An eta(6)-dienyne transition-metal complex

The ruthenium complexes, [(eta5-C5R5)Ru(CH3CN)3]PF6 (1-Cp*, R = Me; 1-Cp, R = H), underwent reaction with both 1-(2-chloro-1-methylvinyl)-2-pentynyl-(Z)-cyclopentene (6-Z) and 1-(2-chloro-1-methylvinyl)-2-pentynyl-(E)-cyclopentene (6-E) to give (eta5-C5R5)Ru[eta6-(5-chloro-4-methyl-6-propylindan)]PF6 (7-Cp*, R = Me; 7-Cp, R = H). In a similar fashion, reaction of 1-Cp and 1-Cp* with 1-isopropenyl-2-pent-1-ynylcyclopentene (8) led to the formation of (eta5-C5R5)Ru(eta6-4-methyl-6-propylindan)]PF6 (9-Cp*, R = Me; 9-Cp, R = H). The reaction of 1-Cp* with 8 at -60 degrees C in CDCl3 solution led to observation of the eta6-dienyne complex, (eta5-C5Me5)Ru[eta6-(1-isopropenyl-2-pent-1-ynylcyclopentene)]PF6 (10), by 1H NMR spectroscopy. Complexes 7-Cp and 10 were characterized by X-ray crystallographic analysis.     

Coordinatively unsaturated semisandwich complexes of ruthenium with phosphinoamine ligands and related species: a complex containing (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane in a new coordination form kappa(3)P,P',N-eta(2)-P,N

The syntheses of the chloro complexes [Ru(eta5-C5R5)Cl(L)] (R = H, Me; L = phosphinoamine ligand) (1a-d) have been carried out by reaction of [(eta5-C5H5)RuCl(PPh3)2] or {(eta5-C5Me5)RuCl}4 with the corresponding phosphinoamine (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane), R,R-dippach, or 1,2-bis(((diisopropylphosphino)amino)ethane), dippae. The chloride abstraction reactions from these compounds lead to different products depending on the starting chlorocomplex and the reaction conditions. Under argon atmosphere, chloride abstraction from [(eta5-C5Me5)RuCl(R,R-dippach)] with NaBAr'4 yields the compound [(eta5-C5Me5)Ru(kappa3P,P'-(R,R)-dippach)][BAr'4] (2b) which exhibits a three-membered ring Ru-N-P by a new coordination form of this phosphinoamine. However, under the same conditions the reaction starting from [(eta5-C5Me5)RuCl(dippae)] yields the unsaturated 16 electron complex [(eta5-C5Me5)Ru(dippae)][BAr'4] (2d). The bonding modes of R,R-dippach and dippae ligands have been analyzed by DFT calculations. The possibility of tridentate P,N,P-coordination of the phosphinoamide ligand to a fragment [(eta5-C5Me5)Ru]+ is always present, but only the presence of a cyclohexane unit in the ligand framework converts this bonding mode in a more favorable option than the usual P,P-coordination. Dinitrogen [(eta5-C5R5)Ru(N2)(L)][BAr'4] (3a-d) and dioxygen complexes [(eta5-C5H5)Ru(O2)(R,R-dippach)][BPh4] (4a) and [(eta5-C5Me5)Ru(O2)(L)][BPh4] (4b,d) have been prepared by chloride abstraction under dinitrogen or dioxygen atmosphere, respectively. The presence of 16 electron [(eta5-C5H5)Ru(R,R-dippach)]+ species in fluorobenzene solutions of the corresponding dinitrogen or dioxygen complexes in conjunction with the presence of [BAr'4]- gave in some cases a small fraction of [Ru(eta5-C5H5)(eta6-C6H5F)][BAr'4] (5a), which has been isolated and characterized by X-ray diffraction.     

Unprecedented syndioselectivity and syndiotactic polyolefin melting temperature: polypropylene and poly(4-methyl-1-pentene) from a highly active, sterically expanded eta1-fluorenyl-eta1-amido zirconium complex

The structurally unique, sterically expanded eta1-fluorenyl-eta1-amido single-site precatalyst, Me2Si(eta1-N-tBu)(eta1-C29H36)ZrCl2.OEt2 (3), upon activation with methylaluminoxane (MAO), is remarkably active and constitutes the most syndioselective alpha-olefin polymerization catalyst system yet reported. 3/MAO affords as-prepared syndiotactic polypropylene with [rrrr] > 99% and unprecedented melting temperatures for the unannealed (165 degrees C) and annealed (174 degrees C) polymers. The activity of this system is 4 times that of the prototypical syndioselective catalyst Me2C(eta5-C5H4)(eta5-C13H8)ZrCl2/MAO. The high activity and syndioselectivity of 3/MAO can be extended to the production of syndiotactic poly(4-methyl-1-pentene) with a record melting temperature of 215 degrees C and [rrrr] = 97%.     

