233283-64-2

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• 109-72-8 n-butyllithium 
• 233283-59-5 [Mo(NC₆H₃-i-Pr₂-2,6)2(C₆H₄CH₂NMe₂-2)2] 

Relevant academic research and scientific papers

Controlled radical polymerization of styrene in the presence of lithium molybdate(V) complexes and benzylic halides

The new lithium molybdate(V) complexes [LiMo(NAr)2(C-N)R] (C-N=C6H4(CH2NMe2)-2; R=(C-N) (5), Me (6), CH2SiMe3 (7), p-tolyl (8)), have been generated in situ from reaction of the corresponding molybdenum(VI) complexes [Mo(NAr)2(C-N)R] (C-N=C6H4(CH2NMe2)-2; R=(C-N) (1), Me (2), CH2SiMe3 (3), p-tolyl (4)) with n-BuLi. The nature of these radical anions was studied by EPR spectroscopy. The spectra of toluene solutions of in situ prepared complexes 5-8 revealed the presence of two different paramagnetic species, i.e. a molybdenum compound with distinct giso- and Aiso-values and an unidentified radical with a sometimes strong signal at g=1.986±0.001, lacking any hyperfine coupling. Extended Hueckel calculations on the crystal structure of 5 showed that the single electron occupies a molybdenum centered orbital, merely dx2-y2 in character. In situ prepared complexes 5-8 were successfully applied in the atom transfer radical polymerization (ATRP) of styrene using benzyl chloride as the initiator. The efficiency of the benzyl chloride initiator is rather poor (6-18%). Reaction of the lithium molybdate(V) complex 5 with (α-chloroethyl)benzene and (α-bromoethyl)benzene resulted in the formation of 1, LiCl and LiBr, respectively. The molecular weights as well as the molecular weight distributions show that the catalytic system, BzCl/5-8, catalyses styrene polymerization successfully but does not exercise much control over the polymerization reaction due to the poor initiator efficiency of benzyl chloride and probably the extreme air-sensitivity of the lithium molybdate(V) compounds. The unidentified radical (g=1.986±0.001) is unable to initiate radical polymerization but possibly influences the ATRP activity.

Organomolybdenum(VI) and lithium organomolybdate(VI) and -(V) complexes with C,N-chelating aminoaryl ligands

The synthesis and characterization of new, five-coordinate molybdenum bis(imidoaryl) complexes [Mo(NAr)2(C-AT)X] (Ar = C6H3i-Pr2-2,6; C-N= [C6H4(CH2NMe2)-2]-; X = Cl (1), Me (2), Et (3), Bu (4), CH2SiMe3 (5), (p-tolyl) (6), (C-N) (7)) is reported. The solid-state structure of 2 has been elucidated by single-crystal X-ray analysis. Compounds 2, 3, 4, 5, and 6 react with alkyl- or aryllithium compounds to form lithium molybdate(VI) derivatives, of which [Li(DME)Mo(NAr)2(C-N(Me)(p-tolyl)] (10), formed by the reaction of 2 with [Li-(p-tolyl)], has been structurally (X-ray) characterized. Thermal activation of these lithium molybdates leads to the formation of paramagnetic lithium molybdate(V) compounds instead of the anticipated molybdenum(VI) alkylidenes. The actual temperature (between -10 and 80 °C) at which paramagnetic Mo(V) radical anions are formed is dependent on both the type of alkyl or aryl substituent (introduced via LiR′) and the solvent. The synthesis of [LiMo-(NAr)2(C-N)2] (11) by reaction of 7 with n-BuLi is described. The initially formed lithium molybdate(VI) compound [Li(DME)nMo(NAr)2(C-N(n-Bu)] is not stable at room temperature and converts directly to the lithium molybdate(V) derivative 11. The solid-state structure of 11 has been elucidated by single-crystal X-ray analysis. None of the lithium molybdate(VI) nor -(V) derivatives described herein are active catalysts for ROMP, as thermal activation does not lead to the formation of a molybdenum alkylidene complex but to electron transfer and formation of a lithium molybdate(V) instead. However, upon treatment of a solution of any of the molybdate(V) derivatives with dry air, catalytic ROMP is observed.