Dioxomolybdenum(VI) complexes containing N-heterocyclic carbenes (original) (raw)
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Molybdenum(VI) dioxo complexes with macrocyclic amine ligands
Polyhedron, 1993
Reaction of Mo02C12 with the tetradentate amine ligand 1,4,8,1 Ztetraazacyclopentadecane ([ 1 SIaneNd) yields the molybdenum(V1) dioxo complex [MOO, ([lS]aneN,-H)]Cl (I), a rare example of a cationic complex containing the Moos'+ unit. The 0x0 ligands are cis and the macrocyclic amine coordinates in a non-planar fashion, as revealed by X-ray crystal structure and NMR data. One of the nitrogen donors cis to the 0x0 groups has been deprotonated to give an amide ligand (NR,-). In contrast, reaction of Mo02C1, with tetramethylcyclam (1,4,8,1 I-tetramethyl-1,4,8,11-tetraazacyclotetradecane, TMC) yields the neutral adduct MoO~C~~(~~-TMC) (III), in which only two of the amine nitrogens are coordinated. An X-ray structure of III shows it to have an all-& octahedral geometry, very unusual for M002X2L2 complexes, with one 0x0 ligand tram to an amine and the other trunS to a chloride. Compounds [MoO,([lS]aneN,-H)]BPh, II and III are not very stable in solution ; II is not reduced electrochemically or by PPh,.
Dimethyl)dioxomolybdenum(VI) complexes: syntheses and catalytic applications
Journal of Molecular Catalysis A-chemical, 2000
Reaction of MoO 2 Br 2 S 2 complexes [S=THF, CH 3 CN] with bidentate nitrogen donor ligands (L 2 ) leads to complexes of the type MoO 2 Br 2 L 2 in good yields, L 2 =substituted bipyridylphenantroline, 1,4-R 2 -diazabutadiene and bipyrimidine. Treatment of the latter complexes with Grignard reagents at low temperatures yields complexes of the general formula MoO 2 (CH 3 ) 2 L 2 and MoO 2 (C 2 H 5 ) 2 (diphenylphenantroline). 1 H NMR and IR data are comparatively indifferent to the ligand changes. The 95 Mo NMR data of selected complexes reflect the donor capability of the organic ligands. Mass spectroscopy and temperature-dependent 95 Mo NMR spectroscopy show a significant stability of the Mo-N bond. The compound MoO 2 (CH 3 ) 2 (bipyrimidine) was additionally examined by single crystal X-ray analysis.
Molybdenum Oxo and Imido Complexes of β-Diketiminate Ligands: Synthesis and Structural Aspects
Inorganic Chemistry, 2008
Treatment of [MoO 2 (η 2-Pz) 2 ] (Pz) 3,5-di-tert-butylpyrazolate) with the diketiminate ligand NacNacH (NacNac) CH[C(Me)NAr] 2-, Ar) 2,6-Me 2 C 6 H 3) at 55°C leads under reduction of the metal to the formation of the dimeric molybdenum(V) compound [{MoO 2 (NacNac)} 2 ] (1). The compound was characterized by spectroscopic means and by X-ray crystal structure analysis. The dimer consists of a [Mo 2 O 4 ] 2+ core with a short Mo−Mo bond (2.5591-(5) Å) and one coordinated diketiminate ligand on each metal atom. The reaction of [MoO 2 (η 2-Pz) 2 ] with NacNacH in benzene at room temperature leads to a mixture of 1 and the monomeric molybdenum(VI) compound [MoO 2-(NacNac)(η 2-Pz)] (2). From such solutions, yellow crystals of 2 suitable for X-ray structural analysis were obtained revealing the coordination of one bidentate NacNac and one η 2-coordinate Pz ligand. This renders the two oxo groups inequivalent. Further high oxidation state molybdenum compounds containing the NacNac ligand were obtained by the reaction of [Mo(NAr) 2 Cl 2 (dme)] (Ar) 2,6-Me 2 C 6 H 3) and [Mo(N-t-Bu) 2 Cl 2 (dme)] (dme) dimethoxyethane) with 1 equiv of the potassium salt NacNacK forming [Mo(NAr) 2 Cl(NacNac)] (3) and [Mo(N-t-Bu) 2 Cl(NacNac)] (4), respectively, in good yields. The X-ray structure analysis of 3 revealed a penta-coordinate compound where the geometry is best described as trigonal-bipyramidal.
