Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Abstract

The salt metathesis reactions of the yttrium methanediide iodide complex [Y(BIPM)(I)(THF) 2 ] (BIPM = {C(PPh 2 NSiMe 3 ) 2 }) with the group 1 silanide ligand-transfer reagents MSiR 3 (M = Na, R 3 = t Bu 2 Me or t Bu 3 ; M = K, R 3 = (SiMe 3 ) 3 ) gave the yttrium methanediide silanide complexes [Y(BIPM)(Si t Bu 2 Me)(THF)] ( 1 ), [Y(BIPM)(Si t Bu 3 )(THF)] ( 2 ), and [Y(BIPM){Si(SiMe 3 ) 3 }(THF)] ( 3 ). Complexes 1–3 provide rare examples of structurally authenticated rare earth metal–silicon bonds and were characterized by single-crystal X-ray diffraction, multinuclear NMR and ATR-IR spectroscopies, and elemental analysis. Density functional theory calculations were performed on 1–3 to probe their electronic structures further, revealing predominantly ionic Y–Si bonding. The computed Y–Si bonds show lower covalency than Y=C bonds, which are in turn best represented by Y + –C – dipolar forms due to the strong σ-donor properties of the silanide ligands investigated; these observations are in accord with experimentally obtained 13 C{ 1 H} and 29 Si{ 1 H} NMR data for 1–3 and related Y(III) BIPM alkyl complexes in the literature. Preliminary reactivity studies were performed, with complex 1 treated separately with benzophenone, azobenzene, and N , N ′-dicyclohexyl-carbodiimide. 29 Si{ 1 H} and 31 P{ 1 H} NMR spectra of these reaction mixtures indicated that 1,2-migratory insertion of the unsaturated substrate into the Y–Si bond is favored, while for the latter substrate, a [2 + 2]-cycloaddition reaction also occurs at the Y=C bond to afford [Y{C(PPh 2 NSiMe 3 ) 2 [C(NCy) 2 ]-κ 4 C , N , N ′, N ′}{C(NCy) 2 (Si t Bu 2 Me)-κ 2 N , N ′}] ( 4 ); these reactivity profiles complement and contrast with those of Y(III) BIPM alkyl complexes.

Comparison of group 4 and thorium M(iv) substituted cyclopentadienyl silanide complexes

“…Electronic energy densities, H(r), are all negative as expected and for heavy atoms the Laplacian values (∇ 2 ρ(r), range: 0.04-0.07) are insignificant, as we have commented on previously in DFT analyses of diamagnetic f-block silanide complexes. 19,43,44 The QTAIM parameters extracted are consistent with the NBO data and bond indices and a visual evaluation of the HOMOs, which all indicate that the Th-Si bond of 4 is less covalent than the Zr-Si bond of 1 and the Hf-Si bonds of 2, 3 and 5. Conversely, the metal-bound silanide resonance in the 29 Si NMR spectrum of 4 (−66.31 ppm) is downfield to that of 1 (−80.74 ppm) and 2 (−77.11 ppm), which would indicate lower polarity of the Th-Si bond.…”

