High oxidation state monopentamethylcyclopentadienyltungsten methyl complexes including the first d0 complex containing a highly distorted methylene ligand, W(.eta.5-C5Me5)(CH3)3(CH2)

Synthesis, Reactivity, and Computational Studies of the Cationic Tungsten Methyl Complex [W(NPh)(N2Npy)Me]+ and Related Compounds (N2Npy = MeC(2-C5H4N)(CH2NSiMe3)2)

“…47 As mentioned, 2-BAr F 4 and 2-MeBAr F 3 were characterized by NMR spectroscopy. The 1 H and 13 F 4 ] (3-BAr F 4 ), which was isolated in 76% yield.…”

Metal Alkyls with Alkylidynic Metal‐Carbon Bond Character: Key Electronic Structures in Alkane Metathesis Precatalysts

“…Thealkylidyne (triple-bond) character in the W À Cbonds of WMe 6 is not exclusive to this molecule.S imilar axially symmetric chemical shift tensors of alkyl ligands are also calculated for molecules such as TaMe 5 (Figure 3a) [30] or even for the axial carbon of the isoelectronic piano-stool structures Cp*TaMe 4 ( Figure 3b)and [Cp*WMe 4 ] + (Figure 3c), indicating that these molecules also feature atriple bond character in their M À CH 3 bonds. [9,37] Theo ccurrence of at riple bond character in the metal-carbon bonds of these compounds is noteworthy;w hile TaMe 5 is ar ather instable complex, its silica-grafted analogue is active in alkane metathesis. [14] In contrast, the related compound Cp*TaMe 4 remains inactive towards alkanes when grafted on silica (see below).…”

“…[9] It is noteworthy that the isoelectronic [Cp*WMe 4 ] + is reported to undergo facile decomposition yielding bridging alkylidyne species,c onsistent with the propensity of this compound to undergo a-H abstraction and the triple-bond character of the WÀCb ond. [37] Thet riple bond character is also retained in some of the methyl groups of the silica-supported congeners of WMe 6 and TaMe 5 ,indicated by their relatively deshielded and almost axially symmetric chemical shift tensors upon immobilization, suggesting that in these compounds the alkyl ligands keep their alkylidynic character,hence their ability to generate alkylidyne species after grafting on silica (Figure 3c, the tensors of all carbon atoms are shown in Figure S4 in the Supporting Information). In contrast, silica-supported Thealkylidynic nature of some of these alkyl compounds is noteworthy as alkylidynes have been proposed as key intermediates in alkane metathesis.…”

Activation of propargylic alcohols by dimolybdenum tris(μ-thiolate) complexes: Influence of the substituents R in HCCCR2(OH)-vinylidene/allenylidene transformation. Reactivity of allenylidene complexes

“…Several other l-alkylidyne-molybdenum species, such as [Mo 2 Cp 2 (l-SMe) 3 (l-CCH 2 n-Pr)], [Mo 2 Cp(l-SMe) 3 -{l-(g 5 -C 5 H 4 )(t-BuN)CN(t-Bu)C}] and [Mo 2 Cp(l-SMe) 2 -{l-(g 5 -C 5 H 4 )(xylN)CN(xyl)C}{l-OCNRR 0 }] complexes, have been structurally characterised [28,30]. The coordination of the bridging carbon atom in 14 resembles those of the corresponding atoms in other l-alkylidyne bimetallic complexes, for example [(C 5 Me 5 )WMe(l 2 -CCH 3 )] 2 [31] and [Mo 2 Cp 2 (l-SMe) 3 (l-CCH 2 n-Pr)] [28] and the length of the Mo-Mo single bond [2.578(2) Å ] is typical of the values reported for other [Mo 2 Cp 2 (l-SMe) 3 (l-X)] complexes [17]. The methyl groups of the thiolate bridges again adopt the anti-orientation.…”