Different C-C coupling reactions of permethyltitanocene and permethylzirconocene with disubstituted 1,3-butadiynes

Herein we describe different C-C coupling reactions of permethyltitanocene and -zirconocene with disubstituted 1,3-butadiynes. The outcomes of these reactions vary depending on the metals and the diyne substituents. The reduction of [Cp2*MCl2] (Cp* = C5Me5; M = Ti, Zr) with Mg in the presence of disubstituted butadiynes RC triple bond C-C triple bond CR' is suitable for the synthesis of different C-C coupling products of the diyne and the permethylmetallocenes, and provides a new method for the generation of functionalized pentamethyl-cyclopentadienyl derivatives. For M = Zr and R = R' = tBu, the reaction gives, by a twofold activation of one pentamethylcyclopentadienyl ligand, the complex [Cp*Zr[-C(=C=CHtBu)-CHtBu-CH2-eta5-C5Me3-CH2-]] (3), containing a fulvene ligand that is coupled to the modified substrate (allenic subunit). When using the analogous permethyltitanocene fragment "Cp2*Ti", the reaction depends strongly on the substituents R and R'. The coupling product of the butadiyne with two methyl groups of one of the pentamethylcyclopentadienyl ring systems, [Cp*Ti[eta5-C5Me3-(CH2-CHR-eta2-C2-CHR'-CH2)]], is obtained with R = R' = tBu (4) and R = tBu, R' = SiMe3 (5). In these complexes one pentamethylcyclopentadienyl ligand is annellated to an eight-membered ring with a C-C triple bond, which is coordinated to the titanium center. A different activation of both pentamethylcyclopentadienyl ligands is observed for R = R' = Me, resulting in the complex [[eta5-C5Me4(CH2)-]Ti[-C(=CHMe)-C(=CHMe)-CH2-eta5-C5Me4]] (6), which displays a fulvene as well as a butadienyl-substituted pentamethylcyclopentadienyl ligand. The influence exerted by the size of the metal is illustrated in the reaction of [Cp2*ZrCl2] with MeC triple bond C-C triple bond CMe. Here the five-membered metallacyclocumulene complex [Cp2*Zr(eta4-1,2,3,4-MeC4Me)] (7) is obtained. The reaction paths found for R = R' = Me are identical to those formerly described for R = R' = Ph.     

Synthesis, characterisation, crystal structures, reactivity, and electrochemistry of ruthenium-nitrido, ruthenium-cobalt-imido and ruthenapyrrolidone carbonyl clusters containing alkyne ligands

Thermolysis of [Ru3(CO)9(mu3-NOMe)(mu3-eta2-PhC2Ph)] (1) with two equivalents of [Cp*Co(CO)2] in THF afforded four new clusters, brown [Ru5(CO)8(mu-CO)3(eta5-C5Me5)(mu5-N)(mu4-eta2-PhC2Ph)] (2), green [Ru3Co2(CO)7(mu3-CO)(eta5-C5Me5)2(mu3-NH)[mu4-eta8-C6H4-C(H)C(Ph)]] (3), orange [Ru3(CO)7(mu-eta6-C5Me4CH2)[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (4) and pale yellow [Ru2(CO)6[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (5). Cluster 2 is a pentaruthenium mu5-nitrido complex, in which the five metal atoms are arranged in a novel "spiked" square-planar metal skeleton with a quadruply bridging alkyne ligand. The mu5-nitrido N atom exhibits an unusually low frequency chemical shift in its 15N NMR spectrum. Cluster 3 contains a triangular Ru2Co-imido moiety linked to a ruthenium-cobaltocene through the mu4-eta8-C6H4C(H)C(Ph) ligand. Clusters 4 and 5 are both metallapyrrolidone complexes, in which interaction of diphenylacetylene with CO and the NOMe nitrene moiety were observed. In 4, one methyl group of the Cp* ring is activated and interacts with a ruthenium atom. The "distorted" Ru3Co butterfly nitrido complex [Ru3Co(CO)5(eta5-C5Me5)(mu4-N)(mu3-eta2-PhC2Ph)(mu-I)2I] (6) was isolated from the reaction of 1 with [Cp*Co(CO)I2] heated under reflux in THF, in which a Ru-Ru wing edge is missing. Two bridging and one terminal iodides were found to be placed along the two Ru-Ru wing edges and at a hinge Ru atom, respectively. The redox properties of the selected compounds in this study were investigated by using cyclic voltammetry and controlled potential coulometry. 15N magnetic resonance spectroscopy studies were also performed on these clusters.     

