CH CMe Research Articles

Multifaceted role of silver salts as ligand scavengers and different behavior of nickel and palladium complexes: beyond halide abstraction.

The reaction of [NiArBr(PPh3)2] with AgBF4 brings about the abstraction of both the halide and phosphine from the nickel center by silver. When the reaction is carried out in CH2Cl2/toluene a mixture of the cationic aquo derivatives [NiAr(H2O)(PPh3)2]BF4 (2) and [NiAr(H2O)2(PPh3)]BF4 (3) is formed, along with AgBr and [Ag(PPh3)n]BF4. When the same reaction is carried out in acetone as the solvent, it leads to the completely different complex [NiAr(κ2-O, O-MeC(O)CH2C(OH)Me2)(PPh3)] (5), bearing a chelating ligand formed by the aldol self-condensation of acetone. Phosphine abstraction by silver is less favorable for the analogous palladium(II) complexes and only occurs if a large excess of AgBF4 is used. Thus, silver salts can be safely used as halide scavengers for palladium derivatives. However, the generation of cationic Ni complexes from neutral precursors by halide extraction with a silver salt may produce naked species, different than those expected, and highly reactive in certain media.

Reactivity of frustrated Lewis pairs with BOC protected diazocarboxylates: FLP capture of diazene.

Reactions of (tBuO2CN)2 with FLPs are examined. B(C6F5)3 interacts with the carbonyl oxygen atoms inducing loss of CH2CMe2; however, in the presence of basic donors, the protons are intercepted affording the salts [Hbase]2 [((C6F5)3BO2CN)2] (base = tBu3P 1, NC5H2Ph32, HNC5H6Me43). In contrast, in the presence of (o-Tol)3P, a proton transfers to the diazo-N atom affording (o-Tol)3PN(CO2tBu)NHB(C6F5)34. Further addition of B(C6F5)3 to 4 prompts loss of olefin CH2CMe2 and CO2 affording (o-Tol)3PNHNHB(C6F5)35. The course of these reactions is examined by extensive DFT calculations. The nature of 5 is consistent with the FLP reduction of a diazene fragment.

Silver(I) complexes based on diorganoselenium(II) ligands with amino or hydroxo functionalities

The diorganoselenide [Me2C(OH)CH2]2Se (1) was prepared by reacting the in situ obtained Na2Se with 1‐chloro‑2‐methyl‐2‐propanol. Reactions of 1 and [2-(Me2NCH2)C6H4]2Se (2) with appropriate silver(I) salts in 1:1 molar ratio resulted in metal complexes of type [Ag(X)Se{CH2C(OH)Me2}2] [X = OSO2CF3 (OTf) (3), OClO3 (4)] and [Ag(X)Se{C6H4(CH2NMe2)-2}2] [X = OSO2CF3 (5), ONO2 (6)], respectively. The ligand 1 and the silver complexes were investigated by appropriate spectroscopic methods, both in solution and in solid state: multinuclear NMR (1H, 13C, 19F, 77Se), ESI+ mass spectrometry, IR spectroscopy and molar conductivity. The metal complexes behave as 1:1 electrolytes in 10−3 MeOH solutions, while in solid state the anionic ligands behave as monodentate moieties. Complexes 4 and 5 were investigated by single‐crystal X‐ray diffraction. The crystal of 4 contains two similar independent molecules, 4a and 4b, for which was observed the migration of one OH hydrogen from ligand 1 to the OClO3 group, thus resulting in [Ag(HClO4)Se{OCCH2Me2}{(OH)CCH2Me2}], where ligand 1 behaves as an O,Se monometallic biconective moiety. In 5 the ligand 2 acts as a N,Se,N monometallic triconective moiety. In both compounds Ag(I) is surrounded by the donor atoms in a trigonal pyramidal coordination geometry. Strong Se→Ag intermolecular interactions in 4 resulted in 1D coordination polymers built by 4a and 4b molecules, respectively, while in the crystal of 5 no interaction between heavy atoms was observed. Supramolecular networks based on H‧‧‧O contacts are formed in both compounds.

Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors: Synthesis and Characterization of Pt[CH2CMe2CH2CH═CH2]2 and the Impact of Ligand Design on the Deposition Process

We describe the synthesis and characterization of three platinum(II) ω-alkenyl complexes of stoichiometry Pt[CH2CMe2(CH2)xCH═CH2]2 where x is 0, 1, or 2, as well as some related platinum(II) compounds formed as byproducts during their synthesis. The ω-alkenyl ligands in all three complexes, cis-bis(η1,η2-2,2-dimethylbut-3-en-1-yl)platinum (2), cis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)platinum (3), and cis-bis(η1,η2-2,2-dimethylhex-5-en-1-yl)platinum (4), bind to Pt by means of a Pt–alkyl sigma bond at one end of the ligand chain and a Pt–olefin pi interaction at the other; the olefins reversibly decomplex from the Pt centers in solution. The good volatility of 3 (10 mTorr at 20 °C), its ability to be stored for long periods without decomposition, and its stability toward air and moisture make it an attractive platinum chemical vapor deposition (CVD) precursor. CVD of thin films from 3 shows no nucleation delay on several different substrates (SiO2/Si, Al2O3, and VN) and gives films that are unusually smooth. At 330 °C in the absence of a reactive gas, the precursor deposits platinum containing 50% carbon, but in the presence of a remote oxygen plasma, the amount of carbon is reduced to below the Rutherford backscattering spectroscopy (RBS) detection limit without affecting the film smoothness. Under hot wall CVD conditions at 250 °C in the absence of a co-reactant, 72% of the carbon atoms in 3 are released as hydrogenated products (largely 4,4-dimethylpentenes), 22% are released as dehydrogenated products (all of which are the result of skeletal rearrangements), and 6% remain in the film. Some conclusions about the CVD mechanism are drawn from this product distribution.

Cis versus Trans: The Coordination Environment about the Tin(IV) Atom in Spirocyclic Amino Alcohol Derivatives.

The syntheses of amino alcohols MeN(CH2 CH2 CMe2 OH)2 (1), MeN(CMe2 CH2 OH)(CH2 CMe2 OH) (2), MeN(CH2 CH2 CH2 OH)(CH2 CMe2 OH) (3), MeN(CH2 CH2 CMe2 OH)(CH2 CMe2 OH) (4), MeN(CH2 CH2 CMe2 OH)(CH2 CH2 OH) (5), and MeN(CH2 CH2 OH) (CH2 CH2 CH2 OH) (6) as well as spirocyclic tin(IV) alkoxides spiro-[nBuN(CH2 CMe2 O)2 ]2 Sn (7), spiro-[MeN(CH2 CH2 CMe2 O)2 ]2 Sn (8), spiro-[para-FC6 H4 N (CH2 CMe2 O)2 ]2 Sn (9), spiro-[MeN(CMe2 CH2 O)(CH2 CMe2 O)]2 Sn (10), spiro-[MeN(CH2 CH2 CH2 O)(CH2 CMe2 O)]2 Sn (11), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CMe2 O)]2 Sn (12), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CH2 O)]2 Sn (13) and spiro-[MeN(CH2 CH2 O)(CH2 CH2 CH2 O)]2 Sn (14) are reported. The compounds were characterized by 1 H, 13 C (1-14) and 119 Sn (7-14) NMR and IR spectroscopy, EIMS and single-crystal XRD (2, 7-10 and 13, 14). Graph-set analyses were performed for compounds [(MeNH(CMe2 CH2 OH)(CH2 CMe2 OH)][HC(O)O] (2 a) and 2. The coordination environment about the tin(IV) centre of the spirocyclic compounds and their possible stereoisomers were analysed by DFT calculations (spiro-[MeN(CH2 CMe2 O)2 ]2 Sn, 8-10 and 13).

Organotin Selenide Clusters and Hybrid Capsules.

Several compounds with unique structural motifs that have already been known from organotin sulfide chemistry, but remained unprecedented in organotin selenide chemistry so far, have been synthesized. The reaction of [(R1 Sn)4 Se6 ] (R1 =CMe2 CH2 C(O)Me) with N2 H4 ⋅H2 O/(SiMe3 )2 Se and PhN2 H3 /(SiMe3 )2 Se led to the formation of [{(R2 Sn)2 SnSe4 }2 (μ-Se)2 ] (1; R2 =CMe2 CH2 C(Me)NNH2 ) and [{(R3 Sn)2 SnSe4 }2 (μ-Se)2 ] (2; R3 =CMe2 CH2 C(Me)NNPhH)). The addition of ortho-phthalaldehyde to [(R2 Sn)4 Se6 ] yielded a cluster with intramolecular bridging of the organic groups, namely, [(R4 Sn2 )2 Se6 ] (3; R4 =(CMe2 CH2 C(Me)NNCH)2 C6 H4 ). The introduction of organic ligands with longer chains finally allowed the isolation of inorganic-organic capsules of the type [(μ-R)3 (Sn3 Se4 )2 ]X2 , with R=(CMe2 CH2 C(Me)NNHC(O))2 (CH2 )4 and X=[SnC3 ], Cl (4 a, b) or R=CMe2 CH2 C(Me)NNH)2 and X=[SnCl3 ] (5). The capsules enclose solvent molecules and/or anions as guests. All compounds were characterized by means of single-crystal X-ray diffraction studies, NMR spectroscopy, and mass spectrometry.

