Gallium Methylene

Abstract

Despite the eminent importance of metal alkylidene species for organic synthesis and industrial catalytic processes, molecular homoleptic metal methylene compounds [M(CH2)n] as the simplest representatives, have remained elusive. Reports on this topic date back to 1955 when polymeric [Li2(CH2)]n and [Mg(CH2)]n were accessed by pyrolysis of methyllithium and dimethylmagnesium, respectively. However, the insoluble salt‐like composition of these compounds has impeded their application as valuable reagents. We report that rare‐earth metallocene methyl complexes [(C5Me5)2Ln{(μ‐Me)2GaMe2}] (Ln=Lu, Y) trigger the formation of homoleptic gallium methylene [Ga8(μ‐CH2)12] from trimethylgallium [GaMe3] (Me=methyl) via a cascade C−H bond activation involving the dodecametallic clusters [(C5Me5)6Ln3(μ3‐CH2)6Ga9(μ‐CH2)9] as crucial intermediates. Such gallium methylene compounds feature a reversible [Ga8(μ‐CH2)12]/[Ga6(μ‐CH2)9] oligomer switch in donor solvents and act as Schrock‐type methylene‐transfer reagents.

Geminal C–Cl and Si–Cl bond activation of chloromethanes and chlorosilanes by gallanediyl LGa

“…Compound 5, which is exceptionally stable in both solid-state and solution under inert gas atmosphere, belongs to the very short list of structurally characterized group 13 element methylene complexes, which includes the parent Ga methylene [Ga 8 (µ-CH 2 ] 12 ], [25] Al methylene [R 2 Al] 2 CH 2 (R = Cl, CH(SiMe 3 ) 2 , 2,4,6-i-Pr 3 C 6 H 2 , N(Me 2 CCH 2 ) 2 CH 2 , N(SiMe 3 ) 2 ), [26] and In methylene complexes [(L)X 2 In] 2 CH 2 (X = Cl, Br; L = Me 2 NC 2 H 4 NMe 2 ), [27] respectively. In addition, several Please do not adjust margins Please do not adjust margins methylene complexes were obtained from two-fold C-Cl bond activation of DCM by silylenes, [28] stannylenes, [29] and a digermene, [30] respectively.…”

“…For the same reason, the CCl 3 resonance of 3 was not observed. The CH 2 (−1.02 ppm) and CH 2 (−12.4 ppm) resonances of Ga methylene complex 5 appear at even higher frequency as a result of the high electron density at the central CH 2 moiety imposed by the two electropositive gallyl substituents, and are comparable to those of THF and pyridine adducts of the parent Ga methylene [Ga 8 (µ-CH 2 ] 12 ] (δ 1H 0.63-−0.49 ppm) [25] and [R 2 Al] 2 CH 2 (δ 1H R = CH(SiMe 3 ) 2 −0.50; 2,4,6-i-Pr 3 C 6 H 2 −0.66; N(SiMe 3 ) 2 −0.67 ppm), [26] while those of the double silylene insertion product {[H 2 CC(SiMe 3 ) 2 ] 2 (Cl)Si} 2 CH 2 formed by reaction of two equivalents of silylene [H 2 CC(SiMe 3 ) 2 ] 2 Si with dichloromethane are found at lower frequency (δ 1H 1.43 ppm; δ 13C 20.2 ppm). [28b] In contrast to CH 2 Cl 2 , 1, and 5, the observed 1 H NMR chemical shifts of the SiH protons in HSiCl 3 (5.39 ppm), 4 (5.69 ppm), and 6 (4.30 ppm) show no distinct trend.…”

Galliummethylen

“…Rührt man den Überstand der ursprünglichen Reaktionsmischung nach Versetzen mit weiteren acht ¾quivalenten Molekülstrukturen von 4 (A) und 5 (B). [31] Abbildung 3. Molekülstruktur von 6 Lu .…”

“…Molekülstruktur von 6 Lu . [31] 7, Ga-(m 3 -CH 2 ) = 2.125(6) ), ähnlich wie sie für[ GaMe 4 ] À -Einheiten bekannt sind. [25] Die Lu-C(Methylen)-Abstände von 2.510 6 bestätigt.…”

“…Synthese von 2, 3 und 6 sowie die Molekülstrukturen der Galliummethylene 2 und 3. [31] d = Tage;e xc. = Überschuss.…”