Development of versatile and silver-free protocols for gold(I) catalysis

The use of a versatile N‐heterocyclic carbene (NHC) gold(I) hydroxide precatalyst, [Au(OH)(IPr)], (IPr=N,N′‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) permits the in situ generation of the [Au(IPr)]⁺ ion by simple addition of a Brønsted acid. This cationic entity is believed to be the active species in numerous catalytic reactions. ¹H NMR studies in several solvent media of the in situ generation of this [Au(IPr)]⁺ ion also reveal the formation of a dinuclear gold hydroxide intermediate [{Au(IPr)}₂(μ‐OH)], which is fully characterized and was tested in gold(I) catalysis.     

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh₃)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh₃)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=ⁱPr or ^tBu, P*CHP*) and the complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh₃)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh₃)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh₃)] complexes and chiral [RuCl(P*CP*)(PPh₃)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.     

Aggregation and Degradation of White Phosphorus Mediated by N‐Heterocyclic Carbene Nickel(0) Complexes

The reaction of zerovalent nickel compounds with white phosphorus (P₄) is a barely explored route to binary nickel phosphide clusters. Here, we show that coordinatively and electronically unsaturated N‐heterocyclic carbene (NHC) nickel(0) complexes afford unusual cluster compounds with P₁, P₃, P₅ and P₈ units. Using [Ni(IMes)₂] [IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene], electron‐deficient Ni₃P₄ and Ni₃P₆ clusters have been isolated, which can be described as superhypercloso and hypercloso clusters according to the Wade–Mingos rules. Use of the bulkier NHC complexes [Ni(IPr)₂] or [(IPr)Ni(η⁶‐toluene)] [IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene] affords a closo‐Ni₃P₈ cluster. Inverse‐sandwich complexes [(NHC)₂Ni₂P₅] (NHC=IMes, IPr) with an aromatic cyclo‐P₅^? ligand were identified as additional products.     

Pyrrole‐2‐carbaldehyde Thiosemicarbazonates of Nickel(II) and Palladium(II): Synthesis,Structure, and Spectroscopy

Complexes of pyrrole‐2‐carbaldehyde thiosemicarbazones, [(C₄H₄N⁴)(H)C²=N³–N²(H)–C¹(=S)–N¹HR; R = Ph, H₂L¹; Me, H₂L²; H, H₂L³] with nickel(II) and palladium(II) are described. The reaction of nickel(II) acetate with H₂L¹ in methanol in 1:1 molar ratio yielded a complex of composition, [Ni(κ²‐N³,S‐HL¹)₂] ( 1 ). Likewise reaction of NiCl₂ with H₂L² in 1:1 molar ratio in acetonitrile in the presence of triethylamine base followed by the addition of pyridine did not yield the anticipated [Ni(κ³‐N⁴,N³,S‐L²)(py)] complex, moreover a bis‐square‐planar complex, [Ni(κ²‐N³,S‐HL²)₂] ( 2 ) was formed. However, in the presence of bipyridine (bipy), it yielded the addition product, [Ni(κ²‐N³,S‐HL²)₂(κ²‐N, N‐bipy)] ( 3 ). Reaction of PdCl₂(κ²‐P, P–PPh₂–CH₂–PPh₂) with H₂L³ in toluene in the presence of triethylamine has yielded a complex of stoichiometry, [Pd(κ³‐N⁴,N³,S–L³)(κ¹‐P–PPh₂–CH₂–P(O)Ph₂] ( 4 ). The ligands (HL¹)^– and (HL²)^– are chelating to Ni^II metal atom as anions binding through N³,S‐donor atoms with pendant pyrrole groups, and (L³)^2– is chelating to the Pd^II metal atom as dianion through N⁴,N³,S‐donor atoms (pyrrole is N⁴‐bonded). Fourth site in 4 is bonded to one P‐donor atom of PPh₂–CH₂–P(O)Ph₂, whose pendant –PPh₂ group involves auto oxidation to –P(O)PPh₂ during reaction. These complexes were characterized using analytical data, IR, NMR (¹H, ³¹P) spectroscopy and X‐ray crystallography. Complexes 1 , 2 , and 4 have square‐planar arrangement, whereas complex 3 is octahedral.     

