Syntheses of Tungsten tert-Butylimido and Adamantylimido Alkylidene Complexes Employing Pyridinium Chloride As the Acid

Abstract

Routes to new tungsten alkylidene complexes that contain t-butylimido or adamantylimido ligands have been devised that begin with a reaction between WCl6 and four equivalents of HNR(TMS) to give [W(NR)2Cl(-Cl)(RNH2)]2 (R = t-Bu or 1-adamantyl). Alkylation leads to W(NR)2(CH2R')2 (R' = t-Bu or CMe2Ph) which upon treatment with pyridinium chloride yields W(NR)(CHR')Cl2py2 complexes, from which W(NR)(CHR')(Pyrrolide)2 and two W(NR)(CHR')(Pyrrolide)(OAr) complexes (OAr = hexamethyl-or hexaisopropylterphenoxide) have been prepared. Science Foundation (CHE-1111133 to R.R.S.) for financial support. The X-ray diffractometer was purchased with the help of funding from the National Science Foundation (NSF) under Grant Number CHE-0946721. We thank Professor Kit Cummins for the suggestion that hydrogen bonding is present in 1a.Supporting Information Available. Experimental details for the synthesis of all compounds and details of the X-ray structural studies. Supporting Information is available free of charge via the Internet at http://pubs.acs.org. S2 Experimental SectionGeneral. All air and moisture sensitive materials were manipulated under a nitrogen atmosphere in a Vacuum Atmospheres glovebox or on a dual-manifold Schlenk line. All glassware, including NMR tubes, was oven-dried prior to use. Diethyl ether, pentane, toluene, dichloromethane, 1,2-dimethoxyethane, and benzene were degassed and passed through activated alumina columns and stored over 4 Å Linde-type molecular sieves prior to use. Deuterated solvents were dried over 4 Å Linde-type molecular sieves prior to use. 1 H and 13 C NMR spectra were acquired at room temperature using Varian 300MHz or 500MHz spectrometers. Chemical shifts for 1 H and 13 C spectra are reported as parts per million relative to tetramethylsilane and referenced to the residual 1 H/ 13 C resonances of the deuterated solvent ( 1 H () : benzene 7.16, chloroform 7.26, methylene chloride 5.32; 13 C () : benzene 128.06, chloroform 77.16, methylene chloride 53.84). N-t-butyltrimethylsilylamine was either prepared from TMSCl and t-BuNHLi in ether or purchased from Sigma-Aldrich. The synthesis of N-trimethylsilyl(1-adamantyl)amine has been reported previously; i our preparation employed the n-butyllithium and chlorotrimethylsilane. Pyridinium chloride was purchased from Sigma-Aldrich or Alfa Aesar and sublimed before use. Ethereal solutions of HCl were prepared by bubbling HCl gas into diethyl ether; these solutions were titrated before use. Neopentyl Grignard ii , HMTOH iii , HIPTOH iv , and ZnCl 2 (dioxane) v were prepared according to literature procedures. All other reagents were used as received.[W(N-t-Bu) 2 Cl(μ-Cl)(t-BuNH 2 )] 2 (1a).The following procedure was adapted from a recent publication. vi A solution of N-t-butyltrimethylsilylamine (25 g, 172 mmol) in 30 mL toluene was added slowly over a period of 50 min to WCl 6 (15.2 g, 38.33 mmol) in 150 mL of toluene. The reaction mixture was stirred for 24 h at room temperature. The dark green mixture was filtered through a pad of Celite, a...

Synthesis and Evaluation of Molybdenum and Tungsten Monoaryloxide Halide Alkylidene Complexes for Z-Selective Cross-Metathesis of Cyclooctene and Z-1,2-Dichloroethylene

“…A 1 H NMR analysis of 5 showed a single alkylidene resonance at 8.24 ppm that we assign to the syn isomer (JCH = 117 Hz; JWH = 15 Hz). 17 An attempt to prepare 5(MeCN) through addition of acetonitrile to a solution of 5 led to formation of a mixture of 5(MeCN) and what we propose to be W(N-t-Bu)[NC(Me)=CHCMe2Ph](OHMT)Cl (6; eq 1). Attempts to isolate 6 from the mixture in pentane yielded colorless crystals of 5(MeCN), the structure of which was confirmed through an X-ray study (vide infra).…”

Molybdenum and Tungsten Monoalkoxide Pyrrolide (MAP) Alkylidene Complexes That Contain a 2,6-Dimesitylphenylimido Ligand

“…The alkylidene ligand in the major component is in the syn orientation and is slightly twisted with an N1-W1-C1-C2 dihedral angle of 12.25 °. The W1-C1 bond length is 1.875(2) Å, the W1-N1-C21 angle is 173.4(3) °, and the C2-C1-W1 angle is 147.33 (19) °, all typical of Group 6 MAP complexes. When the molecule is viewed along the C21-N1-W1 axis, one mesityl group of the NAr* ligand is seen to be located over the alkoxide while the other mesityl group falls between the pyrrolide and alkylidene ligands.…”

“…Its low solubility in CH 2 Cl 2 allows W(NAr*)(CHCMe 2 Ph)Cl 2 (bipy) to be extracted and thereby separated from t-BuNH 3 Cl. Bipy adducts have been employed as synthetic intermediates previously, 19,20 in part because their low solubility allows them to be obtained readily in pure form. ZnCl 2 or ZnCl 2 (1,4-dioxane) can be employed to remove 2,2-bipyridine or 1,10-phenanthroline from Mo imido alkylidene complexes.…”

High‐Oxidation State Molybdenum and Tungsten Complexes Relevant to Olefin Metathesis

“…An analogous adamantylimido complex, {W(NAd) 2 (μ-Cl)(t-BuNH 2 )Cl} 2 (NAd, N-1-admantyl), can also be formed in high yield [39]. These species can be alkylated directly with a neopentyl or neophyl Grignard reagent to give the W(NR) 2 (CH 2 R ′ ) 2 complexes (R = t-Bu or Ad; R ′ = t-Bu or CMe 2 Ph).…”

“…For example, Mo(NR)(CHCMe 2 R ′ ) (Pyr) 2 (bipy) (NR = NAr, NAd, NAr Me2 , NAr iPr , NAr Cl , NAr tBu , and NAr Mes ; R ′ = Me, Ph) can be prepared and readily isolated [55]. The sonication of a mixture containing the bispyrrolide bipy adduct, HMTOH, and ZnCl 2 (dioxane) (to remove the bipy) led to formation of MAP species of the type Mo(NR) [39]. Interestingly, attempts to prepare bipy adducts of bisdimethylpyrrolide complexes led to the formation of imido alkylidyne complexes of the type Mo(NR)(CCMe 2 R ′ )(Me 2 Pyr)(bipy) through the ligand-induced migration of an alkylidene α proton to a dimethylpyrrolide ligand (Eq.…”