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[Ni(IMes)2] reacts with chloroboranes via oxidative addition to form rare unsupported Ni-boryls. In contrast, the oxidative addition of hydridoboranes is not observed and products from competing reaction pathways are identified. Computational studies relate these differences to the mechanism of oxidative addition: B–Cl activation proceeds via nucleophilic displacement of Cl−, while B–H activation would entail high energy concerted bond cleavage. [ABSTRACT FROM AUTHOR]

The use of a sterically demanding pincer ligand to prepare an unusual square planar aluminium complex is reported. Due to the constrained geometry imposed by the ligand scaffold, this four-coordinate aluminium centre remains Lewis acidic and reacts via differing metal-ligand cooperative pathways for activating ketones and CO2. It is also a rare example of a single-component aluminium system for the catalytic reduction of CO2 to a methanol equivalent at room temperature. [ABSTRACT FROM AUTHOR]

The complexes Ag(L)n[WCA] (L=P4S3, P4Se3, As4S3, and As4S4; [WCA]=[Al(ORF)4]− and [F{Al(ORF)3}2]−; RF=C(CF3)3; WCA=weakly coordinating anion) were tested for their performance as ligand‐transfer reagents to transfer the poorly soluble nortricyclane cages P4S3, P4Se3, and As4S3 as well as realgar As4S4 to different transition‐metal fragments. As4S4 and As4S3 with the poorest solubility did not yield complexes. However, the more soluble silver‐coordinated P4S3 and P4Se3 cages were transferred to the electron‐poor Fp+ moiety ([CpFe(CO)2]+). Thus, reaction of the silver salt in the presence of the ligand with Fp−Br yielded [Fp−P4S3][Al(ORF)4] (1 a), [Fp−P4S3][F(Al(ORF)3)2] (1 b), and [Fp−P4Se3][Al(ORF)4] (2). Reactions with P4S3 also yielded [FpPPh3−P4S3][Al(ORF)4] (3), a complex with the more electron‐rich monophosphine‐substituted Fp+ analogue [FpPPh3]+ ([CpFe(PPh3)(CO)]+). All complex salts were characterized by single‐crystal XRD, NMR, Raman, and IR spectroscopy. Interestingly, they show characteristic blueshifts of the vibrational modes of the cage, as well as structural contractions of the cages upon coordination to the Fp/FpPPh3 moieties, which oppose the typically observed cage expansions that lead to redshifts in the spectra. Structure, bonding, and thermodynamics were investigated by DFT calculations, which support the observed cage contractions. Its reason is assigned to σ and π donation from the slightly P−P and P−E antibonding P4E3‐cage HOMO (e symmetry) to the metal acceptor fragment. [ABSTRACT FROM AUTHOR]

Upon coordinating P4 to electron poor cyclopentadienyl‐iron cations, the average P−P bond distances shrink and the respective P4 breathing mode in the Raman spectra (600 cm−1, P4, free) is blueshifted by >40 cm−1 in [CpFe(CO)(L)(η1‐P4)]+ cations (L=CO or PPh3). Analysis suggests that this corresponds to an umpolung of the bonding from more phosphidic in the known, electron‐rich systems to more phosphonium‐like in the reported electron‐poor versions. This may open new functionalization pathways for white phosphorus P4. [ABSTRACT FROM AUTHOR]

The ruthenium–zinc heterobimetallic complexes, [Ru(IPr)2(CO)ZnMe][BArF4] (7), [Ru(IBiox6)2(CO)(THF)ZnMe][BArF4] (12) and [Ru(IMes)′(PPh3)(CO)ZnMe] (15), have been prepared by reaction of ZnMe2 with the ruthenium N-heterocyclic carbene complexes [Ru(IPr)2(CO)H][BArF4] (1), [Ru(IBiox6)2(CO)(THF)H][BArF4] (11) and [Ru(IMes)(PPh3)(CO)HCl] respectively. 7 shows clean reactivity towards H2, yielding [Ru(IPr)2(CO)(η2-H2)(H)2ZnMe][BArF4] (8), which undergoes loss of the coordinated dihydrogen ligand upon application of vacuum to form [Ru(IPr)2(CO)(H)2ZnMe][BArF4] (9). In contrast, addition of H2 to 12 gave only a mixture of products. The tetramethyl IBiox complex [Ru(IBioxMe4)2(CO)(THF)H][BArF4] (14) failed to give any isolable Ru–Zn containing species upon reaction with ZnMe2. The cyclometallated NHC complex [Ru(IMes)′(PPh3)(CO)ZnMe] (15) added H2 across the Ru–Zn bond both in solution and in the solid-state to afford [Ru(IMes)′(PPh3)(CO)(H)2ZnMe] (17), with retention of the cyclometallation. [ABSTRACT FROM AUTHOR]

