An official website of the United States government
Abstract The chemical dynamics of the elementary reaction of ground state atomic silicon (Si;3P) with germane (GeH4; X1A1) were unraveled in the gas phase under single collision condition at a collision energy of 11.8±0.3 kJ mol−1exploiting the crossed molecular beams technique contemplated with electronic structure calculations. The reaction follows indirect scattering dynamics and is initiated through an initial barrierless insertion of the silicon atom into one of the four chemically equivalent germanium‐hydrogen bonds forming a triplet collision complex (HSiGeH3;3i1). This intermediate underwent facile intersystem crossing (ISC) to the singlet surface (HSiGeH3;1i1). The latter isomerized via at least three hydrogen atom migrations involving exotic, hydrogen bridged reaction intermediates eventually leading to the H3SiGeH isomeri5. This intermediate could undergo unimolecular decomposition yielding the dibridged butterfly‐structured isomer1p1(Si(μ‐H2)Ge) plus molecular hydrogen through a tight exit transition state. Alternatively, up to two subsequent hydrogen shifts toi6andi7, followed by fragmentation of each of these intermediates, could also form1p1(Si(μ‐H2)Ge) along with molecular hydrogen. The overall non‐adiabatic reaction dynamics provide evidence on the existence of exotic dinuclear hydrides of main group XIV elements, whose carbon analog structures do not exist.
more »
« less
Gas Phase Preparation of the Elusive Monobridged Ge( μ ‐H)GeH Molecule through Nonadiabatic Reaction Dynamics
Abstract The hitherto elusive monobridged Ge(μ‐H)GeH (X1A′) molecule was prepared in the gas phase by bimolecular reaction of atomic germanium with germane (GeH4). Electronic structure calculations revealed that this reaction commenced on the triplet surface with the formation of a van der Waals complex, followed by insertion of germanium into a germanium‐hydrogen bond over a submerged barrier to form the triplet digermanylidene intermediate (HGeGeH3); the latter underwent intersystem crossing from the triplet to the singlet surface. On the singlet surface, HGeGeH3predominantly isomerized through two successive hydrogen shifts prior to unimolecular decomposition to Ge(μ‐H)GeH isomer, which is in equilibrium with the vinylidene‐type (H2GeGe) and dibridged (Ge(μ‐H2)Ge) isomers. This reaction leads to the formation of cyclic dinuclear germanium molecules, which do not exist on the isovalent C2H2surface, thus deepening our understanding of the role of nonadiabatic reaction dynamics in preparing nonclassical, hydrogen‐bridged isomers carrying main group XIV elements.
more »
« less
- Award ID(s):
- 1853541
- PAR ID:
- 10445799
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 28
- Issue:
- 10
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The previously unknown silylgermylidyne radical (H3SiGe; X2A′′) was prepared via the bimolecular gas phase reaction of ground state silylidyne radicals (SiH; X2Π) with germane (GeH4; X1A1) under single collision conditions in crossed molecular beams experiments. This reaction begins with the formation of a van der Waals complex followed by insertion of silylidyne into a germanium‐hydrogen bond forming the germylsilyl radical (H3GeSiH2). A hydrogen migration isomerizes this intermediate to the silylgermyl radical (H2GeSiH3), which undergoes a hydrogen shift to an exotic, hydrogen‐bridged germylidynesilane intermediate (H3Si(μ‐H)GeH); this species emits molecular hydrogen forming the silylgermylidyne radical (H3SiGe). Our study offers a remarkable glance at the complex reaction dynamics and inherent isomerization processes of the silicon‐germanium system, which are quite distinct from those of the isovalent hydrocarbon system (ethyl radical; C2H5) eventually affording detailed insights into an exotic chemistry and intriguing chemical bonding of silicon‐germanium species at the microscopic level exploiting crossed molecular beams.more » « less
