Trimethylscandium

Abstract

The hitherto unknown homoleptic tetramethylaluminate complex [Sc(AlMe 4 ) 3 ] could be obtained by reacting the ate complex [Li 3 ScMe 6 (thf) 1.2 ] with AlMe 3 in the cold. It cocrystallizes with AlMe 3 as [Sc-(AlMe 4 ) 3 (Al 2 Me 6 ) 0.5 ] and decomposes at ambient temperature in n-pentane via multiple C−H bond activations to the mixed methyl/methylidene complex [Sc 3 (μ 3 -CH 2 ) 2 (μ 2 -CH 3 ) 3 (AlMe 4 ) 2 (AlMe 3 ) 2 ]. Donor-induced methylaluminate cleavage of [Sc(AlMe 4 ) 3 (Al 2 Me 6 ) 0.5 ] produced [ScMe 3 ] n in good yield, which could be derivatized with trimethyltriazacyclononane (Me 3 TACN) to form the structurally characterizable [(Me 3 TACN)ScMe 3 ]. Additionally, half-sandwich complex [Cp*Sc(AlMe 4 ) 2 ] and sandwich complex [Cp* 2 Sc(AlMe 4 )] were accessible by salt metathesis reactions from [Sc-(AlMe 4 ) 3 (Al 2 Me 6 ) 0.5 ] and KCp* (Cp* = C 5 Me 5 ). 45 Sc NMR spectroscopy was applied as a significant probe to evidence the existence of [ScMe 3 ] n . Compounds [(Me 3 TACN)ScMe 3 ] (+624.6 ppm) and [ScMe 3 (thf) x ] (+601.7 ppm) gave large 45 Sc NMR shifts, revealing the strong deshielding effect of the σ-bonded alkyl ligands on the scandium nuclei. Ultimately, cationized [Sc(AlMe 4 ) 3 (Al 2 Me 6 ) 0.5 ] was employed in isoprene polymerization, leading to polymers in high yields (>95%) and with high (>90%) cis-1,4-polyisoprene content.

Reduced Arene Complexes of Scandium

“…The larger sum of the angles between the three anilide ligands in 1 (343.8°) than the angle sum between the anilide and chloride ligands in 2 (326.2°) reveals a lower degree of pyramidalization of 18 % in 1 (compared to 38 % in 2 ) . Notable spectroscopic features are the very broad 45 Sc NMR signals at δ =359 ( 1 , Δν 1/2 =15 000 Hz) and 373 ppm ( 2 , Δν 1/2 =10 000 Hz) (Figure ), close to that of the homoleptic tris(amide) complex [Sc{N(SiMe 3 ) 2 } 3 ] ( δ ( 45 Sc)=396 ppm) . The high‐field shift is likely caused by the higher coordination number (four vs. three) of the scandium centers in 1 and 2 …”

“…Notable spectroscopic features are the very broad 45 Sc NMR signals at δ =359 ( 1 , Δν 1/2 =15 000 Hz) and 373 ppm ( 2 , Δν 1/2 =10 000 Hz) (Figure ), close to that of the homoleptic tris(amide) complex [Sc{N(SiMe 3 ) 2 } 3 ] ( δ ( 45 Sc)=396 ppm) . The high‐field shift is likely caused by the higher coordination number (four vs. three) of the scandium centers in 1 and 2 …”

“…Replacing the naphthalenide against the anthracenide ligand had no effect on the chemical shift of the 45 Sc NMR signal (Figure ). Considering that the 45 Sc resonances highly depend on the coordination number of the scandium center, the almost equal 45 Sc chemical shift in 1 , 2 , and 3‐Naph‐K indicate that the metal center in the reduced compound is four‐coordinate, whereby the weak interactions from the peripheral C=C bonds have only a small effect.…”

Carbenaporphyrins: No Longer Missing Ligands in N‐Heterocyclic Carbene Chemistry

“…To probe a potential ring current in our CTP ligand, we added CpLi to a solution of complex 8 in [D 8 ]THF (Scheme 2). The formation of complex 9 is detected in the 45 Sc NMR with a signal at 136.4 ppm, which is about 150 ppm at higher field than that of 8 and a good indicator for the substitution by a Cp ring [50] . The Cp−H signal is detected at δ ( 1 H)=5.21 ppm (LiCp: δ ( 1 H)=5.69 ppm), which is comparable to other CpSc complexes [51] .…”

Carbenaporphyrine: eine Lücke in der Chemie N‐heterocyclischer Carbene schließt sich

“…Um einen potenziellen Ringstrom in unserem CTP‐Liganden zu untersuchen, haben wir eine Lösung von Komplex 8 in [D 8 ]THF mit LiCp umgesetzt (Schema 2). Die Bildung des Komplexes 9 kann im 45 Sc‐NMR‐Spektrum mit einem Signal bei 136.4 ppm bestätigt werden, das um ungefähr 150 ppm im Vergleich zu Komplex 8 hochfeldverschoben ist und einen guten Indikator für die Substitution durch einen Cp‐Ring darstellt [50] . Das Cp‐H‐Signal wird bei δ ( 1 H)=5.21 ppm (LiCp: δ ( 1 H)=5.69 ppm) detektiert, was mit anderen CpSc‐Komplexen vergleichbar ist [51] .…”