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The use of a bis(diphenyl)phosphine functionalized β-diketiminato ligand, [HC{(CH3 )C}2 {(ortho-[P(C6 H5 )2 ]2 C6 H4 )N}2 ]- (PNac), as a support for germanium(II) and tin(II) chloride and phosphaketene compounds, is described. The conformational flexibility and hemilability of this unique ligand provide a versatile coordination environment that can accommodate the electronic needs of the ligated elements. For example, chloride abstraction from [(PNac)ECl] (E=Ge, Sn) affords the cationic germyliumylidene and stannyliumylidene species [(PNac)E]+ in which the pendant phosphine arms associate more strongly with the Lewis acidic main group element centers, providing further electronic stabilization. In a similar fashion, chemical decarbonylation of the germanium phosphaketene [(PNac)Ge(PCO)] with tris(pentafluorophenyl)borane affords a "push-pull" stabilized phosphinidene in which one of the phosphine groups of the ligand backbone associates with the low valent phosphinidene center.

Reaction of a nucleophilic germylene Ge[CH(SiMe3)2]2 with the phosphanyl phosphaketene [{(H2C)(NDipp)}2P]PCO induces decarbonylation to form a phosphanyl phosphagermene [{(H2C)(NDipp)}2P]P=Ge[CH(SiMe3)2]2 (1; Dipp=2,6‐diisopropyl‐phenyl). Addition of CO2 or MeCN to 1 results in [3+2]‐cycloaddition reactions to afford five‐membered heterocycles. This mode of reactivity is reminiscent of that observed for frustrated Lewis pairs, with the pendant phosphanyl group acting as a base and the germanium center as a Lewis acid. Contrastingly, 1,2‐addition across the P=Ge bond was observed when using ammonia, small primary amines (NH2nP), or metal complexes (e. g. Au(PPh3)Cl and ZnEt2). These latter reactions allow for the one‐step synthesis of metal phosphide complexes. [ABSTRACT FROM AUTHOR]

We describe two contrasting transmetallation reactions between the gold(I) cyaphide complex, Au(IDipp)(CP) (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), and low oxidation state main-group and transition-metal complexes. The reactivity observed highlights the pseudo-halide character of the cyaphide ion. [ABSTRACT FROM AUTHOR]

We describe our efforts to access a compound with an Al=P double bond by reaction of Al(Nacnac) towards [H2CN(Dipp)]2P(PCO) (Nacnac=HC[C(Me)N(Dipp)]2; Dipp=2,6‐iPr2C6H3). Our observations are consistent with the formation of a transient phosphanyl‐phosphaalumene at low temperatures (−70 °C), however this species was found to readily undergo intramolecular C−H activation of the β‐diketiminato ligand upon warming to room temperature. The reactivity of the transient complex toward small molecules including dihydrogen, carbon dioxide, phosphaketenes, amines and silanes could be explored at low temperatures, showcasing that the target compound can react as both a frustrated Lewis pair (via the pendant phosphanyl moiety) or in hydroelementation reactions of the Al=P bond. The elusive target molecule could be trapped by addition of a Lewis base (tetrahydrofuran) affording an isolable molecular species that reacts in an analogous fashion to the base‐free compound. [ABSTRACT FROM AUTHOR]

The electronic properties, coordination chemistry and reactivity of metal complexes of a planar (C2v symmetric) acridane‐derived geometrically constrained phosphine, P(NNN), are described. On complexation to metal centers, the phosphine was found to adopt a distorted trigonal pyramidal structure with a high barrier to pyramidal inversion (22.3 kcal/mol at 298 K for Au[P(NNN)]Cl). Spectroscopic data and theoretical calculations carried out at the density functional level of theory indicate that P(NNN) is a moderate σ‐donor, with significant π‐acceptor properties. Despite the distortion undergone by the phosphorus atom on coordination to metal centers, the P(NNN) ligand retains its ability to react with small molecule substrates with polar E−H bonds (MeOH, NH2Ph, NH3). It does so in a concerted fashion across one of the P−N bonds, and reversibly in the case of amine substrates. This cooperative bond activation chemistry may ultimately prove beneficial in catalysis. [ABSTRACT FROM AUTHOR]

