Pilar Gómez-Sal

Construction of Heterometallic Cubanes [{Ti3Cp(μ3‐CMe)}(μ3‐O)3{Mo(CO)3}]

Incorporation of M(CO)(3) fragments by trinuclear Ti complexes [{Ti(3)Cp (µ(3)-CR)}(µ-O)(3)] and [{Ti(3)Cp (µ(3)-N)}(µ-NH)(3)] (Cp*=eta(5)-C(5)Me(5)) leads to the formation of an unprecedented class of heterometallic clusters with cubane structure [e.g., Eq. (a)]. Density functional calculations on these complexes indicate the existence of electron delocalization in the Ti(3)M cores (M=Cr, Mo, W).

Monopentamethylcyclopentadienyltitanium(IV) halo-alkoxides, alkyl-alkoxides and acetylacetonates

Abstract Reactions of (C 5 Me 5 )TiCl 3 with lithium alkoxides in 1:1 or 1:2 molar ratio have given the halo-alkoxides (C 5 Me 5 )TiCl 3− n (OR) n ( n = 1, R = Me, SiPh 3 ; n = 2, R = SiPh 3 ) and (C 5 Me 5 )TiCl (O 2 R′)(R′ = C 6 H 4 , C 6 H 3 -4- t Bu). Protonolysis of (C 5 Me 5 TiMe 3 with HOSiPh 3 and Hacac gives (C 5 Me 5 )TiMe(OSiPh 3 ) 2 and (C 5 Me 5 )TiMe 2 (acac), and (C 5 Me 5 )TiCl 2 Me likewise gives (C 5 Me 5 )TiCl 2 (OC 6 H 3 -2.6-Me 2 ) and (C 5 Me 5 )TiCl 2 (acac). The crystal structure of (C 5 Me 5 )TiCl 2 (OC 6 H 3 -2,6-Me 2 ) has been determined and shows it to be monomeric, with a symmetry plane, a TiO distance of 1.785(2) A, and a TiOC angle of 162.3(2)°.

Reaction of imines with N-iodosuccinimide (NIS): unexpected formation of stable 1 : 1 complexes

Imines react with N-iodosuccinimide (NIS) to afford unexpected 1 : 1 complexes and the structure of one of these was determined by single-crystal X-ray diffraction; the reaction seems to be very general for substituted cyclic imines with solid stable complexes obtained in high yields; this is the first reported example of a halogen bonding interaction involving the C=N bond and NIS.

Synthesis and molecular structure of the first organometallic nitride cubane: [{Ti(η5-C5Me5)}4(µ3-N)4]

The ammonolysis of [Ti(η5-C5Me5)(NMe2)3] at 90 °C affords the nitride complex [{Ti(η5-C5Me5)}4(µ3-N)4]; the X-ray crystal structure analysis shows a Ti4N4 core clearly similar to the structural motif of cubic titanium nitride.

Monocyclopentadienyl alkyl alkylidene niobium(V) and tantalum(V) complexes. X-ray crystal structure of Ta(η5-Cp′)(CH2SiMe3)2(CHSiMe3)

Abstract Reactions of monocyclopentadienyl complexes M(η5-Cp′)Cl4 with trimethylsilylmethyl lithium leads to the formation of alkylidene derivatives M(η5-Cp′)(CH2SiMe3)2(CHSiMe3), where M = Nb (1); Ta (2); Cp′= C5Me5 and M = Ta; Cp′ Me3Si(C5H4) (3), 1,3-(Me3Si)2(C5H3) (4). The new complexes were characterized by 1H and 13C NMR spectroscopy and the molecular structure of 2 was studied by X-ray diffraction methods.

Azinium-N-(2′-azinyl)aminides: synthesis, structure and reactivity

Abstract Several azinium-N-(2′-azinyl)aminides are reported. The structure of pyridinium-N-(2′-pyridyl)aminide has been studied, both in solution and in crystalline state, and results have been compared. In non-polar solvents, the aminides present a planar conformation stabilized by an intramolecular hydrogen bond. The reactivity toward electrophiles confirms the structural data, producing either N- or C- substitutions under mild conditions.

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.