The Marriage of Peripherally Metallated and Directly Linked Porphyrins: Bromidobis(phosphine)platinum(II) as a Cation‐Stabilizing Substituent on Directly Linked and Fused Triply Linked Diporphyrins

A meso‐bromidoplatiniobis(triphenylphosphine) η¹‐organometallic porphyrin monomer was prepared by the oxidative addition of meso‐bromoZnDPP (DPP=dianion of 5,15‐diphenylporphyrin) to a platinum(0) species. The meso–meso directly linked dimeric porphyrin ( 5 ) was prepared from this monomer by silver(I)‐promoted oxidative coupling and planarized to give a triply linked dizinc(II) porphyrin dimer ( 8 ). Acidic demetallation of 8 afforded the bis(free base) 9 . Dimer 5 was demetallated then remetallated with nickel(II) to give the dinickel(II) analogue 10 , the X‐ray crystal structure of which showed a twisted molecule with ruffled, orthogonal NiDPP rings, terminated by square‐planar trans‐[Pt(PPh₃)₂Br] units. New compounds were fully characterized spectroscopically, and the fused diporphyrin exhibited a broad, low‐energy, near‐IR electronic absorption band near 1100 nm. Electrochemical measurements of this series indicate that the organometallic fragment is a strong electron donor towards the porphyrin ring. The triply linked organometallic diporphyrin has a substantially lowered first one‐electron oxidation potential (?0.35 V versus the ferrocene/ferrocenium couple (Fc/Fc⁺)) and a narrow HOMO–LUMO gap of 0.96 V. Solutions prepared for NMR spectroscopy slowly decompose with degradation of the signals, which is attributed to partial oxidation to the cation radical. This paramagnetic species can be reduced in situ by hydrazine to restore the NMR spectrum to its former appearance. The combined influence of the two [Pt(PPh₃)₂Br] electron‐donating substituents is sufficient to make dimer 5 too aerobically unstable to allow further elaboration.     

Functionalized Fluorophosphonium Ions

Efforts to prepare an elusive donor-free phosphenium ion, [R₂P]⁺, led us to synthesize functionalized fluorophosphonium cations of the type [R₂P(F)X]⁺ (X=SiEt₃, H, F), which were obtained from the related neutral fluorophosphines R₂PF and R₂PF₃ upon protonation and reaction with solvated [Et₃Si]⁺ ions (R=2,6-Mes₂C₆H₃). The hypothetical reductive elimination of [R₂P(F)SiEt₃]⁺ and [R₂P(F)H]⁺ affording [R₂P]⁺, Et₃SiF and HF, respectively, was calculated to be endothermic by 40.1 and 190.6 kJ mol⁻¹.     

Addition von kationischen Lewis‐Säuren [M′Ln]+ (M′Ln = Fe(CO)2Cp,Fe(CO)(PPh3)Cp,Ru(PPh3)2Cp,Re(CO)5, ${1 \over 2}$ Pt(PPh3)2, W(CO)3Cp an die anionischen Thiocarbonyl‐Komplexe [HB(pz)3(OC)2M(CS)]− (M = Mo,W; pz = 3,5‐dimethylpyrazol‐1‐yl)

Addition of Cationic Lewis Acids [M′L_n]⁺ (M′L_n = Fe(CO)₂Cp, Fe(CO)(PPh₃)Cp, Ru(PPh₃)₂Cp, Re(CO)₅, Pt(PPh₃)₂, W(CO)₃Cp to the Anionic Thiocarbonyl Complexes [HB(pz)₃(OC)₂M(CS)]⁻ (M = Mo, W; pz = 3,5‐dimethylpyrazol‐1‐yl) Adducts from Organometallic Lewis Acids [Fe(CO)₂Cp]⁺, [Fe(CO)(PPh₃)Cp]⁺, [Ru(PPh₃)₂Cp]⁺, [Re(CO)₅]⁺, [ Pt(PPh₃)₂]⁺, [W(CO)₃Cp]⁺ and the anionic thiocarbonyl complexes [HB(pz)₃(OC)₂M(CS)]⁻ (M = Mo, W) have been prepared. Their spectroscopic data indicate that the addition of the cations occurs at the sulphur atom to give end‐to‐end thiocarbonyl bridged complexes [HB(pz)₃(OC)₂MCSM′L_n].     