Dinitrogen functionalization with terminal alkynes, amines, and hydrazines promoted by [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2): observation of side-on and end-on diazenido complexes in the reduction of N2 to hydrazine

Functionalization of the N2 ligand in the side-on bound dinitrogen complex, [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2), has been accomplished by addition of terminal alkynes to furnish acetylide zirconocene diazenido complexes, [(eta5-C5Me4H)2Zr(C[triple bond]CR)]2(mu2,eta2,eta2-N2H2) (R = nBu, tBu, Ph). Characterization of [(eta5-C5Me4H)2Zr(C[triple bond]CCMe3)]2(mu2,eta2,eta2-N2H2) by X-ray diffraction revealed a side-on bound diazenido ligand in the solid state, while variable-temperature 1H and 15N NMR studies established rapid interconversion between eta1,eta1 and eta2,eta2 hapticity of the [N2H2]2- ligand in solution. Synthesis of alkyl, halide, and triflato zirconocene diazenido complexes, [(eta5-C5Me4H)2ZrX]2(mu2,eta1,eta1-N2H2) (X = Cl, I, OTf, CH2Ph, CH2SiMe3), afforded eta1,eta1 coordination of the [N2H2]2- fragment both in the solid state and in solution, demonstrating that sterically demanding, in some cases pi-donating, ligands can overcome the electronically preferred side-on bonding mode. Unlike [(eta5-C5Me4H)2ZrH]2(mu2,eta2,eta2-N2H2), the acetylide and alkyl zirconocene diazenido complexes are thermally robust, resisting alpha-migration and N2 cleavage up to temperatures of 115 degrees C. Dinitrogen functionalization with [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2) was also accomplished by addition of proton donors. Weak Br?nsted acids such as water and ethanol yield hydrazine and (eta5-C5Me4H)2Zr(OH)2 and (eta5-C5Me4H)2Zr(OEt)2, respectively. Treatment of [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2) with HNMe2 or H2NNMe2 furnished amido or hydrazido zirconocene diazenido complexes that ultimately produce hydrazine upon protonation with ethanol. These results contrast previous observations with [(eta5-C5Me5)2Zr(eta1-N2)]2(mu2,eta1,eta1-N2) where loss of free dinitrogen is observed upon treatment with weak acids. These studies highlight the importance of cyclopentadienyl substituents on transformations involving coordinated dinitrogen.     

Formation of a bridging planar trimethylenemethane dianion from a neopentyl precursor via sequential beta-alkyl elimination and C-H activation

The reaction of neopentyllithium, Me3CCH2Li, with [(C5Me5)2Sm][(mu-Ph)2BPh2], 1, was investigated as a route to the unsolvated alkyl, [(C5Me5)2Sm(CH2CMe3)]x, and found to generate the first f element trimethylenemethane dianion complex, [(C5Me5)2Sm]2[mu-eta3:eta3-C(CH2)3], 2. Formation of the [C4H6]2- trimethylenemethane ligand from the [C5H11]1- neopentyl precursor can be explained by a combination of a beta-methyl elimination reaction to form isobutene and [(C5Me5)2SmMe]3, 3, with subsequent C-H activation reactions. This sequence has been modeled in several ways, including the synthesis of 2 from reactions of 3 with CH2=CMe2 and 3 with the 2-methylallyl complex, (C5Me5)2Sm[CH2C(Me)CH2], 4.     