The extreme electron withdrawing properties of the perfluoropyridinoxy ligand –OC5F4N were used for the preparation of new (weakly) coordinating borate and aluminate anions of the type [E(OC5F4N)4]– (E = B or Al). These new anions are based on the potent parent Lewis acids E(OC5F4N)3, which possess exceptionally high calculated fluoride ion affinities (FIAs) of 500 and 587 kJ mol–1 for E = B and Al respectively. For aluminum, this extreme Lewis acidity dominates the chemistry and from mixtures of the neutral polymeric Lewis acid [Al(OC5F4N)3]n, the five‐ and six‐coordinate complexes Al(OC5F4N)3(OEt2)2 (1) and [Al(OC5F4N)2(µ‐OC5F4N) (NCMe)2]2 (2) were crystallized upon addition of ether or MeCN. The aluminate salts M[Al(OC5F4N)4] (M = Li or K) were prepared from the reaction between the alcohol 4‐HO–C5F4N and either LiAlH4 or K[AlEt4] respectively. The aluminate anion [Al(OC5F4N)4]– remains Lewis acidic coordinating small donor molecules forming [Al(OC5F4N)4(L)]– (L = THF or NMe3) and even supports formation and structural characterisation of the aluminum dianion containing salt [Na(OEt2)2][Na][Al(OC5F4N)5] (8). The from NaBH4 and 4‐HO–C5F4N accessible borate salt Na[B(OC5F4N)4] shows increased kinetic stability in comparison to the aluminum analogue. Very electron withdrawing ...! Perfluoropyridinoxy ligands (–OC5F4N) possess extreme electron withdrawing properties that have been used to prepare (weakly) coordinating anions based on the Lewis superacids E(OC5F4N)3 (E = B or Al). The –OC5F4N ligand supports formation of neutral 5‐ and six‐coordinate aluminum species, a Lewis acidic aluminate anion, and even an aluminum dianion! [ABSTRACT FROM AUTHOR]

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This Review gives a comprehensive overview of the most topical weakly coordinating anions (WCAs) and contains information on WCA design, stability, and applications. As an update to the 2004 review, developments in common classes of WCA are included. Methods for the incorporation of WCAs into a given system are discussed and advice given on how to best choose a method for the introduction of a particular WCA. A series of starting materials for a large number of WCA precursors and references are tabulated as a useful resource when looking for procedures to prepare WCAs. Furthermore, a collection of scales that allow the performance of a WCA, or its underlying Lewis acid, to be judged is collated with some advice on how to use them. The examples chosen to illustrate WCA developments are taken from a broad selection of topics where WCAs play a role. In addition a section focusing on transition metal and catalysis applications as well as supporting electrolytes is also included. Leave me alone! Cations that (almost) do not interact with their counterion can be prepared by combining them with the right weakly coordinating anion (WCA). A selection of suitable WCAs, their most useful starting materials, pathways to introduce a WCA into a fundamental or applied system, and an overview of current WCA applications are described in this Review. [ABSTRACT FROM AUTHOR]

