Titanium–Alkaline Earth Molecular Oxides as Supports for Carbanions Derived from μ₃‐Ethylidyne Groups

Abstract

Treatment of the μ3‐ethylidyne complex [{TiCp*(μ‐O)}3(μ3‐CMe)] (1) (Cp* = η5‐C5Me5) with the alkaline earth amides [M{N(SiMe3)2}2(thf)2] (M = Mg, Ca, Sr) promotes the deprotonation of the alkylidyne moiety μ3‐CMe and leads to the oxoheterometallocubane derivatives [{(thf)x(Me3Si)2NM}(μ3‐O)3{Ti3Cp*3(μ3‐CCH2)}] [M = Mg, x = 0 (2a); Ca, x = 1 (3); Sr, x = 1 (4)]. In the case of the magnesium amide, complex 2a is obtained together with the isomer [{(Me3Si)2NMg}(μ3‐O)3{Ti3Cp*3(μ3‐η2‐CHCH)}] (2b). The addition of pentamethylcyclopentadiene (C5Me5H) or triphenylmethanol (Ph3COH) to these compounds causes the displacement of the amide fragment to give the heterometallocubanes [RM(μ3‐O)3{Ti3Cp*3(μ3‐C2H2)}] [R = C5Me5, M = Ca (5), Sr (6); R = Ph3CO, M = Mg (7a,b), Ca (8), Sr (9)]. This substitution can also be performed on 3 and 4 by treatment with the starting complex 1, which gives the corner‐shared doublecubanes [M{(μ3‐O)3(Ti3Cp*3)(μ3‐CCH2)}2] [M = Ca (11), Sr (12)]. Complexes 2a,b do not react with 1, and heating of this mixture affords the edge‐linked double cubane [Mg(μ4‐O)(μ3‐O)2{Ti3Cp*3(μ3‐CCH)}]2 (10). The combination of the barium reagents [Ba(CH2Ph)2] or [Ba{N(SiMe3)2}2] with 1 leads to the corner‐shared double cubane [Ba{(μ3‐O)3(Ti3Cp*3)(μ3CCH2)}2] (13). The molecular structures of 3 and 10 have been established by single‐crystal X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Co-complexation of Lithium Gallates on the Titanium Molecular Oxide {[Ti(η5-C5Me5)(μ-O)}3(μ3-CH)]

“…On the other hand, the NMR spectra for complexes 3 and 4 show a single set of signals assigned to the η 5 -C 5 Me 5 ligands, indicating a local C 3 v symmetry for the alkylidyne starting material 1 . This experimental fact suggests the existence of a fluxional process involving free rotation of the preorganized oxo derivative 1 around the lithium gallate fragment, as that observed in complexes [{(thf)(Me 3 Si) 2 NM}(μ 3 -O) 3 {Ti 3 (η 5 -C 5 Me 5 ) 3 (μ 3 -CCH 2 )}] (M = Ca, Sr) and [{Cl 2 (RN)Ti}(μ 3 -NH) 3 {Ti 3 (η 5 -C 5 Me 5 ) 3 (μ 3 -N)}] (R = CMe 3 , 2,4,6-Me 3 C 6 H 2 ) . The μ-NMe 2 and μ-O-2,6-Me 2 C 6 H 3 moieties show their characteristic signals, while the μ 3 -CH units were not detected in the 13 C{ 1 H} NMR spectra, likely due to the aforementioned fluxional process.…”

Incorporation of Boron, Aluminum, and Gallium Derivatives into [{Ti(η5-C5Me5)(μ-O)}3(μ3-CR)] (R = H, Me)

“…Recently, we decided to investigate the incorporation of group 1 and 2 derivatives into the vacant vertex of the incomplete cube structure of derivatives 1 and 2 (Scheme ). In these reactions, the products exhibit a cube-type unit, where the metal cation is filling the last vertex to build new cage structures (heterometallocubane and corner- or edge-shared heterometallodicubane species) …”