Ternary Mixed-Valence Organotin Copper Selenide Clusters.

Reactions of the organotin selenide chloride clusters [(R1 SnIV )3 Se4 Cl] (A, R1 =CMe2 CH2 C(O)Me) or [(R1 SnIV )4 Se6 ] (B) with [Cu(PPh3 )3-x Clx ] yield cluster compounds with different inorganic, mixed-valence core structures: [Cu4 SnII SnIV6 Se12 ], [Cu2 SnII2 SnIV4 Se8 Cl2 ], [Cu2 SnII SnIV4 Se8 ], [Cu2 SnII2 SnIV2 Se4 Cl4 ], and [Cu2 SnIV2 Se4 ]. Five of the compounds, namely [(CuPPh3 )2 {(R1 SnIV )2 Se4 }] (1), [(CuPPh3 )2 SnII {(R2 SnIV )2 Se4 }2 ] (2), [(CuPPh3 )2 (SnII Cl)2 {(RSnIV )2 Se4 }2 ] (3) [(CuPPh3 )2 (SnII Cu2 ){(R1 SnIV )2 Se4 }3 ] (4), and [Cu(CuPPh3 )(SnII Cu2 ){(R1 SnIV )2 Se4 }3 ] (5) are structurally closely related. They are based on [(CuPPh3 )2 {(RSnIV )2 Se4 }n ] aggregates comprising [(RSnIV )2 Se4 ] and [CuPPh3 ] building units, which are linked by further metal atoms. A sixth compound, [(CuPPh3 )2 (SnII Cl)2 {(R1 SnIV Cl)Se2 }2 ] (6), differs from the others by containing [(RSnIV Cl)Se2 ] units instead, which affects the absorption properties. The compounds were analyzed by single-crystal X-ray diffraction, NMR and 119 Sn Mössbauer spectroscopy, DFT calculations as well as optical absorption experiments.

Formation and Reactivity of Organo-Functionalized Tin Selenide Clusters.

Reactions of R(1) SnCl3 (R(1) =CMe2 CH2 C(O)Me) with (SiMe3 )2 Se yield a series of organo-functionalized tin selenide clusters, [(SnR(1) )2 SeCl4 ] (1), [(SnR(1) )2 Se2 Cl2 ] (2), [(SnR(1) )3 Se4 Cl] (3), and [(SnR(1) )4 Se6 ] (4), depending on the solvent and ratio of the reactants used. NMR experiments clearly suggest a stepwise formation of 1 through 4 by subsequent condensation steps with the concomitant release of Me3 SiCl. Furthermore, addition of hydrazines to the keto-functionalized clusters leads to the formation of hydrazone derivatives, [(Sn2 (μ-R(3) )(μ-Se)Cl4 ] (5, R(3) =[CMe2 CH2 CMe(NH)]2 ), [(SnR(2) )3 Se4 Cl] (6, R(2) =CMe2 CH2 C(NNH2 )Me), [(SnR(4) )3 Se4 ][SnCl3 ] (7, R(4) =CMe2 CH2 C(NNHPh)Me), [(SnR(2) )4 Se6 ] (8), and [(SnR(4) )4 Se6 ] (9). Upon treatment of 4 with [Cu(PPh3 )3 Cl] and excess (SiMe3 )2 Se, the cluster fragments to form [(R(1) Sn)2 Se2 (CuPPh3 )2 Se2 ] (10), the first discrete Sn/Se/Cu cluster compound reported in the literature. The derivatization reactions indicate fundamental differences between organotin sulfide and organotin selenide chemistry.

The mechanism of a phosphazene-phosphazane rearrangement.

