Molecular structures of monomeric gallium trichloride, indium trichloride and lead tetrachloride by gas electron diffraction

Abstract

Gas electron diffraction data for monomeric GaCI,, monomeric InCI, and PbCI, have been recorded with nozzle temperatures of about 380,480 and 20 "C respectively. The data for GaCI, and InCI, are consistent with equilibrium structures of D,, symmetry and bond distances r, = 210.8(3) and 228.9(5) p m respectively. The data for PbCI, are consistent with an equilibrium structure of T, symmetry and r, = 237.3(3) pm. Bond energies and distances from the literature show that the M-CI bonds in MCI(g) are stronger, but longer, than in MCl,(g) for M = Al, Ga or In, and that M-CI bonds in MCl,(g) are stronger, but longer, than in MCI,(g) for M = Ge, Sn or Pb. It is suggested that the relative weakness of the bonds in group-valent chlorides is due to the energy required t o promote the Group 1 3 metal atoms from the 'P(s2p) ground states to 4P(sp2) valence states, or t o promote the Group 1 4 metal atoms from ,P(s2p2) ground states to 5S(sp3) valence states. Further that the decreasing stability of the group-valent relative t o subvalent chlorides as the Groups are descended is due both t o increasing promotional energies and t o decreasing M-CI bond strengths.Several years ago we reviewed the structures of chlorides of main-group elements (Groups 1 and 2 and 12-17) and discussed the variation of element-to-chlorine bond distances across the Periodic Table .' Since then we wished to determine the structures of the remaining homoleptic chlorides of main-group elements which are stable under the conditions of gas electron diffraction (GED), and have published the structures of SeCl,,' TeCl,,, BiCl, and (monomeric) CdC12.5 The gas-phase structure of ZnC1, has been determined by the Hungarian GED group.6 An up-to-date survey of the structures of gaseous metal halides has recently been published by Hargitta.7 In this article we report the gas-phase structures of monomeric GaCl,, monomeric InCl, and PbCl, and discuss the structure and bonding in group-valent and sub-valent chlorides of the Group 13 and 14 elements based on bond energies, bond distances and bond-stretch force constants.

Molecular structure of monomeric scandium trichloride by gas electron diffraction and density functional theory calculations on ScCl3 and Sc2Cl6 †

“…Both the Sc᎐Cl and La᎐Cl MBEs are larger than those of the Group 13 analogues, MCl 3 , M = B, Al, Ga or In, which range from 456 to 327 kJ mol Ϫ1 . 25 While the MBEs of the Group 13 trichlorides decrease as the group is descended, those of the Group 3 trichlorides appear to increase.…”

“…Before going on to discuss the molecular structures of the monomeric trichlorides of the heavier Group 3 metals, yttrium and lanthanum, we pause to note that while the bond distances in the Group 13 trichlorides MCl 3 , M = Al, Ga or In, are 6 to 11 pm shorter than the bond distance in the monochlorides MCl, 25 the bond distance in ScCl 3 is 6 pm longer than in ScCl, 222.9 pm. 26 An early GED investigation of YCl 3 indicated that the equilibrium structure is planar.…”

Molecular structure of monomeric uranium tetrachloride determined by gas electron diffraction at 900 K, gasphase infrared spectroscopy and quantum-chemical density-functional calculations

“…In our study of PbCl, we found the gas to contain a mole fraction x of 0.19(3) gaseous Cl,. 29 The refinement of UCl, was therefore repeated with the mole fraction of C1, (with known bond distance and vibrational amplitude) as an additional adjustable parameter: the mole fraction was found to be x(C1,) = 0.21(4) and the R factor decreased to 0.0517.…”

High-Temperature Gas-Phase Electron Diffraction: Unexpected Dimer Structures Among Metal Halides

“…These molecules get into the second part of the nozzle that is heated to a much higher temperature and where the dimers dissociate into monomers. This system has been used in our laboratory to determine the structure of, e.g., monomeric Group 13 trihalides [14,15] and other monomeric metal halides and also in the Oslo Electron Diffraction Group [16]. Finally, special high-temperature nozzle systems were developed for carrying out diffraction experiments on reactive and unstable species prepared during the diffraction experiments [17,18].…”