Stoichiometric and catalytic reactivity of the N-heterocyclic carbene ruthenium hydride complexes [Ru(NHC)(L)(CO)HCl] and [Ru(NHC)(L)(CO)H(eta2-BH4)] (L=NHC, PPh3)

Thermolysis of [Ru(AsPh3)3(CO)H2] with the N-aryl heterocyclic carbenes (NHCs) IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) or the adduct SIPr.(C6F5)H (SIPr=1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene), followed by addition of CH2Cl2, affords the coordinatively unsaturated ruthenium hydride chloride complexes [Ru(NHC)2(CO)HCl] (NHC=IMes , IPr , SIPr ). These react with CO at room temperature to yield the corresponding 18-electron dicarbonyl complexes . Reduction of and [Ru(IMes)(PPh3)(CO)HCl] () with NaBH4 yields the isolable borohydride complexes [Ru(NHC)(L)(CO)H(eta2-BH4)] (, L=NHC, PPh3). Both the bis-IMes complex and the IMes-PPh3 species react with CO at low temperature to give the eta1-borohydride species [Ru(IMes)(L)(CO)2H(eta1-BH4)] (L=IMes , PPh3), which can be spectroscopically characterised. Upon warming to room temperature, further reaction with CO takes place to afford initially [Ru(IMes)(L)(CO)2H2] (L=IMes, L=PPh3) and, ultimately, [Ru(IMes)(L)(CO)3] (L=IMes , L=PPh3). Both and lose BH3 on addition of PMe2Ph to give [Ru(IMes)(L)(L')(CO)H2](L=L'=PMe2Ph; L=PPh3, L'=PMe2Ph). Compounds and have been tested as catalysts for the hydrogenation of aromatic ketones in the presence of (i)PrOH and H2. For the reduction of acetophenone, catalytic activity varies with the NHC present, decreasing in the order IPr>IMes>SIMes.     

Dithiocarboxylate complexes of ruthenium(II) and osmium(II)

The ruthenium(II) complexes [Ru(R)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh) are formed on reaction of IPr·CS(2) with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh(3))(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) are formed in the same manner when ICy·CS(2) is employed. The ligand IMes·CS(2) reacts with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] to form the compounds [Ru(R)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh). Two osmium analogues, [Os(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) and [Os(C(C≡CPh)=CHPh)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS(2) is used, an unusual product, [Ru(κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IDip)Cl(CO)(PPh(3))(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] also reacts with IMes·CS(2) and NH(4)PF(6) to yield the analogous product [Ru{κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IMes}Cl(CO)(PPh(3))(2)](+)via the intermediate [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+). Structural studies are reported for [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)]PF(6) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)]PF(6).     

Synthesis, structure, and reactivity of ruthenium carboxylato and 2-oxocarboxylato complexes bearing the bis(3,5-dimethylpyrazol-1-yl)acetato ligand

A series of ruthenium(II) acetonitrile, pyridine (py), carbonyl, SO2, and nitrosyl complexes [Ru(bdmpza)(O2CR)(L)(PPh3)] (L = NCMe, py, CO, SO2) and [Ru(bdmpza)(O2CR)(L)(PPh3)]BF4 (L = NO) containing the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand, a N,N,O heteroscorpionate ligand, have been prepared. Starting from ruthenium chlorido, carboxylato, or 2-oxocarboxylato complexes, a variety of acetonitrile complexes [Ru(bdmpza)Cl(NCMe)(PPh3)] (4) and [Ru(bdmpza)(O2CR)(NCMe)(PPh3)] (R = Me (5a), R = Ph (5b)), as well as the pyridine complexes [Ru(bdmpza)Cl(PPh3)(py)] (6) and [Ru(bdmpza)(O2CR)(PPh3)(py)] (R = Me (7a), R = Ph (7b), R = (CO)Me (8a), R = (CO)Et (8b), R = (CO)Ph) (8c)), have been synthesized. Treatment of various carboxylato complexes [Ru(bdmpza)(O2CR)(PPh3)2] (R = Me (2a), Ph (2b)) with CO afforded carbonyl complexes [Ru(bdmpza)(O2CR)(CO)(PPh3)] (9a, 9b). In the same way, the corresponding sulfur dioxide complexes [Ru(bdmpza)(O2CMe)(PPh3)(SO2)] (10a) and [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) were formed in a reaction of the carboxylato complexes with gaseous SO2. None of the 2-oxocarboxylato complexes [Ru(bdmpza)(O2C(CO)R)(PPh3)2] (R = Me (3a), Et (3b), Ph (3c)) showed any reactivity toward CO or SO2, whereas the nitrosyl complex cations [Ru(bdmpza)(O2CMe)(NO)(PPh3)](+) (11) and [Ru(bdmpza)(O2C(CO)Ph)(NO)(PPh3)](+) (12) were formed in a reaction of the acetato 2a or the benzoylformato complex 3c with an excess of nitric oxide. Similar cationic carboxylato nitrosyl complexes [Ru(bdmpza)(O2CR)(NO)(PPh3)]BF4 (R = Me (13a), R = Ph (13b)) and 2-oxocarboxylato nitrosyl complexes [Ru(bdmpza)(O2C(CO)R)(NO)(PPh3)]BF4 (R = Me (14a), R = Et (14b), R = Ph (14c)) are also accessible via a reaction with NO[BF4]. X-ray crystal structures of the chlorido acetonitrile complex [Ru(bdmpza)Cl(NCMe)(PPh3)] (4), the pyridine complexes [Ru(bdmpza)(O2CMe)(PPh3)(py)] (7a) and [Ru(bdmpza)(O2CC(O)Et)(PPh3)(py)] (8b), the carbonyl complex [Ru(bdmpza)(O2CPh)(CO)(PPh3)] (9b), the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b), as well as the nitrosyl complex [Ru(bdmpza)(O2C(CO)Me)(NO)(PPh3)]BF4 (14a), are reported. The molecular structure of the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) revealed a rather unusual intramolecular SO2-O2CPh Lewis acid-base adduct.     

