Syntheses and Molecular Structures of New Calix[4]arene Molybdenum and Tungsten Complexes

Abstract

An unusual disproportionation reaction of the molybdenum(IV) and tungsten(IV) chlorides [MCl4L2] (M=Mo, L=Et2S, Et2O; M=W; L= Et2S) in the presence of p-tBu-calix[4]arene (Cax(OH)4) and triethylamine leads to d0 complexes [(CaxO4)[CaxO2(OH)2]M] (1) and d3 compounds (HNEt3)2[(CaxO4)2M2] (2). Complexes la (M = Mo), 1b (M = W), and the HCl adduct of 2a (M = Mo) have been structurally characterized. Compound 1a represents one of the few examples of a well-characterized molybdenum(VI) hexa-alkoxide complex of the type [Mo(OR)6]. Isolation and structural characterization of the side product [(CaxO4W)[kappa2(O)-kappa1(O)-CaxO3(OH)](CaxO4WCl)] (3) suggests the intermediacy of chloro-containing calix[4]arene complexes in these reaction mixtures. The reaction of 1a with HCI provides [CaxO4MoCl2] (4a), the first well-defined example of a mixed molybdenum(VI) alkoxide halide compound of the general formula [MoClx(OR)6-x].

Stoichiometric and Catalytic Aryl−Cl Activation and Borylation using NHC‐stabilized Nickel(0) Complexes

“…First of all, our studies revealt he importance of the base, because when no base was used the borylated product was observed in only 31 %y ield ( With the optimized base in hand, we then investigated the influence of the solvent on our reaction. Yields of 4a decreasedt o3 7% (n-hexane), 23 %( acetonitrile) 33 %( methyl tert-butyl ether,M TBE), and 29 %( THF) ( Table 1, entries 10, [12][13][14], whereas toluene as the solventg ave a9 9% yield of the borylated product 4a (Table 1, entry 11). Thus, the best solvents are hydrocarbonsw ithareasonably high boilingp oint.…”

Stoichiometric and catalytic C–Cl activation of Aryl Chlorides using an NHC-stabilized nickel(0) complex

“…All reactions and subsequent manipulations involving organometallic reagents were performed under nitrogen or argon atmosphere using standard Schlenk techniques as reported previously [14]. Elemental analyses were performed in the microanalytical laboratory of the author's department.…”

Synthesis and Reactivity of NHC‐Stabilized Iron(II)–Mesityl Complexes

“…All reactions and subsequent manipulations were performed under an argon atmosphere using standard Schlenk techniques, as reported previously. [41] Elemental analyses were performed in the micro analytical laboratory of the Institute for Inorganic Chemistry at the University of Würzburg, with an Elementar vario micro cube. NMR spectra were recorded with a Bruker Avance 200 ( 1 H, 199.9 MHz; 13 C, 50.3 MHz) and Bruker Avance 500 ( 1 H, 500.1 MHz; 13 C, 125.8 MHz), using C 6 D 6 and [D 8 ]THF as the solvent.…”