Synthesis, characterization and reactivity of new complexes of titanium and zirconium containing a potential tridentate amidinato-cyclopentadienyl ligand

Group 4 metal complexes [M(eta(5)-C(5)Me(4)SiMe(2)-eta(1)-N-2R)(NMe(2))(2)] (R = pyridine, pyrazine, pyrimidine, thiazole, M = Ti; R = pyridine, thiazole; M = Zr) containing the tetramethylcyclopentadienyl-dialkylsilyl bridged amidinato as pendant ligand, were synthesized and characterized by elemental analysis, solution (1)H, (13)C and (15)N NMR spectroscopy and experimental (13)C and (15)N CPMAS in the solid state. The crystal structures of [Ti(eta(5)-C(5)Me(4)SiMe(2)-eta(1)-N-2R)(NMe(2))(2)] (R = pyridine, pyrazine, pyrimidine, thiazole) were determined by single crystal X-ray diffraction studies. All compounds exhibit a distorted tetrahedral geometry, with the ansa-monocyclopentadienyl-amido ligands acting in a bidentate mode. The [M(eta(5)-C(5)Me(4)SiMe(2)-eta(1)-N-2R)(NMe(2))(2)] (R = pyridine, thiazole; M = Zr, Ti) complexes are ethylene polymerization catalysts in the presence of MAO and they are active precursors in regioselective catalytic hydroamination operating with an anti-Markovnikov mechanism.     

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

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.     

Molecular nitrides containing group 4 and 5 metals: single and double azatitanocubanes

Treatment of [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) with the imido complexes [Ti(NAr)Cl(2)(py)(3)] (Ar=2,4,6-C(6)H(2)Me(3)) and [Ti(NtBu)Cl(2)(py)(3)] in toluene affords the single azatitanocubanes [[Cl(2)(ArN)Ti]( micro(3)-NH)(3)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (2.C(7)H(8)) and [[Cl(2)Ti](micro(3)-N)(2)(micro(3)-NH)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [[M(NtBu)(NHtBu)Cl(2)(NH(2)tBu)](2)] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [[Cl(2)(tBuN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (M=Nb (4), Ta (5)), both complexes react with 2,4,6-trimethylaniline to yield the analogous species [[Cl(2)(ArN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (Ar=2,4,6-C(6)H(2)Me(3), M=Nb (6.C(7)H(8)), Ta (7.C(7)H(8))). Also the azaheterodicubanes [M[micro(3)-N)(2)(micro(3)-NH)](2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2C(7)H(8) [M=Ti (8.2C(7)H(8)), Zr (9.2C(7)H(8))], and [M[(micro(3)-N)(5)(micro(3)-NH)][Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2 C(7)H(8) (Nb (10.2C(7)H(8)), Ta (11.2C(7)H(8))) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe(2))(x)] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 degrees C. X-ray crystal structure determinations were performed for 6 and 10, which revealed a cube- and double-cube-type core, respectively. For complexes 2 and 4-7 we observed and studied by DNMR a rotation or trigonal-twist of the organometallic ligands [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) and [(micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]](1-). Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.     

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.     

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.     

A new mode of reactivity for pyridine N-oxide: C-H activation with uranium(IV) and thorium(IV) bis(alkyl) complexes

Uranium(IV) and thorium(IV) bis(alkyl) complexes of the type (C5Me5)2AnR2 (An = U, Th; R = CH3, CH2Ph) activate the sp2 and sp3 hybridized C-H bonds in pyridine N-oxide and lutidine N-oxide to produce the corresponding cyclometalated complexes, (C5Me5)2An(R)[eta2-(O,C)-ONC5H4] and (C5Me5)2An(R)[eta2-(O,C)-ON-2-CH2-5-CH3-C5H3]. These provide rare examples of C-H activation chemistry mediated by actinide metal centers. This chemistry is in contrast to the known oxygen atom transfer reactivity patterns of pyridine N-oxides with oxophilic metal complexes and constitutes a new mode of reactivity for pyridine N-oxides.     

