Antonio Manzanero

Synthetic and reactivity studies of mono- and dicyclopentadienyl titanium, zirconium and hafnium complexes with the chlorodimethylsilyl-cyclopentadienyl ligand. X-ray molecular structure of Hf{(η5-C5H4)SiMe2OSiMe2(η5-C5H4)}Cl2 and Zr(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2-η-NtBu)Cl

Abstract Reaction of the disilylated cyclopentadiene C5H4(SiClMe2)(SiMe3) with HfCl4, in heptane, gave the monocyclopentadienyl complex Hf(η5-C5H4SiClMe2)Cl3 (1c). Addition of two equivalents of C5H5(SiClMe2) to a solution of MCl4, in toluene under reflux and in the presence of two equivalents of NEt3, afforded the dichloro derivatives M(η5-C5H4SiClMe2)2Cl2 [M=Ti (2a), Hf (2c)]. Compounds 2a and 2c react with a stoichiometric amount of water with selective hydrolysis of the SiCl bonds to give the tetramethyldisiloxane-bridged diciclopentadienyl complexes M{(η5-C5H4)SiMe2OSiMe2(η5-C5H4)}Cl2 [M=Ti (3a), Hf (3c)]. The reaction of the trichloro metal compounds M(η5-C5H4SiClMe2)Cl3 with Tl(1,3-tBu2C5H3), K(C5Me5) or Tl(C5H5) afforded the dichloro mixed dicyclopentadienyl MCp′(η5-C5H4SiClMe2)Cl2 derivatives [Cp′=1,3-tBu2C5H3, M=Ti (4a), Zr (4b), Hf (4c); Cp′=C5Me5, M=Zr (5b), Hf (5c); Cp′=C5H5, M=Hf (6c)]. The SiCl bond of the mixed dicyclopentadienyl complexes M(η5-1,3-tBu2C5H3)(η5-C5H4SiClMe2)Cl2, [M=Ti (4a), Zr (4b), Hf (4c)] reacts selectively with one equivalent of LiNHtBu in toluene at 50–60°C to give the amidosilyl(cyclopentadienyl) compounds M(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2NHtBu)Cl2, [M=Ti (7a), Zr (7b), Hf (7c)]. The same reaction with two equivalents of the lithium amide gives the ansa-cyclopentadienylsilyl-amido compounds M(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2-η-NtBu)Cl [M=Ti (8a), Zr (8b), Hf (8c)]. The X-ray molecular structure of Hf{(η5-C5H4)SiMe2OSiMe2(η5-C5H4)}Cl2 (3c) and Zr(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2-η-NtBu)Cl (8b) have been determined by diffraction methods.Financial support for this research by DGICYT (Project PB97-0776) is gratefully acknowledged.

Dicyclopentadienyl titanium and zirconium complexes with the double bridged bis(dimethylsilanodiyl) dicyclopentadienyl [(Me2Si)2(η5-C5 H3)2]2- ligand: X-ray molecular structure of [Ti{(SiMe2)2(η5-C5H3)2}Me2]

Financial support for this research by DGICYT (Project PB92-0178-C) is gratefully acknowledged. A,M. is grateful to Consejeria Educacion (CAM) for a fellowship.

Mixed-dicyclopentadienyl niobium and tantalum complexes: synthesis and reactivity X-ray molecular structures of Ta(η5-C5Me5)(η5-C5H4SiMe3)Cl2 and Ta(η5-C5Me5){η5-C5H3(SiMe3)2}H3

Abstract MCp∗ Cl4, ( Cp ∗ = η 5 - C 5 Me 5 ) reacts with LiCp (Cp = C5H4(SiMe3)(Cp′); C5H3(SiMe3)2 (Cp″)) and sodium amalgam, in 1:1:1 molar ratio to give the paramagnetic dicyclopentadienyl niobium and tantalum(IV) complexes, MCp∗ CpCl2, (M = Nb, Cp = Cp′ 1; Cp″ 2; M = Ta, Cp = Cp′ 3; Cp″ 4). Reactions of 3 and 4 with 1 2 equivalent of PCl5 afford the diamagnetic trichlorocomplexes TaCp∗ CpCl3, (Cp = Cp′ 5; Cp″ 6), while oxidation with dry O2 gives the diamagnetic dinuclear complexes [TaCp∗ CpCl2]2(μ-O), (Cp = Cp′ 7; Cp″ 8), and with air are transformed into the corresponding oxoderivatives TaCp∗ CpCl(O), (Cp = Cp′ 9; Cp″ 10). Treatment of compounds 3 and 4 with a slight excess of lithium aluminium hydride affords the trihydrido complexes TaCp∗ CpH3 (Cp = Cp′ 11; Cp″ 12). The trihydrido complex 12 reacts with two-electron donor ligands on heating to yield the hydrido tantalum(III) compounds TaCp∗ Cp″H(L) (L = CO 13, C2H414, RNC 15). All the new complexes were characterized by usual IR and NMR spectroscopic methods. The crystal structures of 3 and 12 were determined by X-ray diffraction studies. Crystals of 3 are orthorhombic, space group P212121, with Z = 4 in a unit cell of dimensions a = 11.775(5) A , b = 12.821(1) A , c = 13.037(7) A . Crystals of 12 are triclinic, space group P 1 with Z = 2 in a unit cell of dimensions a = 7.384(4) A , b = 10.861(2) A , c = 16.731(3) A , α = 75.94(2)°, β = 84.75(3)° and γ = 72.57(4)°. Both structures were solved from diffractometer data by a combination of direct and Fourier methods and refined by full-matrix least squares fit on the basis of 4088 (3) and 4594 (12) observed reflections to R and Rw values of 0.040 and 0.064 (3) and 0.022 and 0.033 (12) respectively.

