Structure of a scandium-(silicon-bridged Cp, Cp*) complex

Schaefer, William P.; Köhn, R.; Bercaw, John E.

doi:10.1107/s0108270191008375

Cited by 7 publications

(3 citation statements)

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“…The Sc−C(alkyl) bond distance, 2.248(2) Å, is comparable to those of the formerly mentioned β-diketiminato complex, 2.210(9) and 2.245(9) Å . Sc−C bond lengths for other neutral monoalkyl complexes range from 2.243(8) to 2.346(2) Å. − …”

Section: Resultssupporting

confidence: 64%

“…29 Sc-C bond lengths for other neutral monoalkyl complexes range from 2.243(8) to 2.346(2) Å. [30][31][32][33] The 1 H NMR spectrum of 7b in C 6 D 6 shows a set of resonances comparable to those for 7a, except for the lutidine ring and the alkyl ligand, whose broad signals indicate rapid structural fluctuation. For example, the N-methylene groups display two broad singlets at 5.42 and 4.57 ppm.…”

Section: Resultsmentioning

confidence: 99%

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Organo-Rare-Earth Complexes Supported by Chelating Diamide Ligands

et al. 2003

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The synthesis of a series of heteroleptic ate-complex-free rare-earth(III) diamide complexes by alkane and amine elimination reactions, starting from Ln(CH 2 SiMe 3 ) 3 (THF) 2 and Ln-(NiPr 2 ) 3 (THF) x (x ) 1, Ln ) Sc, Lu; x ) 2, Ln ) Y), respectively, is described. 2,6-Bis(((2,6diisopropylphenyl)amino)methyl)pyridine (H 2 BDPPpyr) formed monomeric complexes of the types (BDPPpyr)Ln(CH 2 SiMe 3 )(THF) x (x ) 1, Ln ) Sc, Lu; x ) 2, Ln ) Y) and (BDPPpyr)-Ln(NiPr 2 )(THF) (Ln ) Sc, Lu), which display enhanced stability for the smaller metal center scandium, for diisopropylamide coordination, and in donor solvents such as THF. Conversion of the silylalkyl complexes into their amide derivatives via secondary alkane elimination, i.e., reaction with HNEt 2 and HN(SiHMe 2 ) 2 , increased the complex stability. The mono-THF adduct complexes (BDPPpyr)Sc(L)(THF) show a nonfluxional structure in solution, which contrasts the dynamic behavior of the corresponding bis-THF adduct complexes of the larger elements lutetium and yttrium. Sterically less encumbered 2,6-bis((mesitylamino)methyl)pyridine (H 2 BMespyr) gave the less stable complexes (BMespyr)Ln(CH 2 SiMe 3 )(THF) x (x ) 1, Ln ) Sc; x ) 2, Ln ) Lu; the Y derivative could not be isolated). Again, subsequent silylalkyl/silylamide ligand exchange gave the complexes (BMespyr)Ln[N(SiHMe 2 ) 2 ](THF), exhibiting considerably increased stability. The complexes (BDPPoxyl)Ln(CH 2 SiMe 3 )(THF) (Ln ) Sc, Lu, Y), derived from a nonfunctionalized diamide ligand (H 2 BDPPoxyl ) 1,2-bis-(((2,6-diisopropylphenyl)amino)methyl)benzene), were isolated in high yields. The 4-and 5-coordinate complexes (BDPPoxyl)Sc(CH 2 SiMe 3 )(THF) and (BDPPpyr)Sc(CH 2 SiMe 3 )(THF), respectively, were also characterized by X-ray diffraction structure determinations. All of the 5-coordinate scandium complexes derived from the BDPPpyr ligand effectively polymerize methyl methacrylate in a living manner (M w /M n < 1.5), affording mainly atactic polymer at ambient temperature.

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Section: Resultssupporting

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Organo-Rare-Earth Complexes Supported by Chelating Diamide Ligands

et al. 2003

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“…1. Bond distances and angles are generally within normal ranges; the Si-C( cyclopentadienyl) bond is 1.827 ( 4) A, much shorter than the Si-CH 3 bonds [average 1.873 (6) A, compared to 1.86 A expected (Allen, Kennard, Watson, Brammer, Orpen & Taylor, 1987)] and much shorter than others we have measured recently [average 1.867 (14) A (Marsh, Schaefer, Coughlin & Bercaw, 1992;Schaefer, Kohn & Bercaw, 1992)]. The cyclopentadienyl ring shows evidence of localized double bonds, in that the C-C bonds to Cl average 1.426 (6) A, C2-C3 and C4-C5 average 1.385 16and C3-C4 is 1.410 (7) A.…”

Section: Commentmentioning

confidence: 59%