N. R. Walker and A. C. Legon, J. Chem. Phys., 137, 174302, (2012). Non-covalent interactions with CuCl and AgCl are strong enough to lengthen C≡C by ≈0.02 Å and increase HCC angle by several degrees. Angular geometries of C2H2HCl, C2H2ClF and C2H2Cu Cl and C2H2AgCl are isomorphic Pseudo-π character of cyclopropane Coulson-Moffitt model of cyclopropane → sp3 hybridization of C, overlap of lobes on adjacent C atoms ‘bent’ bond of a pseudo-π type. Pseudo- complexes of cyclopropane with CuCl or AgCl? How to synthesize molecules BMCl inside a Pate-type broadband FTMW spectrometer Broadband rotational spectrum of cyclopropane with CuCl Upward pointing: Observed Down pointing: Simulated (PGOPHER) Blue: c-C3H6 -63 Cu-35Cl Red: c-C3H6-65Cu-35Cl Note: ‘fuzz’ is nuclear quadrupole hfs arising from two quadrupolar nuclei (63,65Cu,35Cl) Broadband rotational spectrum of cyclopropane with AgCl Upward pointing: Observed Down pointing: Simulated (PGOPHER) Blue: c-C3H6- 107Ag-35Cl Red: c-C3H6 -109Ag-35Cl Note: less ‘fuzz’ because only one quadrupolar nucleus (35Cl) Ground-state spectroscopic constants of naturally abundant isotopologues Spectroscopic c-C3H6-63Cu-35Cl constant c-C3H6-65Cu-35Cl c-C3H6-107Ag-35Cl c-C3H6-109Ag-35Cl A0/MHz B0/MHz C0/MHz ΔJ/kHz ΔJK/kHz χaa(Cl)/MHz χaa(Cu)/MHz 18059(17) 1237.15080(43) 1185.54119(42) 0.1329(51) 2.40(17) -24.252(69) 57.307(85) 18058(19) 1236.92315(40) 1185.32951(52) [0.1329] [2.40] -24.50(16) 52.97(22) 18495.501(10) 984.56142(39) 953.08595(41) 0.0991(23) 3.665(92) -31.26(26) … 18493.480(38) 984.42325(32) 952.95698(30) [0.0991] [3.665] -31.18(26) … Pa/(u Å2) Pb/(u Å2) Pc/(u Å2) 403.401(13) 22.884(13) 5.101(13) 403.476(15) 22.885(15) 5.101(15) 508.11634(15) 22.13805(15) 5.18633(15) 508.18675(12) 22.13940(12) 5.1879(12) N σRMS/kHz 91 10.8 32 10.7 34 10.3 33 9.4 Isotopologues investigated cyclopropaneCuCl (8 isotopologues) cyclopropaneAgCl (8 isotopologues) c-C3H6-63,65Cu-35Cl c-C3H6-107,109Ag-35Cl c-C3H6-63Cu-37Cl c-CD2C2H4-63,65Cu-35Cl ( CD2 on a-axis) c-C3H6-107,109Ag-37Cl c-CD2C2H4-107,109Ag-35Cl ( CD2 on a-axis) c-C2H4CD2-63,65Cu-35Cl (CD2 off a-axis) c-C2H4CD2-107,109Ag-35Cl (CD2 off a-axis) c-C2H4CD2-63Cu-37Cl (CD2 off a-axis) A0 independent of Cu or Cl isotope A0 independent of Ag or Cl isotope Planar moments are revealing! 