The reactivity of N-heterocyclic carbenes and their precursors with [Ru(3)(CO)(12)

The ambient temperature reaction of the N-heterocyclic carbenes (NHCs) 1,3-dimesitylimidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp) with the triruthenium cluster [Ru(3)(CO)(12)], in a 3 : 1 stoichiometric ratio, results in homolytic cleavage of the cluster to quantitatively afford the complexes [Ru(CO)(4)(NHC)] (; NHC = IMes, ; NHC = IDipp). Reaction of the 2-thione or hydrochloride precursors to IMes, i.e. S[double bond, length as m-dash]IMes and IMes.HCl, with the same triruthenium cluster affords the complexes [Ru(4)(mu(4)-S)(2)(CO)(9)(IMes)(2)] () and [Ru(4)(mu(4)-S)(CO)(10)(IMes)(2)] () (3 : 1 and 2 : 1 reaction), and [{Ru(mu-Cl)(CO)(2)(IMes)}(2)] () (3 : 1 reaction) respectively. By contrast, the complex [Ru(3)(mu(3)-S)(2)(CO)(7)(IMeMe)(2)] (), where IMeMe is 1,3,4,5-tetramethylimidazol-2-ylidene, is the sole product of the 2 : 1 stoichiometric reaction of S[double bond, length as m-dash]IMeMe with [Ru(3)(CO)(12)]. Compounds -, and have been structurally characterised by single crystal X-ray diffraction.     

C-H activation and C=C double bond formation reactions in iridium ortho-methyl arylphosphane complexes

The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species.     

Synthetic routes to [Au(NHC)(OH)] (NHC = N-heterocyclic carbene) complexes

New procedures for the synthesis of [Au(NHC)(OH)] are reported. Initially, a two-step reaction via the digold complex [{Au(NHC)}(2)(μ-OH)][BF(4)] was probed, enabling the preparation of the novel [Au(SIPr)(OH)] complex and of its previously reported congener [Au(IPr)(OH)]. After further optimization, a one-step procedure was developed.     

Behavior of neutral phosphido derivatives of platinum and palladium toward silver centers