Ammonolysis of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives

Ammonolyses of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives [Ti(eta5-C5Me5)X3] (X = NMe2, Me, Cl) have been carried out in solution to give polynuclear nitrido complexes. Reaction of the tris(dimethylamido) derivative [Ti(eta5-C5Me5)(NMe2)3] with excess of ammonia at 80-100 degrees C gives the cubane complex [[Ti(eta5-C5Me5)]4(mu3-N)4] (1). Treatment of the trimethyl derivative [Ti(eta5-C5Me5)Me3] with NH3 at room temperature leads to the trinuclear imido-nitrido complex [[Ti(eta/5-CsMes)(mu-NH)]3(mu3-N)] (2) via the intermediate [[Ti(eta5-C5Me5)Me]2(mu-NH)2] (3). The analogous reaction of [Ti(eta5-C5Me5)Me3] with 2,4,6-trimethylaniline (ArNH2) gives the dinuclear imido complex [[Ti(eta5-C5Me5)Me])2(mu-NAr)2] (4) which reacts with ammonia to afford [[Ti(eta5-C5Me5)(NH2)]2(mu-NAr)2] (5). Complex 2 has been used, by treatments with the tris(dimethylamido) derivatives [Ti(eta5-C5H5-nRn)(NMe2)3], as precursor of the cubane nitrido systems [[Ti4(eta5-C5Me5)3(eta5-C5H5-nRn)](mu3-N)4] [R = Me n = 5 (1), R = H n = 0 (6), R = SiMe3 n = 1 (7), R = Me n = 1 (8)] via dimethylamine elimination. Reaction of [Ti(eta5-C5Me5)Cl3] or [Ti(eta5-C5Me5)(NMe2)Cl2] with excess of ammonia at room temperature gives the dinuclear complex [[Ti2(eta5-C5Me5)2Cl3(NH3)](mu-N)] (9) where an intramolecular hydrogen bonding and a nonlineal nitrido ligand bridge the "Ti(eta5-C5Me5)Cl(NH3)" and "Ti(eta5-C5Me5)Cl2" moieties. The molecular structures of [[Ti(eta5-C5Me5)Me]2 (mu-NAr)2] (4) and [[Ti2(eta5-C5Me5)2Cl3(NH3)](mu-N)] (9) have been determined by X-ray crystallographic studies. Density functional theory calculations also have been conducted on complex 9 to confirm the existence of an intramolecular N-H...Cl hydrogen bond and to evaluate different aspects of its molecular disposition.     

Construction of [(eta5-C5Me5)WS3Cu3]-based supramolecular compounds from preformed incomplete cubane-like clusters [PPh4][(eta5-C5Me5)WS3(CuX)3] (X = CN, Br)

Approaches to the assembly of (eta5-C5Me5)WS3Cu3-based supramolecular compounds from two preformed incomplete cubane-like clusters [PPh4][(eta5-C5Me5)WS3(CuX)3] (X = CN, 1a; X = Br, 1b) have been investigated. Treatment of 1a with LiBr/1,4-pyrazine (1,4-pyz), pyridine (py), LiCl/py, or 4,4'-bipyridine (4,4'-bipy) and treatment of 1b with 4,4'-bipy gave rise to a new set of W/Cu/S cluster-based compounds, [Li[((eta5-C5Me5)WS3Cu3(mu3-Br))2(mu-CN)3].C6H6]infinity (2), [(eta5-C5Me5)WS3Cu3(mu-CN)2(py)]infinity (3), [[PPh4][(eta5-C5Me5)WS3Cu3(mu3-Cl)(mu-CN)(CN)].py]infinity (4), [PPh4]2[(eta5-C5Me5)WS3Cu3(CN)2]2(mu-CN)2.(4,4'-bipy) (5), and [[(eta5-C5Me5)WS3Cu3Br(mu-Br)(4,4'-bipy)].Et2O]infinity (6). The structures of 2-6 have been characterized by elemental analysis, IR spectra, and single-crystal X-ray crystallography. Compound 2 displays a 1D ladder-shaped chain structure built of square-like [[(eta5-C5Me5)WS3Cu3(mu3-Br)(mu-CN)]4](mu-CN)2(2-) anions via two pairs of Cu-mu-CN-Cu bridges. Compound 3 consists of a single 3D diamond-like network in which each (eta5-C5Me5)WS3Cu3 unit, serving as a tetrahedral node, interconnects with four other nearby units through Cu-mu-CN-Cu bridges. Compound 4 contains a 1D zigzag chain array made of cubane-like [(eta5-C5Me5)WS3Cu3(mu3-Cl)(mu-CN)(CN)]- anions linked by a couple of Cu-mu-CN-Cu bridges. Compound 5 contains a dimeric structure in which the two incomplete cubane-like [(eta5-C5Me5)WS3(CuCN)2(mu-CN)]- anions are strongly held together via a pair of Cu-mu-CN-Cu bridges. Compound 6 contains a 2D brick-wall layer structure in which dimers of [(eta5-C5Me5)WS3Cu3Br(4,4'-bipy)]2 are interconnected via four Cu-mu-Br-Cu bridges. The successful construction of (eta5-C5Me5)WS3Cu3-based supramolecular compounds 2-6 from the geometry-fixed clusters 1a and 1b may expand the scope of the rational design and construction of cluster-based supramolecular assemblies.     

