Synthesis and Characterization of β‐Diketiminate Aluminum Compounds and Their Use in the Ring‐Opening Polymerization of ε‐Caprolactone

Four aluminum alkyl compounds, [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlMe₂] ( 1 ), [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlEt₂] ( 2 ), [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlMe₂] ( 3 ), and [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlEt₂] ( 4 ), bearing β‐diketiminate ligands [CH{(Me)CN‐2,4,6‐MeC₆H₂}]₂ (L¹H) and [CH{(Me)CN‐2‐ⁱPrC₆H₄}]₂ (L²H) were obtained from the reactions of trimethylaluminum, triethylaluminum with the corresponding β‐diketiminate, respectively. All compounds were characterized by ¹H NMR and ¹³C NMR spectroscopy, single‐crystal X‐ray structural analysis, and elemental analysis. Compounds 1 – 4 were found to catalyze the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) with good activity.     

Beryllium Halide Complexes Incorporating Neutral or Anionic Ligands: Potential Precursors for Beryllium Chemistry

Reactions of the beryllium dihalide complexes [BeX₂(OEt₂)₂] (X=Br or I) with N,N,N′,N′‐tetramethylethylenediamine (TMEDA), a series of diazabutadienes, or bis(diphenylphosphino)methylene (DPPM) have yielded the chelated complexes, [BeX₂(TMEDA)], [BeX₂{(RN=CH)₂}] (R=tBu, mesityl (Mes), 2,6‐diethylphenyl (Dep) or 2,6‐diisopropylphenyl (Dip)), and the non‐chelated system, [BeI₂(κ¹‐P‐DPPM)₂]. Reactions of lithium or potassium salts of a variety of β‐diketiminates have given both three‐coordinate complexes, [{HC(RCNAr)₂}BeX] (R=H or Me; Ar=Mes, Dep or Dip; X=Br or I); and four‐coordinate systems, [{HC(MeCNPh)₂}BeBr(OEt₂)] and [{HC(MeCNDip)(MeCNC₂H₄NMe₂}BeI]. Alkali metal salts of ketiminate, guanidinate, boryl/phosphinosilyl amide, or terphenyl ligands, lead to dimeric [{BeI{μ‐[(OCMe)(DipNCMe)]CH}}₂], and monomeric [{iPr₂NC(NMes)₂}BeI(OEt₂)], [κ²‐N,P‐{(HCNDip)₂B}(PPh₂SiMe₂)NBeI(OEt₂)] and [{C₆H₃Ph₂‐2,6}BeBr(OEt₂)], respectively. Compound [{HC(MeCNPh)₂}BeBr(OEt₂)] undergoes a Schlenk redistribution reaction in solution, affording the homoleptic complex, [{HC(MeCNPh)₂}₂Be]. The majority of the prepared complexes have been characterized by X‐ray crystallography and multi‐nuclear NMR spectroscopy. The structures and stability of the complexes are discussed, as is their potential for use as precursors in poorly developed low oxidation state beryllium chemistry.     

Transition‐Metal‐Mediated Cleavage of Fluoro‐Silanes under Mild Conditions

Si?F bond cleavage of fluoro‐silanes was achieved by transition‐metal complexes under mild and neutral conditions. The Iridium‐hydride complex [Ir(H)(CO)(PPh₃)₃] was found to readily break the Si?F bond of the diphosphine‐ difluorosilane {(o‐Ph₂P)C₆H₄}₂Si(F)₂ to afford a silyl complex [{[o‐(iPh₂P)C₆H₄]₂(F)Si}Ir(CO)(PPh₃)] and HF. Density functional theory calculations disclose a reaction mechanism in which a hypervalent silicon species with a dative Ir→Si interaction plays a crucial role. The Ir→Si interaction changes the character of the H on the Ir from hydridic to protic, and makes the F on Si more anionic, leading to the formation of H^δ+???F^δ? interaction. Then the Si?F and Ir?H bonds are readily broken to afford the silyl complex and HF through σ‐bond metathesis. Furthermore, the analogous rhodium complex [Rh(H)(CO)(PPh₃)₃] was found to promote the cleavage of the Si?F bond of the triphosphine‐monofluorosilane {(o‐Ph₂P)C₆H₄}₃Si(F) even at ambient temperature.     

