Reactions of ytterbium(II) amides with various Brønsted acids, CS2 or LiNR2; crystal structures of [{Yb(NR2)(µ-OCBut3)}2] and [Yb(OCBut3)2(thf)2](R = SiMe3, thf = tetrahydrofuran)

Abstract

The reactions of [{Yb(NR₂)(µ-NR₂)}₂]I or [Yb(NR₂)₂(OEt₂)₂]II(R = SiMe₃) with various Brønsted acids, carbon disulfide or LiNR₂ with N,N,N′,N′-tetramethylethylenediamine (tmen) afforded the following complexes: (a)[{Yb(NR₂)(µ-OCBu^t₃)}₂]1 from I and 2 Bu^t₃COH; (b)[{Yb(OCBu^t₃)(µ-OCBu^t₃)}₂]2 and [Yb(OCBu^t₃)₂(thf)₂]3 from I and 4 Bu^t₃COH in hexane or tetrahydrofuran (thf), respectively; (c)[{Yb(OCBu^t₃)(OR′)}_x]4a(R′= C₆H₂Bu^t₂-2,6-Me-4) from 1 and 2 HOR′; (d)[Yb(OCBu^t₃)(OR′)(thf)₂]4b from 4a and an excess of thf; (e)[Yb(OCBu^t₃)(OR′)(py)_x]4c from 4b and and excess of pyridine (py); (f) Yb(O₃SCF₃)₂(dme)5(dme = 1,2-dimethoxyethane) from II and 2 HO₃SCF₃; (g)[Yb(tmhd)₃]6 from I and 4 Htmhd (Bu^tCOCH₂COBu^t); (h) Yb(S₂CNR₂)₂7 from II and 2 CS₂; and (i)[Li{Yb(NR₂)₃}(tmen)]8 from II, LiNR₂ and tmen. A Single-crystal X-ray diffraction study established 1 to be dimeric with asymmetrically bridging ^–OCBu^t₃ ligands. In this molecule the four-membered Yb₂O₂ ring has a fold angle of 24° about the O(1)⋯ O(2) direction, reducing the steric strain between adjacent bulky groups by bringing the two NR₂ groups slightly above the plane. Complex 3 is monomeric with the alkoxo and the tetrahydrofuran ligands in a distorted-tetrahedral configuration about the ytterbium. One of the alkoxo ligands is bound in a conventional way with the Yb–O–C angle almost linear [175(2)°], while the other Yb–O–C angle is significantly smaller [155(3)°].