Indenyl zirconium dinitrogen chemistry: N2 coordination to an isolated zirconium sandwich and synthesis of side-on, end-on dinitrogen compounds

Exposure of the isolable zirconocene sandwich compounds, (eta(5)-C5Me5)(eta(5)-C9H5-1-R(1)-3-R(2))Zr (R(1) = Me, (i)Pr, (t)Bu; R(2) = Me) to one atmosphere of dinitrogen resulted in N2 coordination. X-ray diffraction and NMR spectroscopy establish that the resulting dimeric dinitrogen compounds contain an unusual mu2,eta(2)-bridging indenyl ring and a weakly activated N2 ligand. N2 coordination from the isolable zirconium sandwich compounds is extremely sensitive to the number and size of the indenyl subsituents. Compounds bearing two [(i)Pr] or three methyl substituents are stable as eta(9) sandwich compounds for weeks under dinitrogen likely due to the inability to dimerize through a two-atom N2 bridge. Performing the reduction of (eta(5)-C5Me5)(eta(5)-C9H5-1-R(1)-3-R(2))ZrCl2 (R(1) = (i)Pr, (t)Bu; R(2) = Me; R(1) = R(2) = SiMe3) under an N2 atmosphere produced a different outcome; rare examples of side-on, end-on zirconium dinitrogen compounds were isolated and in one case, crystallographically characterized. Protonolysis studies with weak Br?nsted acids were used to evaluate the relative activation of the bridging dinitrogen ligands.     

Reduction of bis

The reduction of symmetric, fully-substituted titanocene dichlorides bearing two pendant omega-alkenyl groups, [TiCl2(eta5-C5Me4R)2], R = CH(Me)CH= CH2 (1a). (CH2)2CH=CH2 (1b) and (CH2)3CH=CH2 (1c), by magnesium in tetrahydrofuran affords bis(cyclopentadienyl)titanacyclopentanes [Ti(IV)[eta1:eta1: eta5:eta5-C5Me4CH(Me)CH(Ti)CH2CH(CH2(Ti))CH(Me)C5Me4]] (2a), [Ti(IV)[eta1:eta1:eta5: eta5-C5Me4(CH2)2CH(Ti)(CH2)2CH(Ti)(CH2)2C5Me4]] (2b) and [Ti(IV)[eta1:eta1:eta5:eta5-C5Me4(CH2)2CH(Ti)CH(Me)CH(Me)CH(Ti)(CH2)2C5Me4]](2c), respectively, as the products of oxidative coupling of the double bonds across a titanocene intermediate. For the case of complex 1c, a product of a double bond isomerisation is obtained owing to a preferred formation of five-membered titanacycles. The reaction of the titanacyclopentanes with PbCl2 recovers starting materials 1a from 2a and 1b from 2b, but complex 2c affords, under the same conditions, an isomer of 1c with a shifted carbon - carbon double bond, [TiCl[eta5-C5Me4(CH2CH2CH=CHMe)]2] (1c'). The titanacycles 2a-c can be opened by HCl to give ansa-titanocene dichlorides ansa-[[eta5:eta5-C5Me4CH(Me)CH2CH2CH(Me)CH(Me)C5Me4]TiCl2] (3a), ansa-[[eta5:eta5-C5Me4(CH2)8C5Me4]TiCl2] (3b), along with a minor product ansa-[[eta5:eta5-C5Me4CH2CH=CH(CH2)5C5Me4]TiCl2] (3b'), and ansa-[[eta5:eta5-CsMe4(CH2)3CH(Me)CH(Me)CH=CHCH2C5Me4]TiCl2] (3c), respectively, with the bridging aliphatic chain consisting of five (3a) and eight (3b, 3b' and 3c) carbon atoms. The course of the acidolysis changes with the nature of the pendant group; while the cyclopentadienyl ring-linking carbon chains in 3a and 3b are fully saturated, compounds 3c and 3b' contain one asymetrically placed carbon-carbon double bond, which evidently arises from the beta-hydrogen elimination that follows the HCl addition.     

Synthetic, reactivity, and structural studies on half-sandwich (eta5-C5Me5)Be and related compounds: halide, alkyl, and iminoacyl derivatives

