Synthesis and Reactivity of Tungsten(II) Methylene Complexes

Abstract

Treatment of the methyl complex Tp′(CO)(PhC 2 Me)W-Me (1) or Tp(CO)(PhC 2 Ph)W-Me (2) with trityl cation yields the corresponding methylene complex [Tp′(CO)(PhC 2 Me)WdCH 2 ]-[PF 6 ] (3) (Tp′ ) hydridotris-(3,5-dimethylpyrazolyl)borate) or [Tp(CO)(PhC 2 Ph)WdCH 2 ][PF 6 ] (4) (Tp ) hydridotris(pyrazolyl)borate). The carbene complex (3) is unusually persistent for a methylene complex. Complexes 3 and 4 display electrophilic behavior, as evidenced both by addition of nucleophiles and by methylene transfer to electron rich olefins. When bound to either carbene 3 or 4, arylimines are activated toward nucleophilic attack by ethyl diazoacetate (EDA). The net result of the addition of excess arylimine followed by excess EDA to a solution of either 3 or 4 is catalytic aziridine formation. X-ray diffraction studies have revealed the structures of [Tp′(CO)(PhC 2 Me)W-CH 2 PMe 3 ][PF 6 ] (7) and [Tp′(CO)(PhC 2 -Me)W-CH 2 N(Me)dC(H)(Ph)][PF 6 ] (15). The relative stabilities of 3 and 4 are discussed as well as the mechanism of aziridine catalysis.

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

“…Mixing the reagents immediately resulted in a color change to dark brown, and VT NMR spectroscopy showed signals in the 31 P{ 1 H} (s, 52.07 ppm), 13 49 and the C1 symmetry are consistent with P-C bond formation, giving 6, [53][54] unexpectedly suggesting some electrophilic carbene character in electron-rich, anion 5. [53][54][55] The small 1 J(P,CCH2) spin-spin coupling 56 observed for 6 is consistent with phosphonium ylide complexation to transition metal centers; ligation results in rehybridization-C(sp 2 ) to C(sp 3 )-that is reflected in the smaller one-bond scalar coupling constant. 57 The structure of 6 was confirmed in a single-crystal XRD study, which corroborated the assignment of the h 1 -C-bound ylide moiety (see the SI).…”

Oxidative Reactions of the MoIV Dialkyl Complex [{(3‐CF3C6H4NCH2CH2)2NMe}Mo(CH2SiMe3)2]

“…[11,12] As the 2-butyne ligand in 1 is not "locked" on the NMR timescale, its orientation must be dictated by interligand interactions and related effects in the solid state. [11,12] As the 2-butyne ligand in 1 is not "locked" on the NMR timescale, its orientation must be dictated by interligand interactions and related effects in the solid state.…”

“…10 [(CF 3 N 2 NMe)Mo(CHSiMe 3 )(η 2 ‐MeCCMe)] appears to be the first “Mo VI ” complex with both an alkylidene and alkyne group in the coordination sphere of molybdenum, although two “W VI ” examples are known in the literature 11. 12 As the 2‐butyne ligand in 1 is not “locked” on the NMR timescale, its orientation must be dictated by interligand interactions and related effects in the solid state. In the tungsten compounds noted above,11, 12 the alkyne is oriented in a more‐random fashion.…”

“…12 As the 2‐butyne ligand in 1 is not “locked” on the NMR timescale, its orientation must be dictated by interligand interactions and related effects in the solid state. In the tungsten compounds noted above,11, 12 the alkyne is oriented in a more‐random fashion.…”

“…Unfortunately, the nature of the final metal-containing product could not be determined. (4); N(2)ÀMo(1)ÀS(1) = 87.80 (11), N(2)ÀMo(1)À S(1A) = 164.33 (11), N(1)ÀMo(1)ÀN(2) = 78.19 (15), N(1)ÀMo(1)ÀN(3) = 115.75 (17), N(2)ÀMo(1)ÀN(3) = 79.48 (15), Mo(1)ÀMo(1A) = 2.7077 (8), N(1)ÀMo(1)ÀS(1) = 118.08 (12), N(3)ÀMo(1)ÀS(1) = 120.27 (12). Scheme 2.…”