A Disilene Base Adduct with a Dative Si-Si Single Bond.

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.

Homolytic N-H activation of ammonia: hydrogen transfer of parent iridium ammine, amide, imide, and nitride species.

The redox series [Ir(n)(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 Ir(III) imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective Ir(II) amido and Ir(IV) 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.

[IrCl{N(CHCHPtBu2)2}]-: a versatile source of the Ir(I)(PNP) pincer platform.

The iridium(II) complex [IrCl{N(CHCHPtBu2)2}] is reduced by KC8 to give the anionic iridium(I) pincer complex [IrCl{N(CHCHPtBu2)2}](-) which was isolated and fully characterized upon stabilization of the counter cation with crown ether as [K(15-cr-5)2][IrCl{N(CHCHPtBu2)2}]. This unprecedented anionic iridium(I) pincer complex completes the unusual, structurally characterized Ir(I)/Ir(II)/Ir(III) redox series [IrCl{N(CHCHPtBu2)2}](-/0/+), all in a square-planar coordination geometry, emphasizing the versatility of this PNP pincer ligand in stabilizing a broad range of oxidation states. The anionic chloro complex is a versatile source of the Ir(PNP) platform. Its reactivity was examined towards chloride ligand substitution against CO and N2, 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.

Synthesis and reactivity of a transient, terminal nitrido complex of rhodium.

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.

Closed-shell and open-shell square-planar iridium nitrido complexes.

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))].

Square-planar iridium(II) and iridium(III) amido complexes stabilized by a PNP pincer ligand.

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.