The half-sandwich compounds [(eta(5)-C(5)Me(5))BeX] (X=Cl, 1 a; Br, 1 b), readily prepared from the reaction of the halides BeX(2) and M[C(5)Me(5)] (M=Na or K), are useful synthons for other (eta(5)-C(5)Me(5))Be organometallic compounds, including the alkyl derivatives [(eta(5)-C(5)Me(5))BeR] (R=Me, 2 a; CMe(3), 2 b; CH(2)CMe(3), 2 c; CH(2)Ph, 2 d). The latter compounds can be obtained by metathetical exchange of the halides 1 with the corresponding lithium reagent and exhibit NMR signals and other properties in accord with the proposed formulation. Attempts to make [(eta(5)-C(5)Me(5))BeH] have proved fruitless, probably due to instability of the hydride toward disproportionation into [Be(C(5)Me(5))(2)] and BeH(2). The half-sandwich iminoacyl [(eta(5)-C(5)Me(5))Be(C(NXyl)Cp')] and [(eta(5)-C(5)Me(4)H)Be(C(NXyl)Cp')]3, 6 where Xyl=C(6)H(3)-2,6-Me(2) and Cp'=C(5)Me(5) or C(5)Me(4)H, are formed when the beryllocenes [Be(C(5)Me(5))(2)], [Be(C(5)Me(4)H)(2)], and [Be(C(5)Me(5))(C(5)Me(4)H)] are allowed to react with CNXyl. Isolation of three different iminoacyl isomers from the reaction of the mixed-ring beryllocene [(eta(5)-C(5)Me(5))Be(eta(1)-C(5)Me(4)H)] and CNXyl, namely compounds 5 a, 5 b, and 6, provides compelling evidence for the existence in solution of different beryllocene isomers, generated in the course of two very facile processes that explain the solution dynamics of these metallocenes, that is the 1,5-sigmatropic shift of the Be(eta(5)-Cp') unit around the periphery of the eta(1)-Cp' ring, and the molecular inversion rearrangement that exchanges the roles of the two rings.     

Solution structures and dynamic properties of chelated d(0) metal olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) (R = H, Me): Models for the [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" catalysts.

To model the Ti-olefin interaction in the putative [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" Ti-catalyzed olefin polymerization, chelated alkoxide olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) have been investigated. The reaction of [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2) (1a,b; R = H, Me) with HOCMe(2)CH(2)CH(2)CH=CH(2) yields mixtures of [eta(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2)) (2a,b) and [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2)) (3a,b). The reaction of 2a/3a and 2b/3b mixtures with B(C(6)F(5))(3) yields the chelated olefin complexes [[eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)] (4a,b; 71 and 89% NMR yield). The reaction of 2b/3b with [Ph(3)C][B(C(6)F(5))(4)] yields [[eta(5): eta(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)] (5b, 88% NMR yield). NMR studies establish that 4a,b and 5b exist as mixtures of diastereomers (isomer ratios: 4a/4a', 62/38; 4b/4b', 75/25; 5b/5b', 75/25), which differ in the enantioface of the olefin that is coordinated. NMR data for these d(0) metal olefin complexes show that the olefin coordinates to Ti in an unsymmetrical fashion primarily through C(term) such that the C=C pi bond is polarized with positive charge buildup on C(int). Dynamic NMR studies show that 4b/4b' undergoes olefin face exchange by a dissociative mechanism which is accompanied by fast inversion of configuration at Ti ("O-shift") in the olefin-dissociated intermediate. The activation parameters for the conversion of 4b to 4b' (i.e., 4b/4b' face exchange) are: DeltaH = 17.2(8) kcal/mol; DeltaS = 8(1) eu. 4a/4a' also undergoes olefin face exchange but with a lower barrier (DeltaH = 12.2(9) kcal/mol; DeltaS = -2(3) eu), for the conversion of 4a to 4a'.     

eta1:eta2-Alkynyl-bridged W-Si complexes: formation, structure, and reaction with acetone

Reactions of (eta5-C5Me4R)(CO)2(MeCN)WMe (R = Me, Et) with HPh2SiCCtBu gave the novel alkynyl-bridged W-Si complexes, (eta5-C5Me4R)(CO)2W(mu-eta1:eta2-CCtBu)(SiPh2) (R = Me, Et), whose alkynyl ligands bridge the tungsten and silicon atoms in an eta1:eta2-coordination mode. The structures of these complexes were fully characterized, including X-ray crystallography. Treatment of (eta5-C5Me5)(CO)2W(mu-eta1:eta2-CCtBu)(SiPh2) with acetone resulted in acetone insertion into the silicon-alkynyl linkage followed by intramolecular C-H activation of the tBu group to give the chelate-type alkyl-alkene complex, (eta5-C5Me5)(CO)2W(eta1:eta2-CH2CMe2C=CHSiPh2OCMe2).     