The reaction of the neutral binuclear complexes [(R(F))(2)Pt(μ-PPh(2))(2)M(phen)] (phen = 1,10-phenanthroline, R(F) = C(6)F(5); M = Pt, 1; M = Pd, 2) with AgClO(4) or [Ag(OClO(3))(PPh(3))] affords the trinuclear complexes [AgPt(2)(μ-PPh(2))(2)(R(F))(2)(phen)(OClO(3))] (7a) or [AgPtM(μ-PPh(2))(2)(R(F))(2)(phen)(PPh(3))][ClO(4)] (M = Pt, 8; M = Pd, 9), which display an "open-book" type structure and two (7a) or one (8, 9) Pt-Ag bonds. The neutral diphosphine complexes [(R(F))(2)Pt(μ-PPh(2))(2)M(P-P)] (P-P = 1,2-bis(diphenylphosphino)methane, dppm, M = Pt, 3; M = Pd, 4; P-P = 1,2-bis(diphenylphosphino)ethane, dppe, M = Pt, 5; M = Pd, 6) react with AgClO(4) or [Ag(OClO(3))(PPh(3))], and the nature of the resulting complexes is dependent on both M and the diphosphine. The dppm Pt-Pt complex 3 reacts with [Ag(OClO(3))(PPh(3))], affording a silver adduct 10 in which the Ag atom interacts with the Pt atoms, while the dppm Pt-Pd complex 4 reacts with [Ag(OClO(3))(PPh(3))], forming a 1:1 mixture of [AgPdPt(μ-PPh(2))(2)(R(F))(2)(OClO(3))(dppm)] (11), in which the silver atom is connected to the Pt-Pd moiety through Pd-(μ-PPh(2))-Ag and Ag-P(k(1)-dppm) interactions, and [AgPdPt(μ-PPh(2))(2)(R(F))(2)(OClO(3))(PPh(3))(2)][ClO(4)] (12). The reaction of complex 4 with AgClO(4) gives the trinuclear derivative 11 as the only product. Complex 11 shows a dynamic process in solution in which the silver atom interacts alternatively with both Pd-μPPh(2) bonds. When P-P is dppe, both complexes 5 and 6 react with AgClO(4) or [Ag(OClO(3))(PPh(3))], forming the saturated complexes [(PPh(2)C(6)F(5))(R(F))Pt(μ-PPh(2))(μ-OH)M(dppe)][ClO(4)] (M = Pt, 13; Pd, 14), which are the result of an oxidation followed by a PPh(2)/C(6)F(5) reductive coupling. Finally, the oxidation of trinuclear derivatives [(R(F))(2)Pt(II)(μ-PPh(2))(2)Pt(II)(μ-PPh(2))(2)Pt(II)L(2)] (L(2) = phen, 15; L = PPh(3), 16) by AgClO(4) results in the formation of the unsaturated 46 VEC complexes [(R(F))(2)Pt(III)(μ-PPh(2))(2)Pt(III)(μ-PPh(2))(2)Pt(II)L(2)][ClO(4)](2) (17 and 18, respectively) which display Pt(III)-Pt(III) bonds.     

Synthesis of N-heterocyclic carbene rhenium(I) carbonyl complexes

Reaction of aminophosphinimine [RHN(CH(2))(2)N[double bond, length as m-dash]PPh(3)] (R = H, Et) with Re(2)(CO)(10) provided the NH-functionalized carbene rhenium complex [Re(2)(CNHCH(2)CH(2)NR)(CO)(9)] (3a, R = H, 3b, R = Et). Treatment of 3 with Br(2) provided the mono nuclear [Re(CNHCH(2)CH(2)NR)(CO)(4)Br] (1, R = H, 2, R = Et). However, NH-functionalized carbene complexes 1-3 did not undergo N-alkylation with alkyl halides to yield the N-substituted NHC complexes. The direct ligand substitution of [Re(CO)(5)Br] with a carbene donor was employed to prepare [Re(IMes(2))(CO)(4)Br] (6a, IMes(2) = 1,3-di-mesitylimidazol-2-ylidene; 6b, IMes(2) = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene). Analyses of spectroscopic and crystal data of 6a and 6b show similar corresponding data among these complexes, suggesting the saturated and unsaturated NHCs have similar bonding with Re(I) metal centers. Reduction of 6a and 6b with LiEt(3)BH yielded the corresponding hydrido complexes 7a-b [ReH(CO)(4)(IMes(2))], but not 1 and 2. Ligand substitution of 1, 6a and 6b toward 2,2'-bipyridine (bipy) was investigated. Crystal structures of 1, 3a-b, 6a-b and 7b were determined for characterization and comparison.     

Octahedral Ru(II) amido complexes TpRu(L)(L')(NHR) (Tp = hydridotris(pyrazolyl)borate; L = L' = P(OMe)3 or PMe3 or L = CO and L' = PPh3; R = H,Ph, or tBu): synthesis,characterization, and reactions with weakly acidic C-H bonds

