With the help of various theoretical methods, ionization potentials (IPs) have been computed for a panel of small molecules containing atoms of group 14, 15, or 16 and representing different singly, doubly, or triply bonded systems with or without an interacting heteroatom lone pair. Comparison of experimental IP values to theoretical results indicates that (i) the standard outer valence green function (OVGF), density functional theory (DFT), and DeltaSCF methods lead to rather accurate values, (ii) the CASPT2 method systematically underestimates IPs, (iii) the method of deducing IPs from a shift of some standard DFT eigenvalue spectrum is a straightforward approach leading to rather accurate IPs, (iv) the eigenvalue spectrum obtained with the so-called statistical average of different orbital model potential (SAOP) exchange-correlation model potential is an efficient approach leading directly to quite accurate IPs, and (v) a good prediction of the IP spectrum can be obtained from the shifted excitation spectra of the system calculated by the time-dependent DFT (TD-DFT) method. It is also shown that the TD-DFT calculations of the ionized species bring a significant improvement over the calculations of the neutral molecules, indicating that a great part of the electronic relaxation is already taken into account (in a similar way for all ionizations). Finally, in the case of TD-DFT calculations of neutral molecules, the statistical average of different orbital model potential (SAOP) functional does not lead to significantly better results than the B3LYP functional.
New germanium(II)-tungsten complexes [L 2 (X)Ge] n W(CO) 6-n (L 2 ) NPhC(Me)CHC(Me)-NPh, n ) 1, X ) OTf (2); n ) 2, X ) Cl ( 13)) have been synthesized and characterized by X-ray crystallography. In compound 2 the triflate was found to be very weakly coordinating to the germanium in the solid state, and this result is confirmed by DFT calculations. All the spectroscopic data are consistent with the L 2 (X)Ge ligands being good σ-donors and poor π-acceptors in these complexes, similar to the phosphine ligands in homologous R 3 P complexes. Starting from the chlorogermanium(II)-tungsten complexes (L 2 (Cl)Ge) n W(CO) 6-n (n ) 1 (1), n ) 2 ( 13)), metathesis reactions with halide or weakly coordinating anions A -(A -) TfO -, BPh 4 -, PF 6 -) have been investigated as a general approach to obtain the cationic germanium species [L 2 Ge + ] n W(CO) 6-n . In the case of A -) TfO -, spontaneous dissociation of the anion leading to an equilibrium between a neutral and a cationic tetracoordinated germanium species is observed in coordinating solvents. Treatment of L 2 (X)Ge with MX 3 (M ) Ga, X ) Cl; M ) In, X ) I) afforded the neutral complexes L 2 MX 2 (M ) Ga (7) and In (8)) by ligand transfer reactions. The crystal structure of 8 was determined by X-ray structure analysis.
An experimental and theoretical study of the heteroleptic divalent germanium compounds containing the bidentate coordinating monoanionic β-diketiminate ligand L 2 GeΣ (L 2 ) PhNC-(Me)CHC(Me)NPh; Σ ) Cl (1), I (2), Me (3), OMe (4)) has been performed in this contribution. The new stable germanium(II) compounds 3 and 4 have been synthesized by reaction of 1 with RLi (R ) Me, OMe) and fully characterized. The crystal structures of 1-3 and their electronic structures have been determined by X-ray diffraction and UV-photoelectron spectroscopy (UPS), respectively. DFT calculations on 1 and 3 were carried out at the B3LYP level of theory. Natural bond orbital analysis for the model molecules 1′ and 3′ (without phenyl) gives information on the Ge-Σ bonding. It turns out from the NMR, mass spectroscopy, and X-ray molecular geometry properties together with the ab initio calculations that the three-coordinated germanium(II) compound L 2 GeX is best described by a model structure corresponding to a divalent germanium species weakly coordinated with the halide group, L 2 Ge + ‚‚‚X -. This view is confirmed by the particularly low energetic values of the X atom lone-pair ionizations.
Gas-phase UV photoelectron spectra of germylene (GeH 2 ) and its dimethyl analogue (GeMe 2 ) have been recorded, using flash vacuum thermolysis of 3,4-dimethyl-and 1,1,3,4-tetramethylgermacyclopent-3-ene to generate these reactive species in the inlet of the photoelectron spectrometer. The lowest vertical ionization bands for GeH 2 (9.4 eV) and GeMe 2 (8.2 and 10.0 eV) have been located with the aid of time-dependent density functional theory calculations carried out at the B3LYP/6-311G(d,p) level of theory. Similar experiments carried out with 3,4-dimethyl-1,1-diphenylgermacyclopent-3-ene, in an attempt to record the photoelectron spectrum of diphenylgermylene (GePh 2 ), were less conclusive, but are consistent with the theoretically predicted lowest lonization potential of 8.0-8.2 eV for GePh 2 . Photoelectron spectra of the three germacyclopentene derivatives are also reported.
In a vacuum gas–solid reaction (VGSR; see scheme), the kinetically unstable methylenearsane was synthesized by dehydrohalogenation of gaseous chloromethylarsane on solid sodium carbonate and characterized in the gas phase by mass spectrometry and UV photoelectron spectroscopy. A new approach to theoretically evaluate ionization potentials is also demonstrated.
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