1 𝑚𝑖 𝑐𝑖2 = 6𝑚H 𝑐H2 𝑃𝑐 = 2 −𝐼𝑐 + 𝐼𝑎 + 𝐼𝑏 = 𝑖 Mean Pc for H containing isotopologues: c-C3H6-AgCl = 5.1876(10) u Å2 c-C3H6-CuCl = 5.101(15) u Å2 c-C3H6 = 5.026173(6) u Å2 1 𝑚𝑖 𝑏𝑖2 = 2𝑚C 𝑏C2 + 4𝑚H 𝑏H2 𝑃𝑏 = 2 −𝐼𝑏 + 𝐼𝑐 + 𝐼𝑎 = 𝑖 Mean Pb for H containing isotopologues: c-C3H6-AgCl = 22.1386(5) u Å2 c-C3H6-CuCl = 22.879(15) u Å2 c-C3H6 = 20.1254012(6) u Å2 Substantial increases in bC and bH and in r (C-C)Front Geometry of cyclopropaneAgCl rside(C−C) = 1.486(8) Å (1.5016 Å) 57.7(2)⁰ * rfront(C−C) = 1.5886(17) Å (1.5805 Å) Numbers in black: r0 geometry fitted with STRFIT (Z. Kisiel). (in brown: CCSD(T)/cc-pVTZ) r(*Ag) = 2.3071(53) Å (2.3094 Å) r(Ag−Cl) = 2.2869(47) Å (2.2845 Å) Do pseudo-π bonds also be acceptors for hydrogen/halogen bonds? A. C. Legon, P. D. Aldrich and W. H. Flygare, J. Amer. Chem. Soc., 104, 1486-90, (1982). CyclopropaneMCl: non-covalent bond to pseudo-π electrons CyclopropaneHCl: Hydrogen bond to pseudo-π electrons K. Hinds, J.H. Holloway and A.C. Legon, J. Chem. Soc. Faraday Trans., 93, 373-378, (1997). CyclopropaneClF: Halogen bond to pseudo-π electrons Distortions δr0(CC) of π- and pseudo-π bonds on non-covalent interaction with CuCl (relative to free Lewis base) δr(C≡C) = 0.0268(25)Å δr(C=C) = 0.0284(44) Å δrfront (C−C) = 0.1027(9)Å δrside (C−C) = -0.047(4)Å Distortions δr0 (CC) of π- and pseudo-π bonds on non-covalent interaction with AgCl (relative to free Lewis base) δr(C≡C) = 0.0165(22) Å δr(C=C) = 0.0132(18) Å δrfront (C−C) = 0.0733(17)Å δrside (C−C) = -0.029 (8)Å Why does cyclopropane suffer greater distortion than ethyne or ethene? Are the cyclopropaneMCl complexes more strongly bound? BMCl Dissociation energy,* De/kJ mol-1 CC bond distortion δr0(CC)/Å C2H2CuCl 148 0.0268(25) C2H4CuCl 155 0.0284(44) c-C3H6CuCl 105 0.1027(9) C2H2AgCl 98 0.0165(22) C2H4AgCl 94 0.0132(18) c-C3H6AgCl 66 0.0733(17) * Ab initio, CCSD(T)/cc-pVTZ (or better), bsse corrected Why are the CC bond distortions larger in cyclopropane? Ethyne Two + one σ CC bond Ethene One + one σ CC bond Cyclopropane Only a pseudo- CC (single) bond Conclusions 1. Pseudo-π bond of cyclopropane undergoes non-covalent interaction with hydrogen-bond donors, halogen-bond donors and ‘metal’-bond donors. 2. Geometries of hydrogen-bonded, halogen-bonded and ‘metal’-bonded complexes with cyclopropane are isomorphic. Also for ethyne and ethene series. 3. EthyneMCl, etheneMCl and cyclopropaneMCl all show CC bond lengthening on complex formation, but much larger for cyclopropane as Lewis base. Geometry of cyclopropaneCuCl rside(C−C) = 1.468(4) Å (1.5002 Å) 56.5(1)⁰ * Numbers in black: r0 geometry fitted with STRFIT (Z. Kisiel). in brown: CCSD(T)/ccpVTZ) rfront(C−C) = 1.6180(9) Å (1.6154 Å) r(*Cu) = 1.9917(46) Å (1.9584 Å) r(Cu−Cl) = 2.0614(41) Å (2.0672 Å)