The octahedral Ru(II) amine complexes [TpRu(L)(L')(NH(2)R)][OTf] (L = L' = PMe(3), P(OMe)(3) or L = CO and L' = PPh(3); R = H or (t)Bu) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(L')(NH(3))][OTf] or [TpRu(PMe(3))(2)(NH(2)(t)Bu)][OTf] yields the Ru(II) amido complexes TpRu(L)(L')(NH(2)) and TpRu(PMe(3))(2)(NH(t)Bu). Reactions of the parent amido complexes or TpRu(PMe(3))(2)(NH(t)Bu) with phenylacetylene at room temperature result in immediate deprotonation to form ruthenium-amine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] ion pair results in the formation of the Ru(II) phenylacetylide complex TpRu(PMe(3))(2)(C[triple bond]CPh) in >90% yield. The observation that [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] converts to the Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(L')(NH(3))][PhC(2)] yields multiple products is attributed to reluctant dissociation of ammonia compared with the (t)butylamine ligand (i.e., different rates for acetylide/amine exchange). These results are consistent with ligand exchange reactions of Ru(II) amine complexes [TpRu(PMe(3))(2)(NH(2)R)][OTf] (R = H or (t)Bu) with acetonitrile. The previously reported phenyl amido complexes TpRuL(2)(NHPh) [L = PMe(3) or P(OMe)(3)] react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL(2)(C[triple bond]CPh) in quantitative yields. Kinetic studies indicate that the reaction of TpRu(PMe(3))(2)(NHPh) with phenylacetylene occurs via a pathway that involves TpRu(PMe(3))(2)(OTf) or [TpRu(PMe(3))(2)(NH(2)Ph)][OTf] as catalyst. Reactions of 1,4-cyclohexadiene with the Ru(II) amido complexes TpRu(L)(L')(NH(2)) (L = L' = PMe(3) or L = CO and L' = PPh(3)) or TpRu(PMe(3))(2)(NH(t)Bu) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe(3))(2)(H), [Tp(PMe(3))(2)Ru[double bond]C[double bond]C(H)Ph][OTf], [Tp(PMe(3))(2)Ru=C(CH(2)Ph)[N(H)Ph]][OTf], and [TpRu(PMe(3))(3)][OTf] have been independently prepared and characterized. Results from solid-state X-ray diffraction studies of the complexes [TpRu(CO)(PPh(3))(NH(3))][OTf], [TpRu(PMe(3))(2)(NH(3))][OTf], and TpRu(CO)(PPh(3))(C[triple bond]CPh) are reported.     

8-Oxyquinolate iridium(I) complexes and their oxidative-addition reactions

The novel sixteen-electron complex [Ir(Oq)(COD)] (Oq = 8-oxyquinolate; COD = 1,5-cyclooctadiene) adds monodentate phosphines, phosphites or activated olefins irreversibly to give pentacoordinate iridium(I) complexes of the type [Ir(Oq)(COD)L] (L = PPh₃, P(OPh)₃, maleic anhydride or tetracyano-ethylene). Reaction of [Ir(Oq)(COD)] with some diphosphines leads to substitution products of the general formula [Ir(Oq)(diphos)] (diphos = 1,2-bis(diphenylphosphino)ethane or cis-1,2-bis(diphenylphosphino)ethylene). Carbon monoxide displaces the COD group from the complexes giving either [Ir(Oq)(CO)₂] or [Ir(Oq)(CO)L], and the latter undergo oxidative addition reactions with SnCl₄, Me₃SiCl, Me₃SnCl, MeI, allylbromide, PhCOCl, MeCOCl, Cl₂, Br₂, TlCl₃ and HCl leading to novel iridium(III) complexes.     

Novel hydridoirida-beta-diketones containing small molecules, CO, or ethylene: their behavior in coordinating solvents such as dimethylsulfoxide or acetonitrile

New hydridoirida-beta-diketones [IrH[(PPh2(o-C6H4CO))2H](CO)]ClO4 2 and [IrH[(PPh2(o-C6H4CO))2H](olefin)]BF4 (olefin = C2H4, 5; 1-hexene, 10) have been prepared. These complexes may afford new diacylhydridoiridium(III) derivatives. In chloroform solution, complex 2 is in equilibrium with the deprotonated diacylhydride trans-[IrH(PPh2(o-C6H4CO))2(CO)] complex 3. In DMSO, deprotonation of 2 occurs to yield the kinetically favored product 3, which isomerizes to the thermodynamically favored complex cis-[IrH(PPh2(o-C6H4CO))2(CO)] 4. Reprotonation of 4 with HBF4 in chlorinated solvents gives the cation in 2. In coordinating solvents such as dimethyl sulfoxide or acetonitrile, complex 5 undergoes displacement of ethylene to afford [IrH{(PPh2(o-C6H4CO))2H](L)]BF4 (L = DMSO, 7; CH3CN, 9). Complexes 5 and 7 undergo deprotonation by NEt3 to give the corresponding diacylhydrides. The ethylene complex gives only trans-[IrH(PPh2(o-C6H4CO))2(C2H4)] 6, while the dimethyl sulfoxide derivative affords a mixture of trans- and cis-[IrH(PPh2(o-C6H4CO))2(DMSO)] 8. Complex 10 shows inhibited alkene rotation around the Ir-olefin axis. All of the complexes were fully characterized spectroscopically. Single-crystal X-ray diffraction analysis was performed on complexes 3, 4, and 9. The 13C NMR and X-ray data point to a carbenoid character in the carbon atoms bonded to iridium in the irida--diketone fragment, so that it can be considered as an acyl(hydroxycarbene) moiety.     

