Different Modes of Reactivity of Cp*W(NO)(alkyl)(η³-allyl) Complexes with Cyclic Amines: The Influence of the Allyl Ligands

Abstract

Metathesis reactions between Cp*W(NO)(CH 2 EMe 3 )Cl (E ) C or Si) and a variety of bis(allyl)magnesium reagents lead to the formation of 18e Cp*W(NO)(alkyl)(η 3 -allyl) complexes. The compounds 5), and Cp*W(NO)(CH 2 CMe 3 )(η 3 -CH 2 CHCH 2 ) (6) have thus been synthesized in moderate yields. The solid-state molecular structures of 3, 4, 5, and 6 feature σ-π distorted allyl ligands in the endo conformation. Complex 1 effects the concurrent N-H and R-C-H activations of pyrrolidine and piperidine under ambient conditions and forms the alkyl amido complexes Cp*W(NO)(CH 2 CMe 3 )(NC 4 H 7 -2-CMe 2 CHdCH 2 ) (7) and Cp*W(NO)(CH 2 CMe 3 )(NC 5 H 9 -2-CMe 2 CHdCH 2 ) (8), respectively. Complexes 2-5 react with pyrrolidine in a similar manner, but the reaction of 3 to produce Cp*W(NO)(CH 2 CMe 3 )(NC 4 H 7 -2-CH 2 CMedCH 2 ) (10) is not as clean since 3 is thermally unstable at 20 °C. Unfortunately, the concurrent N-H and R-C-H activation transformation encompasses only a very limited range of substrates, namely cyclic amines. Complex 6, which contains an unsubstituted allyl ligand, exhibits a unique mode of reactivity with pyrrolidine and piperidine, incorporating 2 equiv of the amines and forming Cp*W-(NO)(NC 4 H 8 )(CHMeCH 2 NC 4 H 8 ) (13) and Cp*W(NO)(NC 5 H 10 )(CHMeCH 2 NC 5 H 10 ) ( 14), respectively. Plausible mechanisms are suggested to account for the different modes of reactivity of the Cp*W(NO)(alkyl)(η 3allyl) compounds with the cyclic amines. All new complexes have been characterized by conventional spectroscopic methods, and representative compounds have also been subjected to single-crystal X-ray crystallographic analyses.

A new versatile binuclear seven-coordinate complex of molybdenum(II), [(μ-Cl)2{Mo(μ-Cl)(SnCl3)(CO)3}2]2−

“…the formation of an N-C bond between the nitrogen atom of the piperidine ligand and the carbon atom of the allyl ligand. This reaction may occur at the molybdenum atom in a similar way as the formation of a C-C bond recently observed by Legzdins et al during the reaction of an allyl complex of tungsten with cyclic amines [20].…”

Highly Functionalized Cyclohexenes Derived from Benzene: Sequential Tandem Addition Reactions Promoted by Tungsten

“…The thermodynamically controlled protonation of 1 results in the regioselective addition of a proton to form primarily the η 2 -benzenium complex 2A. Previously, we, as well as the Legzdins group, 29,30 reported that allyl complexes of W(NO) systems were hyperdistorted, with one terminus showing a W− C bond length considerably longer than the other. Extensive solid-state molecular structure determinations show that where the W−C bond lengths of the two carbons coordinated to the tungsten are typically ∼2.3 Å, the third allyl carbon (localized carbocation) is ∼2.6−2.8 Å from the tungsten center.…”

Selective Functionalization of a Variety of Hydrocarbon C(sp3)–H Bonds Initiated by Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh)

“…The solvent was removed from the eluate in vacuo to give Cp*W­(NO)­(CH 2 CMe 3 )­(η 3 -CH 2 CHCHPh) ( 1 ) as an orange solid (1.975 g, 31% yield). Characterization data for 1 have been previously reported …”

“…Characterization data for 1 have been previously reported. 15 Preparation of Cp*W(NO)(CH 3 )(η 3 -CH 2 CHCHPh) (2). In a glovebox, a Parr 5500 pressure reactor was charged with a sample of 1 (0.600 g, 1.17 mmol) and cyclohexane (ca.…”

“…The desired product was isolated by column chromatography (2.5 × 6 cm) on a silica support using 0−20% EtOAc Characterization Data for 14b (19%). (15). In a glovebox, a Parr 5500 reactor was charged with 1 (0.300 g, 0.558 mmol) and C 6 H 12 (ca.…”