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The Importance of Dihydrogen Complexes H n Ge(H 2 ) + ( n =0,1) to the Chemistry of Cationic Germanium Hydrides: Advanced Theoretical and Mass Spectrometric Analysis
Author(s) -
Jackson Phillip,
Sändig Nadja,
Diefenbach Martin,
Schröder Detlef,
Schwarz Helmut,
Srinivas Ragampeta
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010105)7:1<151::aid-chem151>3.0.co;2-d
Subject(s) - metastability , chemistry , dissociation (chemistry) , germanium , multireference configuration interaction , ion , diatomic molecule , atomic physics , avoided crossing , bond dissociation energy , molecule , computational chemistry , density functional theory , physics , excited state , basis set , organic chemistry , silicon
Investigations of [Ge,H n ] −/0/+ ( n =2,3) have been performed using a four‐sector mass spectrometer. The results reveal that the complexes H n Ge(H 2 ) + ( n =0,1) play an important role in the unimolecular dissociation of the metastable cations. Theoretical calculations support the experimental observations in most instances, and the established view that the global minimum of [Ge,H 2 ] + is an inserted structure may need reexamination; CCSD(T,full)/cc‐pVTZ//CCSD(T)/6‐311++G(d,p) and B3LYP/cc‐pVTZ studies of three low‐lying cation states ( 2 A 1 HGeH + , 2 B 2 Ge(H 2 ) + and 2 B 1 Ge(H 2 ) + ) indicate a very small energy difference (ca. 4 kcal mol −1 ) between 2 A 1 HGeH + and 2 B 2 Ge(H 2 ) + ; B3LYP favours the ion–molecule complex, whereas coupled‐cluster calculations favour the inserted structure for the global minimum. Single‐point multireference (MR) averaged coupled‐pair functional and MR‐configuration interaction calculations give conflicting results regarding the global minimum. We also present theoretical evidence indicating that the orbital‐crossing point implicated in the spin‐allowed metastable dissociation HGeH + *→Ge(H 2 ) + *→Ge + +H 2 lies above the H‐loss asymptote. Thus, a quantum‐mechanical tunneling mechanism is invoked to explain the preponderance of the H 2 ‐loss signal for the metastable ion.