C–H and H–H Bond Activation by a Cationic Germylyne Complex

Abstract

Reactivities of a cationic germylyne complex [Cp*­(CO)2WGe­(IPr)]­(BAr4 F) (1) [IPr = 1,3-bis­(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene] toward several unsaturated organic substrates and dihydrogen were investigated. Complex 1 underwent activation of the formyl C–H bond of benzaldehyde and the ortho C–H bond of pyridine to afford base-stabilized germylene complexes, indicating that coordination of the heteroatom (O/N) of the substrates to the Lewis acidic Ge center facilitates the C–H bond activation on W. The reactions with alkenes resulted in the terminal C–H bond cleavage on Ge by coordination of the CC double bond to W, giving η3-germaallyl complexes. The reactions with terminal alkynes, on the contrary, proceeded through no C–H bond cleavage to produce metallacyclopropenylgermylenes, which have an unprecedented bonding situation with a lone pair on Ge. Complex 1 also reacted with dihydrogen at room temperature to afford a dihydrido­(dihydrogermyl) complex finally through a hydrido­(hydrogermylene) complex. Characterization of these products including X-ray crystal diffraction study (XRD) and possible reaction mechanisms based on cooperative action at the W–Ge unsaturated bond platform are described.

Neutral Chromium Complex with a Cr≡Si Triple Bond: Synthesis and Photoinduced H−H and Benzene C−H Bond Activation

“…This conversion from a M≡Si bond to a (H)M=Si(H) bond with H 2 is remarkable because a similar conversion was never achieved in the previous systems of W ( A ) and Mo ( B ). Although a similar conversion from a M≡E bond to a (H)M=E(H) bond with H 2 was recently found in our cationic germanium system, [15] there was no previous example in the silicon systems. It should be also mentioned that there are some examples of H 2 addition across the M–tetrel bonds [22]…”

“…Using these complexes, we recently demonstrated their high ability of cycloaddition [13] as well as bond activation of o ‐C−H of diaryl ketones [12b] and formyl C−H of aldehydes [14] . We also found that a cationic complex with a W≡Ge bond activated H 2 and C−H bond of aldehydes and pyridine [15] . However, there has been no reports on activation of H 2 or a C−H bond of a simple arene by silylyne complexes until now.…”

Π‐Character of Chromium Germylyne Complex in the Reactions with Enone, Butadiene, and Alkynes: Formation of Germacycles through [2+4] Cycloaddition with Conjugated Molecules

“…However, cycloaddition reactions using tetrylyne complexes are at an early stage of development. To the best of our knowledge, [2+2] cycloaddition reactions are found in the case of silylyne complexes as reported by Tilley, [6] Filippou, [7] and our groups, [8] and in our neutral [5] and cationic [9] germylyne complexes. We also demonstrated that a germylyne complex Cp*(OC) 2 W≡GeC(SiMe 3 ) 3 ( A ) [10] underwent single and double [2+4] cycloaddition with polar unsaturated substrates such as α , β ‐unsaturated ketones leading to the formation of η 3 ‐allyl tungsten complexes with a five‐membered oxagermacycle framework in a one‐step reaction ( B and C in Scheme 1).…”

Neutral Silylyne Complex of Molybdenum: Synthesis, Properties, and Access to Silaiminoacyl Complexes via [2+3] Cycloaddition

“…For instance, we clearly revealed that Cp*(OC) 2 W≡Si(Eind) ( A ) (Eind=1,1,3,3,5,5,7,7‐octaethyl‐ s ‐hydindacen‐4‐yl) underwent [2+2] cycloaddition with alkynes to afford metallasilacyclodutadiene‐type of complexes, which has a strong contribution of zwitterionic canonical form with a delocalized π‐system at the Si−C−C moiety [16] . On the other hand, we very recently found that a similar [2+2] cycloaddition reaction of a cationic germylyne complex with a terminal alkyne produced a metallacyclopropenylgermylene with a lone pair on Ge, rather than an expected metallagermacyclodutadiene [19] . Obviously the structures of products are greatly influenced by the nature of heavy p‐block element, its combination with the metal center, and charge, etc.…”