Insertion of Isocyanide into Metal−Carbon Bonds of Alkylchloro(pentamethylcyclopentadienyl)niobium- and -tantalum Complexes − X-ray Structure of [TaCp*Cl2(CH2CMe2Ph){η2-C(CH2CMe2Ph)=N(2,6-Me2C6H3)}] and Unexpected Decomposition of Alkyldichloro(η2-iminoacyl) Complexes of Tantalum

Methylation of NbCp*Cl2Me2 using excess ZnMe2 gives NbCp*ClMe3 (1) which has been found to exhibit a Berry pseudorotation process on the NMR time scale (log A = 12.2 ± 0.3, Ea = 12.2 ± 0.4 kcal·mol−1, ΔH≠ = 11.6 ± 0.4 kcal·mol−1, ΔS≠ = −4.4 ± 1.3 e.u., ΔG≠298K = 12.9 kcal·mol−1). Alternatively, lithium dimethylamide reacts with NbCp*Cl2Me2 to form NbCp*Me2(NMe2)2 (2) which decomposes in solution under the elimination of methane to give the (dimethylamido)methylazaniobacyclopropane derivative NbCp*Me(NMe2)(η2-CH2NMe) (3). Reaction of NbCp*Cl2Me2 with 1 equiv. of 2,6-Me2C6H3NC results in a double methyl group migration to give the dichloroazaniobacyclopropane complex [NbCp*Cl2{η2-CMe2N(2,6-Me2C6H3)}] (4). Dialkyldichloro complexes TaCp*Cl2R2 [Cp* = η5-C5Me5; R = CH2SiMe3 (5), CH2CMe2Ph (6), CH2CMe3 (7), CH2C6H5 (8)] were obtained by treating TaCp*Cl4 with the requisite amounts of the appropriate alkylating agents. Reactions of the dialkyldichloro complexes TaCp*Cl2R2 (5−8) with 1 equiv. of 2,6-Me2C6H3NC resulted in migration of only one of the two alkyl groups to give (alkyl)dichloro(η2-iminoacyl) complexes [TaCp*Cl2R{η2-C(R)=NAr}] [Ar = 2,6-Me2C6H3; R = CH2SiMe3 (9), CH2CMe2Ph (10), CH2CMe3 (11), CH2C6H5 (12)]. The molecular structure of complex 10 has been determined by X-ray diffraction analysis. The η2-iminoacyl complexes 9−12 decompose in [D6]benzene or n-hexane solutions to give [TaCp*Cl2{N(2,6-Me2C6H3)}] and the corresponding trans or cis olefins R′−CH=CH−CH2−R′ [R′ = SiMe3 (9o), CMe2Ph (10o), CMe3 (11o), C6H5 (12o)]. A mechanism for this reaction is proposed. All the new compounds have been characterized by IR spectrophotometry, 1H- and 13C{1H}-NMR spectroscopy, and elemental analysis.

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.

Pentamethylcyclopentadienyl halo- and alkyl-alkoxo tantalum(V) complexes. Crystal structure of TaCp*(CH2SiMe3) 2{η2-O(2-CH2-6-MeC6H3)}

Abstract Reaction of TaCp∗Cl4 with MOR (M  Li, Na) in different molar ratios gives halo alkoxides TaCp ∗ Cl n ( OR ) 4−n (n = 3: R  t Bu 1 ; SiPh 3 2 ; 2,6- Me 2 C 6 H 3 3 ; n = 2: R = t Bu 4 ; SiPh 3 5 ; 2,6- Me 2 C 6 H 3 6 ; n = 1: R = SiMe 3 7 ) in good yields. The alkylidene complex TaCp∗(CH2SiMe3)2(CHSiMe3) is hydrolyzed in the presence of traces of water to give the oxo dialkyl derivative [TaCp∗(Ch2SiMe3)2O]n8, and reacts with 1 equivalent of 2,6-Me2C6H3NC affording a new η2-iminoacyl compound TaCp ∗ ( Ch 2 SiMe 3 ) CHSiME 3 ){η 2 - C(CH 2 Sime 3 ) N (2,6- Me 2 C 6 H 3 )} 9. Reactions of TaCP∗(CH2SiMe3)2(CHSiMe3) with 1 equivalent of C6H5OH and 4-MeC6H3(OH)2 result in the formation of the alkyl phenoxo TaCp∗(CH2SiMe3)3(OC6H5) 10 and 4-methyl pyrocatecholate TaCp∗(CH2SiMe3)2(O2C6H3Me) 11, whereas the relaxed reaction with 2,6-Me2C6H3OH leads to the cyclic alkyl-alkoxo compound TaCp ∗ ( CH 2 SiMe 3 ) 2 {η 2 - O (2- CH 2 -6- MeC 6 H 3 )]} 12. All the complexe were characterized by IR and NMR (1H and 13C) spectroscopy. The crystal and molecular structure of 12 has been determined. Crystals of 12 are triclinic, space group P 1 − with Z = 2 in a unit cell of dimensions a = 9.151(5) A , b = 11.835(5) A , c = 14.045(4) A , α = 89.35(3)°, β = 72.34(3)° and γ = 88.51(4)°, V = 1449(1) A 3 . Final values of R = 0.025 and Rw = 0.0655 were obtained from 5547 reflections measured (5070, > 2σ(1)).