Premium
Reactions of Rhenium and Technetium Nitrido Complexes with ER 3 Fragments (E = B, Ga, Al, C, P; R = H, Alkyl, Aryl)
Author(s) -
Abram Ulrich,
SchmidtBrücken Burkhard,
Hagenbach Adelheid,
Hecht Maren,
Kirmse Reinhard,
Voigt Andreas
Publication year - 2003
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200390145
Subject(s) - rhenium , chemistry , adduct , nucleophile , electrophile , reactivity (psychology) , lewis acids and bases , medicinal chemistry , aryl , alkyl , stereochemistry , metal , inorganic chemistry , organic chemistry , catalysis , alternative medicine , pathology , medicine
Abstract Terminal ‘N 3— ’ ligands in rhenium and technetium nitrido complexes are sufficiently nucleophilic to react with Lewis acids under formation of nitrido‐bridged compounds. The reactivity of the nucleophilic centre and the nature of the formed compounds are strongly dependent on the Lewis acid and the composition of the metal complex used. Air‐stable compounds with Re≡N‐ER 3 bridges are formed when ER 3 is BR 3 (R = H, Cl, Br, Ethyl, Phenyl, C 6 F 5 ), BCl 2 Ph, GaCl 3 , CPh 3 + , or PPh 3 . The six‐co‐ordinate rhenium(V) complexes [ReNX 2 (PMe 2 Ph) 3 ] (X = Cl, Br), [ReN(X)(Et 2 dtc)(PMe 2 Ph) 2 ] (Et 2 dtc — = diethyldithiocarbamate) and [ReN(Et 2 dtc) 2 (PMe 2 Ph)] have been proved to be excellent starting materials for this type of reactions, whereas the five‐co‐ordinate precursors [ReNCl 2 (PPh 3 ) 2 ], [ReN(Et 2 dtc) 2 ], [ReN{Ph 2 P(S)NP(S)Ph 2 } 2 ] or [ReNCl 4 ] — only react with the most reactive Lewis bases of the examples mentioned above such as BCl 2 Ph or B(C 6 F 5 ) 3 . The rhenium‐nitrido bond lengths remain almost unchanged by the adduct formation, whereas a significant decrease of the trans ‐influence of the nitrido complexes has been observed as can be seen by a shortening of the corresponding bond lengths or dimerization of five‐co‐ordinate precursors. Electrophilic attack of the Lewis acid to a donor atom of the equatorial co‐ordination sphere of the rhenium complex results in the formation of ‘underco‐ordinate’ metal centres which resemble to di‐, tri or tetrameric units with asymmetric nitrido bridges between each two rhenium atoms. EPR spectroscopy is an excellent tool to reflect the formation of nitrido bridges at the paramagnetic (d 1 ) [ReNX 4 ] — core (X = F, Cl, Br, NCS). The spectral parameters derived for the products of reactions of [ReNCl 4 ] — with various boron compounds indicate an increase of the covalency of the equatorial Re‐L bonds as a consequence of the formation of a nitrido bridge. The tendency for the formation of nitrido bridges with Lewis acids is significantly lower for technetium compounds compared to their rhenium analogues. Only a few examples with BH 3 and BPhCl 2 have been established.