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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]

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]

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 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]

Reaction of [Ru(IPr)2(CO)H]BArF4 with ZnEt2 forms the heterobimetallic species [Ru(IPr)2(CO)ZnEt]BArF4 (2), which features an unsupported Ru-Zn bond. 2 reacts with H2 to give [Ru(IPr)2(CO)(η²-H2)(H)2ZnEt]BArF4 (3) and [Ru(IPr)2(CO)(H)2ZnEt]BArF4 (4). DFT calculations indicate that H2 activation at 2 proceeds via oxidative cleavage at Ru with concomitant hydride transfer to Zn. 2 can also activate hydridic E-H bonds (E = B, Si), and computed mechanisms for the facile H/H exchange processes observed in 3 and 4 are presented. [ABSTRACT FROM AUTHOR]

Halide abstraction from the ruthenium N-heterocyclic carbene complex Ru(IPr)2(CO)HCl (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with NaBAr4F (BAr4F = B{C6H3(3,5-CF3)2}4) gave the salt [Ru(IPr)2(CO)H]BAr4F (2), which was shown through a combined X-ray/neutron structure refinement and quantum theory of atoms in molecules (QTAIM) study to contain a bifurcated Ru...η³-H2C ξ-agostic interaction involving one iPr substituent of the IPr ligand. This system complements the previously reported [Ru(IMes)2(CO)H]+ cation (IMes =1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), where a non-agostic form is favored. Treatment of 2 with CO, H2, and the amine-boranes H3B·NR2H (R = Me, H) gave [Ru(IPr)2(CO)3H]BAr4F (3), [Ru(IPr)2(CO)(η²-H2)H]BAr4F (4), and [Ru(IPr)2(CO)(κ²-H2BH·NR2H)H]BAr4F (R = Me, 5; R = H, 6), respectively. Heating 5 in the presence of Me3SiCH=CH2 led to alkene hydroboration and formation of the C-H activated product [Ru(IPr)(IPr)'(CO)]BAr4F (7). X-ray characterization of 3 and 5-7 was complemented by DFT calculations, and the mechanism of H2/H exchange in 4 was also elucidated. Treatment of 2 with HBcat resulted in Ru-H abstraction to form the boryl complex [Ru(IPr)2(CO)(Bcat)] BAr4F (8), which proved to be competent in the catalytic hydroboration of 1-hexene. In 8, a combined X-ray/neutron structure refinement and QTAIM analysis suggested the presence of a single Ru···η²-HC ξ-agostic interaction. [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 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]

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]

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]

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.

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]