Chemistry surrounding monomeric copper(I) methyl, phenyl, anilido, ethoxide, and phenoxide complexes supported by N-heterocyclic carbene ligands: reactivity consistent with both early and late transition metal systems

Monomeric copper(I) alkyl complexes that possess the N-heterocyclic carbene (NHC) ligands IPr, SIPr, and IMes [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] react with amines or alcohols to release alkane and form the corresponding monomeric copper(I) amido, alkoxide, or aryloxide complexes. Thermal decomposition reactions of (NHC)Cu(I) methyl complexes at temperatures between 100 and 130 degrees C produce methane, ethane, and ethylene. The reactions of (NHC)Cu(NHPh) complexes with bromoethane reveal increasing nucleophilic reactivity at the anilido ligand in the order (SIPr)Cu(NHPh) < (IPr)Cu(NHPh) < (IMes)Cu(NHPh) < (dtbpe)Cu(NHPh) [dtbpe = 1,2-bis(di-tert-butylphosphino)ethane]. DFT calculations suggest that the HOMO for the series of Cu anilido complexes is localized primarily on the amido nitrogen with some ppi(anilido)-dpi(Cu) pi-character. [(IPr)Cu(mu-H)]2 and (IPr)Cu(Ph) react with aniline to quantitatively produce (IPr)Cu(NHPh)/dihydrogen and (IPr)Cu(NHPh)/benzene, respectively. Analysis of the DFT calculations reveals that the conversion of [(IPr)Cu(mu-H)]2 and aniline to (IPr)Cu(NHPh) and dihydrogen is favorable with DeltaH approximately -7 kcal/mol and DeltaG approximately -9 kcal/mol.     

Syntheses, structures, and reactivities of mono- and dinuclear iridium thiolato complexes containing nitrosyl ligands

Reactions of the iridium(III) nitrosyl complex [Ir(NO)Cl2(PPh3)2] (1) with hydrosulfide and arenethiolate anions afforded the square-pyramidal iridium(III) complex [Ir(NO)(SH)2(PPh3)2] (2) with a bent nitrosyl ligand and a series of the square-planar iridium(I) complexes [Ir(NO)(SAr)2(PPh3)] (3a, Ar = C6H2Me3-2,4,6 (Mes); 3b, Ar = C6H3Me2-2,6 (Xy); 3c, Ar = C6H2Pri3-2,4,6) containing a linear nitrosyl ligand, respectively. Complex 1 also reacted with alkanethiolate anions or alkanethiols to give the thiolato-bridged diiridium complexes [Ir(NO)(mu-SPri)(SPri)(PPh3)]2 (4) and [Ir(NO)(mu-SBut)(PPh3)]2 (5). Complex 4 contains two square-pyramidal iridium(III) centers with a bent nitrosyl ligand, whereas 5 contains two tetrahedral iridium(0) centers with a linear nitrosyl ligand and has an Ir-Ir bond. Upon treatment with benzoyl chloride, 3a and 3b were converted into the (diaryl disulfide)- and thiolato-bridged dichlorodiiridium(III) complexes [[IrCl(mu-SC6HnMe4-nCH2)(PPh3)]2(mu-ArSSAr)] (6a, Ar = Mes, n = 2; 6b, Ar = Xy, n = 3) accompanied by a loss of the nitrosyl ligands and cleavage of a C-H bond in an ortho methyl group of the thiolato ligands. Similar treatment of 4 gave the dichlorodiiridium complex [Ir(NO)(PPh3)(mu-SPri)3IrCl2(PPh3)] (7), which has an octahedral dichloroiridium(III) center and a distorted trigonal-bipyramidal Ir(I) atom with a linear nitrosyl ligand. The detailed structures of 3a, 4, 5, 6a, and 7 have been determined by X-ray crystallography.     

