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A Decade of Dinuclear Technetium Complexes with Multiple Metal–Metal Bonds
Author(s) -
Poineau Frederic,
Forster Paul M.,
Todorova Tanya K.,
Johnstone Erik V.,
Kerlin William M.,
Gagliardi Laura,
Czerwinski Kenneth R.,
Sattelberger Alfred P.
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201402340
Subject(s) - chemistry , metal , bond order , crystallography , transition metal , electronic structure , technetium , bond length , computational chemistry , crystal structure , catalysis , organic chemistry , nuclear chemistry
Transition metal complexes with multiple metal–metal bonds exhibit interesting catalytic and biological properties. One element whose metal–metal bond chemistry has been poorly studied is technetium. Currently, only 25 technetium complexes with multiple metal–metal bonds have been structurally characterized. The nature of metal–metal interactions in these complexes, as well as the influence of ligands on the bonding in the Tc 2 n + unit ( n = 6, 5, 4) are not well understood. In order to better understand the influence of ligands on the Tc–Tc bonding, a study of the solid‐state and electronic structure of dinuclear complexes with the Tc 2 n + unit ( n = 6, 5, 4) has been performed. Dinuclear technetium complexes ( n Bu 4 N) 2 Tc 2 X 8 , Tc 2 (O 2 CCH 3 ) 4 X 2 , Tc 2 (O 2 CCH 3 ) 2 Cl 4 , cesium salts of Tc 2 X 8 3– , and Tc 2 X 4 (PMe 3 ) 4 (X = Cl, Br) were synthesized; their molecular and electronic structures, as well as their electronic absorption spectra, were studied by a number of physical and computational techniques. The structure and bonding in these systems have been investigated by using multiconfigurational quantum calculations. For all these complexes, the calculated geometries are in very good agreement with those determined experimentally. Bond order analysis demonstrates that all these complexes exhibit a total bond order of approximately 3. Analysis of individual effective bond order (EBO) components shows that these complexes have similar σ components, while the strength of their π components follows the order Tc 2 X 4 (PMe 3 ) 4 > Tc 2 X 8 3– > Tc 2 (O 2 CCH 3 ) 2 Cl 4 > Tc 2 X 8 2– . Calculations indicate that the δ components are the weakest bond in Tc 2 X 8 n – ( n = 2, 3) and Tc 2 (O 2 CCH 3 ) 2 Cl 4 . Further analysis of Tc 2 X 8 3– and Tc 2 X 4 (PMe 3 ) 4 (X = Cl, Br) indicates that the electronic structure of the Tc 2 5+ and Tc 2 4+ units is insensitive to the nature of the coordinating ligands. The electronic absorption spectra of Tc 2 X 8 n – ( n = 2, 3), Tc 2 (O 2 CCH 3 ) 2 Cl 4 , and Tc 2 X 4 (PMe 3 ) 4 (X = Cl, Br) were studied in solution, and assignment of the transitions was performed by multiconfigurational quantum chemical calculations. For the Tc 2 X 8 n – ( n = 2, 3; X = Cl, Br) anions and Tc 2 (O 2 CCH 3 ) 2 Cl 4 , the lowest‐energy band is attributed to the δ→δ* transition. For Tc 2 X 4 (PMe 3 ) 4 , the assignment of the transitions follow the following order in energy: δ*→σ* < δ*→π* < δ→σ* < δ→π*.