Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

[Image: see text] 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.