Tris(3,5‐dimethylpyrazolyl)methane‐Based Heterobimetallic Complexes that Contain Zn and CdTransition‐Metal Bonds: Synthesis,Structures, and Quantum Chemical Calculations

Reactions of the tris(3,5‐dimethylpyrazolyl)methanide amido complexes [M′{C(3,5‐Me₂pz)₃}{N(SiMe₃)₂}] (M′=Mg ( 1 a ), Zn ( 1 b ), Cd ( 1 c ); 3,5‐Me₂pz=3,5‐dimethylpyrazolyl) with two equivalents of the acidic Group 6 cyclopentadienyl (Cp) tricarbonyl hydrides [MCp(CO)₃H] (M=Cr ( 2 a ), Mo ( 2 b )) gave different types of heterobimetallic complex. In each case, two reactions took place, namely the conversion of the tris(3,5‐dimethylpyrazolyl)methanide ligand (Tpmd*) into the ‐methane derivative (Tpm*) and the reaction of the acidic hydride M?H bond with the M′?N(SiMe₃)₂ moiety. The latter produces HN(SiMe₃)₂ as a byproduct. The Group 2 representatives [Mg(Tpm*){MCp(CO)₃}₂(thf)] ( 3 a / b ) form isocarbonyl bridges between the magnesium and chromium/molybdenum centres, whereas direct metal–metal bonds are formed in the case of the ions [Zn(Tpm*){MCp(CO)₃}]⁺ ( 4 a / b ; [MCp(CO)₃]^? as the counteranion) and [Cd(Tpm*){MCp(CO)₃}(thf)]⁺ ( 5 a / b ; [Cd{MCp(CO)₃}₃]^? as the counteranion). Complexes 4 a and 5 a / b are the first complexes that contain Zn?Cr, Cd?Cr, and Cd?Mo bonds (bond lengths 251.6, 269.8, and 278.9 pm, respectively). Quantum chemical calculations on 4 a / b* (and also on 5 a / b* ) provide evidence for an interaction between the metal atoms.     

Comparative studies on group III σ‐hole and π‐hole interactions

The σ‐hole of M₂H₆ (M = Al, Ga, In) and π‐hole of MH₃ (M = Al, Ga, In) were discovered and analyzed, the bimolecular complexes M₂H₆···NH₃ and MH₃···N₂P₂F₄ (M = Al, Ga, In) were constructed to carry out comparative studies on the group III σ‐hole interactions and π‐hole interactions. The two types of interactions are all partial‐covalent interactions; the π‐hole interactions are stronger than σ‐hole interactions. The electrostatic energy is the largest contribution for forming the σ‐hole and π‐hole interaction, the polarization energy is also an important factor to form the M···N interaction. The electrostatic energy contributions to the interaction energy of the σ‐hole interactions are somewhat greater than those of the π‐hole interactions. However, the polarization contributions for the π‐hole interactions are somewhat greater than those for the σ‐hole interactions. © 2016 Wiley Periodicals, Inc.     

Reaktionen des [η2-{P–PtBu2}Pt(PPh3)2] und [η2-{P–PtBu2}Pt(dppe)] mit Metallcarbonylen. Bildung von [η2-{(CO)5M · PPtBu2}Pt(PPh3)2] (M = Cr,W) und [η2-{(CO)5Cr · PPtBu2}Pt(dppe)]