The phosphazene-phosphazane rearrangement of N3P3Cl5O(CH2)2OC(=O)CMe=CH2 (8) has been examined in detail using one and two dimensional NMR ((31)P, (1)H) spectroscopy and mass spectrometry. The mixed phosphazene-phosphazane [NPCl2]2[N((CH2)2OC(=O)CMe=CH2)P(O)Cl] (14), [NPCl2]2[NHP(O)Cl] (13) and a two ring assembly [NPCl2]2[NP(O{(NPCl2)2(N((CH2)2OC(=O)CMe=CH2)P(O)}] (15) have all been detected in the product mixture. The rate of the rearrangement has been measured at five temperatures by (31)P and (1)H NMR. The reaction is first order in 8 (T1/2 at 111° is 4.65 hours). The activation enthalpy is positive and the activation entropy is negative. A mechanism involving competing intra and inter molecular processes which fits the product distribution and kinetic data has been proposed. Several other methyacrylphosphazenes were examined under the same thermolysis conditions. The rearrangement was observed and the rates obtained in cases where the (CH2)2 spacer unit of the methacrylate was replaced by linear and branched propyl units. The rearrangement was not observed when the methacrylate was appended to a spirocyclic unit, the spacer unit was extended to the n-butyl group and when the methacrylate unit was replaced by a methoxy group. These results are all consistent with the proposed mechanism. This investigation resolves conflicting results previous reported for the rearrangement.

Highly Reactive NiII‐Bound Nitrile–Oxime Coupling Intermediates Stabilized by Substituting Conventional Nitriles with a Dialkylcyanamide

AbstractNickel(II)‐mediated coupling between the cyanamide Me2NCN and the ketoximes Me(R)C=NOH (R = Me, Ph) gives chelates of the general formula [NiClx(H2O)y{HN=C(NMe2)(ON=C(R)Me)}2]n+ ([1]+: R = Me; x = 1, y = 0; salts with both Cl– and [NiCl4]2– were isolated; [2]2+: R = Me; x = 0, y = 2; salt with Cl– was isolated; [3]+: R = Ph; x = 1, y = 1; salt with Cl– was isolated) and the iminium salts [H2N=C(NMe2)ON=C(R)Me]+ ([4]+: R = Me; salt with [NiCl4]2– was isolated; [5]+: R = Ph; salt with Cl– was isolated). This reaction demonstrates the difference in the reactivity between conventional nitriles and dialkylcyanamides: whereas nitriles RCN (R = Alk, Ar) react with NiII/ketoxime systems to afford (1,3,5‐triazapentadiene)NiII species, formed by postulated nitrile–oxime coupling intermediates, cyanamides under the same conditions give either stable cyanamide–oxime coupling products or the Busch‐type complex [Ni{HN=C(Me)CH2C(Me2)NH2}2]Cl2 ([6]Cl2). The reason for the different stability of the coupling products was interpreted theoretically on the basis of quantum chemical calculations (M06‐L/6‐31G* level of theory). The NMe2 moiety in the chelate ligands leads to an increase in electron‐density delocalization and also stabilizes the systems in terms of electrostatic factors.

From a Stable Silanone Complex to Isolable, Donor‐Supported Silicoxonium Halides [LSi(dmap)OSiMe3]+X−

The first donor-stabilized silylated silicoxonium species [LSi=O-SiMe(3)](+) (L=(RN)C(=CH(2))CH=CMe(NR), R=2,6-iPr(2)C(6)H(3)) have been synthesized from the reaction of the dmap-supported (dmap=p-dimethylaminopyridine) silanone complex [LSi(dmap)=O] (1) with trimethylsilyl halides. Although the reaction with Me(3)SiCl leads directly to the Si=O addition product [LSi(Cl)OSiMe(3)] (2), the ionic silicoxonium bromide [L(dmap)Si=O-SiMe(3)](+)Br(-) (3) can be obtained as a primary product of the reaction with Me(3)SiBr, which affords [LSi(Br)OSiMe(3)] (4) with release of the dmap ligand at room temperature in THF. In the case of Me(3)SiI, the reaction furnishes the silicoxonium iodide [L(dmap)Si=O-SiMe(3)](+)I(-) (5) as the most stable species. Compounds 2-5 were isolated and fully characterized through multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.

