Insertion, Rearrangement, and Coupling Processes in the Reactions of the Unsaturated Hydride Complex [W₂(η⁵-C₅H₅)₂(H)(μ-PCy₂)(CO)₂] with Isocyanides

Abstract

The title complex reacted with stoichiometric amounts of CNR rapidly at room temperature or below to give two types of formimidoyl derivatives: the symmetrically bridged complexes [W 2 Cp 2 (μ-C,N:C,N-HCNR)(μ-PCy 2 )(CO) 2 ] (R = t Bu (W−W = 2.8645(5) Å), 4-C 6 H 4 OMe), and the asymmetrically bridged [W 2 Cp 2 {μ-C:N-HCN(Xyl)}(μ-PCy 2 )(CO) 2 ] (Cp = η 5 -C 5 H 5 ; Xyl = 2,6-C 6 H 3 Me 2 ). The latter complex underwent slow isomerization at room temperature to give the corresponding aminocarbyne derivative [W 2 Cp 2 {μ-CNH(Xyl)}(μ-PCy 2 )(CO) 2 ], which in turn could be decarbonylated through irradiation with UV−vis light to yield the 30-electron aminocarbyne complex [W 2 Cp 2 {μ-CNH(Xyl)}(μ-PCy 2 )(μ-CO)] (W−W = 2.4928(4) Å). Density functional theory calculations revealed that the aminocarbyne complex was the most stable isomer for the three isocyanides under study, while subtle steric effects marked the relative stability of the formimidoyl isomers, which therefore are the kinetic products of these reactions. The reaction of the title complex with excess CN(4-C 6 H 4 OMe) at room temperature gave in good yield the complex [W 2 Cp 2 (μ-C,N:C,C′-HCN(4-C 6 H 4 OMe)C{N(4-C 6 H 4 OMe)})(μ-PCy 2 )(CO) 2 ] (W−W = 2.9370(2) Å), having a 5-electron donor aminocarbene-iminoacyl ligand derived from the N−C coupling of formimidoyl and isocyanide ligands, whereas the analogous reaction with CNXyl gave the aminocarbyne complex [W 2 Cp 2 {μ-CNH(Xyl)}(μ-PCy 2 ){CN(Xyl)}(CO)] (W−W = 2.677(2) Å) having a terminal bent isocyanide ligand.

Bond Forming Reactions Involving Isocyanides at Diiron Complexes

“…Isocyanide insertion into iron bridging hydride bond is observed in the dinuclear complex [Fe2(μ-H)(μ-PCy2)(CO)4(μ-CO)(dppm)] (8), leading to the formation of the bridging formimidoyl complex 9 (Scheme 4) [61]. This reaction is consistent with other similar isocyanide insertions into metal μ-H bond, which are more frequently observed in dinuclear group 6 and 9 metal complexes [62][63][64][65], and provides a unique synthetic route to the formation of bridging formimidoyl ligands.…”

“…Coupling of isocyanide ligands involving dinuclear complexes is far less common [93][94][95]. Thus, the CNR coupling shown in Scheme 12 has a distinctive character for two reasons: It involves a diiron complex, which is rather uncommon [96], and it provides an example of isocyanide coupling taking place via C-N bond formation, which is rarely observed [62,95], with respect to the predominant C-C coupling mode.…”

Formation of a μ3-Acetylide on a Ru3 Cluster via Coupling of μ-Methylene with Isocyanide Accompanied by Elimination of Amine: A Model of Hydrogen-Assisted C–C Bond Formation on a Metal Surface

“…Similar hydride transfer was observed in the reaction of a μ 3 -methylidyne-μ 3 -ethyne complex with t -BuNC, which yielded a μ 3 -dimetalloallyl complex containing a tert -butylamino group . Formation of a μ-aminocarbyne ligand via hydride migration is often reported in the reaction of di- and trinuclear hydrido complexes with isocyanide …”

C–C and C–N Couplings in Reactions of the Benzylidyne-Bridged Complex [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)2] with Small Unsaturated Organics

“…We have previously prepared formimidoyl- and iminoacyl-bridged complexes related to compound 6 through insertion of isocyanides into unsaturated hydride- and alkyl-bridged complexes of the type [M 2 Cp 2 (μ-X)­(μ-PCy 2 )­(CO) 2 ] (M = Mo and W; X = H, Me). , In most cases, the coordination of the C , N -donor ligand in these compounds corresponds to the 5-electron donor μ-η 2 :η 2 mode ( A in Chart ), which in these cases allows the dimetal center to reach electronic saturation. The bridgehead carbon atom in this coordination mode is characterized by a relatively shielded 13 C NMR resonance around 60 ppm which displays a substantial P–C coupling of ca.…”