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XVI [1] Reactions of [g²-{P–P^tBu₂}Pt(PPh₃)₂] and [g²-{P–P^tBu₂}Pt(dppe)] with Metal Carbonyls. Formation of [g²-{(CO)₅M · PP^tBu₂}Pt(PPh₃)₂] (M = Cr, W) and [g²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] [η²-{P–P^tBu₂}Pt(PPh₃)₂] 4 reacts with M(CO)₅ · THF (M = Cr, W) by adding the M(CO)₅ group to the phosphinophosphinidene ligand yielding [η²-{(CO)₅Cr · PP^tBu₂}Pt(PPh₃)₂] 1 , or [η²-{(CO)₅W · PP^tBu₂}Pt(PPh₃)₂] 2 , respectively. Similarly, [η²-{P–P^tBu₂}Pt(dppe)] 5 yields [η²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] 3 . Compounds 1 , 2 and 3 are characterized by their ¹H- and ³¹P-NMR spectra, for 2 and 3 also crystal structure determinations were performed. 2 crystallizes in the monoclinic space group P2₁/n (no. 14) with a = 1422.7(1) pm, b = 1509.3(1) pm, c = 2262.4(2) pm, β = 103.669(9)°. 3 crystallizes in the triclinic space group P1 (no. 2) with a = 1064.55(9) pm, b = 1149.9(1) pm, c = 1693.2(1) pm, α = 88.020(8)°, β = 72.524(7)°, γ = 85.850(8)°.     

New Routes to a Series of σ‐Borane/Borate Complexes of Molybdenum and Ruthenium

A series of agostic σ‐borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room‐temperature reaction of [Cp*Mo(CO)₃Me], 1 with Li[BH₃(EPh)] (Cp*=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [Cp*Mo(CO)₂(μ‐H)BH₂EPh] in good yields. With 2‐mercapto‐benzothiazole, an N,S‐carbene‐anchored σ‐borate complex [Cp*Mo(CO)₂BH₃(1‐benzothiazol‐2‐ylidene)] ( 5 ) was isolated. Further, a transmetalation of the B‐agostic ruthenium complex [Cp*Ru(μ‐H)BHL₂] ( 6 , L=C₇H₄NS₂) with [Mn₂(CO)₁₀] affords a new B‐agostic complex, [Mn(CO)₃(μ‐H)BHL₂] ( 7 ) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)₃] unit. Natural‐bond‐orbital analyses of 5–7 indicate significant delocalization of the electron density from the filled σ_B?H orbital to the vacant metal orbital.     

Characterizing Pressure‐Induced Uranium CH Agostic Bonds

The diuranium(III) compound [UN′′₂]₂(μ‐η⁶:η⁶‐C₆H₆) (N′′=N(SiMe₃)₂) has been studied using variable, high‐pressure single‐crystal X‐ray crystallography, and density functional theory . In this compound, the low‐coordinate metal cations are coupled through π‐ and δ‐symmetric arene overlap and show close metal? CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic‐type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms‐in‐molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa.     

Facile CH Bond Formation by Reductive Elimination at a Dinuclear Metal Site

The electronically unsaturated dirhenium complex [Re₂(CO)₈(µ‐AuPPh₃)(µ‐Ph)] ( 1 ) was obtained from the reaction of [Re₂(CO)₈{µ‐η²‐C(H)?C(H)nBu}(µ‐H)] with [Au(PPh₃)Ph]. The bridging {AuPPh₃} group was replaced by a bridging hydrido ligand to yield the unsaturated dirhenium complex [Re₂(CO)₈(µ‐H)(µ‐Ph)] ( 2 ) by reaction of 1 with HSnPh₃. Compound 2 reductively eliminates benzene upon addition of NCMe at 25 °C. The electronic structure of 2 and the mechanism of the reductive elimination of the benzene molecule in its reaction with NCMe were investigated by DFT computational analyses.     

