Mixed Methyl Aryloxy Rare-Earth-Metal Complexes Stabilized by a Superbulky Tris(pyrazolyl)borato Ligand

Abstract

Various mixed methyl aryloxide complexes Tp tBu,Me LnMe(OAr) (Ln = Y, Lu) were obtained in moderate to high yields according to distinct synthesis protocols dependent on the metal size and sterics of the phenolic proligand. The reaction of Tp tBu,Me LuMe 2 and Tp tBu,Me YMe(AlMe 4 ) via protonolysis with 1 or 2 equiv HOC 6 H 2 tBu 2 -2,6-Me-4 in n-hexane gave the desired complexes Tp tBu,Me LnMe(OAr). Corresponding treatment of Tp tBu,Me LuMe 2 with the sterically less demanding HOC 6 H 3 Me 2 -2,6, HOC 6 H 3 iPr 2 -2,6 and HOC 6 H 3 (CF 3 ) 2 -3,5 led to the formation of the bis(aryloxy) lutetium complexes Tp tBu,Me Lu(OAr) 2 . Application of a salt-metathesis protocol employing Tp tBu,Me LnMe(AlMe 4 ) and the potassium aryloxides KOAr made complexes Tp tBu,Me LnMe(OAr) accessible for the smaller aryloxy ligands as well. All complexes were analyzed by X-ray crystallography to compare the terminal Ln−Me bond lengths and to evaluate the implication of the methyl/aryloxy coordination for the exact cone angles Θ°of the [Tp tBu,Me ] ancillary ligand. Treatment of Tp tBu,Me LnMe(AlMe 4 ) (Ln = Lu, Y) with HOC 6 H 2 tBu 2 -2,6-Me-4 in the presence of 4-(dimethylamino)pyridine (dmap) produced ion-separated complexes [Tp tBu,Me LnMe(dmap) 2 ]-[Me 3 AlOC 6 H 2 tBu 2 -2,6-Me-4)]. The thermal instability of Tp tBu,Me LuMe(OC 6 H 2 tBu 2 -2,6-Me-4) was revealed by the formation of (Tp (tBu-H)/(tBu)2,Me )Lu(OC 6 H 2 tBu 2 -2,6-Me-4) via intramolecular C−H-bond activation.

Mixed Methyl/Chlorido Yttrium(III) Complexes Supported by a Neutral Tridentate N-Donor Ligand

“…The Y–C Me distances average 2.44 Å and hence are considerably shorter compared to the bridging Ln–C methyl bonds in 6-coordinate complexes Y­(AlMe 4 ) 3 (2.508(7) Å), Y­(GaMe 4 ) 3 (2.511(2) Å), or [Li­(tmeda)] 3 [HoMe 6 ] (2.563(18) Å) . Terminal methyl complexes with Y–C distances in a similar range comprise cationic complexes [TpYMe­(dmap) 2 ]­[AlMe 3 OAr] (dmap = dimethylaminopyridine, 2.389(2) Å), [YMe 2 (THF) 5 ]­[BPh 4 ] (2.517(2) Å), [(12-crown-4)­YMe 2 (THF) 2 ]­[BPh 4 ] (2.441(2) Å), [YMe 2 (THF) 5 ]­[AlMe 4 ] (2.468(4) Å), and [(TMTAC) 2 YMe 2 ]­[AlMe 4 ] (TMTAC = trimethyltriazacyclohexane) (2.482(3) Å) or dicationic complexes [YMe­(THF) 6 ]­[BPh 4 ] 2 (2.418(3) Å), [(12-crown-4) 2 YMe]­[AlMe 4 ] 2 (2.410(2) Å), and [(15-crown-5)­YMe­(THF) 2 ]­[AlMe 4 ] 2 (2.405(3) Å) . The terminal methyl bonds of 6-coordinate complexes with electron-withdrawing siloxy ligands tend to be shorter, i.e., [YMe­[(AlMe 2 )­{OSi­(O t Bu) 3 } 2 ]­(AlMe 4 )] 2 (2.373(2) Å), YMe­[(AlMe 2 )­{OSi­(O t Bu) 3 } 2 ]­[OSi­(O t Bu) 3 ] (2.438(2) Å), and [YMe­(GaMe 4 )­(OSi­(O t Bu) 3 )] 2 (2.384(6) Å) .…”

Tale of Three Molecular Nitrides: Mononuclear Vanadium (V) and (IV) Nitrides As Well As a Mixed-Valence Trivanadium Nitride Having a V3N4 Double-Diamond Core

“…Based on the aforementioned results, we examined the less sterically encumbered, methyl-derivatized ligand, Tp t Bu,Me , reported originally by Trofimenko and popularized by Theopold, Parkin, Takats, and Anwander, among others . Accordingly, transmetallation of [VCl 3 (THF) 3 ] with [TlTp t Bu,Me ] in toluene at 65 °C afforded [(Tp t Bu,Me )­VCl 2 ] ( 1 ) in 75% yield as brick-orange plates after workup (Scheme ).…”