Trivalent Rare‐Earth Metal Amide Complexes as Catalysts for the Hydrosilylation of Benzophenone Derivatives with HN(SiHMe₂)₂ by Amine‐Exchange Reaction

Abstract

The rare‐earth metal complexes Ln(L1)[N(SiHMe2)2](thf) (Ln=La, Ce, Y; L1=N,N′′‐bis(pentafluorophenyl)diethylenetriamine dianion) were synthesized by treating Ln[N(SiHMe2)2]3(thf)2 with L1H2. The lanthanum and cerium derivatives are active catalysts for the hydrosilylation of benzophenone derivatives with HN(SiHMe2)2. An amine‐exchange reaction was revealed as a key step of the catalytic cycle, in which Ln−Si−H β‐agostic interactions are proposed to promote insertion of the carbonyl moiety into the Si−H bond.

N-Methylation of Aniline Derivatives with CO2 and Phenylsilane Catalyzed by Lanthanum Hydridotriarylborate Complexes bearing a Nitrogen Tridentate Ligand

“…Electrophilic metal complexes such as early-transition-metal complexes and rare-earth metal complexes catalyze CO 2 hydrosilylation upon activation with Lewis acidic triarylboranes (Figure a–c); however, successive CO 2 hydrosilylation and N -methylation of amines have rarely been achieved due to rapid catalyst deactivation by the interaction of amines with electrophilic metal centers. Our previous finding that excess amines did not deactivate electrophilic rare-earth metal silylamide complexes bearing an N , N ″-bis­(pentafluorophenyl)­diethylenetriamine dianion ligand L , M­( L )­[N­(SiHMe 2 ) 2 ]­(thf) (M = La, Ce), prompted us to investigate the hydrosilylation of CO 2 with PhSiH 3 and the sequential N -methylation of N -alkylaniline derivatives. Thus, we herein report that the lanthanum silylamide complex upon activation with B­(3,4,5-F 3 C 6 H 2 ) 3 generated a catalytically active and amine-tolerant hydridotriarylborate complex, [La­( L )­(thf) 2 ]­[HB­(3,4,5-F 3 C 6 H 2 ) 3 ], as the first catalytically active rare-earth metal complex for the N -methylation of N -alkylanilines via CO 2 hydrosilylation (Figure d).…”

Synthesis and Reactivity of N-heterocyclic Carbene Stabilized Lanthanide(II) Bis(amido) Complexes

“…Among them, lanthanide amides are one of the most practical classes because of their high stability . Therefore, various lanthanide amides with different types of anionic spectator ligands have been synthesized for a study of their reactivity . However, the readily available homoleptic Ln­[N­(SiMe 3 ) 2 ] n ( n = 2, 3) complexes still lack feasible strategies to modulate their reactivity and selectivity, even though Ln­[N­(SiMe 3 ) 2 ] n complexes have already been used as organometallic reagents and catalysts in some cases …”

Ancillary Steric Effects on the Activation of SiH Bonds in Arylsilazido Rare-Earth Compounds

“…In the initial communication of the present work, we reported that Y­{N­(SiHMe 2 )­dipp} 3 (dipp = 2,6-diisopropylphenyl) and acetophenone react via hydrosilylation . Recently, La­{N­(SiHMe 2 ) 2 } 3 (THF) 2 was shown to catalyze the hydrosilylation of benzophenone, proposed to occur through addition of the ketone to the silazido SiH, with the turnover-limiting step being protonolytic substitution of La–N­(SiMe 2 OCHPh 2 ) 2 . The smaller yttrium derivative is not a catalyst for this reaction under related conditions.…”

“…42 Recently, La{N-(SiHMe 2 ) 2 } 3 (THF) 2 was shown to catalyze the hydrosilylation of benzophenone, proposed to occur through addition of the ketone to the silazido SiH, with the turnover-limiting step being protonolytic substitution of La−N(SiMe 2 OCHPh 2 ) 2 . 43 The smaller yttrium derivative is not a catalyst for this reaction under related conditions. Moreover, a relationship between the reactivity of the Ln↼H−Si motif and the spectroscopic and structural features of the compounds is also not yet generally established.…”