Cube-type nitrido complexes containing titanium and zinc/copper

Several azaheterometallocubane complexes containing [MTi3N4] cores have been prepared by the reaction of [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)] (1) with zinc(II) and copper(I) derivatives. The treatment of 1 with zinc dichloride in toluene at room temperature produces the adduct [Cl2Zn{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (2). Attempts to crystallize 2 in dichloromethane gave yellow crystals of the ammonia adduct [(H3N)Cl2Zn{(mu3-NH)Ti3(eta5-C5Me5)3(mu-NH)2(mu3-N)}] (3). The analogous reaction of 1 with alkyl, (trimethylsilyl)cyclopentadienyl, or amido zinc complexes [ZnR2] leads to the cube-type derivatives [RZn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (R = CH2SiMe3 (5), CH2Ph (6), Me (7), C5H4SiMe3 (8), N(SiMe3)2 (9)) via RH elimination. The amido complex 9 decomposes in the presence of ambient light to generate the alkyl derivative [{Me3Si(H)N(Me)2SiCH2}Zn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (10). The chloride complex 2 reacts with lithium cyclopentadienyl or lithium indenyl reagents to give the cyclopentadienyl or indenyl zinc derivatives [RZn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (R = C5H5 (11), C9H7 (12)). Treatment of 1 with copper(I) halides in toluene at room temperature leads to the adducts [XCu{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (X = Cl (13), I (14)). Complex 13 reacts with lithium bis(trimethylsilyl)amido in toluene to give the precipitation of [{Cu(mu4-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}2] (15). Complex 15 is prepared in a higher yield through the reaction of 1 with [{CuN(SiMe3)2}4] in toluene at 150 degrees C. The addition of triphenylphosphane to 15 in toluene produces the single-cube compound [(Ph3P)Cu{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (16). The X-ray crystal structures of 3, 8, 9, and 15 have been determined.     

Synthesis,molecular structure,and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(=CRR') and C5Me5Ru(=CRR') as molecular units

The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato derivative [(eta(5)-C(5)H(5))Ru(kappa(2)-O(2)CCH(3))(PPh(3))], which can be reconverted to the carbene complexes [(eta(5)-C(5)H(5))RuCl(=CR(2))(PPh(3))] in a one-pot reaction with R(2)CN(2) and Et(3)NHCl.     

Structures and reactivity of Zr(IV) chlorobenzene complexes

The synthesis, structures, and unusual reactivity of (C5R5)2ZrR'(ClPh)+ chlorobenzene complexes are described. The reaction of (C5R5)2ZrR'2 with [Ph3C][B(C6F5)4] in C6D5Cl affords [(C5R5)2ZrR'(ClC6D5)][B(C6F5)4] chlorobenzene complexes (1-d5, R' = CH2Ph and (C5R5)2 = (C5H5)2; 2a-d-d5, R' = Me and (C5R5)2 = rac-(1,2-ethylene(bis)indenyl) (2a), (C5H5)2 (2b), (C5H4Me)2 (2c), (C5Me5)2 (2d, C5Me5 = Cp*)). Complexes 1 and 2b,c are thermally robust but are converted to [{(C5R5)2Zr(mu-Cl)}2][B(C6F5)4]2 (4b,c) by a photochemical process in ClPh solution. In contrast, 2d undergoes facile thermal ortho-C-H activation to yield [Cp*2Zr(eta2-C,Cl-2-Cl-C6H4)][B(C6F5)4] (5), which slowly rearranges to [(eta4,eta1-C5Me5C6H4)Cp*ZrCl][B(C6F5)4] (6) via beta-Cl elimination and benzyne insertion into a Zr-CCp* bond. The higher thermal reactivity of 2d versus that of 1 and 2b,c is attributed to steric crowding associated with the Cp* ligands of 2d, which forces a ClPh ortho-hydrogen close to the Zr-Me group.     

High-oxidation-state neutral and cationic tantalum(IV) alkyl complexes that are stable toward beta-hydrogen and beta-methyl eliminations

The synthesis and solid-state structural characterization of a family of homoleptic and mixed dialkyl d1Ta(IV) complexes of the formula, (eta5-C5Me5)TaR1R2[N(i-Pr)C(Me)N(i-Pr)], where R1 = R2 = i-Bu (3), n-Bu (4), and Et (7), and R1 = Me, R2 = i-Bu (10), neopentyl (Np) (11), are reported, along with those for the cationic d1Ta(IV) complex, {(eta5-C5Me5)TaNp[N(i-Pr)C(Me)N(i-Pr)]}[B(C6F5)4] (12). All of the new compounds displayed a remarkably high degree of solution stability toward beta-hydrogen and beta-methyl eliminations/abstractions. Thermolysis of 3 in toluene at 80 degrees C for 18 h provided the Ta(IV) trimethylenemethane (TMM) complex 13.     