Highly luminescent gold(I)-silver(I) and gold(I)-copper(I) chalcogenide clusters

The reactions of [AuClL] with Ag(2)O, where L represents the heterofunctional ligands PPh(2)py and PPh(2)CH(2)CH(2)py, give the trigoldoxonium complexes [O(AuL)(3)]BF(4). Treatment of these compounds with thio- or selenourea affords the triply bridging sulfide or selenide derivatives [E(AuL)(3)]BF(4) (E=S, Se). These trinuclear species react with Ag(OTf) or [Cu(NCMe)(4)]PF(6) to give different results, depending on the phosphine and the metal. The reactions of [E(AuPPh(2)py)(3)]BF(4) with silver or copper salts give [E(AuPPh(2)py)(3)M](2+) (E=O, S, Se; M=Ag, Cu) clusters that are highly luminescent. The silver complexes consist of tetrahedral Au(3)Ag clusters further bonded to another unit through aurophilic interactions, whereas in the copper species two coordination isomers with different metallophilic interactions were found. The first is analogous to the silver complexes and in the second, two [S(AuPPh(2)py)(3)](+) units bridge two copper atoms through one pyridine group in each unit. The reactions of [E(AuPPh(2)CH(2)CH(2)py)(3)]BF(4) with silver and copper salts give complexes with [E(AuPPh(2)CH(2)CH(2)py)(3)M](2+) stoichiometry (E=O, S, Se; M=Ag, Cu) with the metal bonded to the three nitrogen atoms in the absence of AuM interactions. The luminescence of these clusters has been studied by varying the chalcogenide, the heterofunctional ligand, and the metal.     

Structure and bonding in three-coordinate N-heterocyclic carbene adducts of iron(II) bis(trimethylsilyl)amide

The molecular structures, chemical bonding and magnetochemistry of the three-coordinate iron(II) NHC complexes [(NHC)Fe{N(SiMe(3))(2)}(2)] (NHC = IPr, 2; NHC = IMes, 3) are reported.     

Square-planar rhodium(I) complexes partnered with [arachno-6-SB(9)H(12)]- : a route toward the synthesis of new rhodathiaboranes and organometallic/thiaborane salts

Treatment of [RhCl(eta4-diene)]2 (diene = nbd, cod) with the N-heterocyclic ligands 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), 1,10-phenanthroline (phen), and pyridine (py) followed by addition of Cs[arachno-6-SB9H12] affords the corresponding salts, [Rh(eta4-diene)(L2)][SB9H12] [diene = cod, L2 = bpy (1), Me2bpy (3), phen (5), (py)2 (7); diene = nbd, L2 = bpy (2), Me2bpy (4), phen (6), (py)2 (8)]. These compounds are characterized by NMR spectroscopy and mass spectrometry, and in addition, the cod-Rh species 1 and 3 are studied by X-ray diffraction analysis. These saltlike reagents are stable in the solid state, but in solution the rhodium(I) cations, [Rh(eta4-diene)(L2)]+, react with the polyhedral anion [SB9H12]- leading to a chemistry that is controlled by the d8 transition element chelates. The nbd-Rh(I) complexes react faster than the cod-Rh(I) counterparts, leading, depending on the conditions, to the synthesis of new rhodathiaboranes of general formulas [8,8-(L2)-nido-8,7-RhSB9H10] [L2 = bpy (9), Me2bpy (10), phen (11), (py)2 (12)] and [8,8-(L2)-8-(L')-nido-8,7-RhSB9H10] [L' = PPh3, L2 = bpy (13), Me2bpy (14), phen (15); L' = NCCH3, L2 = bpy (16), Me2bpy (17), phen (18)]. Compound 13 is characterized by X-ray diffraction analysis confirming the 11-vertex nido-structure of the rhodathiaborane analogues 14-18. In dichloromethane, 1 and 3 yield mixtures that contain the 11-vertex rhodathiaboranes 9 and 10 together with new species. In contrast, the cod-Rh(I) reagent 5 affords a single compound, which is proposed to be an organometallic rhodium complex bound exo-polyhedrally to the thiaborane cage. In the presence of H2(g) and stoichiometric amounts of PPh3, the cod-Rh(I) reagents, 1, 3, and 5, afford the salts [Rh(H)2(L2)(PPh3)2][SB9H12] [L2 = bpy (19), Me2bpy (20), phen (21)]. Similarly, in an atmosphere of CO(g) and in the presence of PPh3, compounds 1-6 afford [Rh(L2)(PPh3)2(CO)][SB9H12] (L2 = bpy (22), Me2bpy (23), phen (24)]. The structures of 19 and 24 are studied by X-ray diffraction analysis. The five-coordinate complexes [Rh(L2)(PPh3)2(CO)]+ undergo PPh3 exchange in a process that is characterized as dissociative. The observed differences in the reactivity of the nbd-Rh(I) salts versus the cod-Rh(I) analogues are rationalized on the basis of the higher kinetic lability of the nbd ligand and its faster hydrogenation relative to the cod diene.     

