Organomolybdenum(VI) and Lithium Organomolybdate(VI) and -(V) Complexes with C,N-Chelating Aminoaryl Ligands

Abstract

The synthesis and characterization of new, five-coordinate molybdenum bis(imidoaryl) complexes [Mo(NAr) 2 (C-N)X] (Ar) C 6 H 3 i-Pr 2-2,6; C-N) [C 6 H 4 (CH 2 NMe 2)-2]-; X) Cl (1), Me (2), Et (3), Bu (4), CH 2 SiMe 3 (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) n Mo(NAr) 2 (C-N) 2 (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.

Anionic phenoxy-amido rare-earth complexes as efficient catalysts for amidation of aldehydes with amines

“…The distance between Li1 and C16A in complexes ranges from 2.49(1) to 2.56(2) Å, which falls in the range of p contacts between lithium ions and carbon atoms of arene rings reported in the literature (2.31-2.57 Å). [29][30][31]…”

C–H activation of a MeN grouping in one of the CH2NMe2 ortho substituents of a NCN ‘pincer’ ligand in tungsten chemistry: X-ray structure of [WCl2(NPh)(C6H3{CH2NMeCH2}-2-{CH2NMe2}-6)]

“…The reactions between compounds 1- 4 [9]; (iii) accommodate ZnCl 2 as shown in tantalum(V) chemistry [1a] and (iv) play an important role in NCN rearrangement reactions involving the (aryl)C ipso -M, aryl C-H and (NCH 3 )C-M bonds [3]. In the present study the presence of the second ortho-(dimethylamino)methyl functionality possibly causes the formation of insoluble products by strong intermolecular coordination to the zinc/lithium salts.…”

Synthesis, characterization and electrochemical behavior of oxo-bridged (arylimido)[tris(3,5-dimethylpyrazolyl)borato] molybdenum(V) complexes

“…Organo-imido complexes of Mo(V) and Mo(VI) can be prepared by a wide range of methods that often make use of organic compounds as the imido transfer reagent [3,4]. There are several molybdenum imido compounds [5][6][7][8][9][10] and a number of related mixed terminal oxo-imido compounds have previously been reported, for instance [MoTp*(O)Cl(NR)] (R = 4-tolyl and C 6 H 4 NMe 2 -4) [11], [MoCl 2 (Nmes)(O)(bipy)] (mes = 2,4,6-trimethylphenyl) [12] and [TpMo(CH 2 C(Me)(2)Ph)(NAr)(O)] (Ar = 2,6-i-Pr-2-C 6 H 3 , Ph = C 6 H 5 ) [13], but limited information is available for transition metal compounds containing both imido and hydrotris(pyrazolyl)borate type ligands [11,[14][15][16][17][18][19][20][21]. Although a number of systems involving l-ligation in the presence of terminal imido groups have previously been reported [22][23][24][25][26], the chemistry of compounds having both arylimido and l-oxo group in the presence of tris(pyrazolyl)borate co-ligand has not been studied in detail.…”