Lewis acid promoted activation of inert chemical bonds is central to catalysis. The presence of a highly electrophilic central atom having minimum interactions with anions and solvent molecules is a requisite for a reactive Lewis acid. This requirement for a strong Lewis acid is met with by designing a reactive cation of a heavy element, bismuth, bearing the tridentate trispyrazolylborate ligand. The coordination sphere of the electrophilic bismuth dication is stabilized by very weak interactions with the halogen atoms of the weakly nucleophilic tetrakis(pentafluorophenyl)borate anion, chlorobenzene, and ortho‐dichlorobenzene in the solid state. The high electrophilicity at bismuth is demonstrated by the ability of the dication to efficiently catalyze the addition of Si–H to olefins.
The reaction of 1,3,5-trimethyl-1,3,5-triazacyclohexane (TMTAC) with [La{Al(CH(3))(4)}(3)] resulted in C-H activation, leading to the formation of [(TMTAC)La{Al(CH(3))(4)}{(mu(3)-CH(2))[Al(CH(3))(2)(mu(2)-CH(3))](2)}] (1) containing a bis(aluminate) dianion and subsequent extrusion of methane. A similar reaction with [Y{Al(CH(3))(4)}(3)] led to the formation of CH(4), [TMTAC{Al(CH(3))(3)}(2)] (2) and {[(TMTAC)Y][Y(2)(mu(2)-CH(3))][{(mu(6)-C)[Al(mu(2)-CH(3))(2)(CH(3))](3)}{(mu(3)-CH(2))(mu(2)-CH(3))Al(CH(3))(2)}(2)] (3), containing a six-coordinate carbide ion and two [CH(2)Al(CH(3))(3)](2)(-) anions. Compound 3 is a product of multiple C-H activation. This reaction was monitored by in situ(1)H NMR spectroscopy. The analogous reaction with [Sm{Al(CH(3))(4)}(3)] led to the formation of 2, of [(TMTAC)Sm{(mu(2)-CH(3))(CH(3))(2)Al}(2){(mu(3)-CH(2))(2)Al(CH(3))(2)}(2)] (4), which contains a tris(aluminate) trianion, and [{(TMTAC)Sm}{Sm(2)(mu(2)-CH(3))}{(mu(6)-C)[Al(mu(2)-CH(3))(2)(CH(3))](3)}{(mu(3)-CH(2))(mu(2)-CH(3))Al(CH(3))(2)}(2)] (5), which is isostructural to 3. The products were characterised by elemental analyses (except 4, 5), 1 by multinuclear NMR spectroscopy and compounds 1, 2, 3, 4 and 5 by X-ray crystallography. Quantumchemical calculations were undertaken to support the crystallographic data analysis and confirm the structure of 3 and to compare it with an analogous compound where the central six-coordinate carbon has been replaced by oxygen. The investigations point to a mechanism of sterically induced condensation of [Al(CH(3))(4)](-) groups in close proximity in the coordination spheres of the rare-earth metal atoms, which is dependent on the size of these metal atoms.
Dihydrogen activation by metal alkyl complexes via s-bond metathesis is a facile non-redox reaction and a common method for the preparation of rare-earth [1] and early-transition-metal hydrido complexes. [2] The intramolecular CÀH bond activation has been reported for metal alkyl or hydride complexes to give so-called "tucked-in" or "tucked-over" cyclometalated complexes with concomitant liberation of alkane or dihydrogen, [3] predominantly in metallocenes of early transition metals [2b, 4] and f-block elements. [5] The metallocene hydrides of zirconium [6] and samarium [5d] and tris-(amido) actinide hydrides [7] reversibly form the hydrido complex and the cyclometalated complexes by addition and removal of dihydrogen.We have reported a bimetallic trivalent rare-earth-metal complex with two bridging hydrido ligands that adds dihydrogen across a metal-carbon bond and a metal-metal axis. [8] The reverse liberation of dihydrogen by CÀH bond activation was not observed. [9] We have now obtained a rare-earth-metal hydrido complex capable of reversibly binding and releasing dihydrogen under mild conditions. No change in the oxidation state of the metals is involved, as addition and release occur by s-bond metathesis involving a metal-carbon bond. Notably, hydrogenolysis in the solid state was also observed in a single-crystal to single-crystal transformation.The cationic dialkyl lutetium complex [Lu(CH 2 SiMe 3 ) 2 -(thf) 3 ][A] (A = B{3,5-C 6 H 3 (CF 3 ) 2 } 4 ) [10] was treated with the neutral NNNN-type macrocyclic ligand 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (Me 4 TACD = Me 4 [12]aneN 4 ) to give the THF-free dialkyl complex [(Me 4 TACD)Lu-(CH 2 SiMe 3 ) 2 ][A] (1-Lu) in quantitative yield (Scheme 1). Scheme 1. CÀH bond activation in cationic bis(alkyl) complex 1-Lu to give complex 2-Lu.Scheme 2. Preparation of dicationic trihydrido complex 3-Lu.
Stable and isolable cyclometalated monomethyl Au(III) complexes are readily available from the precursor (tpy)Au(Me)Cl, prepared from (tpy)AuCl2 and excess SnMe4. Reaction of (tpy)Au(Me)Cl with suitable silver salts generates (tpy)Au(Me)(X) (X = OAc, OTf). Ligand exchange reactions with (tpy)Au(Me)(OTf) provide the cationic monomethyl Au(III) adducts [(tpy)Au(Me)(L)][OTf] (L = PPh3, THT).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.