-
Abstract Reactions of the IrVhydride [MeBDIDipp]IrH4{BDI=(Dipp)NC(Me)CH(Me)CN(Dipp); Dipp=2,6‐iPr2C6H3} with E[N(SiMe3)2]2(E=Sn, Pb) afforded the unusual dimeric dimetallotetrylenes ([MeBDIDipp]IrH)2(μ2‐E)2in good yields. Moreover, ([MeBDIDipp]IrH)2(μ2‐Ge)2was formed in situ from thermal decomposition of [MeBDIDipp]Ir(H)2Ge[N(SiMe3)2]2. These reactions are accompanied by liberation of HN(SiMe3)2and H2through the apparent cleavage of an E−N(SiMe3)2bond by Ir−H. In a reversal of this process, ([MeBDIDipp]IrH)2(μ2‐E)2reacted with excess H2to regenerate [MeBDIDipp]IrH4. Varying the concentrations of reactants led to formation of the trimeric ([MeBDIDipp]IrH2)3(μ2‐E)3. The further scope of this synthetic route was investigated with group 15 amides, and ([MeBDIDipp]IrH)2(μ2‐Bi)2was prepared by the reaction of [MeBDIDipp]IrH4with Bi(NMe2)3or Bi(OtBu)3to afford the first example of a “naked” two‐coordinate Bi atom bound exclusively to transition metals. A viable mechanism that accounts for the formation of these products is proposed. Computational investigations of the Ir2E2(E=Sn, Pb) compounds characterized them as open‐shell singlets with confined nonbonding lone pairs at the E centers. In contrast, Ir2Bi2is characterized as having a closed‐shell singlet ground state.more » « less
-
Abstract Although alkyl azides are known to typically form imines under direct irradiation, the product formation mechanism remains ambiguous as some alkyl azides also yield the corresponding triplet alkylnitrenes at cryogenic temperatures. The photoreactivity of 3‐azido‐3‐phenyl‐3H‐isobenzofuran‐1‐one (1) was investigated in solution and in cryogenic matrices. Irradiation (λ = 254 nm) of azide 1 in acetonitrile yielded a mixture of imines 2 and 3. Monitoring of the reaction progress using UV‐Vis absorption spectroscopy revealed an isosbestic point at 210 nm, indicating that the reaction proceeded cleanly. Similar results were observed for the photoreactivity of azide 1 in a frozen 2‐methyltetrahydrofuran (mTHF) matrix. Irradiation of azide 1 in an argon matrix at 6 K resulted in the disappearance of its IR bands with the concurrent appearance of IR bands corresponding to imines 2 and 3. Thus, it was theorized that azide 1 forms imines 2 and 3 via a concerted mechanism from its singlet excited state or through singlet alkylnitrene11N, which does not intersystem cross to its triplet configuration. This proposal was supported by CASPT2 calculations on a model system, which suggested that the energy gap between the singlet and triplet configurations of alkylnitrene 1N is 33 kcal/mol, thus making intersystem crossing inefficient.more » « less
-
Abstract Searching for a connection between the two‐electron redox behavior of Group‐14 elements and their possible use as platforms for the photoreductive elimination of chlorine, we have studied the photochemistry of [(o‐(Ph2P)C6H4)2GeIVCl2]PtIICl2and [(o‐(Ph2P)C6H4)2ClGeIII]PtIIICl3, two newly isolated isomeric complexes. These studies show that, in the presence of a chlorine trap, both isomers convert cleanly into the platinum germyl complex [(o‐(Ph2P)C6H4)2ClGeIII]PtICl with quantum yields of 1.7 % and 3.2 % for the GeIV–PtIIand GeIII–PtIIIisomers, respectively. Conversion of the GeIV–PtIIisomer into the platinum germyl complex is a rare example of a light‐induced transition‐metal/main‐group‐element bond‐forming process. Finally, transient‐absorption‐spectroscopy studies carried out on the GeIII–PtIIIisomer point to a ligand arene–Cl.charge‐transfer complex as an intermediate.more » « less