Transient Phosphenium and Arsenium Ions versus Stable Stibenium and Bismuthenium Ions

Fluoride abstraction from bis-m-terphenylelement fluorides (2,6-Mes₂C₆H₃)₂EF (E=P, As) generated the highly reactive phosphenium ion [(2,6-Mes₂C₆H₃)₂P]⁺ and the arsenium ion [(2,6-Mes₂C₆H₃)₂As]⁺, which immediately underwent intramolecular electrophilic substitution and formation of an 1,2,4-trimethyl-6-mesityl-5-m-terphenyl-benzo[b]phospholium ion and an 1,2,4-trimethyl-6-mesityl-5-m-terphenyl-benzo[b]arsolium ion, respectively. The formation of the latter involved a methyl group migration from the ortho-position of a flanking mesityl group to the meta-position. This reactivity of [(2,6-Mes₂C₆H₃)₂E]⁺ (E=P, As) is in sharp contrast to the related stibenium ion [(2,6-Mes₂C₆H₃)₂Sb]⁺ and bismuthenium ion [(2,6-Mes₂C₆H₃)₂Bi]⁺, which have been recently isolated and fully characterized (Angew. Chem. Int. Ed. 2018, 57 , 10080–10084). On the basis of DFT calculations, a mechanism for the rearrangement of the phosphenium and arsenium ions into the phospholium and arsolium ions is proposed, which is not feasible for the stibenium and bismuthenium ions.     

Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)amide Ligands

A study regarding coordination chemistry of the bis(diphenylphosphino)amide ligand Ph₂P‐N‐PPh₂ at Group 4 metallocenes is presented herein. Coordination of N,N‐bis(diphenylphosphino)amine ( 1 ) to [(Cp₂TiCl)₂] (Cp=η⁵‐cyclopentadienyl) generated [Cp₂Ti(Cl)P(Ph₂)N(H)PPh₂] ( 2 ). The heterometallacyclic complex [Cp₂Ti(κ²‐P,P‐Ph₂P‐N‐PPh₂)] ( 3 Ti ) can be prepared by reaction of 2 with n‐butyllithium as well as from the reaction of the known titanocene–alkyne complex [Cp₂Ti(η²‐Me₃SiC₂SiMe₃)] with the amine 1 . Reactions of the lithium amide [(thf)₃Li{N(PPh₂)₂}] with [Cp₂MCl₂] (M=Zr, Hf) yielded the corresponding zirconocene and hafnocene complexes [Cp₂M(Cl){κ²‐N,P‐N(PPh₂)₂}] ( 4 Zr and 4 Hf ). Reduction of 4 Zr with magnesium gave the highly strained heterometallacycle [Cp₂Zr(κ²‐P,P‐Ph₂P‐N‐PPh₂)] ( 3 Zr ). Complexes 2 , 3 Ti , 4 Hf , and 3 Zr were characterized by X‐ray crystallography. The structures and bondings of all complexes were investigated by DFT calculations.     

Metal Derivatives of Heterocyclic‐2‐thiones: Crystal Structures of [Bis(diphenylphosphanyl)propane][bis(pyrimidine‐2‐thiolato)]ruthenium(II) and [Bis(diphenylphosphanyl)methane][bis(pyridine‐2‐thiolato)]ruthenium(II)

Ruthenium(II) Complexes containing pyrimidine‐2‐thiolate (pymS^–) and bis(diphenylphosphanyl)alkanes [Ph₂P–(CH₂)_m–PPh₂, m = 1, dppm; m = 2, dppe; m = 3, dppp; m = 4, dppb] are described. Reactions of [RuCl₂L₂] (L = dppm, dppp) and [Ru₂Cl₄L₃] (L = dppb) with pyrimidine‐2‐thione (pymSH) in 1:2 molar ratio in dry benzene in the presence of Et₃N base yielded the [Ru(pymS)₂L] complexes (pymS^– = pyrimidine‐2‐thiolate; L = dppm ( 1 ); dppp ( 3 ); dppb ( 4 )). The complex [Ru(pymS)₂(dppe)] ( 2 ) was indirectly prepared by the reaction of [Ru(pymS)₂(PPh₃)₂] with dppe. These complexes were characterized using analytical data, IR, ¹H, ¹³C, ³¹P NMR spectroscopy, and X‐ray crystallography (complex 3 ). The crystal structure of the analogous complex [Ru(pyS)₂(dppm)] ( 5 ) with the ligand pyridine‐2‐thiolate (pyS^–) was also described. X‐ray crystallographic investigation of complex 3 has shown two four‐membered chelate rings (N, S donors) and one six‐membered ring (P, P donors) around the metal atom. Compound 5 provides the first example in which Ru^II has three four‐membered chelate rings: two made up by N, S donor ligands and one made up by P, P donor ligand. The arrangement around the metal atoms in each complex is distorted octahedral with cis:cis:trans:P, P:N, N:S, S dispositions of the donor atoms. The ³¹P NMR spectroscopic data revealed that the complexes are static in solution, except 2 , which showed the presence of more than one species.     

