Intermolecular β-Hydrogen Abstraction in Ytterbium, Calcium, and Potassium Tris(dimethylsilyl)methyl Compounds

Abstract

A series of organometallic compounds containing the tris(dimethylsilyl)methyl ligand are described. The potassium carbanions KC(SiHMe2)3 and {KC(SiHMe2)3TMEDA}2 are synthesized by deprotonation of the hydrocarbon HC(SiHMe2)3 with potassium benzyl. {KC(SiHMe2)3TMEDA}2 crystallizes as a dimer with two types of three-center-two-electron K-H-Si interactions: side-on coordination of SiH (∠K-H-Si = 102(2)°) and more obtuse K-H-Si structures (∠K-H-Si ≈ 150°). The divalent calcium and ytterbium compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = 2THF, TMEDA) are prepared from MI2 and 2 equiv of KC(SiHMe2)3. Low 1JSiH coupling constants in the NMR spectra, low-energy νSiH bands in the IR spectra, and short M-Si distances and small M-C-Si angles in the crystal structures suggest β-agostic interactions on each C(SiHMe2)3 ligand. The IR assignments of M{C(SiHMe2)3}2L (L = 2THF, TMEDA) are supported by DFT calculations. The compounds M{C(SiHMe2)3}2L react with 1 or 2 equiv of B(C6F5)3 to give the 1,3-disilacyclobutane {Me2SiC(SiHMe2)2}2 and MC(SiHMe2)3HB(C6F5)3L or M{HB(C6F5)3}2L, respectively. In addition, M{C(SiHMe2)3}2L compounds react with BPh3 to give β-H abstracted products. The compounds M{C(SiHMe2)3}2THF2 react with SiMe3I to yield Me3SiH and disilacyclobutane as the products of β-H abstraction, while M{C(SiHMe2)3}2TMEDA and Me3SiI form a mixture of Me3SiH and the alkylation product Me3SiC(SiHMe2)3 in a 1:3 ratio.

Highly Fluorinated Tris(indazolyl)borate Silylamido Complexes of the Heavier Alkaline Earth Metals: Synthesis, Characterization, and Efficient Catalytic Intramolecular Hydroamination

“…Interestingly, the agostic hydrogen H2a has been unambiguously localized (Ca1···H2a = 2.41(2) ), affording a nearly planar Ca1N7Si2H2a core (torsion angle 6.5 8). Similar geometric features have been noted for other heteroleptic silylamido [69] and tris(dimethylsilyl)methyl [60,70] Ca complexes that also exhibit b-SiÀH agostic interactions. The presence of this interaction is likely to confer a certain degree of stability, since 5 appeared significantly less reactive towards air and moisture than 1.…”

“…The presence of three n SiH frequencies in the SiÀH stretching modes region has been also reported for homoleptic TMEDA-or THF-coordinated Ca complexes containing the {C(SiMe 2 H) 2 } À ligand. [60] Overall, exchange of terminal and bridging amido groups in 4 affords a single set of resonances in the fast exchange limit (A'', Figure 6). By decreasing the temperature, the resonances for the terminal and bridging groups of the {N(SiMe 2 H) 2 } À ligands split into two signals in a 1:2 ratio (A and A').…”

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2013

“…Low 1 J SiH coupling constants in the NMR spectra, low-energy SiH bands in the IR spectra, and short M-Si distances and small M-C-Si angles in the crystal structures suggested ␤-agostic interactions on each C(SiHMe 2 ) 3 ligand. The IR assignments of Yb[C(SiHMe 2 ) 3 ] 2 L (L = 2THF, TMEDA) were supported by DFT calculations [5].…”

“…In addition, the studied Sc(CO) n complexes generally favor the low-spin ground state (doublet) structures except ScCO and Sc(CO) 3 that are in the quartet states. The previously uncertain spectrum bands were assigned to Sc(CO) 4 and Sc(CO) 5 in this work. In all, the appreciable stability suggested that the 18-electron first-row transition metal carbonyls, i.e., Sc(CO) 7 − and Sc(CO) 6 3− could be accessible experimentally [3].…”

“…of B(C 6 F 5 ) 3 according to Scheme 2 to give the 1,3-disilacyclobutane [Me 2 SiC(SiHMe 2 ) 2 ] 2 and YbC(SiHMe 2 ) 3 HB(C 6 F 5 ) 3 L or M[HB(C 6 F 5 ) 3 ] 2 L, respectively [5]. In addition, the compounds Yb[C(SiHMe 2 ) 3 ] 2 L (L = 2THF, TMEDA) reacted with BPh 3 according to Scheme 3 to give ␤-H abstracted products [5].…”