Syntheses and Structures of Ytterbium(II) Hydride and Hydroxide Complexes: Similarities and Differences with Their Calcium Analogues

The Yb(II) hydride complex (DIPP-nacnac)YbH·THF (3-Yb, DIPP-nacnac = CH{(CMe)(2,6-iPr2C6H3N)}2) was
prepared by a mild metathesis reaction of (DIPP-nacnac)Yb[N(SiMe3)2]·THF with PhSiH3. 3-Yb crystallizes as a
dimer with bridging hydride ions, and its geometry is similar to that of the analogue calcium hydride complex
(3-Ca). 3-Yb is well soluble in benzene and remarkably stable in solution at room temperature. Ligand exchange
to the homoleptic Yb(II) complexes takes place at higher temperatures (3-Yb is less stable than the analogue
3-Ca). The soluble hydride complexes 3-Ca and 3-Yb are catalysts for the hydrosilylation of 1,1-diphenylethylene,
but differences in the product distributions are observed. Slow hydrolysis of (DIPP-nacnac)Yb[N(SiMe3)2]·THF gave
reduction of water and unidentified Yb(III) complexes. Fast hydrolysis at low temperature, however, resulted in the
first Yb(II) hydroxide complex, (DIPP-nacnac)Yb(OH)·THF (4-Yb, 20% yield), which is a dimer with bridging hydroxide
ions in the solid state. The crystal structure is isomorphous to that of the calcium analogue 4-Ca. 4-Yb is well
soluble in benzene and considerably more stable against ligand exchange and formation of homoleptic species
than 3-Yb.