A Masked Cuprous Hydride as a Catalyst for Carbonyl Hydrosilylation in Aqueous Solutions

Redox‐unstable cuprous hydridotriphenylborate was isolated as an N‐heterocyclic carbene adduct [(IPr)Cu(HBPh₃)] (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) with good thermal stability. Although this compound displays a contact ion‐pair structure, Cu^IH‐like catalytic activity was envisaged in carbonyl hydrosilylation. Sufficient moisture stability allowed the catalysis in aqueous/organic media. Mechanistic study further showed that a phenyl group on the borate anion is abstracted by [(IPr)Cu]⁺ to give the cationic organocopper complex [(IPr)₂Cu₂(μ‐Ph)][BPh₄].     

Synthesis and Basic Coordination Properties of Side‐chain Functionalized Bis‐phosphonio‐benzophospholides

Salts containing bis‐phosphonio‐benzophospholide cations 2 a – d with an additional donor site in one of the phosphonio‐moieties were synthesized either via quaternisation of the Ph₂P moiety in the neutral phosphonio‐benzophospholide 3 , or via ring‐closure of the functionalized bis‐phosphonium ion 6 . The Ph₂P‐substituted cation 2 d formed chelate complexes [M(k²P,P′‐ 2 d )(CO)_n]⁺ with M(CO)_n = Ni(CO)₂, Fe(CO)₃, Cr(CO)₄. In the latter case, competition between formation of the chelate and a complex [Cr(kP‐ 2 d )₂(CO)₄]²⁺ was observed, and interpreted as a consequence of antagonism between the stabilizing chelate effect and destabilizing ligand–ligand repulsions. The formation of stable Pd^II and Pt^II complexes of 2 d suggests that the chelate effect may also overcome the kinetic inhibition which so far prevented isolation of complexes of these metals with bis‐phosphonio‐benzophospholides. The newly synthesized ligands and complexes were characterized by spectroscopic data, and an X‐ray crystal structure analysis of 2 a [Br]. The reactivity of chelate complexes towards Ph₃P indicates that the ring phosphorus atom is a weaker donor than the pendant Ph₂P‐group.     

Spectroscopic Evidence for a Monomeric Copper(I) Hydride and Crystallographic Characterization of a Monomeric Silver(I) Hydride

(1,3‐bis[2,6‐bis[di(4‐tert‐butylphenyl)methyl]‐4‐methylphenyl]imidazol‐2‐ylidene)CuOPh [(IPr**)CuOPh] reacts with poly(methylhydrosiloxane) as the hydride donor to afford the monomeric (IPr**)CuH complex, which was spectroscopically characterized. The latter is in equilibrium in solution with [(IPr**)CuH]₂, the dimer being exclusively present in the solid state. These results support the hypothesis that copper hydride aggregates dissociate in solution. In contrast, addition of pinacolborane to [(IPr**)AgOPh] at −40 °C allows the isolation of the monomeric (IPr**)AgH complex, which was crystallographically characterized.     

Synthesis,Characterization, and X‐ray Structures of Ru3(CO)9(dotpm)(L) Complexes [L = PPh3, P(C6H4Cl‐p)3, and PPh2(C6H4Br‐p)]

The reaction of Ru₃(CO)₁₀(dotpm) ( 1 ) [dotpm = (bis(di‐ortho‐tolylphosphanyl)methane)] and one equivalent of L [L = PPh₃, P(C₆H₄Cl‐p)₃ and PPh₂(C₆H₄Br‐p)] in refluxing n‐hexane afforded a series of derivatives [Ru₃(CO)₉(dotpm)L] ( 2 – 4 ), respectively, in ca. 67–70 % yield. Complexes 2 – 4 were characterized by elemental analysis (CHN), IR, ¹H NMR, ¹³C{¹H} NMR and ³¹P{¹H} NMR spectroscopy. The molecular structures of 2 , 3 , and 4 were established by single‐crystal X‐ray diffraction. The bidentate dotpm and monodentate phosphine ligands occupy equatorial positions with respect to the Ru triangle. The effect of substitution resulted in significant differences in the Ru–Ru and Ru–P bond lengths.     