19F NMR spectroscopy as useful tool for determining the structure in solution of coordination compounds of MF 5 (M = Nb, Ta)

The salts [S(NMe 2) 3][MF 6] (M = Nb, 2a; M = Ta, 2b) and [S(NMe 2) 3][M 2F 11] (M = Nb, 2c; M = Ta, 2d) have been prepared by reacting MF 5 (M = Nb, 1a; M = Ta, 1b) with [S(NMe 2) 3][SiMe 3F 2] (TASF reagent) in the appropriate molar ratio. The solid state structure of 2b has been ascertained by X-ray diffraction. The 1:1 molar ratio reactions of 1a with a variety of organic compounds (L) give the neutral adducts NbF 5L [L = Me 2CO, 3a; L = MeCHO, 3b; L = Ph 2CO, 3c; L = tetrahydrofuran (thf), 3d; L = MeOH, 3e; L = EtOH, 3f; L = HOCH 2CH 2OMe, 3g; L = Ph 3PO, 3h; L = NCMe, 3i] in good yields. The complexes MF 5L [M = Nb, L = HCONMe 2, 3j; M = Nb, L = (NMe 2) 2CO, 3k; M = Ta, L = (NMe 2) 2CO, 3l; M = Nb, L = OC(Me)CH CMe 2, 3m] have been detected in solution in admixture with other unidentified products, upon 2:1 molar reaction of 1 with the appropriate reagent L. The ionic complexes [NbF 4(tht) 2][NbF 6], 4a, and [NbF 4(tht) 2][Nb 2F 11], 4b, have been obtained by combination of tetrahydrothiophene (tht) and 1a, in 1:1 and 2:3 molar ratios, respectively. The treatment of 1 with a two-fold excess of L leads to the species [MF 4L 4][MF 6] [M = Nb, L = HCONMe 2, 5a; M = Ta, L = HCONMe 2, 5b; M = Nb, L = thf, 5c; M = Ta, L = thf, 5d; M = Nb, L = OEt 2, 5e]. The new complexes have been fully characterised by NMR spectroscopy. Moreover, the revised 19F NMR features of the known compounds MF 5L [M = Ta, L = Me 2CO, 3n; M = Ta, L = Ph 2CO, 3o; M = Ta, L = MePhCO, 3p; M = Ta, L = thf, 3q; M = Nb, L = CH 3CO 2H, 3r; M = Nb, L = CH 2ClCO 2H, 3s; M = Ta, L = CH 2ClCO 2H, 3t], TaF 4(acac), TaF 4(Me-acac) and [TaF(Me-acac) 3][TaF 6] (Me-acac = methylacetylacetonato anion) are reported.

Ketoximate Derivatives of Titanium Alkoxides and Partial Hydrolysis Products Thereof

AbstractCrystalline oximate derivatives of titanium alkoxides [Ti(OR)2(ON=CR′R″)2]2 were obtained when Ti(OR)4 (R = iPr, Et) was treated with various oximes (cyclopentanone oxime, cyclohexanone oxime, acetoxime, ethyl methyl ketoxime or 2,4‐pentandione dioxime). Formation of bis‐substituted derivatives was favored in each case, and only one mono‐substituted derivative, [Ti(OiPr)3(ON=C6H10)]2, was isolated. Two isomers were observed for [Ti(OR)2(ON=CR′R″)2]2, differing by the mutual orientation of the oximate ligands. The NO groups of the oximate ligands are side‐on coordinated to one titanium atom in each case. Three partially hydrolyzed derivatives, viz. Ti6O6(OiPr)6(ON=CR2)6 (CR2 = CMe2 or C5H8) and Ti4O2(OiPr)8(ON=CMe–CH2–CMe=NO)2 were also structurally characterized. In these derivatives the NO groups bridge two titanium atoms.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Me 3SiC [tbnd]C–CMe [dbnd]CH 2 copper(I) β-diketonates: Synthesis, solid state structure, and low-temperature chemical vapour deposition

