Bipyridyl Functionalized NHC-Sulfenyl, Selenenyl Cations; Potential Species for Alkylation Reactions and Ligands in Copper(I) Catalysis.

Reactions of bipyridyl-functionalized imidazole-thiones and selones with MeX (X=I, OTf) afforded sulfenyl and selenenyl cations [(NNC)EMe]X (2/3, E=S, Se). Further reactions of these main-group cations with [Cu(CHCN)]BF, Cu(OTf) furnished dicationic [{Cu(μ-I)(NNC)EMe}][Y] (5/6, Y=BF, OTf) and tricationic copper(I) complexes [Cu{(NNC)EMe}](OTf)BF (7 a/7 b) when employed [(NNC)EMe]I and [(NNC)EMe]OTf respectively. All these cationic complexes were characterized by various spectroscopic techniques, including X-ray diffraction analysis.

NHC Ligand-Enabled Cu(I)-Catalyzed Double Hydroamination: A Regio- and Chemoselective Bicyclization of -Amino 1,6-Diyne.

In this work, we have developed an efficient method for the intramolecular double hydroamination of aniline by employing -amino 1,6-diyne as a potential starting material. This protocol enables easy access to bioactive motif 3,4-dihydro-1-[1,4]oxazino[4,3-]indole through an intramolecular cascade bicyclization and concomitant isomerization pathway in one pot. This transformation has been effectively achieved by utilizing a stereoelectronically tuned, π-accepting NHC-supported copper(I) system.

New cationic coinage metal complexes featuring silyl group functionalized phosphine: syntheses, structures and catalytic studies in alkyne-azide cycloaddition reactions.

A series of coinage metal complexes bearing rarely explored -silylated phosphine is reported. The treatment of diphenyl(2-(trimethylsilyl)phenyl)phosphine (1) with CuCl and [Cu(CHCN)]BF furnished the corresponding neutral [(1)CuCl] (2) and mono-cationic [(1)Cu(CHCN)]BF (3) complexes, respectively. The reactions of 1 with AgX (X = BF, NO) in 2 : 1 ratio furnished the corresponding mono cationic dicoordinate silver(I) complexes of the type [(1)Ag]X (X = BF (4a), NO (4b)).

Dicationic copper(I) complexes bearing ENE (E = S, Se) pincer ligands; catalytic applications in regioselective cyclization of 1,6-diynes.

Two novel dicationic binuclear Cu(I) complexes of the type [{(BPPP)E}Cu][BF] (E = S (3a); Se (3b)) bearing (BPPP)E (BPPP = bis(diphenylphosphino)pyridine) pincer systems were isolated, and structurally characterized. The solid-state structures of 3a/3b display the presence of intermolecular cuprophilic (Cu⋯Cu) interactions between the two monocationic species, and consist of weak Cu⋯S bonding between the two cations. Besides, complex 3a was introduced as a molecular copper(I) catalyst in cyclization reactions, and new protocols were developed for the synthesis of a series of new oxazole and triazole derivatives bearing alkyne-phenyl propargylic ether substituents.

N-Heterocyclic Carbene Analogues of Nucleophilic Phosphinidene Transition Metal Complexes.

Chloride abstraction from the complexes [(η -p-cymene){(IDipp)P}MCl] (2 a, M=Ru; 2 b, M=Os) and [(η -C Me ){(IDipp)P}IrCl] (3 b, IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBAr ) in the presence of trimethylphosphine (PMe ), 1,3,4,5-tetramethylimidazolin-2-ylidene ( IMe) or carbon monoxide (CO) afforded the complexes [(η -p-cymene){(IDipp)P}M(PMe )]BAr ] (4 a, M=Ru; 4 b, M=Os), [(η -p-cymene){(IDipp)P}Os( IMe)]BAr ] (5) and [(η -C Me ){(IDipp)P}IrL][BAr ] (6, L=PMe ; 7, L= IMe; 8, L=CO). These cationic N-heterocyclic carbene-phosphinidene complexes feature very similar structural and spectroscopic properties as prototypic nucleophilic arylphosphinidene complexes such as low-field P NMR resonances and short metal-phosphorus double bonds. Density functional theory (DFT) calculations reveal that the metal-phosphorus bond can be described in terms of an interaction between a triplet [(IDipp)P] cation and a triplet metal complex fragment ligand with highly covalent σ- and π-contributions.