Trialkylhydridoalanate RxR′3-xAlH⊖ [R = CMe3; R′ = CH(SiMe3)2]

Trialkylhydridoalanates R_xR′_3?xAlH^? [R = CMe₃; R′ = CH(SiMe₃)₂] The very strong base tert-butyl lithium reacts in the presence of chelating tetramethylethylendiamine with the aluminium organyls Al[CH(SiMe₃)₂]₂CMe₃ 1 and Al[CH(SiMe₃)₂](CMe₃)₂ 2 not under proton abstraction from the C? H acidic elementorganic substituent, but under β-elimination and addition of the thereby formed LiH to the coordinatively unsaturated aluminium atom. Two alanates — [Hal{CH(SiMe₃)₂}₂CMe₃]^? 3 and [HAl{CH(SiMe₃)₂}(CMe₃)₂]^? 4 each with Li(TMEDA)₂^⊕ as counterion — were isolated; they exhibit separate anions and cations in solid state as shown by a crystal structure determination on 3 . In absence of the chelating amine tert-butyl lithium decomposes under the catalytic effect of the aluminium compound to LiH, which does not add to aluminium and precipitates in a reactive form.     

BH,CH,and BC Bond Activation: The Role of Two Adjacent Agostic Interactions

Tuning the nature of the linker in a L～BHR phosphinoborane compound led to the isolation of a ruthenium complex stabilized by two adjacent, δ‐C? H and ε‐B_sp2? H, agostic interactions. Such a unique coordination mode stabilizes a 14‐electron “RuH₂P₂” fragment through connected σ‐bonds of different polarity, and affords selective B? H, C? H, and B? C bond activation as illustrated by reactivity studies with H₂ and boranes.     

Construction of Hexahydrophenanthrenes By Rhodium(I)‐Catalyzed Cycloisomerization of Benzylallene‐Substituted Internal Alkynes through C−H Activation

The treatment of benzylallene‐substituted internal alkynes with [RhCl(CO)₂]₂ effects a novel cycloisomerization by C(sp²)?H bond activation to produce hexahydrophenanthrene derivatives. The reaction likely proceeds through consecutive formation of a rhodabicyclo[4.3.0] intermediate, σ‐bond metathesis between the C(sp²)?H bond on the benzene ring and the C(sp²)?Rh^III bond, and isomerization between three σ‐, π‐, and σ‐allylrhodium(III) species, which was proposed based on experiments with deuterated substrates.     

Interaction between Anions and Cationic Metal Complexes Containing Tridentate Ligands with exo‐CH Groups: Complex Stability and Hydrogen Bonding

[Re(CO)₃([9]aneS₃)][BAr′₄] ( 1 ), prepared by reaction of ReBr(CO)₅, 1,4,7‐trithiacyclononane ([9]aneS₃) and NaBAr′₄, forms stable, soluble supramolecular adducts with chloride ( 2 ), bromide, methanosulfonate ( 3 ) and fluoride ( 4 ) anions. These new species were characterized by IR, NMR spectroscopy and, for 2 and 3 , also by X‐ray diffraction. The results of the solid state structure determinations indicate the formation of CH???X hydrogen bonds between the anion (X) and the exo‐C?H groups of the [9]aneS₃ ligand, in accord with the relatively large shifts found by ¹H NMR spectroscopy in dichloromethane solution for those hydrogens. The stability of the chloride adduct contrasts with the lability of the [9]aneS₃ ligand in allyldicarbonyl molybdenum complexes recently studied by us. With fluoride, in dichloromethane solution, a second, minor neutral dimeric species 5 is formed in addition to 4 . In 4 , the deprotonation of a C?H group of the [9]aneS₃ ligand, accompanied by C?S bond cleavage and dimerization, afforded 5 , featuring bridging thiolates. Compounds [Mo(η³‐methallyl)(CO)₂(TpyN)][BAr′₄] ( 6 ) and [Mo(η³‐methallyl)(CO)₂(TpyCH)][BAr′₄] ( 7 ) were synthesized by the reactions of [MoCl(η³‐methallyl)(CO)₂(NCMe)₂], NaBAr′₄ and tris(2‐pyridyl)amine (TpyN) or tris(2‐pyridyl)methane (TpyCH) respectively, and characterized by IR and ¹H and ¹³C NMR spectroscopy in solution, and by X‐ray diffraction in the solid state. Compound 6 undergoes facile substitution of one of the 2‐pyridyl groups by chloride, bromide, and methanosulfonate anions. Stable supramolecular adducts were formed between 7 and chloride, bromide, iodide, nitrate, and perrhenate anions. The solid state structures of these adducts ( 12 – 16 ) were determined by X‐ray diffraction. Binding constants in dichloromethane were calculated from ¹H NMR titration data for all the new supramolecular adducts. The signal of the bridgehead C?H group is the one that undergoes a more pronounced downfield shift when tetrabutylammonium chloride was added to 7 , whereas smaller shifts were found for the 2‐pyridyl C(3)?H groups. In agreement, both types of C?H groups form hydrogen bonds to the anions in the solid state structures.     

