Rare earth arylsilazido compounds with inequivalent secondary interactions

Abstract

A new bulky silazido ligand, -N(SiHMe2)Dipp (Dipp = C6H3-2,6-iPr2), supports planar, three-coordinate homoleptic rare earth complexes Ln{N(SiHMe2)Dipp}3 (Ln = Sc, Y, and Lu), each containing three secondary Ln↼HSi interactions and one agostic CH bond. Y{N(SiHMe2)Dipp}3 and acetophenone react via hydrosilylation, rather than by insertion into the Y-N bond or by enolate formation.

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

“…Most significantly, the Si-H signal of 4c at 5.17 ppm correlated with the yttrium chemical resonance at 378.5 ppm in a 1 H-89 Y HSQC experiment (measured at room temperature), which also provided evidence for covalent, non-classical interactions between SiHs and the metal center. 42 In addition, the SiMe signal correlated in 1 H- 15 N HMBC experiments to provide 15 N NMR chemical shifts of 160.9 (3c), 142.3 ppm (4c), and 140.3 ppm (5c) signal. The IR spectra contained bands in the νSi-H region at 2046 and 1908 cm -1 for 3c, 1934 and 1883 cm -1 for 4c, and 1942 and 1877 cm -1 for 5c.…”

“…Salt metathesis reactions of rare-earth chlorides and LiN­(SiHMe 2 )­dipp provide the homoleptic species Ln­{N­(SiHMe 2 )­dipp} 3 in moderate yields (Ln = Sc ( 3c ), Y ( 4c ), Lu ( 5c ); eq ). Fortunately, and in contrast to the THF solvent required for syntheses of 3a – 5a and 4b and 5b , the salt metathesis reactions of 2c proceed in diethyl ether at low temperature. The crude products were recrystallized in pentane to provide analytically pure 3c – 5c . …”

“…In the initial communication of the present work, we reported that Y{N(SiHMe2)dipp}3 (dipp = 2,6-diisopropylphenyl) and acetophenone react via hydrosilylation. 42 Recently, La{N(SiHMe2)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(SiMe2OCHPh2)2. 43 Although the smaller yttrium derivative is not a catalyst for this reaction, a relationship between reactivity of the Ln↼H-Si motif and the spectroscopic and structural features of the compounds is also not yet generally established.…”

“…The cationic or zwitterionic zirconium disilazidos [Cp 2 ZrN­(SiHMe 2 ) 2 ] + and Cp 2 Zr­{N­(SiHMe 2 )­(SiHMeCH 2 B­(C 6 F 5 ) 3 )} react with acetone and formaldehyde to give hydrosilylation products [Cp 2 ZrN­(SiMe 2 OR) 2 ] + (R = Me, CHMe 2 ) or Cp 2 Zr­{N­(SiMe 2 OR)­(Si­(OR)­MeCH 2 B­(C 6 F 5 ) 3 )}. , In addition, [Cp 2 ZrN­(SiHMe 2 ) 2 ] + and 4-dimethylaminopyridine (dmap) react to give a zirconium hydride containing a dmap-coordinated silazido, [Cp 2 ZrH­{N­(SiHMe 2 )­(SiMe 2 dmap)}] + , suggesting that the silicon is the most accessible electrophilic site in [Cp 2 ZrN­(SiHMe 2 ) 2 ] + . 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 .…”

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

“…The distances for O1−C21 (1.441(6) Å) and O2−C34 (1.440(6) Å) are typical C−O single bonds, consistent with the double‐hydrosilylation of benzophenone by two Si−H bonds in 4 a . With respect to carbonyl‐inserted silylamide complexes, formaldehyde‐ and acetone‐inserted zirconium cationic complexes, [Cp 2 ZrN(SiMe 2 OR) 2 ] + (R=Me and i Pr), [15] and an acetophenone‐inserted yttrium complex, Y[N(SiMe 2 OCHMePh)Dipp][N(SiHMe 2 )Dipp] 2 , [16] were reported.…”