Neutral and cationic di(tert-butyl) cyclopentadienyl titanium, zirconium and hafnium complexes. Dynamic NMR study of the ligand-free cations [M(1,3-tBu2-η5-C5H3)(η5-f5H5)(CH3)]+(M=Zr, Hf)

Financial support for this research by DGICYT (Project PB92-0178C) is gratefully acknowledged. J.I.A. acknowledges Repsol Petroleo S.A. for a fellowship. A.M. is grateful to Consejeria Educaci6n (CAM) for a fellowship.

Heterodinuclear TiMo and TiW complexes bridged by the (dimethylsilanediyl) dicyclopentadienyl ligand

Abstract Reactions of the tricarbonyl-molybdenum and -tungsten complexes [M(CO)3(MeCN)3] (M = Mo, W or [Mo(CO)3(mesitylene)] with equimolar amounts of [Ti(η5-Cp′){(η5-C5H3)(SiMe2)2 (C5H4)}Cl2] (Cp′ = C5H5, C5Me5) lead to the heterodinuclear compounds [Ti(η5-Cp′)Cl2{μ-[(SiMe2)2(η5-C5H3)2]}MH(CO)3]. These dinuclear complexes are isolated as single cis- and trans-isomers or as mixtures of both depending on the starting complex and the reaction conditions. The molar ratio of the two resulting isomers is controlled by thermodynamic and kinetic factors which prevent the application of stereoselective methods for some of the products. Reaction of the hydrido cis- and trans-complexes with CCl4 in CH2Cl2 allows the isolation of chloro complexes [Ti(η5-Cp′)Cl2{μ-[(SiMe2)2(η5-C5H3)2]} MCl(CO)3] of the same configuration. All of the new heterodinuclear compounds reported were characterized by their analytical composition, IR and NMR spectroscopy and the molecular structure of cis-[Ti(η5-C5Me5)Cl2{μ-[(SiMe2)2(η5-C5H3)2]}WH(CO)3] was studied by X-ray diffraction methods.

Silyl and siloxanediyl cyclopentadienyl titanium and zirconium complexes: synthesis and reactivity. X-ray molecular structure of [Zr{η5-C5H4SiMe2(μ-OH)}(μ-Cl)Cl2]2

Abstract Chloro(dimethyl)silyl-η5-cyclopentadienyl group 4 metal complexes of the type [M(η5-C5H4Cl)Cl3] ( M = Ti 1 , Zr 2 ) react with thallium salts Tl(C5H4R) (R = H, SiMe3) to give mixed dicyclopentadienyl derivatives [M(η5-C5H4R)(η5-C5H4SiMe2Cl)Cl2], (M = Ti, R = H 3, R = SiMe3 4; M = Zr, R = H 5, R = SiMe3 6) in high yield. Hydrolysis of complexes 3 and 4 affords the dinuclear complexes [Ti(η5-C5H4R)Cl2]2{μ-[(η5-C5H4SiMe2)2O]}] [R = H 7, R = SiMe3 8) containing a siloxanyl bridge, by elimination of two equivalents of HCl. Reactions of complexes 1 with hydroxo containing reagents such as anhydrous LiOH and SiPh2(OH)2 give the derivatives [Ti(η5-C5H4SiMe2Cl)Cl2]2(μ-O)], 9 and Ti[μ-(η5-C5H4SiMe2OSiPh2-η1-O)]Cl2, 10 identified by analytical, spectrometric and spectroscopic data. Treatment of analogous complex 2 with water produces the dimeric monocyclopentadienyl zirconium trichloride adduct [Zr(η5-C5H4SiMe2OH)Cl3]2, 11. Compound 11 has been characterized by X-ray crystallography.

Cis- and trans-titanium complexes with doubly silyl-bridged dicyclopentadienyl ligands: molecular structure of [(TiCl)2 (μ-0) {(SiMe2)2(η5-C5H3)2}]2 (μ-O)2

The reaction of TiCl 4 with Li 2 [(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 ] in toluene at room temperature afforded a mixture of cis - and trans -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] in a molar ratio of after recrystallization. The complex trans -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] was hydrolyzed immediately by the addition of water to THF solutions to give trans -[(TiCl 2 ) 2 ( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] as a solid insoluble in all organic solvents, whereas hydrolysis of cis -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] under different conditions led to the dinuclear μ-oxo complex cis -[(TiCl 2 ) 2 )( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] and two oxo complexes of the same stoichiometry [(TiCl) 2 ( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] 2 ( μ -O) 2 as crystalline solids. Alkylation of cis - and trans -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] with MgCIMe led respectively to the partially alkylated cis -[(TiMe 2 Cl) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] and the totally alkylated trans -[(TiMe 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] compounds. The crystal and molecular structure of the tetranuclear oxo complex [(TiCl) 2 ( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] 2 ( μ -O) 2 was determined by X-ray diffraction.