Intramolecular CH Activation and Metallacycle Aromaticity in the Photochemistry of [FeFe]‐Hydrogenase Model Compounds in Low‐Temperature Frozen Matrices

The [FeFe]‐hydrogenase model complexes [(μ‐pdt){Fe(CO)₃}₂], [(μ‐edt){Fe(CO)₃}₂], and [(μ‐mdt){Fe(CO)₃}₂], where pdt=1,3‐propanedithiolate, edt=1,2‐ethanedithiolate, and mdt=methanedithiolate, undergo wavelength dependent photodecarbonylation in hydrocarbon matrices at 85 K resulting in multiple decarbonylation isomers. As previously reported in time‐resolved solution photolysis experiments, the major photoproduct is attributed to a basal carbonyl‐loss species. Apical carbonyl‐loss isomers are also generated and may undergo secondary photolysis, resulting in β‐hydride activation of the alkyldithiolate bridge, as well as formation of bridging carbonyl isomers. For [(μ‐bdt){Fe(CO)₃}₂], (bdt=1,2‐benzenedithiolate), apical photodecarbonylation results in generation of a 10 π‐electron aromatic FeS₂C₆H₄ metallacycle that coordinates the remaining iron through an η⁵ mode.     

Synthesis, Characterization and Crystal Structures of Some Linked Metal Carbonyl Clusters Derived from Diethynyl-Substituted Silane and Disilane Ligands

The use of diethynylsilane, diethynyldisilane and diethynyldisiloxane in the synthesis of some linked metal carbonyl clusters is demonstrated. New dimeric η²-diyne complexes of cobalt [{Co₂(CO)₆}₂(η²-diyne)], ruthenium [{(μ-H)Ru₃(CO)₉}₂(μ₃-η²,η²-diyne)] and osmium [{(μ-CO)Os₃(CO)₉}₂(μ₃-η²-diyne)] {diyne=HC≡CSi(CH₃)₂C≡CH, HC≡CSi(CH₃)₂–Si(CH₃)₂C≡CH, HC≡CSi(CH₃)₂–O–Si(CH₃)₂C≡CH or HC≡CSi(Ph)₂C≡CH} have been prepared in good yields from the reaction of [Co₂(CO)₈], [Ru₃(CO)₁₂] and [Os₃(CO)₁₀(NCMe)₂] with half an equivalent of the appropriate diyne ligand, respectively. All the twelve compounds have been characterized by IR and ¹H NMR spectroscopies and mass spectrometry. The molecular structures of eight of them have been determined by X-ray crystallography. Structurally, each of the tetracobalt species displays two Co₂C₂ cores adopting the pseudo-tetrahedral geometry with the alkyne bond lying essentially perpendicular to the Co–Co vector. For the group 8 ruthenium and osmium analogues, the hexanuclear carbonyl clusters consist of two trinuclear metal cores with the μ₃-η²,η² bonding mode for the acetylene groups in the former case and μ₃-(η²-||) bonding mode in the latter one. Density functional theory was employed to study the electronic structures of these molecules in terms of the nature of the silyl or disilyl unit and its substituents.     