Isolation of Carbene-Stabilized Arsenic Monophosphide [AsP] and its Radical Cation [AsP] and Dication [AsP].

Arsenic monophosphide (AsP) species supported by two different N-heterocyclic carbenes were prepared by reaction of (IDipp)PSiMe (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with (IMes)AsCl (2) (IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) to afford the dichloride [(IMes)As(Cl)P(IDipp)]Cl (3), which upon reduction with KC furnished heteroleptic [(IMes)AsP(IDipp)] (4). The corresponding mono- and dications [(IMes)AsP(IDipp)][PF ], [5]PF , and [(IMes)AsP(IDipp)][GaCl ] [6][GaCl ] , respectively, were prepared by one-electron oxidation of 4 with ferrocenium hexafluorophosphate, [Fc]PF or by chloride abstraction from 3 with two equivalents of GaCl , respectively. Compounds 4-6 represent rare examples of heterodiatiomic interpnictogen compounds, and X-ray crystal structure determinations together with density functional theory (DFT) calculations reveal a consecutive shortening of the As-P bond lengths and increasing bond order, in agreement with the presence of an arsenic-phosphorus single bond in 4 and a double bond in 6 .

N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry.

N-Heterocyclic carbenes (NHC) are nowadays ubiquitous and indispensable in many research fields, and it is not possible to imagine modern transition metal and main group element chemistry without the plethora of available NHCs with tailor-made electronic and steric properties. While their suitability to act as strong ligands toward transition metals has led to numerous applications of NHC complexes in homogeneous catalysis, their strong σ-donating and adaptable π-accepting abilities have also contributed to an impressive vitalization of main group chemistry with the isolation and characterization of NHC adducts of almost any element. Formally, NHC coordination to Lewis acids affords a transfer of nucleophilicity from the carbene carbon atom to the attached exocyclic moiety, and low-valent and low-coordinate adducts of the p-block elements with available lone pairs and/or polarized carbon-element π-bonds are able to act themselves as Lewis basic donor ligands toward transition metals.

A modular approach to carbene-stabilized diphosphorus species.

Heteroleptic N-heterocyclic dicarbene-diphosphorus species were prepared by reaction of the carbene-phosphinidene adduct (IPr)PSiMe (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with the carbene-phosphorus trichloride adduct (IMes)PCl (2, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene), which furnished the dichloride [(IPr)PPCl(IMes)]Cl (3). Reduction of 3 with potassium graphite (KC) afforded [(IPr)PP(IMes)] (4). The corresponding radical cation [(IPr)PP(IMes)]˙ (5˙) is isolated as [5]PF by reaction of 4 with ferrocenium hexafluorophosphate, whereas complexes containing the corresponding dication [(IPr)PP(IMes)] (6) can be isolated as the gallate and borate salts [6](GaCl) and [6](BAr) by chloride abstraction from 3 with GaCl or sodium tetrakis[bis(3,5-trifluoromethyl)phenyl]borate (NaBAr), respectively.

N-Heterocyclic Carbene-Phosphinidene and Carbene-Phosphinidenide Transition Metal Complexes.

Half-sandwich complexes of the N-heterocyclic carbene-phosphinidene adduct [(IPr)PH] (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were prepared by its reaction with dimeric complexes of the type [LMCl], which afforded the three-legged piano-stool complexes [LMCl{HP(IPr)}] (9a/9b: M = Ru/Os, L = η-p-cymene; 10a/10b: M = Rh/Ir, L = η-CMe). Their conversion into the corresponding carbene-phosphinidenide complexes [LMCl{P(IPr)}] (11a/11b: M = Ru/Os; 12a/12b: M = Rh/Ir) with a two-legged piano stool geometry was studied by NMR spectroscopy in the presence of the strong base 1,8-diazabicyclo[5.4.

N-Heterocyclic carbene-stabilised arsinidene (AsH).

