Miguel Mena

(C5Me5)SiMe3 as a mild and effective reagent for transfer of the C5Me5 ring: an improved route to monopentamethylcyclopentadienyl trihalides of the group 4 elements

Abstract The reaction between (C5Me5)SiMe3 and group 4 element tetrahalides MX4 (M  Ti, X  Cl, Br, I; M  Zr and Hf, X  Cl) gives the corresponding (η5-C5Me5)MX3 derivatives in nearly quantitative yields in a one-step procedure without the need for further purification.

Dialkylamido derivatives of [(η5-C5Me5)TiCl3], [(η5-C5Me5) TiCl22(μ-O)] and [(η5-C5Me5)TiCl3(μ-O)3]: X-ray crystal structure of [(η5-C5Me5)Ti(NMe2)3]

Abstract Reactions of [(η5-C5Me5)TiCl3] with dialkyl and diarylamido-lithium complexes in 1:1, 1:2 or 1:3 molar ratios afford the mono(pentamethylcyclopentadienyl)titanium(IV) dialkylamido- complexes [(η5-C5Me5)TiCl3-n(NR2)n (n = 1; R = Me or SiMe3) (n = 2, R = Me or Ph) (n = 3, R = Me or Et). Similar reactions of [(η5-C5Me5)TiCl 22(μ-O)] and [(η5-C5Me5)TiCl3(μ-O)3] gave the corresponding complexes [(η5-C5Me5)TiCl2-n(NR2)ni2(μ-O)] (n = 1; R = Me or Ph) (n = 2, R = Me) and [(η5-C5Me5)3Ti3Cl3-n(NMe2)n(μ-O) 3] (n = 1 or 3). The crystal structure of [(η5-C5Me5)Ti(NMe2)3] has been established by X-ray crystallography and is shown to be monomeric with the typical three-legged piano- stool structure.

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)°.

Ammonia activation by μ3-alkylidyne fragments supported on a titanium molecular oxide model.

Ammonolysis of the μ(3)-alkylidyne derivatives [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CR)] [R = H (1), Me (2)] produces a trinuclear oxonitride species, [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-N)] (3), via methane or ethane elimination, respectively. During the course of the reaction, the intermediates amido μ-alkylidene [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ-CHR)(NH(2))] [(R = H (4), Me (5)] and μ-imido ethyl species [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ-NH)Et] (6) were characterized and/or isolated. This achievement constitutes an example of characterization of the three steps of successive activation of N-H bonds in ammonia within the same transition-metal molecular system. The N-H σ-bond activation of ammonia by the μ(3)-alkylidyne titanium species has been theoretically investigated by DFT method on [{Ti(η(5)-C(5)H(5))(μ-O)}(3)(μ(3)-CH)] model complex. The calculations complement the characterization of the intermediates, showing the multiple bond character of the terminal amido and the bridging nature of imido ligand. They also indicate that the sequential ammonia N-H bonds activation process goes successively downhill in energy and occurs via direct hydron transfer to the alkylidyne group on organometallic oxides 1 and 2. The mechanism can be divided into three stages: (i) coordination of ammonia to a titanium center, in a trans disposition with respect to the alkylidyne group, and then the isomerization to adopt the cis arrangement, allowing the direct hydron migration to the μ(3)-alkylidyne group to yield the amido μ-alkylidene complexes 4 and 5, (ii) hydron migration from the amido moiety to the alkylidene group, and finally (iii) hydron migration from the μ-imido complex to the alkyl group to afford the oxo μ(3)-nitrido titanium complex 3 with alkane elimination.

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.

Molecular structure of trichloro(η5-pentamethylcyclopentadienyl)zirconium(IV)

Abstract X-ray analysis of the yellow, air-unstable, crystalline compound Cp★ZrCl3 (1) which results from the reaction of ZrCl4 with Cp★SiMe3 confirms the presence of two Cp★ZrCl3 moieties related by a centre of symmetry with two chlorine atoms bridging the metals. 1 is therefore a dimer, despite the molecular structure of [CpZrCl3] which was found to be a polymer.

Hydrolytic studies on (η5-C5Me5)TiMe3; X-ray structure of [(η5-C5Me5)TiMe(µ-O)]3 containing a Ti3O3 ring

Successive hydrolysis of (η5-C5Me5)TiMe3(2) gives first [(η5-C5Me5)TiMe2]2(µ-O)(3) and then [(η5-C5Me5)TiMe(µ-O)]3(4); the crystal structure of (4) reveals a Ti3O3 ring.

Rhodium/Iridium‐Titanium Azaheterometallocubanes

Treatment of [[Ti(eta5-C5Me5)(mu-NH)]3(mu3-N)] (1) with the diolefin complexes [[MCl(cod)]2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) in toluene afforded the ionic complexes [M-(cod)(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)]Cl [M = Rh (2), Ir (3)]. Reaction of complexes 2 and 3 with [Ag(BPh4)] in dichloromethane leads to anion metathesis and formation of the analogous ionic derivatives [M(cod)(mu3-NH)3Ti3-(eta5-C5Me5)3(mu3-N)][BPh4] [M = Rh (4), Ir (5)]. An X-ray crystal structure determination for 5 reveals a cube-type core [IrTi3N4] for the cationic fragment, in which 1 coordinates in a tripodal fashion to the iridium atom. Reaction of the diolefin complexes [[MCl(cod))2] (M = Rh, Ir) and [[RhCl(C2H4)2]2] with the lithium derivative [[Li(mu3-NH)2(mu3-N)-Ti3(eta5-C5Me5)3(mu3-N)]2] x C7H8 (6 C7H8) in toluene gave the neutral cube-type complexes [M(cod)(mu-NH)2(mu3-N)Ti3-(eta5-C5Me5)3(mu3-N)] [M = Rh (7), Ir (8)] and [Rh(C2H4)2(mu3-NH)2(mu3-N)Ti3(eta5-C5Me5)3(mu3-N)] (9), respectively. Density functional theory calculations have been carried out on the ionic and neutral azaheterometallocubane complexes to understand their electronic structures.

Construction of Heterometallic Cubanes [{Ti3Cp*3(μ3‐CR)}(μ3‐O)3{Mo(CO)3}] (R=H, Me; Cp*=η5‐C5Me5) and [{Ti3Cp*3(μ3‐N)}(μ3‐NH)3{M(CO)3}] (M=Cr, Mo, W); Crystal Structure of [{Ti3Cp*3(μ3‐CMe)}(μ3‐O)3{Mo(CO)3}]

Der Einbau von M(CO)3-Fragmenten in die dreikernigen Ti-Komplexe [{Ti3Cp*3(μ3-CR)}(μ-O)3] und [{Ti3Cp*3(μ3-N)}(μ-NH)3] (Cp*=η5-C5Me5) fuhrt zu einer neuen Klasse von Heterometallclustern mit Cubanstruktur [z. B. Gl. (a)]. Dichtefunktionalrechungen deuten auf eine Elektronendelokalisierung in den Ti3M-Gerusten hin (M=Cr, Mo, W).