Coupling reactions of nitrogen atoms represent elementary steps to many important heterogeneously catalysed reactions, such as the Haber-Bosch process or the selective catalytic reduction of NO(x) to give N(2). For molecular nitrido (and related oxo) complexes, it is well established that the intrinsic reactivity, for example nucleophilicity or electrophilicity of the nitrido (or oxo) ligand, can be attributed to M-N (M-O) ground-state bonding. In recent years, nitrogen (oxygen)-centred radical reactivity was ascribed to the possible redox non-innocence of nitrido (oxo) ligands. However, unequivocal spectroscopic characterization of such transient nitridyl {M=N(•)} (or oxyl {M-O(•)}) complexes remained elusive. Here we describe the synthesis and characterization of the novel, closed-shell and open-shell square-planar iridium nitrido complexes [IrN(L(t-Bu))](+) and [IrN(L(t-Bu))] (L(t-Bu)=N(CHCHP-t-Bu(2))(2)). Spectroscopic characterization and quantum chemical calculations for [IrN(L(t-Bu))] indicate a considerable nitridyl, {Ir=N(•)}, radical character. The clean formation of Ir(I)-N(2) complexes via binuclear coupling is rationalized in terms of nitrido redox non-innocence in [IrN(L(t-Bu))].

Irradiation of rhodium(II) azido complex [Rh(N3){N(CHCHPtBu2)2}] allowed for the spectroscopic characterization of the first reported rhodium complex with a terminal nitrido ligand. DFT computations reveal that the unpaired electron of rhodium(IV) nitride complex [Rh(N){N(CHCHPtBu2)2}] is located in an antibonding Rh-N π* bond involving the nitrido moiety, thus resulting in predominant N-radical character, in turn providing a rationale for its transient nature and observed nitride coupling to dinitrogen.

The redox series [Irn(NHx)(PNP)] (n = II–IV, x = 3–0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps. The experimental and computational results suggest that the IrIII imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective IrII amido and IrIV nitrido species. N–H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E–H bond activation.

An experimental and theoretical study of the base-stabilized disilene 1 is reported, which forms at low temperatures in the disproportionation reaction of Si2 Cl6 or neo-Si5 Cl12 with equimolar amounts of NMe2 Et. Single-crystal X-ray diffraction and quantum-chemical bonding analysis disclose an unprecedented structure in silicon chemistry featuring a dative Si→Si single bond between two silylene moieties, Me2 EtN→SiCl2 →Si(SiCl3 )2 . The central ambiphilic SiCl2 group is linked by dative bonds to the amine donor and the bis(trichlorosilyl)silylene acceptor, which leads to push-pull stabilization. Based on experimental and theoretical examinations a formation mechanism is presented that involves an autocatalytic reaction of the intermediately formed anion Si(SiCl3 )3 (-) with neo-Si5 Cl12 to yield 1.

Squaring the circle: the novel dienamido pincer ligand N(CHCHPtBu(2))(2)(-) affords the isolation of the unusual square-planar iridium(II) and iridium(III) amido complexes [IrCl{N(CHCHPtBu(2))(2)}](n) (n=0 (1), +1 (2)). In contrast, the corresponding iridium(I) complex of the redox series (n=-1) is surprisingly unstable. The diamagnetism of 2 is attributed to strong N→Ir π donation.

and N 2 , and oxidative addition of C-electrophiles, C-H bonds and dioxygen, allowing for the isolation of iridium(I) and iridium(III) (PNP) carbonyl, hydrocarbyl and peroxo complexes which were spectroscopically and crystallographically characterized.

The fixation with fixation: Microorganisms have converted atmospheric nitrogen into ammonia for millions of years under ambient conditions, whereas the Haber–Bosch process requires high pressures and temperatures. Some recent studies on the biological and synthetic generation of ammonia should contribute to a better understanding of the mechanism of this reaction, which remains one of the most challenging goals for catalysis.

Koordinationsverbindungen der Edelmetalle nehmen eine zentrale Stellung in der homogenen Katalyse ein. Die Präfe-renz zur geschlossenschaligen elektronischen Struktur prä-destiniert solche Komplexe zu formalen Zwei-ElektronenRedoxreaktionen (oxidative Addition/reduktive Eliminierung).[1] Die Bedeutung von Ein-Elektronen-Reaktionen der Platinmetalle, z. B. bei radikalischen H 2 -, C-H-und C-C-Aktivierungen oder bei katalytischen Oxidationen, wurde bereits demonstriert, [2][3][4][5] dennoch sind voll charakterisierte Metalloradikale noch immer selten.[ [8]Ebenso sind Platinmetallkomplexe mit gerader Valenzelektronenzahl und elektronischer High-Spin-Konfiguration wegen der generell hçheren Ligandenfeldaufspaltung der 4d/ 5d-Metallionen als bei 3d-Metallen sehr selten. Eine Ausnahme bilden quadratisch-planare d 6 -Disilylamidokomplexe vom Typ [MX (L 5 )] (M = Ru, Os; X = F, Cl, I, Trifluormethansulfonat (OTf); L 5 = N(SiMe 2 CH 2 PtBu 2 ) 2 ), die in Analogie zu Eisen(II) eine elektronische Intermediate-SpinKonfiguration aufweisen. [9,10] [Ir(H)Cl(C 8 H 13 )(HL 1 )] (3; R = tBu) [13] wird in situ mit Benzochinon (2.5 ¾quiv.) zum türkisfarbenen 1 in Ausbeuten an isoliertem Produkt von bis zu 60 % oxidiert (Schema 2). [14] Im 31 P-NMR-Spektrum von 1 werden keine Signale beobachtet. Die drei breiten Signale im 1 H-NMR-Spektrum sind stark paramagnetisch verschoben und kçnnen den tBu-Substituenten (d = 10.5 ppm) und je einem Satz von Ligand-