Iron-molybdenum charge-transfer hybrids containing organometallic and inorganic fragments bridged by aryldiazenido ligands in a mu-eta(6):eta(1) coordination mode: syntheses, characterization, X-ray structures, electrochemistry, and theoretical investigation

Representative members of a new family of covalently bonded charge-transfer molecular hybrids, of general formula [(eta5-C5H5)Fe(mu,eta6:eta1-p-RC6H4NN)Mo(eta2-S2CNEt2)3] +PF6- (R: H, 5+PF6-; Me, 6+PF6-; MeO, 7+PF6-) and [(eta5-C5Me5)Fe(mu,eta6:eta1-C6H5NN)Mo(eta2-S2CNEt2)3]+PF6-, 8+PF6-, have been synthesized by reaction of the corresponding mixed-sandwich organometallic hydrazines [(eta5-C5H5)Fe(eta6-p-RC6H4NHNH2)]+PF6- (R: H, 1+PF6-; Me, 2+PF6-; MeO, 3+PF6-) and [(eta5-C5Me5)Fe(eta6-C6H5NHNH2)]+PF6-, 4+PF6-, with cis-dioxomolybdenum(VI) bis(diethyldithiocarbamato) complex, [MoO2(S2CNEt2)2], in the presence of sodium diethyldithiocarbamato trihydrate, NaSC(=S)NEt2.3H2O, in refluxing methanol. These iron-molybdenum complexes consist of organometallic and inorganic fragments linked each other through a pi-conjugated aryldiazenido bridge coordinated in eta6 and eta1 modes, respectively. These complexes were fully characterized by FT-IR, UV-visible, and 1H NMR spectroscopies and, in the case of complex 7+PF6-, by single-crystal X-ray diffraction analysis. Likewise, the electrochemical and solvatochromic properties were studied by cyclic voltammetry and UV-visible spectroscopy, respectively. The electronic spectra of these hybrids show an absorption band in the 462-489 and 447-470 nm regions in CH2Cl2 and DMSO, respectively, indicating the existence of a charge-transfer transition from the inorganic donor to the organometallic acceptor fragments through the aryldiazenido spacer. A rationalization of the properties of 5+PF6--8+PF6- is provided through DFT calculations on a simplified model of 7+PF6-. Besides the heterodinuclear complexes 5+PF6--8+PF6-, the mononuclear molybdenum diazenido derivatives, [(eta1-p-RC6H4NN)Mo(eta2-S2CNEt2)3] (R: H, 9; Me, 10; MeO, 11), resulting from the decoordination of the [(eta5-C5H5)Fe]+ moiety of complexes 5+PF6--7+PF6-, were also isolated. For comparative studies, the crystalline and molecular structure of complex 10.Et2O was also determined by X-ray diffraction analysis and its electronic structure computed.     

The effect of micro-CN linkage isomerism and ancillary ligand set on directional metal-metal charge-transfer in cyanide-bridged dimanganese complexes

The reaction of [Mn(CN)L'(NO)(eta(5)-C(5)R(4)Me)] with cis- or trans-[MnBrL(CO)(2)(dppm)], in the presence of Tl[PF(6)], gives homobinuclear cyanomanganese(i) complexes cis- or trans-[(dppm)(CO)(2)LMn(micro-NC)MnL'(NO)(eta(5)-C(5)R(4)Me)](+), linkage isomers of which, cis- or trans-[(dppm)(CO)(2)LMn(micro-CN)MnL'(NO)(eta(5)-C(5)R(4)Me)](+), are synthesised by reacting cis- or trans-[Mn(CN)L(CO)(2)(dppm)] with [MnIL'(NO)(eta(5)-C(5)R(4)Me)] in the presence of Tl[PF(6)]. X-Ray structural studies on the isomers trans-[(dppm)(CO)(2){(EtO)(3)P}Mn(micro-NC)Mn(CNBu(t))(NO)(eta(5)-C(5)H(4)Me)](+) and trans-[(dppm)(CO)(2){(EtO)(3)P}Mn(micro-CN)Mn(CNBu(t))(NO)(eta(5)-C(5)H(4)Me)](+) show nearly identical molecular structures whereas cis-[(dppm)(CO)(2){(PhO)(3)P}Mn(micro-NC)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me)](+) and cis-[(dppm)(CO)(2){(PhO)(3)P}Mn(micro-CN)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me)](+) differ, effectively in the N- and C-coordination respectively of two different optical isomers of the pseudo-tetrahedral units (NC)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me) and (CN)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me) to the octahedral manganese centre. Electrochemical and spectroscopic studies on [(dppm)(CO)(2)LMn(micro-XY)MnL'(NO)(eta(5)-C(5)R(4)Me)](+) show that systematic variation of the ligands L and L', of the cyclopentadienyl ring substituents R, and of the micro-CN orientation (XY = CN or NC) allows control of the order of oxidation of the two metal centres and hence the direction and energy of metal-metal charge-transfer (MMCT) through the cyanide bridge in the mixed-valence dications. Chemical one-electron oxidation of cis- or trans-[(dppm)(CO)(2)LMn(micro-NC)MnL'(NO)(eta(5)-C(5)R(4)Me)](+) with [NO][PF(6)] gives the mixed-valence dications trans-[(dppm)(CO)(2)LMn(II)(micro-NC)Mn(I)L'(NO)(eta(5)-C(5)R(4)Me)](2+) which show solvatochromic absorptions in the electronic spectrum, assigned to optically induced Mn(I)-to-Mn(II) electron transfer via the cyanide bridge.     