Abstract: The hydride complex [Ru(IPr)2(CO)H][BArF4], 1, reacts with InMe3 with loss of CH4 to form [Ru(IPr)2(CO)(InMe)(Me)][BArF4], 4, featuring an unsupported Ru−In bond with unsaturated Ru and In centres. 4 reacts with H2 to give [Ru(IPr)2(CO)(η2‐H2)(InMe)(H)][BArF4], 5, while CO induces formation of the indyl complex [Ru(IPr)2(CO)3(InMe2)][BArF4], 7. These observations highlight the ability of Me to shuttle between Ru and In centres and are supported by DFT calculations on the mechanism of formation of 4 and its reactions with H2 and CO. An analysis of Ru‐In bonding in these species is also presented. Reaction of 1 with GaMe3 also involves CH4 loss but, in contrast to its In congener, sees IPr transfer from Ru to Ga to give a gallyl complex featuring an η6 interaction of one aryl substituent with Ru. [ABSTRACT FROM AUTHOR]

The room temperature reaction of C6F6 or C6F5H with [Ru(IEt2Me2)2(PPh3)2H2] (1; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) generated a mixture of the trans-hydride fluoride complex [Ru(IEt2Me2)2(PPh3)2HF] (2) and the bis-carbene pentafluorophenyl species [Ru(IEt2Me2)2(PPh3)(C6F5)H] (3). The formation of 3 resulted from C–H activation of C6F5H (formed from C6F6via stoichiometric hydrodefluorination), a process which could be reversed by working under 4 atm H2. Upon heating 1 with C6F5H, the bis-phosphine derivative [Ru(IEt2Me2)(PPh3)2(C6F5)H] (4) was isolated. A more efficient route to 2 involved treatment of 1 with 0.33 eq. of TREAT-HF (Et3N·3HF); excess reagent gave instead the [H2F3]− salt (5) of the known cation [Ru(IEt2Me2)2(PPh3)2H]+. Under catalytic conditions, 1 proved to be an active precursor for hydrodefluorination, converting C6F6 to a mixture of tri, di and monofluorobenzenes (TON = 37) at 363 K with 10 mol% 1 and Et3SiH as the reductant. [ABSTRACT FROM AUTHOR]

The mononuclear N-heterocyclic carbene (NHC) copper alkoxide complexes [(6-NHC)CuO tBu] (6-NHC=6-MesDAC ( 1), 6-Mes ( 2)) have been prepared by addition of the free carbenes to the tetrameric tert-butoxide precursor [Cu(O tBu)]4, or by protonolysis of [(6-NHC)CuMes] (6-NHC=6-MesDAC ( 3), 6-Mes ( 4)) with tBuOH. In contrast to the relatively stable diaminocarbene complex 2, the diamidocarbene derivative 1 proved susceptible to both thermal and hydrolytic ring-opening reactions, the latter affording [(6-MesDAC)Cu(OC(O)CMe2C(O)N(H)Mes)(CNMes)] ( 6). The intermediacy of [(6-MesDAC)Cu(OH)] in this reaction was supported by the generation of Cu2O as an additional product. Attempts to generate an isolable copper hydride complex of the type [(6-MesDAC)CuH] by reaction of 1 with Et3SiH resulted instead in migratory insertion to generate [(6-MesDAC-H)Cu(P( p-tolyl)3)] ( 9) upon trapping by P( p-tolyl)3. Migratory insertion was also observed during attempts to prepare [(6-Mes)CuH], with [(6-Mes-H)Cu(6-Mes)] ( 10) isolated, following a reaction that was significantly slower than in the 6-MesDAC case. The longer lifetime of [(6-Mes)CuH] allowed it to be trapped stoichiometrically by alkyne, and also employed in the catalytic semi-reduction of alkynes and hydrosilylation of ketones. [ABSTRACT FROM AUTHOR]

A single-component ambiphilic system capable of the cooperative activation of protic, hydridic and apolar HX bonds across a Group 13 metal/activated β-diketiminato (Nacnac) ligand framework is reported. The hydride complex derived from the activation of H2 is shown to be a competent catalyst for the highly selective reduction of CO2 to a methanol derivative. To our knowledge, this process represents the first example of a reduction process of this type catalyzed by a molecular gallium complex. [ABSTRACT FROM AUTHOR]