Two mononuclear cobalt(III) complexes exhibiting phenoxazinone synthase activity

Two mononuclear cobalt(III) complexes, namely [LCo(tmtp)(H₂O)]ClO₄?MeOH ( 1 ) (tmtp = tri(m‐tolyl)phosphine) and [LCo(PPh₃)(H₂O)]PF₆ ( 2 ), have been prepared from a polydentate ligand, N,N′‐bis(3‐methoxysalicylidehydene)cyclohexane‐1,2‐diamine ( H ₂ L ). Standard analytical techniques such as elemental analysis and UV–visible and Fourier transform infrared spectroscopies were used to characterize both complexes. The solid‐state molecular structures of both complexes were confirmed from single‐crystal X‐ray diffraction analysis. Structural analyses show that the Co(III) ion occupies the centre of a distorted octahedron in a complex cation: [LCo(tmtp)(H₂O)]⁺ and [LCo(PPh₃)(H₂O)]⁺ for 1 and 2 , respectively. Phenoxazinone synthase activities of both complexes were screened. Kinetic studies and other experimental observations reveal that the reaction follows rate saturation kinetics and proceeds through the formation of a catalyst (complex)–substrate adduct. The turnover number (K_cat) of complex 2 is 54.07 h^?1, exhibiting better catalytic activity compared to 1 (K_cat = 45.11 h^?1).     

Environmentally responsive micelles from polystyrene–poly[bis(potassium carboxylatophenoxy)phosphazene] block copolymers

Amphiphilic diblock copolymers that contained hydrophilic poly[bis(potassium carboxylatophenoxy)phosphazene] segments and hydrophobic polystyrene sections were synthesized via the controlled cationic polymerization of Cl₃P?NSiMe₃ with a polystyrenyl–phosphoranimine as a macromolecular terminator. These block copolymers self‐associated in aqueous media to form micellar structures which were investigated by fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. The size and shape of the micelles were not affected by the introduction of different monovalent cations (Li⁺, K⁺, Na⁺, and Cs⁺) into the stable micellar solutions. However, exposure to divalent cations induced intermicellar crosslinking through carboxylate groups, which caused precipitation of the ionically crosslinked aggregates from solution. This micelle‐coupling behavior was reversible: the subsequent addition of monovalent cations caused the redispersion of the polystyrene‐block‐poly[bis(potassium carboxylatophenoxy)phosphazene] (PS–KPCPP) block copolymers into a stable micellar solution. Aqueous micellar solutions of PS–KPCPP copolymers also showed pH‐dependent behavior. These attributes make PS–KPCPP block copolymers suitable for studies of guest retention and release in response to ion charge and pH. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2912–2920, 2005     

Sulfur‐assisted Chloride and Triphenylphosphine Dissociation of Palladium(II) Complex with Phenyloxythiocarbonyl,PhOC(S), Containing Ligand: X‐Ray Structure of [Pd(PPh3)2{η1‐C(S)OPh}(Cl)]

Treatment of Pd(PPh₃)₄ with phenylchlorothionoformate, PhOC(S)Cl, in dichloromethane at ?20 °C produces the phenyloxythiocarbonyl complex [Pd(PPh₃)₂{η¹‐C(S)OPh}(Cl)], 1 . The ³¹P{¹H} NMR spectrum of 1 shows the dissociation of either the chloride or the triphenylphosphine ligand to form complex [Pd(PPh₃)₂(η²‐SCOPh)][Cl], 2 or the dipalladium complex [Pd(PPh₃)Cl]₂(μ,η²‐SCOPh)₂, 3 . Continuous stirring of the dichloromethane solution of 1 at room temperature for 4 h forms the dipalladinum complex [Pd(PPh₃)Cl]₂(μ,η²‐SCOPh)₂, 3 as the final product. Respective reactions of 1 and Et₂NCS₂Na or dppa {bis(diphenylphosphino)amine} gives complex [Pd(PPh₃){η¹‐C(S)OPh}(η²‐S₂CNEt₂)], 4 or [Pd(PPh₃){η¹‐C(S)OPh}(η²‐dppa)][Cl], 5 . Complex 1 is determined by single‐crystal X‐ray diffraction and crystallized in the monoclinic space group P2₁ with Z = 4. The cell dimensions of 1 are as follows: a = 9.5613(1) Å, b = 33.6732(3) Å, c = 12.2979(1) Å.     

