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Homoleptic Diphosphacyclobutadiene Complexes [M(η 4 ‐P 2 C 2 R 2 ) 2 ] x − (M=Fe, Co; x =0, 1)
Author(s) -
Wolf Robert,
Ehlers Andreas W.,
Khusniyarov Marat M.,
Hartl František,
de Bruin Bas,
Long Gary J.,
Grandjean Fernande,
Schappacher Falko M.,
Pöttgen Rainer,
Slootweg J. Chris,
Lutz Martin,
Spek Anthony L.,
Lammertsma Koop
Publication year - 2010
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/chem.201001913
Subject(s) - homoleptic , chemistry , crystallography , metal , electron paramagnetic resonance , cyclic voltammetry , electrochemistry , stereochemistry , analytical chemistry (journal) , nuclear magnetic resonance , physics , organic chemistry , electrode , chromatography
The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands are reported. Compounds [K([18]crown‐6)(thf) 2 ][Fe(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] (K 1 ), [K([18]crown‐6)(thf) 2 ][Co(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] (K 2 ), and [K([18]crown‐6)(thf) 2 ][Co(η 4 ‐P 2 C 2 Ad 2 ) 2 ] (K 3 , Ad=adamantyl) were obtained from reactions of [K([18]crown‐6)(thf) 2 ][M(η 4 ‐C 14 H 10 ) 2 ] (M=Fe, Co) with t BuCP ( 1 , 2 ), or with AdCP ( 3 ). Neutral sandwiches [M(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] ( 4 : M=Fe 5 : M=Co) were obtained by oxidizing 1 and 2 with [Cp 2 Fe]PF 6 . Cyclic voltammetry and spectro‐electrochemistry indicate that the two [M(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] − /[M(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] moieties can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1 – 5 were characterized by multinuclear NMR, EPR ( 1 and 5 ), UV/Vis, and Mössbauer spectroscopies ( 1 and 4 ), mass spectrometry ( 4 and 5 ), and microanalysis ( 1 – 3 ). The molecular structures of 1 – 5 were determined by using X‐ray crystallography. Essentially D 2 d ‐symmetric structures were found for all five complexes, which show the two 1,3‐diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal–ligand π bonding in 1 – 5 . Possible oxidation state assignments for the metal ions are discussed.