Heteroatom-Substituted Carbene Complexes of High-Valent Tungsten:  Tp‘W(O)X(C(R)OSiR₃) Derivatives

Abstract

Reaction of Tp′W(O)(I)(CO) (1; Tp′ ) hydridotris(3,5-dimethylpyrazolyl)borate) with MeLi followed by trapping of the resultant anion by ClSiPh 2 Me leads to the formation of a single isomer of the tungsten(VI) heteroatom-substituted carbene complex Tp′W(O)(I)(dC(Me)-OSiPh 2 Me) (5a). The connectivity of complex 5a was confirmed by X-ray crystallography and spectral data. The acyl intermediate in the reaction, [Tp′W(O)(I)(C(O)Me)][Li] (6), was observed by spectroscopic techniques. Trapping of the acyl intermediate 6 with H + yields the neutral hydroxy carbene complex Tp′W(O)(I)(dC(Me)OH) (5c). Reaction of complex 1 with PhLi generates the anionic phenyl-acyl complex [Tp′W(O)(I)(C(O)Ph)][Li] ( 8), which may be trapped with ClSiPh 2 Me, yielding the phenyl carbene complex Tp′W(O)(I)(dC(Ph)-OSiPh 2 Me) (7). Carbene complex 5a reacts with AgSO 3 CF 3 to form silver iodide and a coordinated triflate complex, Tp′W(O)(OSO 2 CF 3 )(dC(Me)OSiPh 2 Me) (9). In contrast to the acyl product formed with MeLi and 1, combining LiCuMe 2 with 1 leads to the replacement of iodide by a methyl group to form Tp′W(O)(Me)(CO) (2). Protonation of this methyl tungsten complex (2) in CH 2 Cl 2 in the presence of acetonitrile yields methane and the cationic nitrile adduct [Tp′W(O)(CO)(NCMe)] + (3), while protonation of 2 in neat acetonitrile produces a cationic hydroxy carbene complex, [Tp′W(O)(NCMe)(dC(Me)OH)] + (4).

Synthesis and Reactivity of Re(III) and Re(V) Fischer Carbenes

“…Complexes 8 are rare examples of carbenes featuring an oxo ligand and a heterosubstituted carbene ligand. Other examples include the neutral complex Tp′W­(O)­(I)­(C­(R)­OR′) (Tp′ = hydridotris­(3,5-dimethylpyrazolyl)­borate; R = Me, Ph; R′ = H, SiPh 2 Me) and the cationic hydroxy carbene complex [Tp′W­(O)­(NCMe)­(=C­(Me)­OH)] + , reported by the Templeton group . In addition, W­[C­(Ph)­C 3 H 3 N 2 BHPz 2 )]­(O)­(Br 2 ) was reported by Mayr and co-workers .…”

“…In contrast, Fischer carbene complexes with metals in high or intermediate oxidation states are quite rare, possibly because of the inability of metals to stabilize π-accepting carbonyl ligands. − Our group has recently described a unique mechanism for the generation of rhenium­(V) acyl complexes that does not involve the prior formation of a carbonyl species but instead involves the direct insertion of CO into a Re–R (R = H, alkyl, aryl) bond. − In this paper we show that this strategy can be utilized to generate rare Re­(III) and Re­(V) Fischer carbene complexes.…”

Heterobimetallic Complexes of Rhenium and Zinc: Potential Catalysts for Homogeneous Syngas Conversion

“…While addition of a main-group metal alkyl to M–CO is a standard route for generating an acyl, no such reactions of alkyl Zn reagents with rhenium carbonyls appear to have been reported. Addition of ZnMe 2 to a CD 2 Cl 2 solution of 1 results in rapid formation of [Re(κ 1 ( P )-PNN·ZnMe)(μ 2 -COMe)(CO) 4 ][OTf] ( 5-Me ), in which the Zn is bound to both the pendent bpy group and the oxygen of the newly formed acyl (eq ).…”

Crystal and electronic structure, lattice dynamics and thermal properties of Ag(i)(SO3)R (R = F, CF3) Lewis acids in the solid state

“…Reactions of activation of the carbon-halogen bond predominate the practical use of AgSO 3 CF 3 and they are responsible for the spectacular success of this inorganic reagent in organic chemistry. [6][7][8][9][10][11] AgOTf is also useful for selected technological and industrial applications, such as: (i) the Lewis acid catalyzed intermolecular substitution of hydroxyl groups in carbohydrates to afford polysaccharides or oligosaccharides; 12 (ii) the addition, isomerisation or ring closing reactions to afford polycyclic heteroaromatic compounds; 13 (iii) initiation of the carbocationic polymerization for a wide variety of monomers such as epoxides, tetrahydrofurans, oxazolines, vinyls, and lactones; 14 and (iv) the synthesis of ethers, 15 to mention just a few.…”