A single-component ambiphilic system capable of the cooperative activation of protic, hydridic and apolar HX bonds across a Group 13 metal/activated β-diketiminato (Nacnac) ligand framework is reported. The hydride complex derived from the activation of H2 is shown to be a competent catalyst for the highly selective reduction of CO2 to a methanol derivative. To our knowledge, this process represents the first example of a reduction process of this type catalyzed by a molecular gallium complex. [ABSTRACT FROM AUTHOR]

The electrophilic character of free diamidocarbenes (DACs) allows them to activate inert bonds in small molecules, such as NH3 and P4. Herein, we report that metal coordinated DACs also exhibit electrophilic reactivity, undergoing attack by Zn and Cd dialkyl precursors to afford the migratory insertion products [(6-MesDAC-R)MR] (M=Zn, Cd; R=Et, Me; Mes=mesityl). These species were formed via the spectroscopically characterised intermediates [(6-MesDAC)MR2], exhibiting barriers to migratory insertion which increase in the order MR2 = ZnEt2 < ZnMe2 < CdMe2. Compound [(6-MesDAC-Me)CdMe] showed limited stability, undergoing deposition of Cd metal, by an apparent β-H elimination pathway. These results raise doubts about the suitability of diamidocarbenes as ligands in catalytic reactions involving metal species bearing nucleophilic ligands (M-R, M-H). [ABSTRACT FROM AUTHOR]

The modes of interaction of donor-stabilized Group 13 hydrides (E=Al, Ga) were investigated towards 14- and 16-electron transition-metal fragments. More electron-rich N-heterocyclic carbene-stabilized alanes/gallanes of the type NHC⋅EH3 (E=Al or Ga) exclusively generate κ2 complexes of the type [M(CO)4(κ2-H3E⋅NHC)] with [M(CO)4(COD)] (M=Cr, Mo), including the first κ2 σ-gallane complexes. β-Diketiminato (′nacnac′)-stabilized systems, {HC(MeCNDipp)2}EH2, show more diverse reactivity towards Group 6 carbonyl reagents. For {HC(MeCNDipp)2}AlH2, both κ1 and κ2 complexes were isolated, while [Cr(CO)4(κ2-H2Ga{(NDippCMe)2CH})] is the only simple κ2 adduct of the nacnac-stabilized gallane which can be trapped, albeit as a co-crystallite with the (dehydrogenated) gallylene system [Cr(CO)5(Ga{(NDippCMe)2CH})]. Reaction of [Co2(CO)8] with {HC(MeCDippN)2}AlH2 generates [(OC)3Co(μ-H)2Al{(NdippCme)2CH}][Co(CO)4] ( 12), which while retaining direct AlH interactions, features a hitherto unprecedented degree of bond activation in a σ-alane complex. [ABSTRACT FROM AUTHOR]

Cationic half-sandwich ruthenium complexes featuring κ[sup 2]-bound aminoborane ligands can readily be accessed from 16-electron precursors via chloride abstraction in the presence of H[sub 2]BNR[sub 2] (R = [sup i]Pr, Cy). Complexes [Cp*Ru(L) (κ[sup 2]-H[sub 2]BNR[sub 2])][BAr[sup f][sub 4]] (2a:R = [sup i]Pr, L = PCy[sub 3]; 2b:R = [sup i]Pr, L = PPh[sub 3]; 2c: R = [sup i]Pr, L= 1,3-bis-(2,4,6-trimethylphenyl)-imidazol-2-ylidene; 3a: R = Cy, L = PCy[sub 3]; Ar[sup f] = C[sub 6]H[sub 3](CF[sub 3])[sub 2]-3,5) were isolated in yields of ~60 %, and characterised in the solid state by X-ray crystallography (for 2a, 2c, and 3a). Low-field B NMR shifts for the coordinated aminoborane fragment, together with short Ru···B contacts (of the order of 1.97 Å) imply a relatively tightly bound borane ligand, a finding which is given further credence by the results of density functional theory studies (e.g. bond dissociation energies intherange24 kcal mol[sup -1];1 kcal mol[sup -1] = 4.186 kJ mol[sup -1]). In terms of reactivity, κ[sup 2] systems of this type, while potentially offering a versatile route to asymmetric κ[sup 1] systems, in fact undergo borane extrusion even in the presence of a single equivalent of added ligand. [ABSTRACT FROM AUTHOR]