Mononuclear and dinuclear palladium and nickel complexes of phosphinimine-based tridentate ligands

The tridentate bis-phosphinimine ligands O(1,2-C(6)H(4)N=PPh(3))(2)1, HN(1,2-C(2)H(4)N=PR(3))(2) (R = Ph 2, iPr 3), MeN(1,2-C(2)H(4)N=PPh(3))(2)4 and HN(1,2-C(6)H(4)N=PPh(3))(2)5 were prepared. Employing these ligands, monometallic Pd and Ni complexes O(1,2-C(6)H(4)N=PPh(3))(2)PdCl(2)6, RN(1,2-CH(2)CH(2)N=PPh(3))(2)PdCl][Cl] (R = H 7, Me 8), [HN(1,2-CH(2)CH(2)N=PiPr(3))(2)PdCl][Cl] 9, [MeN(1,2-CH(2)CH(2)N=PPh(3))(2)PdCl][PF(6)] 10, [HN(1,2-CH(2)CH(2)N=PPh(3))(2)NiCl(2)] 11, [HN(1,2-CH(2)CH(2)N=PR(3))(2)NiCl][X] (X = Cl, R = iPr 12, X = PF(6), R = Ph 13, iPr 14), and [HN(1,2-C(6)H(4)N=PPh(3))(2)Ni(MeCN)(2)][BF(4)]Cl 15 were prepared and characterized. While the ether-bis-phosphinimine ligand 1 acts in a bidentate fashion to Pd, the amine-bis-phosphinimine ligands 2-5 act in a tridentate fashion, yielding monometallic complexes of varying geometries. In contrast, initial reaction of the amine-bis-phosphinimine ligands with base followed by treatment with NiCl(2)(DME), afforded the amide-bridged bimetallic complexes N(1,2-CH(2)CH(2)N=PR(3))(2)Ni(2)Cl(3) (R = Ph 16, iPr 17) and N(1,2-C(6)H(4)N=PPh(3))(2)Ni(2)Cl(3)18. The precise nature of a number of these complexes were crystallographically characterized.     

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.     

Lewis base character of the phosphorus atom in phosphanido-niobocene complexes. Synthesis of new early-early homo- and heterobimetallic entities

The reaction of phosphanido complexes [Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)(PPh(2))] [L = CO (1), CNXylyl (2)] with early transition metal halides in high oxidation states has been carried out. New bimetallic niobocene complexes [{Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)}(μ-PPh(2))(MCl(5))] [M = Nb, L = CO (3), L = CNXylyl (4); M = Ta, L = CO (5), L = CNXylyl (6)] have been successfully synthesized by the reaction with [MCl(5)](2) (M = Nb or Ta). In a similar way [{Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)}(μ-PPh(2))(MCl(4))] [M = Ti, L = CO (13), CNXylyl (14); M = Zr, L = CO (15), CNXylyl (16)] were synthesized using MCl(4) (M = Ti or Zr). Solutions of complexes 4-6 in chloroform produced new ionic derivatives [Nb(η(5)-C(5)H(4)SiMe(3))(2)(P(H)Ph(2))(L)] [MCl(6)] [M = Nb, L = CO (7), L = CNXylyl (8); M = Ta, L = CO (9), L = CNXylyl (10)]. Ionic complexes [Nb(η(5)-C(5)H(4)SiMe(3))(2)(P(Cl)Ph(2))(L)] [NbCl(4)O(thf)] [L = CO (11), CNXylyl (12)] were formed from solutions in thf - rapidly in the case of 3 but more slowly for 4. New heterometallic complexes [Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)(μ-PPh(2)){(Ti(η(5)-C(5)R(5))Cl(3)}] [R = H, L = CO (17), CNXylyl (18); R = CH(3), L = CO (19), CNXylyl (20)] were synthesized by the reaction of 1 or 2 with [Ti(η(5)-C(5)R(5))Cl(3)] (R = H or CH(3)). All of these compounds were characterized by IR and multinuclear NMR spectroscopy, and the molecular structures of 9 and 12 were determined by single-crystal X-ray diffraction.     

Preparation and characterization of diarylphosphazene and diarylphosphinohydrazide complexes of titanium, tungsten and ruthenium and phosphorylketimido complexes of rhenium