Paramagnetic NMR Shifts of Tris-Hypersilanide Early f-Block Metal(III) Complexes

“…27 More broadly, the applications of f-block silicon chemistry include σbond metathesis reactions promoted by Ln silanide complexes, 28,29 the addition of Ln silicides to low-alloy steels, 30 and the use of An silicides as high density nuclear fuels. [31][32][33][34] Most structurally authenticated f-block silanide complexes contain the hypersilanide ligand, {Si(SiMe3)3}, or related derivatives; 27,35 selected examples include [Ln{Si(SiMe3)3}2(THF)3] (Ln = Sm, Eu, Yb), 36 [Yb(C5Me5){Si(SiMe3)3}(THF)2], 37 [Y{Si(SiMe3)3}(I)2(THF)3], 38 [Sc(Cp)2{Si(SiMe3)3}(THF)] (Cp = C5H5), 39 [K (18-crown-6)][Ln(Cp)3{Si(SiMe3)3}] (Ln = Ho, Tm; Cp = cyclopentadienyl), 40 [{K (18-crown-6)}2Cp][Ln(Cp)3{Si(SiMe3)3}] (Ln = Ce, Sm, Gd, Tm), 40 [M(Cp′′)2{Si(SiMe3)3}] (M = La, Ce, Nd, U; Cp′′ = {C5H3(SiMe3)2-1,3}), 41 [Y{C(PPh2SiMe3)2}{Si(SiMe3)3}(THF)], 42 [U{N( t Bu)(C6H3Me2-3,5)}{Si(SiMe3)3}], 43 [U(C5H4SiMe3)3{Si(SiMe3)3}], 44 and [K(sol1)][U{[Si(SiMe3)2SiMe2]2O}(sol2)(I)2] (sol1 = (DME)4, sol2 = DME; sol1 = 18-crown-6, sol2 = DME or (THF)2). 45 Recently, we used a combination of 29 Si NMR spectroscopy and density functional theory (DFT) calculations to quantify covalency in diamagnetic nf 14 M(II)-Si bonds for M = Yb and No.…”

Tris-Silanide f-Block Complexes: Insights into Paramagnetic Influence on NMR Chemical Shifts

“…Molecular lanthanide (Ln) and actinide (An) alkyl chemistry is well-developed, with numerous examples of homoleptic Ln­(III) tris -alkyl complexes. , Conversely, f-block silanide chemistry is relatively immature and Ln­(III) tris -silanide complexes are unknown to date . More broadly, the applications of f-block silicon chemistry include σ-bond metathesis reactions promoted by Ln silanide complexes, , the addition of Ln silicides to low-alloy steels, and the use of An silicides as high density nuclear fuels. − Most structurally authenticated f-block silanide complexes contain the hypersilanide ligand, {Si­(SiMe 3 ) 3 } − , or related derivatives; , selected examples include [Ln­{Si­(SiMe 3 ) 3 } 2 (THF) 3 ] (Ln = Sm, Eu, Yb), [Yb­(C 5 Me 5 )­{Si­(SiMe 3 ) 3 }­(THF) 2 ], [Y­{Si­(SiMe 3 ) 3 }­(I) 2 (THF) 3 ], [Sc­(Cp) 2 {Si­(SiMe 3 ) 3 }­(THF)] (Cp = C 5 H 5 ), [K­(18-crown-6)]­[Ln­(Cp) 3 {Si­(SiMe 3 ) 3 }] (Ln = Ho, Tm; Cp = cyclopentadienyl), [{K­(18-crown-6)} 2 Cp]­[Ln­(Cp) 3 {Si­(SiMe 3 ) 3 }] (Ln = Ce, Sm, Gd, Tm), [M­(Cp”) 2 {Si­(SiMe 3 ) 3 }] (M = La, Ce, Nd, U; Cp” = {C 5 H 3 (SiMe 3 ) 2 -1,3}), [Y­{C­(PPh 2 SiMe 3 ) 2 }­{Si­(SiMe 3 ) 3 }­(THF)], [U­{N­( t Bu)­(C 6 H 3 Me 2 -3,5)}­{Si­(SiMe 3 ) 3 }], [U­(C 5 H 4 SiMe 3 ) 3 {Si­(SiMe 3 ) 3 }], and [K­(sol1)]­[U­{[Si­(SiMe 3 ) 2 SiMe 2 ] 2 O}­(sol2)­(I) 2 ] (sol1 = (DME) 4 , sol2 = DME; sol1 = 18-crown-6, sol2 = DME or (THF) 2 ) . Recently, we used a combination of 29 Si NMR spectroscopy and density functional theory (DFT) calculations to quantify covalency in diamagnetic n f 14 M­(II)–Si bonds for M = Yb and No .…”