The ene-yne copper(I) β-diketonates [(η 2-TMSMB)Cu(β-diketonate)] (β-diketonate = ac etyl ac etonate/acac, 5; = 1,3- d i-tert- b utyl ac etonate/dbac, 6; = 1,1,1,5,5,5- h exa f luoroacetyl ac etonate/hfac, 7; TMSMB = 4- T ri M ethyl S ilyl-2- M ethyl- B ut-1-ene-3-yne, Me 3SiC C–CMe CH 2) are accessible by the reaction of [(η 2-TMSMB)Cu(μ-Cl)] 2 ( 3) with [Na(β-diketonate)] (β-diketonate = acac, 4a; = dbac, 4b; = hfac, 4c) in a 1:2 molar ratio. Complexes 6 and 7 are also formed, when Cu 2O ( 8) is reacted with H-hfac ( 9a) or H-dbac ( 9b), respectively. The solid state structure of 7 is reported. The copper(I) ion possesses a planar environment caused by the η 2-coordinated TMSMB ligand and the chelate-bound hfac group, while the CMe CH 2 entity stays free. The thermal properties of 5– 7 were determined by applying T hermo G ravimetry (TG) and D ifferential S canning C alorimetry (DSC). All complexes decompose in a two-step process beginning at ca. 85 °C. Elimination of TMSMB produces [Cu(β-diketonate)] which disproportionates to give [Cu(β-diketonate) 2] and elemental copper. Preliminary hot-wall C hemical V apour D eposition experiments (CVD) were carried out with 7. Copper films were deposited onto TiN-coated oxidised silicon wafers at a precursor vaporisation temperature of 50 °C and a deposition temperature of 145 °C. The films were characterised by SEM and EDX.

Molecular templating using titanium(iv)(oxo)alkoxides and titanium(iv)(oxo)aryloxides

Crystalline materials obtained by reacting titanium(IV) isopropoxide (1) with widely different ligands such as 1,3-propanediol, 2,2′-biphenol or triphenylacetic acid using acetone as a solvent have been characterised using single-crystal X-ray diffraction, 1H, 13C and 17O NMR spectroscopies and theoretical modelling. In the case of the previously described [Ti3(μ3-O)(OPri)4(μ-OPri)3{Me2C(O)CHC(O)CH2C(O)Me2}] complex (2), the importance of the simultaneous use of HSQC, HBMC and ROESY techniques for a full spatial attribution of all resonances was demonstrated. The optimised molecular structure of (2) and its associated dynamics have also been used to demonstrate that more shielded 1H and 13C resonances and shorter relaxation times were expected for more rigid bridging OR groups relative to terminal ones. A templating effect linked to the steric decompression that may occur when the rather constrained molecular structure of [Ti3(μ3-O)(μ3-OPri)(μ-OPri)3(OPri)6] (3) meets acetone molecules in their enol form, (3) + 3 CH2C(OH)CH3 → (2) + 3 HOPri, is proposed, explaining why exactly three acetone molecules should undergo aldol condensation and why new complexes such as [Ti3(μ3-O)(μ3-OH)(OPri)6(μ-OPri)3] (4) or [Ti3(μ3-O)(μ-OOCPh3)2(μ-OPri)3(OPri)5] (5) may be isolated and characterised.

Thermal Activation of Hydrocarbon C−H Bonds Initiated by a Tungsten Allyl Complex

Gentle thermolysis of the allyl complex, CpW(NO)(CH(2)CMe(3))(eta(3)-H(2)CCHCMe(2)) (1), at 50 degrees C in neat hydrocarbon solutions results in the loss of neopentane and the generation of transient intermediates that subsequently activate solvent C-H bonds. Thus, thermal reactions of 1 with tetramethylsilane, mesitylene, and benzene effect single C-H activations and lead to the exclusive formation of CpW(NO)(CH(2)SiMe(3))(eta(3)-H(2)CCHCMe(2)) (2), CpW(NO)(CH(2)C(6)H(3)-3,5-Me(2))(eta(3)-H(2)CCHCMe(2)) (3), and CpW(NO)(C(6)H(5))(eta(3)-H(2)CCHCMe(2)) (4), respectively. The products of reactions of 1 with other methyl-substituted arenes indicate an inherent preference of the system for the activation of stronger arene sp(2) C-H bonds. For example, C-H bond activation of p-xylene leads to the formation of CpW(NO)(CH(2)C(6)H(4)-4-Me)(eta(3)-H(2)CCHCMe(2)) (5) (26%) and CpW(NO)(C(6)H(3)-2,5-Me(2))(eta(3)-H(2)CCHCMe(2)) (6) (74%). Mechanistic and labeling studies indicate that the transient C-H-activating intermediates are the allene complex, CpW(NO)(eta(2)-H(2)C=C=CMe(2)) (A), and the eta(2)-diene complex, CpW(NO)(eta(2)-H(2)C=CHC(Me)=CH(2)) (B). Intermediates A and B react with cyclohexene to form CpW(NO)(eta(3)-CH(2)C(2-cyclohexenyl)CMe(2))(H) (18) and CpW(NO)(eta(3)-CH(2)CHC)(Me)CH(2)C(beta)H(C(4)H(8))C(alpha)H (19), respectively, and intermediate A can be isolated as its PMe(3) adduct, CpW(NO)(PMe(3))(eta(2)-H(2)C=C=CMe(2)) (20). Interestingly, thermal reaction of 1 with 2,3-dimethylbut-2-ene results in the formation of a species that undergoes eta(3) --> eta(1) isomerization of the dimethylallyl ligand following the initial C-H bond-activating step to yield CpW(NO)(eta(3)-CMe(2)CMeCH(2))(eta(1)-CH(2)CHCMe(2)) (21). Thermolyses of 1 in alkane solvents afford allyl hydride complexes resulting from three successive C-H bond-activation reactions. For instance, 1 in cyclohexane converts to CpW(NO)(eta(3)-C(6)H(9))(H) (22) with dimethylpropylcyclohexane being formed as a byproduct, and in methylcyclohexane it forms the two isomeric complexes, CpW(NO)(eta(3)-C(7)H(11))(H) (23a,b). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2, 3, 4, 18, 19, 20, and 21 have been established by X-ray crystallographic analyses.