Reaction of the proligand Ph2PN(SiMe3)2 (L1) with WCl6 gives the oligomeric phosphazene complex [WCl4(NPPh2)]n, 1 and subsequent reaction with PMe2Ph or NBu4Cl gives [WCl4(NPPh2)(PMe2Ph)] (2) or [WCl5(NPPh2)][NBu4] (3), respectively. DF calculations on [WCl5(NPPh2)][NBu4] show a W=N double bond (1.756 A) and a P-N bond distance of 1.701 A, which combined with the geometry about the P atom suggests, there is no P-N multiple bonding. Reaction of L1 with [ReOX3(PPh3)2] in MeCN (X = Cl or Br) gives [ReX2(NC(CH3)P(O)Ph2)(MeCN)(PPh3)](X = Cl, 4, X = Br, 5) which contains the new phosphorylketimido ligand. It is bound to the rhenium centre with a virtually linear Re-N-C arrangement (Re-N-C angle = 176.6 degrees, when X = Cl) and there is multiple bonding between Re and N (Re-N = 1.809(7) A when X = Cl). The proligand Ph2PNHNMe2(L2H) reacts with [(C5H5)TiCl3] to give [(C5H5)TiCl2(Me2NNPPh2)] (6). An X-ray crystal structure of the complex shows the ligand (L2) is bound by both nitrogen atoms. Reaction of the proligands Ph2PNHNR2[R2 = Me2 (L2H), -(CH2CH2)2NCH3 (L3H), (CH2CH2)2CH2 (L4H)] with [{RuCl(mu-Cl)(eta6-p-MeC6H4iPr)}2] gave [RuCl2(eta6-p-MeC6H4iPr)L] {L = L2H (7), L3H (8), L4H (9)}. The X-ray crystal structures of 7-9 confirmed that the phosphinohydrazine ligand is neutral and bound via the phosphorus only. Reaction of complexes 7-9 with AgBF4 resulted in chloride ion abstraction and the formation of the cationic species [RuCl(6-p-MeC6H4iPr)(L)]+ BF4- {(L = L2H (10), L3H (11), L4H (12)}. Finally, reaction of complex 6 with [{RuCl(mu-Cl)(eta6-p-MeC6H4iPr)}2] gave the binuclear species [(eta6-p-MeC6H4iPr)Cl2Ru(mu2,eta3-Ph2PNNMe2)TiCl2(C5H5)], 13.     

Synthetic and structural experiments on yttrium, cerium and magnesium trimethylsilylmethyls and their reaction products with nitriles; with a note on two cerium beta-diketiminates

The yttrium, cerium and magnesium bis(trimethylsilyl)methyls [Ln[CH(SiMe3)2]3][Ln = Y (1), Ce (2)], and the known compound Mg[[CH(SiMe3)2]2 (C) and [Mg(mu-Br)[CH(SiMe3)2](OEt2)]2 (D) formed the crystalline nitrile adducts [1(NCBut)2] (5), [2(NCPh)] (6), [C(NCR)2][R = But (8), Ph (9), C6H3Me2-2,6 (10)] and [Mg(mu-Br)[CH(SiMe3)2](NCR)]2 [R = But (11), Ph (12), C6H3Me2-2,6 (13)], rather than beta-diketiminato-metal insertion products. The beta-diketiminato-cerium complex [Ce[(N(SiMe3)C(C6H4But-4))2CH][N(SiMe3)2]2] (16) was obtained from [Ce[N(SiMe3)2]3] and the beta-diketimine H[[N(SiMe3)C(C6H4But-4)]2CH]]. The cerium alkyl 2 and [Ln[CH(SiMe3)(SiMe2OMe)]3][Ln = Y (3), Ce (4)] were obtained from the appropriate lithium alkyl precursor and [Ce(OC6H2But2-2,6-Me-4)3] or LnCl3, respectively. Heating complex 3 with benzonitrile in toluene afforded 2,2-dimethyl-4,6-diphenyl-5-trimethylsilyl-1,3-diaza-2-silahexa-1,3-diene (7), a member of a new class of heterocycles. The X-ray structures of the crystalline compounds, D, [Mg[CH(SiMe3)2]2(OEt2)2], the known [Ce(Cl)[(N(SiMe3)C(Ph))2CH]2] (E) and 16 are reported. The cerium alkyl (like 1) has one close Ce...C contact for each ligand, attributed to a gamma-C-Ce agostic interaction. The Ln alkyls and have a trigonal prismatic arrangement of the chelating ligands (each of the same chirality at Calpha) around the metal. In an arene solution at 313 K exists as two isomers, as evident from detailed NMR spectroscopic experiments.     

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.     