The factors governing 1,3‐dipolar cycloaddition reactions involving C≡P‐containing compounds are computationally explored in detail using quantum chemical tools. To this end, the parent process involving tBuN3 and tBuCP is analyzed and compared to the analogous reaction involving organometallic cyaphide complexes (metal=Au, Pt, Ge, Mg), in order to understand the role of the metal fragment in such transformations. It is found that while the metal fragment does not significantly influence the aromaticity of the corresponding concerted transition states or the regioselectivity of the transformation, it may modify the reactivity of the cyaphide complexes (i. e. Ge and Mg cyaphide complexes are comparatively more reactive). The computed reactivity trends and the factors behind the regioselectivity of the cycloaddition reaction are quantitatively analyzed with the help of the activation strain model in combination with the energy decomposition analysis method. [ABSTRACT FROM AUTHOR]

The reactivity of aluminium compounds is dominated by their electron deficiency and consequent electrophilicity; these compounds are archetypal Lewis acids (electron-pair acceptors). The main industrial roles of aluminium, and classical methods of synthesizing aluminium-element bonds (for example, hydroalumination and metathesis), draw on the electron deficiency of species of the type AlR.sub.3 and AlCl.sub.3.sup.1,2. Whereas aluminates, [AlR.sub.4].sup.-, are well known, the idea of reversing polarity and using an aluminium reagent as the nucleophilic partner in bond-forming substitution reactions is unprecedented, owing to the fact that low-valent aluminium anions analogous to nitrogen-, carbon- and boron-centred reagents of the types [NX.sub.2].sup.-, [CX.sub.3].sup.- and [BX.sub.2].sup.- are unknown.sup.3-5. Aluminium compounds in the +1 oxidation state are known, but are thermodynamically unstable with respect to disproportionation. Compounds of this type are typically oligomeric.sup.6-8, although monomeric systems that possess a metal-centred lone pair, such as Al(Nacnac).sup.Dipp (where (Nacnac).sup.Dipp = (NDippCR).sub.2CH and R = .sup.tBu, Me; Dipp = 2,6-.sup.iPr.sub.2C.sub.6H.sub.3), have also been reported.sup.9,10. Coordination of these species, and also of ([eta].sup.5-C.sub.5Me.sub.5)Al, to a range of Lewis acids has been observed.sup.11-13, but their primary mode of reactivity involves facile oxidative addition to generate Al(iii) species.sup.6-8,14-16. Here we report the synthesis, structure and reaction chemistry of an anionic aluminium(i) nucleophile, the dimethylxanthene-stabilized potassium aluminyl [K{Al(NON)}].sub.2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene). This species displays unprecedented reactivity in the formation of aluminium-element covalent bonds and in the C-H oxidative addition of benzene, suggesting that it could find further use in both metal-carbon and metal-metal bond-forming reactions.An aluminium compound is synthesized in which the aluminium is formally anionic; reactions with various substrates suggest that this compound acts as the nucleophilic partner in both metal-carbon and metal-metal bond-forming reactions., Author(s): Jamie Hicks [sup.1] , Petra Vasko [sup.1] [sup.2] , Jose M. Goicoechea [sup.1] , Simon Aldridge [sup.1] Author Affiliations:(1) Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, [...]

Reaction of the tris‐hypersilyl nonagermanide Zintl cluster salt, K[Ge9(Hyp)3] (Hyp=Si(SiMe3)3) with [Rh(η2,η2‐L)Cl]2 (L=1,5‐cyclooctadiene, COD; norbornadiene, NBD) afforded eleven‐ and twelve‐vertex homo‐multimetallic clusters by cluster core expansion. Using a stepwise procedure, starting from the Zintl cluster [Rh(COD){Ge9(Hyp)3}] and [Ir(COD)Cl]2, this methodology was expanded for the synthesis of eleven‐vertex hetero‐multimetallic clusters. A mechanism for the formation of these first examples of closo eleven‐vertex Zintl clusters is proposed, informed by density functional theory calculations. [ABSTRACT FROM AUTHOR]

We review the known chemistry of the cyaphide ion, (C≡P)−. This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini‐review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well‐established salt‐metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation. [ABSTRACT FROM AUTHOR]