First Dinuclear Copper/Gallium Complexes: Supporting Cu0 and CuI Centres by Low‐Valent Organogallium Ligands

The synthesis and structural characterisation of low‐valent dinuclear copper(I) and copper(0) complexes supported by organogallium ligands has been accomplished for the first time by the reductive coordination reaction of [GaCp*] (Cp*=pentamethylcyclopentadienyl) and [Ga(ddp)] (ddp=HC(CMeNC₆H₃‐2,6‐iPr₂)₂ 2‐diisopropylphenylamino‐4‐diisopropylphenylimino‐2‐pentene) with readily available copper(II) and copper(I) precursors. The treatment of CuBr₂ and Cu(OTf)₂ (OTf=CF₃SO₃) with [Ga(ddp)] under mild conditions resulted in elimination of [Ga(L)₂(ddp)] (L=Br, OTf) and afforded the novel gallium(I)/copper(I) compounds [{(ddp)GaCu(L)}₂] (L=Br ( 1 ), OTf ( 2 )). The single‐crystal X‐ray structure determinations of 1 and 2 reveal that these molecules are composed of {(ddp)GaCu(L)} dimeric units, with planar Cu^I? Ga^I four‐membered rings and short Cu^I???Cu^I distances, with 2 exhibiting the shortest Cu^I???Cu^I contact reported to date of 2.277(3) Å. The all‐gallium coordinated dinuclear [Cu₂(GaCp*)(μ‐GaCp*)₃Ga(OTf)₃] ( 3 ) is formed when Cu(OTf)₂ is combined with [GaCp*] instead of [Ga(ddp)]. Notably, in the course of this redox reaction Lewis acidic Ga(OTf)₃ is formed, which coordinates to one of the electron‐rich copper(0) centres. Compound 3 is suggested as the first case of a structurally characterised complex of copper(0). By changing the copper(II) to a copper(I) source, that is, [Cu(cod)₂][OTf] (cod=1,5‐cyclooctadiene), the salt [Cu₂(GaCp*)₃(μ‐GaCp*)₂][OTf]₂ ( 4 ) is formed, the cationic part of which is related to previously described isoelectronic dinuclear d¹⁰ complexes of the type [M₂(GaCp*)₅] (M=Pd, Pt).     

Observation of Main‐Group Tricarbonyls [B(CO)3] and [C(CO)3]+ Featuring a Tilted One‐Electron Donor Carbonyl Ligand

A combined experimental and theoretical study on the main‐group tricarbonyls [B(CO)₃] in solid noble‐gas matrices and [C(CO)₃]⁺ in the gas phase is presented. The molecules are identified by comparing the experimental and theoretical IR spectra and the vibrational shifts of nuclear isotopes. Quantum chemical ab initio studies suggest that the two isoelectronic species possess a tilted η¹(μ₁‐CO)‐bonded carbonyl ligand, which serves as an unprecedented one‐electron donor ligand. Thus, the central atoms in both complexes still retain an 8‐electron configuration. A thorough analysis of the bonding situation gives quantitative information about the donor and acceptor properties of the different carbonyl ligands. The linearly bonded CO ligands are classical two‐electron donors that display classical σ‐donation and π‐back‐donation following the Dewar–Chatt–Duncanson model. The tilted CO ligand is a formal one‐electron donor that is bonded by σ‐donation and π‐back‐donation that involves the singly occupied orbital of the radical fragments [B(CO)₂] and [C(CO)₂]⁺.     

CH Bond Activation with Triel Metals: Indium and Gallium Zwitterions through Internal Hydride Abstraction in Rigid Salan Ligands