Pentabenzylcyclopentadienyl)molybdenum Complexes: Synthesis, Structures and Redox Properties
European Journal of Inorganic Chemistry, 2007
[MCpBz(CO)3]2 (M = Mo 3, W 4; CpBz = pentabenzylcyclopentadienyl) complexes were prepared by reaction of Li[MCpBz(CO)3] [M = Mo (1), W (2)] with FeIII. [MoCpBz(CO)2]2 (5) can be prepared by thermal elimination of CO from 3 and also by reaction of 1 with C3H5Br. The steric bulk of the CpBz ligands causes all the dimers to exist either in the solid state or in solution as the trans isomers. The hydrido complexes [MH(CpBz)(CO)3] [M = Mo (6), W (7)] were prepared by reactions of 1 and 2 with H+. Cyclic voltammetry and controlled potential coulometry of 5 in CH2Cl2, thf and CH3CN were performed and mechanisms for the redox behaviour are proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and structure of a series of new haloaryl imido complexes of molybdenum
Polyhedron, 2001
The synthesis of a series of mono-and bis-haloarylimido molybdenum(VI) complexes is described. Two methods of introducing the electron poor imido functionality are employed, first the condensation of substituted anilines with Na 2 MoO 4 in the presence of Me 3 SiCl/NEt 3 , secondly the sulfinyl amine metathesis with [Mo(O) 2 Cl 2 (dme)] (1). The latter method works even in cases, when the first one does not work. Crystal structures of three complexes [Mo(NC 6 F 5 )(O)Cl 2 (dme)] (2a), [Mo(N-2,6-Cl 2 C 6 H 3 ) 2 Cl 2 (dme)] (3b) and [Mo(N-2,4,6-Br 3 C 6 H 2 ) 2 Cl 2 (dme)] (4) are reported. The unusually small Mo N C(Ar) angle of 149.1(5)°has been found in the structure of 4.
Polyhedron, 2009
Eight new molybdenum(VI) complexes with 4-(diethylamino)salicylaldehyde and 2-hydroxy-3-methoxybenzaldehyde thiosemicarbazones have been prepared. They were characterized as mononuclear [MoO 2 LD] or dinuclear [{MoO 2 L} 2 D] complexes. In all the compounds the MoO 2 2+ core is coordinated by a tridentate ONS thiosemicarbazonato ligand and by the N-donor molecule (imidazole, pyridine or c-picoline). All the complexes were characterized by chemical analysis, IR spectroscopy and thermogravimetry. Three of the mononuclear complexes, dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(pyridine)]molybdenum(VI), dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(c-picoline)]molybdenum(VI) and dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(imidazole)]molybdenum(VI) were also characterized by single-crystal X-ray structural analysis. A spectrophotometric method for the determination of molybdenum based on extraction of ion-pairs formed by the cationic surfactant and the [MoO(SCN) 4 ] À anion is described.
Synthesis of Chelate-Supported Dialkyl and Alkylidene Complexes of Molybdenum(VI)
Organometallics, 1999
The use of chelating diamide [o-(Me 3 SiN) 2 C 6 H 4 ] 2as a coligand for high-oxidation early transition metal complexes has been investigated. Reaction of Mo(NPh) 2 Cl 2 DME with Li 2 [o-(Me 3 SiN) 2 C 6 H 4 ] afforded green microcrystals of [Mo(NPh)(µ-NPh)(o-(Me 3 SiN) 2 C 6 H 4)] 2 (1), while reaction of Mo(NPh) 2 Cl 2 DME with H 2 [o-(Me 3 SiN) 2 C 6 H 4 ] gave Mo(NPh)Cl 2 (o-(Me 3-SiN) 2 C 6 H 4)(NH 2 Ph) (2). Two derivatives of 2 are reported, Mo(NPh)Cl 2 (o-(Me 3 SiN) 2 C 6 H 4)-(PMe 3) (3) and Mo(NPh)Cl 2 (o-(Me 3 SiN) 2 C 6 H 4)(THF) (4). Structural studies of 3 are reported. Reaction of 3 or 4 with RMgX (X) Cl or Br) gave Mo(NPh)R 2 (o-(Me 3 SiN) 2 C 6 H 4) (R) Me 5, Ph 6, CH 2 CMe 3 7, CH 2 Ph 8, CH 2 SiMe 3 9). Reaction of 2 with RMgCl (R) CH 2 CMe 3 , CH 2-SiMe 3) gave mixtures of Mo(NPh)R 2 (o-(Me 3 SiN) 2 C 6 H 4) and Mo(NPh) 2 R 2. Both Mo(NPh) 2-(CH 2 CMe 3) 2 (10) and Mo(NPh) 2 (CH 2 SiMe 3) 2 (11) were isolated form the reaction of Mo(NPh) 2 Cl 2 DME and RMgCl (R) CH 2 CMe 3 , CH 2 SiMe 3). The alkylidene, Mo(NPh)(C(H)-CMe 3)(o-(Me 3 SiN) 2 C 6 H 4)(PMe 3) (13), was isolated from the reaction of 7 and an excess of PMe 3 at 80°C, while Mo(NPh)(C(H)SiMe 3)(o-(Me 3 SiN) 2 C 6 H 4)(PMe 3) (14) was only observed by 1 H NMR under similar conditions.