Scrutinizing low-spin Cr(II) complexes

The oxidation state of the chromium center in the following compounds has been probed using a combination of chromium K-edge X-ray absorption spectroscopy and density functional theory: [Cr(phen)(3)][PF(6)](2) (1), [Cr(phen)(3)][PF(6)](3) (2), [CrCl(2)((t)bpy)(2)] (3), [CrCl(2)(bpy)(2)]Cl(0.38)[PF(6)](0.62) (4), [Cr(TPP)(py)(2)] (5), [Cr((t)BuNC)(6)][PF(6)](2) (6), [CrCl(2)(dmpe)(2)] (7), and [Cr(Cp)(2)] (8), where phen is 1,10-phenanthroline, (t)bpy is 4,4'-di-tert-butyl-2,2'-bipyridine, and TPP(2-) is doubly deprotonated 5,10,15,20-tetraphenylporphyrin. The X-ray crystal structures of complexes 1, [Cr(phen)(3)][OTf](2) (1'), and 3 are reported. The X-ray absorption and computational data reveal that complexes 1-5 all contain a central Cr(III) ion (S(Cr) = (3)/(2)), whereas complexes 6-8 contain a central low-spin (S = 1) Cr(II) ion. Therefore, the electronic structures of 1-8 are best described as [Cr(III)(phen(?))(phen(0))(2)][PF(6)](2), [Cr(III)(phen(0))(3)][PF(6)](3), [Cr(III)Cl(2)((t)bpy(?))((t)bpy(0))], [Cr(III)Cl(2)(bpy(0))(2)]Cl(0.38)[PF(6)](0.62), [Cr(III)(TPP(3?-))(py)(2)], [Cr(II)((t)BuNC)(6)][PF(6)](2), [Cr(II)Cl(2)(dmpe)(2)], and [Cr(II)(Cp)(2)], respectively, where (L(0)) and (L(?))(-) (L = phen, (t)bpy, or bpy) are the diamagnetic neutral and one-electron-reduced radical monoanionic forms of L, and TPP(3?-) is the one-electron-reduced doublet form of diamagnetic TPP(2-). Following our previous results that have shown [Cr((t)bpy)(3)](2+) and [Cr(tpy)(2)](2+) (tpy = 2,2':6',2"-terpyridine) to contain a central Cr(III) ion, the current results further refine the scope of compounds that may be described as low-spin Cr(II) and reveal that this is a very rare oxidation state accessible only with ligands in the strong-field extreme of the spectrochemical series.     

Synthesis and characterization of [Cu(NHC)2]X complexes: catalytic and mechanistic studies of hydrosilylation reactions

The preparation of two series of [Cu(NHC)2]X complexes (NHC=N-heterocyclic carbene, X=PF6 or BF4) in high yields from readily available materials is reported. These complexes have been spectroscopically and structurally characterized. The activity of these cationic bis-NHC complexes in the hydrosilylation of ketones was examined, and both the ligand and the counterion showed a significant influence on the catalytic performance. Moreover, when compared with related [Cu(NHC)]-based systems, these cationic complexes proved to be more efficient under similar reaction conditions. The activation step of [Cu(NHC)2]X precatalysts towards hydrosilylation was investigated by means of 1H NMR spectroscopy. Notably, it was shown that one of the N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) ligands in [Cu(IPr)2]BF4 is displaced by tBuO(-) in the presence of NaOtBu, producing the neutral [Cu(IPr)(OtBu)]. This copper alkoxide is known to be a direct precursor of an NHC-copper hydride, the actual active species in this transformation. Furthermore, reagent loading and counterion effects have been rationalized in light of the species formed during the reaction.     

Dimethylsulfoxide as a ligand for RhI and IrI complexes--isolation, structure, and reactivity towards X-H bonds (X=H, OH, OCH3)