N-Heterocyclic carbene adducts of the parent arsinidene (AsH) were prepared by two different synthetic routes, either by reaction of As(SiMe) with 2,2-difluoroimidazolines followed by desilylation or by reaction of [Na(dioxane)][AsCO] with imidazolium chlorides.

N-Heterocyclic Carbene-Phosphinidene Complexes of the Coinage Metals.

Coinage metal complexes of the N-heterocyclic carbene-phosphinidene adduct IPr⋅PPh (IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were prepared by its reaction with CuCl, AgCl, and [(Me2 S)AuCl], which afforded the monometallic complexes [(IPr⋅PPh)MCl] (M=Cu, Ag, Au). The reaction with two equivalents of the metal halides gave bimetallic [(IPr⋅PPh)(MCl)2 ] (M=Cu, Au); the corresponding disilver complex could not be isolated. [(IPr⋅PPh)(CuOTf)2 ] was prepared by reaction with copper(I) trifluoromethanesulfonate.

N-heterocyclic carbene-phosphinidyne transition metal complexes.

The N-heterocyclic carbene-phosphinidene adduct IPrPSiMe3 is introduced as a synthon for the preparation of terminal carbene-phosphinidyne transition metal complexes of the type [(IPrP)MLn ] (MLn =(η(6) -p-cymene)RuCl) and (η(5) -C5 Me5 )RhCl). Their spectroscopic and structural characteristics, namely low-field (31) P NMR chemical shifts and short metal-phosphorus bonds, show their similarity with arylphosphinidene complexes. The formally mononegative IPrP ligand is also capable of bridging two or three metal atoms as demonstrated by the preparation of bi- and trimetallic RuAu, RhAu, Rh2 , and Rh2 Au complexes.

Colloidal nickel/gallium nanoalloys obtained from organometallic precursors in conventional organic solvents and in ionic liquids: noble-metal-free alkyne semihydrogenation catalysts.

Efforts to replace noble-metal catalysts by low-cost alternatives are of constant interest. The organometallic, non-aqueous wet-chemical synthesis of various hitherto unknown nanocrystalline Ni/Ga intermetallic materials and the use of NiGa for the selective semihydrogenation of alkynes to alkenes are reported. Thermal co-hydrogenolysis of the all-hydrocarbon precursors [Ni(COD)2] (COD = 1,5-cyclooctadiene) and GaCp* (Cp* = pentamethylcyclopentadienyl) in high-boiling organic solvents mesitylene and n-decane in molar ratios of 1 : 1, 2 : 3 and 3 : 1 yields the nano-crystalline powder materials of the over-all compositions NiGa, Ni2Ga3 and Ni3Ga, respectively.

Low-valent Ge(2) and Ge(4) species trapped by N-heterocyclic gallylene.

Much π and no σ: quantum chemical calculations showed that the Ge atoms of the Ga(2)Ge(2) core in Ge(2)[Ga(DPP)](2) are not bonded by σ interactions, but rather by a transannular π interaction. The compound is formed by reduction of (PCy(3))⋅GeCl(2) with Ga(DDP)/KC(8) which also yielded a further product Ge(4)[Ga(DPP)](2) with a Ge(4) tetrahedron (DDP=HC(CMeNC(6)H(3)-2,6-iPr(2))(2)).

P-P bond activation of P4 tetrahedron by group 13 carbenoid and its bis molybdenum pentacarbonyl adduct.

Activation of white phosphorus with Ga(DDP) (DDP = 2-diiso-propylphenylamino-4-diiso-propylphenylimino-2-pentene) afforded [(DDP)Ga(P(4))] (1) by insertion of the Ga(I) center at one of the six P-P bonded edges of the P(4) tetrahedron. Further reaction of 1 with three equivalents of Mo(CO)(6) results in the formation of [(DDP)Ga(eta(2:1:1)-P(4)){Mo(CO)(5)}(2)] x 2 toluene (2). Compounds 1 and 2 are characterized by (1)H, (13)C, and (31)P NMR spectroscopy, elemental analysis, and single crystal X-ray structural analysis.