Synthesis and structural characterization of PHP[(C(5)Me(4))(2)], a monodentate chiral phosphine derived from intramolecular C-C coupling of tetramethylcyclopentadienyl groups: an evaluation of steric and electronic properties

The chiral monodentate phosphine PhP[(C(5)Me(4))(2)] is readily obtained by oxidation of the lithium complex Li(2)[PhP(C(5)Me(4))(2)] with I(2), which couples the two cyclopentadienyl groups to form a five-membered heterocyclic ring. The steric and electronic properties of PhP[(C(5)Me(4))(2)] have been evaluated by X-ray diffraction and IR spectroscopic studies on a variety of derivatives, including Ph[(C(5)Me(4))(2)]PE (E = S, Se), Cp*MCl(4)[P[(C(5)Me(4))(2)]Ph] (M = Mo, Ta), Ir[P[(C(5)Me(4))(2)]Ph](2)(CO)Cl, and CpFe(CO)[PhP[(C(5)Me(4))(2)]]Me. For comparison purposes, derivatives of the related phospholane ligand PhP[Me(2)C(4)H(6)] have also been investigated, including Ph[Me(2)C(4)H(6)]PS, Ir[Ph[Me(2)C(4)H(6)]](2)(CO)Cl, Ir[Ph[Me(2)C(4)H(6)]](2)(CO)Me, Ir[PPh[Me(2)C(4)H(6)]](COD)(Cl), and Pd[P[Me(2)C(4)H(6)]Ph][eta(2)-C(6)H(4)C(H)(Me)NMe(2)]Cl. The steric and electronic properties of PhP[(C(5)Me(4))(2)] are determined to be intermediate between those of PPh(2)Me and PPh(3). Thus, the crystallographic cone angles increase in the sequence PPh(2)Me (134.5 degrees) < PhP[(C(5)Me(4))(2)] (140.2 degrees) < PPh(3) (148.2 degrees), while the electron donating abilities decrease in the sequence PPh(2)Me > PhP[(C(5)Me(4))(2)] > PPh(3). Finally, PhP[(C(5)Me(4))(2)] has a smaller cone angle and is less electron donating than the structurally similar phosphine, PhP[Me(2)C(4)H(6)].     

Photochemical reactions of [CH2(eta5-C5H4)2][Rh(C2H4)2]2 with silanes: evidence for Si-C and C-H activation pathways

Photochemical reaction of [CH2(eta5-C5H4)2][Rh(C2H4)2]2 1 with dmso led to the stepwise formation of [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(dmso)] 2a and [CH2(eta5-C5H4)2][Rh(C2H4)(dmso)]2 2b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH2(eta5-C5H4)2][Rh(CH2=CHSiMe3)2]2, 3a, 3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d6-benzene, H/D exchange between the solvent and the alpha-proton of the vinylsilane is revealed. In addition evidence for two isomers of the solvent complex [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(eta2-toluene)] was obtained in these and related experiments when the photolysis was completed at low temperature without substrate, although no evidence for H/D exchange was observed. Photolysis of 1 with Et3SiH yielded the sequential substitution products [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiEt3)H] 4a, [CH2(eta5-C5H4)2][Rh(C2H4)(SiEt3)H]2 4b, [CH2(eta5-C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2] 4c and [CH2(eta5-C5H4)2][Rh(SiEt3)2(H)2]2 4d; deuteration of the alpha-ring proton sites, and all the silyl protons, of 4d was demonstrated in d6-benzene. This reaction is further complicated by the formation of two Si-C bond activation products, [CH2(eta5-C5H4)2][RhH(mu-SiEt2)]2 5 and [CH2(eta5-C5H4)2][(RhEt)(RhH)(mu-SiEt2)2] 6. Complex 5 was also produced when 1 was photolysed with Et2SiH2. When the photochemical reactions with Et3SiH were repeated at low temperatures, two isomers of the unstable C-H activation products, the vinyl hydrides [CH2(eta5-C5H4)2][{Rh(SiEt3)H}{Rh(SiEt3)}(mu-eta1,eta2-CH=CH2)] 7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(eta5-C5H4)CH2(C5H3SiEt3)][Rh(SiEt3)2(H)2]2 8 while 4b formed [CH2(C5H3SiEt3)2][Rh(SiEt3)2(H)2]2 (9a and 9b) upon reaction with excess silane. The corresponding photochemical reaction with Me3SiH yielded the expected products [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H] 10a, [CH2(eta5-C5H4)2][Rh(C2H4)(SiMe3)H]2 10b, [CH2(eta5-C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2] 10c and [CH2(eta5-C5H4)2][Rh(SiMe3)2(H)2]2 10d. However, three Si-C bond activation products, [CH2(eta5-C5H4)2][(RhMe)(RhH)(mu-SiMe2)2] 11, [CH2(eta5-C5H4)2][(Rh{SiMe3})(RhMe)(mu-SiMe2)2] 12 and [CH2(eta5-C5H4)2][(Rh{SiMe3})(RhH)(mu-SiMe2)2] 13 were also obtained in these reactions.     