Coordination Chemistry of Gold Catalysts in Solution: A Detailed NMR Study

Coordination chemistry of gold catalysts bearing eight different ligands [L=PPh₃, JohnPhos (L2), Xphos (L3), DTBP, IMes, IPr, dppf, S‐tolBINAP (L8)] has been studied by NMR spectroscopy in solution at room temperature. Cationic or neutral mononuclear complexes LAuX (L=L2, L3, IMes, IPr; X=charged or neutral ligand) underwent simple ligand exchange without giving any higher coordinate complexes. For L2AuX the following ligand strength series was determined: MeOH?hex‐3‐yne <MeCN≈OTf^??Me₂S<2,6‐lutidine<4‐picoline<CF₃CO₂^?≈DMAP<TMTU<PPh₃<OH^?≈Cl^?. Some heteroligand complexes DTBPAuX exist in solution in equilibrium with the corresponding symmetrical species. Binuclear complexes dppf(AuOTf)₂ and S‐tolBINAP(AuOTf)₂ showed different behavior in exchange reactions with ligands depending on the ligand strength. Thus, PPh₃ causes abstraction of one gold atom to give mononuclear complexes LLAuPPh₃⁺ and (Ph₃P)_nAu⁺, but other N and S ligands give ordinary dicationic species LL(AuNu)₂²⁺. In reactions with different bases, LAu⁺ provided new oxonium ions whose chemistry was also studied: (DTBPAu)₃O⁺, (L2Au)₂OH⁺, (L2Au)₃O⁺, (L3Au)₂OH⁺, and (IMesAu)₂OH⁺. Ultimately, formation of gold hydroxide LAuOH (L=L2, L3, IMes) was studied. Ligand‐ or base‐assisted interconversions between (L2Au)₂OH⁺, (L2Au)₃O⁺, and L2AuOH are described. Reactions of dppf(AuOTf)₂ and S‐tolBINAP(AuOTf)₂ with bases provided more interesting oxonium ions, whose molecular composition was found to be [dppf(Au)₂]₃O₂²⁺, L8(Au)₂OH⁺, and [L8(Au)₂]₃O₂²⁺, but their exact structure was not established. Several reactions between different oxonium species were conducted to observe mixed heteroligand oxonium species. Reaction of L2AuNCMe⁺ with S^2? was studied; several new complexes with sulfide are described. For many reversible reactions the corresponding equilibrium constants were determined.     

Stable ‐ESiMe3 Complexes of CuI and AgI (E=S,Se) with NHCs: Synthons in Ternary Nanocluster Assembly

As a part of efforts to prepare new “metallachalcogenolate” precursors and develop their chemistry for the formation of ternary mixed‐metal chalcogenide nanoclusters, two sets of thermally stable, N‐heterocyclic carbene metal–chalcogenolate complexes of the general formula [(IPr)Ag?ESiMe₃] (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene; E=S, 1 ; Se, 2 ) and [(iPr₂‐bimy)Cu?ESiMe₃]₂ (iPr₂‐bimy=1,3‐diisopropylbenzimidazolin‐2‐ylidene; E=S, 4 ; Se, 5 ) are reported. These are prepared from the reaction between the corresponding carbene metal acetate, [(IPr)AgOAc] and [(iPr‐bimy)CuOAc] respectively, and E(SiMe₃)₂ at low temperature. The reaction of [(IPr)Ag?ESiMe₃] 1 with mercury(II) acetate affords the heterometallic complex [{(IPr)AgS}₂Hg] 3 containing two (IPr)Ag?S^? fragments bonded to a central Hg^II, representing a mixed mercury–silver sulfide complex. The reaction of [(iPr₂‐bimy)Cu‐SSiMe₃]₂, which contains a smaller N‐heterocyclic‐carbene, with mercuric(II) acetate affords the high nuclearity cluster, [(iPr₂‐bimy)₆Cu₁₀S₈Hg₃] 6 . The new N‐heterocyclic carbene metal–chalcogenolate complexes 1 , 2 , 4 , 5 and the ternary mixed‐metal chalcogenolate complex 3 and cluster 6 have been characterized by multinuclear NMR spectroscopy (¹H and ¹³C), elemental analysis and single‐crystal X‐ray diffraction.