Treatment of the thioether-substituted secondary phosphanes R2PH(C6H4-2-SR1) [R2=(Me3Si)2CH, R1=Me ( 1PH), iPr ( 2PH), Ph ( 3PH); R2= tBu, R1=Me ( 4PH); R2=Ph, R1=Me ( 5PH)] with nBuLi yields the corresponding lithium phosphanides, which were isolated as their THF ( 1- 5Pa) and tmeda ( 1- 5Pb) adducts. Solid-state structures were obtained for the adducts [R2P(C6H4-2-SR1)]Li(L) n [R2=(Me3Si)2CH, R1= nPr, (L) n=tmeda ( 2Pb); R2=(Me3Si)2CH, R1=Ph, (L) n=tmeda ( 3Pb); R2=Ph, R1=Me, (L) n=(THF)1.33 ( 5Pa); R2=Ph, R1=Me, (L) n=([12]crown-4)2 ( 5Pc)]. Treatment of 1PH with either PhCH2Na or PhCH2K yields the heavier alkali metal complexes [{(Me3Si)2CH}P(C6H4-2-SMe)]M(THF) n [M=Na ( 1Pd), K ( 1Pe)]. With the exception of 2Pa and 2Pb, photolysis of these complexes with white light proceeds rapidly to give the thiolate species [R2P(R1)(C6H4-2-S)]M(L) n [M=Li, L=THF ( 1Sa, 3Sa- 5Sa); M=Li, L=tmeda ( 1Sb, 3Sb- 5Sb); M=Na, L=THF ( 1Sd); M=K, L=THF ( 1Se)] as the sole products. The compounds 3Sa and 4Sa may be desolvated to give the cyclic oligomers [[{(Me3Si)2CH}P(Ph)(C6H4-2-S)]Li]6 (( 3S)6) and [[ tBuP(Me)(C6H4-2-S)]Li]8 (( 4S)8), respectively. A mechanistic study reveals that the phosphanide-thiolate rearrangement proceeds by intramolecular nucleophilic attack of the phosphanide center at the carbon atom of the substituent at sulfur. For 2Pa/ 2Pb, competing intramolecular β-deprotonation of the n-propyl substituent results in the elimination of propene and the formation of the phosphanide-thiolate dianion [{(Me3Si)2CH}P(C6H4-2-S)]2−. [ABSTRACT FROM AUTHOR]

Thermally robust expanded ring carbene adducts of AlH3 have been synthesized with a view to probing their ligating abilities via Al–H σ-bond coordination. While κ2 binding to the 14-electron [Mo(CO)4] fragment is readily demonstrated, interaction with [Mo(CO)3] results in μ:κ1,κ1 and μ:κ2,κ2 bridging linkages rather than terminal κ3 binding. [ABSTRACT FROM AUTHOR]

A metal templated synthetic approach gives access to [Cp*Fe(CO)2{B(NMesCMe)2CH}][BArf4], and represents the first example of coordinative trapping of the elusive [B(NRCMe)2CH] fragment. [ABSTRACT FROM AUTHOR]

Correction for 'Heterobimetallic ruthenium–zinc complexes with bulky N-heterocyclic carbenes: syntheses, structures and reactivity' by Maialen Espinal-Viguri et al., Dalton Trans., 2019, 48, 4176–4189, DOI: 10.1039/C8DT05023F. [ABSTRACT FROM AUTHOR]

Highlights from the article: Umpolung of the P4-Bonding Situation in [CpFe(CO)(L)( 1-P4)]+ Cations (L=CO or PPh3) B A low barrier to the exchange b of metalated and non-metalated phosphorus atoms is observed in white phosphorus complexes of electron poor cyclopentadienyl iron cations. Analysis of the bonding present in these systems identifies a formal Umpolung in the Fe-P bond resulting from the electron deficient nature of the iron center.