A general study of [(eta5-Cp')2Ti(eta2-Me3SiC2SiMe3)]-catalyzed hydroamination of terminal alkynes: regioselective formation of Markovnikov and anti-Markovnikov products and mechanistic explanation (Cp'=C5H5, C5H4Et, C5Me5)

A general study of the regioselective hydroamination of terminal alkynes in the presence of [(eta5-Cp)2Ti(eta2-Me3SiC2SiMe3)] (1), [(eta5-CpEt)2Ti(eta2-Me3SiC2SiMe3)] (CpEt=ethylcyclopentadienyl) (2), and [(eta5-Cp*)2Ti(eta2-Me3SiC2SiMe3)] (Cp*=pentamethylcyclopentadienyl) (3) is presented. While aliphatic amines give mainly the anti-Markovnikov products, anilines and aryl hydrazines yield the Markovnikov isomer as main products. Interestingly, using aliphatic amines such as n-butylamine and benzylamine the different catalysts lead to a significant change in the observed regioselectivity. Here, for the first time a highly selective switch from the Markovnikov to the anti-Markovnikov product is observed simply by changing the catalyst. Detailed theoretical calculations for the reaction of propyne with different substituted anilines and tert-butylamine in the presence of [(eta5-C5H5)Ti(=NR)(NHR)] (R=4-C6H4X; X=H, F, Cl, CH3, 2,6-dimethylphenyl) reveal that the experimentally observed regioselectivity is determined by the relative stability of the corresponding pi-complexes 10. While electrostatic stabilization favors the Markovnikov performance for aniline, the steric repulsive destabilization disfavors the Markovnikov performance for tert-butylamine.     

Synthesis of beta-P,N aminophosphines and coordination chemistry to Pd(II). X-ray structures of [PdCl2(Ph2PCH(Ph)NHPh-kappaP,kappaN)] and PdCl(eta3-C3H5)(Ph2PCH2CH(Ph)NHPh-kappaP)

The reaction of the C=N bond in PhCH=NPh with the carbanionic species Ph2PCH2-, leading to the N-phenyl beta-aminophosphine Ph2PCH2CH(Ph)NHPh, L1, is described. This molecule reacts with different organic electrophiles to afford related compounds Ph2PCH2CH(Ph)NPhX (X = SiMe3, L2; COPh, L4), [Ph2MePCH2CH(Ph)NHPh]+(I-), L3, and [Ph2PCH2CH(Ph)N(Ph)CO]2, L5, containing two amido and two phosphino functions. The coordination properties of L1, L2, and L4 have been studied in palladium chemistry. The X-ray structure of [PdCl2(Ph2PCH2CH(Ph)NHPh-kappaP,kappaN)] shows the bidentate coordination mode for the L1 ligand with equatorial C(Ph)-N(Ph) phenyl groups. [PdCl2(Ph2PCH2CH(Ph)NHPh-kappaP,kappaN)] crystallizes at 298 K in the space group P2(1)/n with cell parameters a = 10.689(2) A, b = 21.345(3) A, c = 12.282(2) A, beta = 90.294(12) degrees, Z = 4, D(calcd) = 1.526. The reaction between 2 equiv of L1 and [PdCl(eta3-C3H5)]2 affords the [PdCl(eta3-C3H5)(Ph2PCH2CH(Ph)NHPh-kappaP)] complex in which an unexpected N-H.Cl intramolecular interaction has been observed by an X-ray diffraction analysis. [PdCl(eta3-C3H5)(Ph2PCH2CH(Ph)NHPh-kappaP)] crystallizes at 298 K in the monoclinic space group Cc with cell parameters a = 10.912(1) A, b = 17.194(2) A, c = 14.169(2) A, beta = 100.651(9) degrees, Z = 4, D(calcd) = 1.435. Neutral and cationic alkyl or allyl palladium chloride complexes containing L1 are also reported as well as a neutral allyl palladium chloride complex containing L4. Variable-temperature 31P[1H] NMR studies on the allyl complexes show that the eta3/eta1 allyl interconversion is enhanced by a positive charge and also by a N-H.Cl intramolecular interaction.     

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'.