Syntheses and characterization of mu,eta(1),eta(1)-3,5-di-tert-butylpyrazolato derivatives of aluminum

The 3,5-di-tert-butylpyrazolato (3,5-tBu(2)pz) derivatives of aluminum [(eta(1),eta(1)-3,5-tBu(2)pz)(mu-Al)R(1)R(2)](2) (R(1) = R(2) = Me 1; R(1) = R(2) = Et, 2; R(1) = R(2) = Cl, 3; R(1) = R(2) = I, 4; [(eta(2)-3,5-tBu(2)pz)(3)Al], 5; [Al(2)(eta(1),eta(1)-3,5-tBu(2)pz)(2)(mu-E)(C triple bond CPh)(2)] (E = S (6), Se (7), Te (8)) have been prepared in good yield. Compounds 1 and 2 were obtained by the reactions of H[3,5-tBu(2)pz] with Me(3)Al and Et(3)Al, respectively. Reaction of [(eta(1),eta(1)-3,5-tBu(2)pz)(mu-Al)H(2)](2) with the pyrazole H[3,5-tBu(2)pz] gave [(eta(2)-3,5-tBu(2)pz)(3)Al] (5). The reaction of [(eta(1),eta(1)-3,5-tBu(2)pz)(mu-Al)R(2)](2) (R = H, Me) and I(2) yielded 4, while the reaction of 1 equiv of K[3,5-tBu(2)pz] and AlCl(3) afforded 3. In addition, the reaction of [Al(2)(eta(1),eta(1)-3,5-tBu(2)pz)(2)(mu-E)H(2)] and HC triple bond CPh gave 6, 7, and 8. All compounds have been characterized by elemental analysis, NMR, and mass spectroscopy. The molecular structure analyses of compounds 1, 3, 6, and 7 by X-ray crystallography showed that complexes 1 and 3 are dimeric with two eta(1),eta(1)-pyrazolato groups in twisted conformation while 6 and 7 with two eta(1),eta(1)-pyrazolato groups display a boat conformation.     

Kinetics and mechanism of N2 hydrogenation in bis(cyclopentadienyl) zirconium complexes and dinitrogen functionalization by 1,2-addition of a saturated C-H bond

The rates of hydrogenation of the N2 ligand in the side-on bound dinitrogen compounds, [(eta(5)-C5Me4H)2Zr]2(mu2,eta(2),eta(2)-N2) and [(eta(5)-C5Me5)(eta(5)-C5H2-1,2-Me2-4-R)Zr]2(mu2,eta(2),eta(2)-N2) (R = Me, Ph), to afford the corresponding hydrido zirconocene diazenido complexes have been measured by electronic spectroscopy. Determination of the rate law for the hydrogenation of [(eta(5)-C5Me5)(eta(5)-C5H2-1,2,4-Me3)Zr]2(mu2,eta(2),eta(2)-N2) establishes an overall second-order reaction, first order with respect to each reagent. These data, in combination with a normal, primary kinetic isotope effect of 2.2(1) for H2 versus D2 addition, establish the first H2 addition as the rate-determining step in N2 hydrogenation. Kinetic isotope effects of similar direction and magnitude have also been measured for hydrogenation (deuteration) of the two other zirconocene dinitrogen complexes. Measuring the rate constants for the hydrogenation of [(eta(5)-C5Me5)(eta(5)-C5H2-1,2,4-Me3)Zr]2(mu2,eta(2),eta(2)-N2) over a 40 degrees C temperature range provided activation parameters of deltaH(double dagger) = 8.4(8) kcal/mol and deltaS(double dagger) = -33(4) eu. The entropy of activation is consistent with an ordered four-centered transition structure, where H2 undergoes formal 1,2-addition to a zirconium-nitrogen bond with considerable multiple bond character. Support for this hypothesis stems from the observation of N2 functionalization by C-H activation of a cyclopentadienyl methyl substituent in the mixed ring dinitrogen complexes, [(eta(5)-C5Me5)(eta(5)-C5H2-1,2-Me2-4-R)Zr]2(mu2,eta(2),eta(2)-N2) (R = Me, Ph), to afford cyclometalated zirconocene diazenido derivatives.