Ammonothermal Synthesis, Crystal Structure, and Properties of the Ytterbium(II) and Ytterbium(III) Amides and the First Two Rare-Earth-Metal Guanidinates, YbC(NH)3 and Yb(CN3H4)3

We report the oxidation-controlled synthesis of the ytterbium amides Yb­(NH2)2 and Yb­(NH2)3 and the first rare-earth-metal guanidinates YbC­(NH)3 and Yb­(CN3H4)3 from liquid ammonia. For Yb­(NH2)2, we present experimental atomic displacement parameters from powder X-ray diffraction (PXRD) and density functional theory (DFT)-derived hydrogen positions for the first time. For Yb­(NH2)3, the indexing proposal based on PXRD arrives at R3̅, a = 6.2477(2) Å, c = 17.132(1) Å, V = 579.15(4) Å3, and Z = 6. The oxidation-controlled synthesis was also applied to make the first rare-earth guanidinates, namely, the doubly deprotonated YbC­(NH)3 and the singly deprotonated Yb­(CN3H4)3. YbC­(NH)3 is isostructural with SrC­(NH)3, as derived from PXRD (P63/m, a = 5.2596(2) Å, c = 6.6704(2) Å, V = 159.81(1) Å3, and Z = 2). Yb­(CN3H4)3 crystallizes in a structure derived from the [ReO3] type, as studied by powder neutron diffraction (Pn3̅, a = 13.5307(3) Å, V = 2477.22(8) Å3, and Z = 8 at 10 K). Electrostatic and hydrogen-bonding interactions cooperate to stabilize the structure with wide and empty channels. The IR spectra of the guanidinates are compared with DFT-calculated phonon spectra to identify the vibrational modes. SQUID magnetometry shows that Yb­(CN3H4)3 is a paramagnet with isolated Yb3+ (4f13) ions. A CONDON 2.0 fit was used to extract all relevant parameters.