Lutetium‐Methanediide‐Alkyl Complexes: Synthesis and Chemistry

Abstract

The first four-coordinate methanediide/alkyl lutetium complex (BODDI)Lu2 (CH2 SiMe3 )2 (μ2 -CHSiMe3 )(THF)2 (BODDI=ArNC(Me)CHCOCHC(Me)NAr, Ar=2,6-iPr2 C6 H3 ) (1) was synthesized by a thermolysis methodology through α-H abstraction from a Lu-CH2 SiMe3 group. Complex 1 reacted with equimolar 2,6-iPrC6 H3 NH2 and Ph2 C+O to give the corresponding lutetium bridging imido and oxo complexes (BODDI)Lu2 (CH2 SiMe3 )2 (μ2 -N-2,6-iPr2 C6 H3 )(THF)2 (2) and (BODDI)Lu2 (CH2 SiMe3 )2 (μ2 -O)(THF)2 (3). Treatment of 3 with Ph2 C=O (4 equiv) caused a rare insertion of Lu-μ2 -O bond into theC=O group to afford a diphenylmethyl diolate complex 4. Reaction of 1 with PhN=C=O (2 equiv) led to the migration of SiMe3 to the amido nitrogen atom to give complex (BODDI)Lu2 (CH2 SiMe3 )2 -μ-{PhNC(O)CHC(O)NPh(SiMe3 )-κ(3) N,O,O}(THF) (5). Reaction of 1 withtBuN=C formed an unprecedented product (BODDI)Lu2 (CH2 SiMe3 ){μ2 -[η(2) :η(2) -tBuN=C(=CH2 )SiMe2 CHC=NtBu-κ(1) N]}(tBuN=C)2 (6) through a cascade reaction of N=C bond insertion, sequential cyclometalative γ-(sp(3) )-H activation, C=C bond formation, and rearrangement of the newly formed carbene intermediate. The possible mechanistic pathways between 1, PhN=C=O, and tBuN=C were elucidated by DFT calculations.

Lutetium‐Methanediide‐Alkyl Complexes: Unique Reactivity toward Carbodiimide and Pyridine

“…An X‐ray diffraction study illustrated that the insertion reaction of two equivalents of CyN=C=NCy into Lu‐µ 2 ‐CHSiMe 3 bond of 1 led to a cascade reaction containing Si‐C bond cleavage, SiMe 3 migration and Si‐N bond formation . This result is similar to that observed in the reaction of complex 1 with two equivalents of phenyl isocyanate . Unexpectedly, the C–H bond of pyridine was activated by Lu‐CH 2 SiMe 3 to form the Lu‐ o ‐pyridine bond, which further inserted into another CyN=C=NCy molecule (Scheme ).…”

“…The alkyl protons of the two LuCH 2 SiMe 3 species show an AB spin system at –0.40 and –0.34 ppm correlating with a broad carbon signal at 42.50 ppm. The singlet signal at 0.92 ppm in the 1 H NMR spectrum and 117.16 ppm in the 13 C NMR spectrum can be assigned to the newly generated methanediide unit Lu‐µ 2 ‐CHSiMe 3 , very close to that of complex 1 …”

“…Recently, our group found that rare‐earth metal alkylidene complex 1 could be in‐situ generated through α ‐H abstraction of Ln‐CH 2 SiMe 3 in the course of the reaction of β ‐oxo‐ δ ‐diimine ligand with two equivalents of Lu(CH 2 SiMe 3 ) 3 (THF) 2 (Figure ) . The reaction of the lutetium alkylidene alkyl complex with some small molecules such as aniline, benzophenone, isocyanate and isocynide afforded organometallic complexes with novel structures.…”

Potential Precursors for Terminal Methylidene Rare‐Earth‐Metal Complexes Supported by a Superbulky Tris(pyrazolyl)borato Ligand

“…[3] Notwithstanding, such bridging alkylidenem oieties were accessed in mixed methyl/methylidene, [4] methyl/chloride, [5] cubane-like methylidene complexes, [6] and the first four-coordinate methandiide alkyl lutetium complex. [7] Also, Lewis acid-stabilized [8] or pincerlike rare-earth-metal alkylidenec omplexes [9] have been reported. Recent advances in the latter areas are represented by the syntheses of the first bridged bis-alkylidene scandium complex, [10] an on-pincer-type monometallic phosphinoalkylidene scandium complex, [11] and silyl-thiophosphinoyl alkylidene as well as phosphinomethylidener are-earth-metal compounds.…”

Formation and ligand-based reductive chemistry of bridged bis-alkylidene scandium(iii) complexes

“…Some pincer-like rare-earth alkylidene complexes have been reported independently by Cavell, 4 Liddle, 5 and Mézailles. 6 Very recently, Cui et al reported the lutetium methanediide-alkyl complexes, 7 and Chen et al reported the non-pincer-type mononuclear scandium alkylidene complexes. 8 Furthermore, rare-earth methylidene complexes were also stabilized by chloride bridges 9 or Lewis-acids such as AlMe 3 .…”