Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

The salt metathesis reactions of the yttrium methane-diide iodide complex [Y(BIPM)(I)(THF)2] (BIPM = {C-(PPh2NSiMe3)2}) with the group 1 silanide ligand-transfer reagents MSiR3 (M = Na, R3 = tBu2Me or tBu3; M = K, R3 = (SiMe3)3) gave the yttrium methanediide silanide complexes [Y(BIPM)(SitBu2Me)(THF)] (1), [Y(BIPM)(SitBu3)(THF)] (2), and [Y(BIPM){Si(SiMe3)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 sigma-donor properties of the silanide ligands investigated; these observations are in accord with experimentally obtained 13C{1H} and 29Si{1H} 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. 29Si{1H} and 31P{1H} 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(PPh2NSiMe3)2[C(NCy)2]-kappa 4C,N,N ',N '}{C(NCy)2(SitBu2Me)-kappa 2N,N '}] (4); these reactivity profiles complement and contrast with those of Y(III) BIPM alkyl complexes.

Automated summary

The salt metathesis reactions of the yttrium methane-diide iodide complex [Y(BIPM)(I)(THF)2] with the group 1 silanide ligand-transfer reagents MSiR3 (M = Na, R3 = tBu2Me or tBu3; M = K, R3 = (SiMe3)3) yielded the yttrium methanediide silanide complexes [Y(BIPM)(SitBu2Me)(THF)] (1), [Y(BIPM)(SitBu3)(THF)] (2), and [Y(BIPM){Si(SiMe3)3}-(THF)] (3). These complexes provide rare examples of structurally authenticated rare earth metal-silicon bonds and were characterized by various spectroscopic techniques. Density functional theory calculations revealed the predominantly ionic Y-Si bonding in 1-3. Reactivity studies showed the preferential 1,2-migratory insertion of unsaturated substrate into the Y-Si bond, as well as [2+2] cycloaddition reaction at the Y=C bond with certain substrates.