Novel neutral and cationic Rh(I) and Ir(I) complexes that contain only DMSO molecules as dative ligands with S-, O-, and bridging S,O-binding modes were isolated and characterized. The neutral derivatives [RhCl(DMSO)(3)] (1) and [IrCl(DMSO)(3)] (2) were synthesized from the dimeric precursors [M(2)Cl(2)(coe)(4)] (M=Rh, Ir; COE=cyclooctene). The dimeric Ir(I) compound [Ir(2)Cl(2)(DMSO)(4)] (3) was obtained from 2. The first example of a square-planar complex with a bidentate S,O-bridging DMSO ligand, [(coe)(DMSO)Rh(micro-Cl)(micro-DMSO)RhCl(DMSO)] (4), was obtained by treating [Rh(2)Cl(2)(coe)(4)] with three equivalents of DMSO. The mixed DMSO-olefin complex [IrCl(cod)(DMSO)] (5, COD=cyclooctadiene) was generated from [Ir(2)Cl(2)(cod)(2)]. Substitution reactions of these neutral systems afforded the complexes [RhCl(py)(DMSO)(2)] (6), [IrCl(py)(DMSO)(2)] (7), [IrCl(iPr(3)P)(DMSO)(2)] (8), [RhCl(dmbpy)(DMSO)] (9, dmbpy=4,4'-dimethyl-2,2'-bipyridine), and [IrCl(dmbpy)(DMSO)] (10). The cationic O-bound complex [Rh(cod)(DMSO)(2)]BF(4) (11) was synthesized from [Rh(cod)(2)]BF(4). Treatment of the cationic complexes [M(coe)(2)(O=CMe(2))(2)]PF(6) (M=Rh, Ir) with DMSO gave the mixed S- and O-bound DMSO complexes [M(DMSO)(2)(DMSO)(2)]PF(6) (Rh=12; Ir=in situ characterization). Substitution of the O-bound DMSO ligands with dmbpy or pyridine resulted in the isolation of [Rh(dmbpy)(DMSO)(2)]PF(6) (13) and [Ir(py)(2)(DMSO)(2)]PF(6) (14). Oxidative addition of hydrogen to [IrCl(DMSO)(3)] (2) gave the kinetic product fac-[Ir(H)(2)Cl(DMSO)(3)] (15) which was then easily converted to the more thermodynamically stable product mer-[Ir(H)(2)Cl(DMSO)(3)] (16). Oxidative addition of water to both neutral and cationic Ir(I) DMSO complexes gave the corresponding hydrido-hydroxo addition products syn-[(DMSO)(2)HIr(micro-OH)(2)(micro-Cl)IrH(DMSO)(2)][IrCl(2)(DMSO)(2)] (17) and anti-[(DMSO)(2)(DMSO)HIr(micro-OH)(2)IrH(DMSO)(2)(DMSO)][PF(6)](2) (18). The cationic [Ir(DMSO)(2)(DMSO)(2)]PF(6) complex (formed in situ from [Ir(coe)(2)(O=CMe(2))(2)]PF(6)) also reacts with methanol to give the hydrido-alkoxo complex syn-[(DMSO)(2)HIr(micro-OCH(3))(3)IrH(DMSO)(2)]PF(6) (19). Complexes 1, 2, 4, 5, 11, 12, 14, 17, 18, and 19 were characterized by crystallography.     

Azametallacycles from Ag(I)- or Cu(II)-promoted coupling reactions of dialkylcyanamides with oximes at Pt(II)

The dialkylcyanamide complexes cis-[PtCl(NCNR(2))(PPh(3))(2)][BF(4)] 1 and cis-[Pt(NCNR(2))(2)(PPh(3))(2)][BF(4)](2) 2 (R = Me or Et) have been prepared by treatment of a CH(2)Cl(2) solution of cis-[PtCl(2)(PPh(3))(2)] with the appropriate dialkylcyanamide and one or two equivalents of Ag[BF(4)], respectively. Compounds 2 can also be obtained from 1 by a similar procedure. Their reaction with oximes, HON=CR'R' ' (R'R' ' = Me(2) or C(4)H(8)), in CH(2)Cl(2) and in the presence of Ag[BF(4)] or Cu(CH(3)COO)(2), leads to the novel type of azametallacycles cis-[Pt(NH=C(ON=CR'R")-NR2)(PPh3)2][BF4]2 4 upon an unprecedented coupling of the organocyanamides with oximes, in a process that proceeds via the mixed oxime-organocyanamide species cis-[Pt(NCNR(2))(HON=CR'R' ')(PPh(3))(2)][BF(4)](2) 3, and is catalyzed by either Ag(+) or Cu(2+) which activate the ligating organocyanamide by Lewis acid addition to the amide group. In contrast, in the organonitrile complexes cis-[Pt(NCR)(2)(PPh(3))(2)][BF(4)](2) 5 (R = C(6)H(4)OMe-4 or Et), obtained in a similar way as 2 (but by using NCR instead of the cyanamide), the ligating NCR is not activated by the Lewis acid and does not couple with the oximes. The spectroscopic properties of those complexes are reported along with the molecular structures of 2b (R = Et), 4a1 (R = Me, R'R' ' = Me(2)), and 4b1 (R = Et, R'R' ' = Me(2)), as established by X-ray crystallography which indicates that in the former complex the amide-N-atoms are trigonal planar, whereas in the latter (4a1 and 4b1) the five-membered rings are planar with a localized N=C double bond (imine group derived from the cyanamide) and the exocyclic amide and alkylidene groups (in 4b1) are involved in two intramolecular H-bonds to the oxygen atom of the ring.