That the inert dinitrogen molecule can act as a ligand to a transition metal complex is one of the key discoveries in inorganic chemistry of the past century. This feature article summarises a body of work up to 2010 that describes a particularly attractive route to dinitrogen complexes that involves the direct reaction of N(2) with metal hydride derivatives. This process is shown to be general across the transition series and, depending on the metal, different levels of activation of the coordinated dinitrogen unit are observed.
Copycat: An accurate synthetic model for Rieske type [2Fe‐2S] cluster has been prepared that emulates structural and spectroscopic features of the natural protein sites, including the characteristic low gav value in the EPR spectra of the reduced [2Fe‐2S]+ species. The picture shows the crystal structure of the molecule (C gray, Fe red, N blue, S yellow), its EPR spectrum after reduction (bottom) and its Mössbauer spectrum (top).
The
previously elusive diphosphadibenzo[a,e]pentalene core skeleton was assembled via a surprisingly
straightforward cyclization pathway starting from R2P-substituted
2,2′-diphosphinotolanes
(R = Ph,
i
Pr). The resulting P-protected
diylidic compounds 4 (R = Ph,
i
Pr) were converted to the corresponding P-bridged ladder stilbenes
via two consecutive oxidation steps: upon selective one-electron oxidation,
the persistent radical monocations 5 (R = Ph,
i
Pr) were obtained and further oxidized to afford
the respective fluorescent and air-stable dications 6 (R = Ph,
i
Pr).
A series of synthetic [2Fe-2S] complexes with terminal thiophenolate ligands and tethered ether or thioether moieties has been prepared and investigated in order to provide models for the potential interaction of additional donor atoms with the Fe atoms in biological [2Fe-2S] clusters. X-ray crystal structures have been determined for six new complexes that feature appended Et (1(C)), OMe (1(O)), or SMe (1(S)) groups, or with a methylene group (2(C) ), an ether-O (2(O)), or an thioether-S (2(S)) linking two aryl groups. The latter two systems provide a constrained chelate arrangement that induces secondary bonding interactions with the ether-O and thioether-S, which is confirmed by density functional theory (DFT) calculations that also reveal significant spin density on those fifth donor atoms. Structural consequences of the secondary bonding interactions are analyzed in detail, and effects on the spectroscopic and electronic properties are probed by UV-vis, Mössbauer, and (1)H NMR spectroscopy, as well by SQUID measurements and cyclic voltammetry. The potential relevance of the findings for biological [2Fe-2S] sites is considered.
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