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The steric tuning of a tridentate acridane‐derived NNN pincer ligand allows for the isolation of a strictly T‐shaped phosphine that exhibits ambiphilic reactivity. Well‐defined phosphorus‐centered reactivity towards nucleophiles and electrophiles is reported, contrasting with prior reports on this class of compounds. Reactions towards oxidants are also described. The latter result in the two‐electron oxidation of the phosphorus atom from +III to +V and are accompanied by a strong geometric distortion of the NNN pincer ligand. By contrast, cooperative activation of E−H (HCl, HBcat, HOMe) bonds proceeds with retention of the phosphorus redox state. When using H2O as a substrate, the reaction results in the full disassembly of H2O to its constituent atoms, highlighting the potential of this platform for small molecule activation reactions. [ABSTRACT FROM AUTHOR]

The reactions of a terminal aluminium imide with a range of oxygen‐containing substrates have been probed with a view to developing its use as a novel main group transfer agent for the [NR]2− fragment. We demonstrate transfer of the imide moiety to [N2], [CO] and [Ph(H)C] units driven thermodynamically by Al−O bond formation. N2O reacts rapidly to generate the organoazide DippN3 (Dipp=2,6‐iPr2C6H3), while CO2 (under dilute reaction conditions) yields the corresponding isocyanate, DippNCO. Mechanistic studies, using both experimental and quantum chemical techniques, identify a carbamate complex K2[(NON)Al‐{κ2−(N,O)−N(Dipp)CO2}]2 (formed via [2+2] cycloaddition) as an intermediate in the formation of DippNCO, and also in an alternative reaction leading to the generation of the amino−dicarboxylate complex K2[(NON)Al{κ2−(O,O′)−(O2C)2N‐(Dipp)}] (via the take‐up of a second equivalent of CO2). In the case of benzaldehyde, a similar [2+2] cycloaddition process generates the metallacyclic hemi‐aminal complex, Kn[(NON)Al{κ2−(N,O)−(N(Dipp)C(Ph)(H)O}]n. Extrusion of the imine, PhC(H)NDipp, via cyclo‐reversion is disfavoured thermally, due to the high energy of the putative aluminium oxide co‐product, K2[(NON)Al(O)]2. However, addition of CO2 allows the imine to be released, driven by the formation of the thermodynamically more stable aluminium carbonate co‐product, K2[(NON)Al(κ2−(O,O′)−CO3)]2. [ABSTRACT FROM AUTHOR]

Two lithium phospha‐enolates [RP=C(SiiPr3)OLi]2 were prepared by reaction of triisopropyl silyl phosphaethynolate, iPr3SiPCO, with aryl lithium reagents LiR (R=Mes: 1,3,5‐trimethyl phenyl; or Mes*: 1,3,5,‐tri‐tertbutyl phenyl). Monomer/dimer aggregation of the enolates can be modulated by addition of 12‐crown‐4. Substitution of lithium for a heavier alkali metal was achieved through initial formation of a silyl enol ether, followed by reaction with KOtBu to form the corresponding potassium phospha‐enolate [MesP=C(SiiPr3)OK]2. On addition of water, the enolates are protonated to afford RP=C(SiiPr3)(OH). For the sterically less demanding system (R=Mes), this phospha‐enol rapidly tautomerises to the corresponding acyl phosphine MesP(H)C(SiiPr3)(O), which on heating extrudes CO. In contrast, bulkier phospha‐enol (R=Mes*) is stable to rearrangement at room temperature and thermally decomposes to RH and iPr3SiPCO. [ABSTRACT FROM AUTHOR]

The reaction of TaMe3Cl2 with the rigid acridane‐derived trisamine H3NNN yields the tantalum(V) complex [TaCl2(NNNcat)]. Subsequent reaction with dioxygen results in the full four‐electron reduction of O2 yielding the oxido‐bridged bimetallic complex [{TaCl2(NNNsq)}2O]. This dinuclear complex features an open‐shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X‐ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O2 activation was investigated by DFT calculations revealing initial binding of O2 to the tantalum(V) center followed by complete O2 scission to produce a terminal oxido‐complex. [ABSTRACT FROM AUTHOR]