Synthesis and reactivity of μ-butadienyl diruthenium cations

Propargyl alcohols HCCCR 2OH (R=H, Me or Ph) react with [Ru 2(CO)(MeCN)(μ-CO)(μ-CH 2)(η-C 5H 5) 2] ( 2) to form the allylidene complexes [Ru 2(CO)(μ-CO){μ-η 1,η 3-C(CR 2OH)CHCH 2}(η-C 5H 5) 2] ( 4a, R=H; 4b, R=Me; 4c, R=Ph). Treatment of complexes 4a– c with HBF 4 removes the hydroxide group as water, giving the 2-butadienyl complexes [Ru 2(CO)(μ-CO)(μ-η 2,η 3-CR 2CCHCH 2)(η-C 5H 5) 2][BF 4] ( 5a, R=H; 5b, R=Me; 5c, R=Ph). The reactivity of 5a– c towards nucleophiles and bases is described. With hydride, 5a– c undergo nucleophilic attack at the C(R 2) carbon to give the allylidene complexes [Ru 2(CO)(μ-CO){μ-η 1,η 3-C(CR 2H)CHCH 2}(η-C 5H 5) 2] ( 6a, R=H; 7, R=Me; 11, R=Ph) and, in the case of 5c, the butadiene complex [Ru 2(CO) 2(μ-η 2,η 2-CPh 2CHCHCH 2)(η-C 5H 5) 2] ( 12) and the allene complex [Ru 2(CO) 2(μ-η 2,η 2-CPh 2CCHMe)(η-C 5H 5) 2] ( 13), formally due to attack at the μ-C and CH 2 carbons, respectively. The complexes 5a– c react with methyl lithium to undergo nucleophilic attack predominantly at the C(R 2) carbon, giving methylated allylidene complexes [Ru 2(CO)(μ-CO){μ-η 1,η 3-C(CR 2Me)CHCH 2}(η-C 5H 5) 2] ( 6b, R=Me; 9, R=Me; 14, R=Ph). With 5b and 5c methyl lithium also acts as a base, abstracting protons to give the novel divinylcarbene complex [Ru 2(CO)(μ-CO){μ-η 1,η 3-C(CMeCH 2)CHCH 2}(η-C 5H 5) 2] ( 8) and the μ-butatriene complex [Ru 2(CO) 2(μ-η 2,η 2-CPh 2CCCH 2)(η-C 5H 5) 2] ( 15), respectively. Complexes 8 and 15 are formed exclusively by treating 5b and 5c, respectively, with diazabicyclo[5.4.0]undec-7-ene (DBU). Complexes 8 and 9 were also prepared in good yield by reaction of complex 2 with 2-methyl-1-buten-3-yne {CH 2C(Me)CCH} and t-butylacetylene, respectively. Treatment of complex 8 with HBF 4 resulted in protonation at each of the methylene groups, affording 5b and isomeric [Ru 2(CO)(μ-CO){μ-η 2,η 3-CH(Me)CC(Me)CH 2}(η-C 5H 5) 2][BF 4] ( 10). The structures of 5b, 5c and 8 were established by X-ray diffraction.