The hydropyrimidine salan (salan=N,N′‐dimethyl‐N,N′‐bis[(2‐hydroxyphenyl)methylene]‐1,2‐diaminoethane) proteo‐ligands with a rigid backbone {ON^(CH₂)^NO}H₂ react with M(CH₂SiMe₃)₃ (M=Ga, In) to yield the zwitterions {ON^(CH⁺)^NO}M^?(CH₂SiMe₃)₂ (M=Ga, 2 ; In, 3 ) by abstraction of a hydride from the ligand backbone followed by elimination of dihydrogen. By contrast, with Al₂Me₆, the neutral‐at‐metal bimetallic complex [{ON^(CH₂)^NO}AlMe]₂ ( [1]₂ ) is obtained quantitatively. The formation of indium zwitterions is also observed with sterically more encumbered ligands containing o‐Me substituents on the phenolic rings, or an N (CHPh) N moiety in the heterocyclic core. Overall, the ease of C?H bond activation follows the order Al?Ga<In. Experimental data based on model complexes, XRD studies, and ²H NMR spectroscopy show that the formation of the Ga/In zwitterion involves rapid release of SiMe₄ followed by evolution of H₂, and suggest the formation of a transient metal‐hydride species. DFT calculations indicate that the systems {ON^(CH₂)^NO}H₂+M(CH₂SiMe₃)₃ (M=Al, Ga, In) all initially lead to the formation of the neutral monophenolate dihydrocarbyl species through a single protonolysis. From here, the thermodynamic product, the model neutral‐at‐metal complex 1 , is formed in the case of aluminum after a second protonolysis. On the other hand, lower activation energy pathways lead to the generation of zwitterionic complexes 2 and 3 in the cases of gallium and indium, and the formation of these zwitterions obeys a strict kinetic control; the computations suggest that, as inferred from the experimental data, the reaction proceeds through an instable metal‐hydride species, which could not be isolated synthetically.     

Transition‐Metal‐Mediated Cleavage of a SiSi Double Bond

Reaction of carbene‐stabilized disilicon ( 1 ) with Fe(CO)₅ gives the 1:1 adduct L:Si?Si[Fe(CO)₄]:L (L:=C{N(2,6‐Prⁱ₂C₆H₃)CH}₂) ( 2 ) at room temperature. At raised temperature, however, 2 may react with another equivalent of Fe(CO)₅ to give L:Si[μ‐Fe₂(CO)₆](μ‐CO)Si:L ( 3 ) through insertion of both CO and Fe₂(CO)₆ into the Si₂ core, which represents the first experimental realization of transition metal‐carbonyl‐mediated cleavage of a Si?Si double bond. The structures and bonding of both 2 and 3 have been investigated by spectroscopic, crystallographic, and computational methods.     

Group 13 Ligand Supported Heavy‐Metal Complexes: First Structural Evidence for Gallium–Lead and Gallium–Mercury Bonds

Heavy‐metal complexes of lead and mercury stabilized by Group 13 ligands were derived from the oxidative addition of Ga(ddp) (ddp=HC(CMeNC₆H₃‐2,6‐iPr₂)₂, 2‐diisopropylphenylamino‐4‐diisopropyl phenylimino‐2‐pentene) with corresponding metal precursors. The reaction of Me₃PbCl and Ga(ddp) afforded compound [{(ddp)Ga(Cl)}PbMe₃] ( 1 ) composed of Ga? Pb^IV bonds. In addition, the monomeric plumbylene‐type compound [{(ddp)Ga(OSO₂CF₃)}₂Pb(thf)] ( 2 a ) with an unsupported Ga‐Pb^II‐Ga linkage was obtained by the reaction of [Pb(OSO₂CF₃)₃] with Ga(ddp) (2 equiv). Compound 2 a falls under the rare example of a discrete plumbylene‐type compound supported by a nonclassical ligand. Interesting structural changes were observed when [Pb(OSO₂CF₃)₃] ? 2 H₂O was treated with Ga(ddp) in a 1:2 ratio to yield [{(ddp)Ga(μ‐OSO₂CF₃)}₂(OH₂)Pb] ( 2 b ) at below ?10 °C. Compound 2 b consists of a bent Ga‐Pb‐Ga backbone with a bridging triflate group between the Ga? Pb bond and a weakly interacting water molecule at the gallium center. Similarly, the reaction of mercury thiolate Hg(SC₆F₅) with Ga(ddp) (2 equiv) produced the bimetallic homoleptic compounds anti‐[{(ddp)Ga(SC₆F₅)}₂Hg] ( 3 a ) and gauche‐[{(ddp)Ga(SC₆F₅)}₂Hg] ( 3 b ), respectively, with a linear Ga‐Hg‐Ga linkage. Compounds 1 – 3 were structurally characterized and these are the first examples of compounds comprised of Ga? Pb^II, Ga? Pb^IV, and Ga? Hg bonds.