Syntheses, Structures, and Reactivities of Homometallic Rare‐Earth‐Metal Multimethyl Methylidene and Oxo Complexes

Abstract

Unsolvated, trinuclear, homometallic, rare-earth-metal multimethyl methylidene complexes [{(NCN)Ln(μ(2)-CH(3))}(3)(μ(3)-CH(3))(μ(3)-CH(2))] (NCN = L = [PhC{NC(6)H(4)(iPr-2,6)(2)}(2)](-); Ln = Sc (2a), Lu (2b)) have been synthesized by treatment of [(L)Ln{CH(2)C(6)H(4)N(CH(3))(2)-o}(2)] (Ln = Sc (1a), Lu (1b)) with two equivalents of AlMe(3) in toluene at ambient temperature in good yields. Treatment of 1 with three equivalents of AlMe(3) gives the heterometallic trinuclear complexes [(L)Ln(AlMe(4))(2)] (Ln = Sc (3a), Lu (3b)) in good yields. Interestingly, 2 can also be generated by recrystallization of 3 in THF/toluene, thereby indicating that the THF molecule can also induce C-H bond activation of 2. Reaction of 2 with one equivalent of ketones affords the trinuclear homometallic oxo-trimethyl complexes [{(L)Ln(μ(2) -CH(3))}(3) (μ(3)-CH(3))(μ(3)-O)] (Ln = Sc(4a), Lu(4b)) in high yields. Complex 4b reacts with one equivalent of cyclohexanone to give the methyl abstraction product [{(L)Lu(μ(2) -CH(3) )}(3) (μ(3) -OC(6)H(9))(μ(3)-O)] (5b), whereas reaction of 4b with acetophenone forms the insertion product [{(L)Lu(μ(2)-CH(3))}(3){μ(3)-OCPh(CH(3))(2)}(μ(3)-O)] (6b). Complex 4a is inert to ketone under the same conditions. All these new complexes have been characterized by elemental analysis, NMR spectroscopy, and confirmed by X-ray diffraction determination.

Rare‐Earth‐Metal Methylidene Complexes

“…[23] Analogous compounds to the complexes 12 a and 12 b were obtained by changing the alkyl substituents at the 1,3,5-triazacyclohexane ligand. [23,24] For the reaction of [La{Al(CH 3 ) 4 } 3 ] with TiPTAC no further products were obtained, [23] whereas in the reaction of [Sm{Al(CH 3 ) 4 } 3 ] with TiPTAC a second product, the divalent species [(TiPTAC)Sm{Al(CH 3 ) 4 }{m 2 -Al(CH 3 ) 4 }] 2 (16), was formed (Scheme 10). [24] In compounds 15, the Ln-CH 2 distances are 2.542(4) and 2.521(4) (15 a), as well as 2.464 (8) La)).…”

“…Complexes 3 a,b were obtained by adding two equivalents of AlMe 3 to the rare-earth-metal alkyl complexes [LLn{CH 2 C 6 H 4 N(CH 3 ) 2 -o} 2 ] (Scheme 3). [16] The isolated trinuclear complexes are thermally stable up to 210 8C (3 a) and 180 8C (3 b), respectively. They build a hexagonal bipyramid with alternating Ln atoms and m 2 -CH 3 groups in the equatorial plane and the m 3 -CH 3 and m 3 -CH 2 groups in the apical position.…”

“…The metal ions bear an octahedral coordination geometry with average Ln-CH 2 distances of 2.367 (3 a) and 2.376 (3 b). [16] A similar thulium complex, [{Cp'Tm(m 2 -CH 3 )} 3 (m 3 -CH 3 )-(m 3 -CH 2 )], (Cp' = trimethylsilylcyclopentadienyl, 4) was obtained by the reaction of [{Cp'Tm(CH 3 ) 2 } 3 ] with one equivalent of AlMe 3 at room temperature (Scheme 4). [17]…”

Methylidenkomplexe der Seltenerdmetalle

“…2.310(5) und 2.385(5) (Lu-CH 2 ). [15] Über [16] Ein 4 ] mit mittleren Ln-CH 2 -Abständen von 2.38(4) (5 a) und 2.37(4) (5 b) bilden. Diese Verbindungen sind die einzigen bekannten Methylidenkomplexe, die nur aus "LLnCH 2 "-Einheiten bestehen.…”

“…Wird 3 b mit zwei ¾quivalenten Acetophenon umgesetzt, erhält mal stattdessen eine Seltenerdmetalloxo-Methylalkoxo-Verbindung (23). [16] Bei der Umsetzung von 4 mit einem ¾quivalent Benzophenon wurde die Verbindung [Cp' 3 Tm 3 (m 2 -CH 3 ) 3 -{(C 6 H 4 ) 2 C(O)CH 3 }] (24) isoliert, welche ein pincerähnliches Bis(benzo-1,2-diyl)ethoxytrianion enthält (Schema 15). Es wird angenommen, dass die Reaktion über eine nukleophile Addition der Methylidengruppe an der Carbonylgruppe verläuft.…”