Acetimine and 2-Methyl-2-amino-4-iminopentane Complexes of Palladium(II)

By reaction between the labile complex cis-[Pd(C6F5)2(PhCN)2] and aqueous ammonia-acetone solutions the palladium complexes [Pd(C6F5)2L2] [L = NH3 (1), NHCMe2 (2) and L2 = NHC(Me)CH2C(Me2)NH2 (3)] are obtained. The reaction product depends on the experimental conditions used. The cationic complexes [Pd(dmba)L2]ClO4 [L = NH3 (5), NHCMe2 (6) and L2 = NH C(Me)CH2C(Me2)NH2 (7)] with the N,C-chelating 2-(dimethylaminomethyl)phenyl (dmba) ligand have been obtained by treating [(dmba)Pd(μ-Cl)2Pd(dmba)] with AgClO4 in aqueous ammonia−acetone solution. The mono(acetimine) complex [Pd(dmba)(PPh3)(NHCMe2)]ClO4 (8) is obtained by a similar procedure starting from [Pd(dmba)(PPh3)Cl]. The crystal structures of 1−3 and 6 and 7 have been determined; there is extensive hydrogen bonding (N−H···F−C or N−H···OClO3) in all the compounds.

Synthesis and reactivity of the rhodium monocarbollide complexes [1-NHCMe 2-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10] and [1-NH 3-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10

The carborane 7-NHCMe 2- nido-7-CB 10H 12 reacts with [RhCl(PPh 3) 3] in toluene at reflux temperatures to give the charge-compensated 16-electron Rh(III) complex [1-NHCMe 2-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10] ( 1) in good yield. The structure of this product was established by X-ray diffraction (XRD). Upon methanolysis 1 affords [1-NH 3-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10] ( 2), also a 16-electron charge-compensated Rh(III) complex. Some reactions of 2 were investigated. At room temperature, in the presence of Na 2CO 3, it reacts with acetic, methacrylic, and crotonic anhydrides to give the complexes [1,2-μ-{NHC(R)O}-2-PPh 3- closo-2,1-RhCB 10H 10] [R=Me ( 3), CMeCH 2 ( 4a), and ( E)-CHCHMe ( 4b)], respectively. Benzoyl bromide with 2 and Na 2CO 3 yields [1,2-μ-{NHC(Ph)O}-2-PPh 3- closo-2,1-RhCB 10H 10] ( 5). An XRD study of 4a established that the acyl group is coordinated to the rhodium through the oxygen. In the crystal molecules lie pair-wise linked by a BH⇀Rh bridge so that in one molecule the rhodium atom has a 16-electron valence shell and in the other an 18-electron configuration. However, in solution NMR studies reveal that only monomeric molecules occur. With CNBu t in the presence of Na 2CO 3, compound 2 affords [1-NH 2-2,2-(CNBu t ) 2-2-PPh 3- closo-2,1-RhCB 10H 10] ( 7), the structure of which was determined by XRD. The NMR parameters of the new compounds are reported and discussed.

An ‘Old Hydride’ in a new synthesis: a convenient approach to Grubbs-type carbene complexes (PPh 3) 2Cl 2RuCHCHCR 2 and their hexacoordinate acetonitrile adducts

A convenient synthetic route to Grubbs-type complexes (PPh 3) 2Cl 2RuCHCHCR 2 by reacting Wilkinson's hydride (PPh 3) 3Ru(H)Cl with propargyl or allenyl chlorides, and the isolation of an adduct complex (CH 3CN)(PPh 3) 2Cl 2RuCHCHCMe 2 ( 3) by treatment of (PPh 3) 3Ru(H)Cl with 3-chloro-3-methyl-1-butyne in the presence of CH 3CN are reported. NMR studies in CD 2Cl 2 show hexacoordinate (CH 3CN)(PPh 3) 2Cl 2RuCHCHCMe 2 ( 3) to be in equilibrium with CH 3CN and pentacoordinate (PPh 3) 2Cl 2RuCHCHCMe 2 ( 2), the solid state structure of which is presented. X-ray characterization of [(CH 3CN) 3(PPh 3) 2RuCHCHCMe 2](OTf) 2 ( 6), the first mononuclear, dicationic complex derived from a Grubbs-type carbene, obtained by treatment of (CH 3CN)(PPh 3) 2Cl 2RuCHCHCMe 2 ( 3) with trimethylsilyl triflate in the presence of an excess of CH 3CN has been performed. This result indicates the possibility of stabilizing such species by labile donor ligands.