Heteroleptic Lanthanide Compounds with Chalcogenolate Ligands: Reduction of PhNNPh/PhEEPh (E = Se or Te) Mixtures with Ln (Ln = Ho, Er, Tm, Yb). Thermolysis Can Give LnN or LnE

Lanthanide metals reduce mixtures of azobenzene and PhEEPh (E = Se or Te) in pyridine to give the bimetallic
compounds [(py)2Ln(EPh)(PhNNPh)]2 (E = Se, Ln = Ho (1), Er (2), Tm (3), Yb (4); E = Te, Ln = Ho (5), Er
(6), Tm (7), Yb (8)). The structures of [(py)2Er(μ-η2-η2-PhNNPh)(SePh)]2·2py (2) and [(py)2Ho(μ-η2-η2-PhNNPh)(TePh)]2·2py (5) have been determined by low-temperature single-crystal X-ray diffraction, and the nearly identical
unit cell volumes of the remaining compounds indicate they are most likely isomorphous to 2 or 5. In all compounds,
the Ln(III) ions are bridged by a pair of μ-η2-η2-PhNNPh ligands that, from the N−N bond length, have clearly
been reduced to dianions. Charge is balanced by the single terminal EPh ligand on each Ln, and the coordination
sphere is saturated by two pyridine donors to give seven coordinate metal centers. Thermal decomposition of 5
gives HoTe, 8 gives a mixture of YbN and YbTe, and 1 does not give a crystalline solid-state product. Crystal
data (Mo Kα, 153(2) K) are as follows:  2, monoclinic group P21/n, a = 11.864(3) Å, b = 14.188(2) Å, c =
17.624(2) Å, β = 91.62(2)°, V = 2965(1) Å3, Z = 4; 5, triclinic space group P1̄, a = 10.349(2) Å, b = 17.662(4)
Å, c = 17.730(8) Å, α = 75.82(3)°, β = 74.11(3)°, γ = 89.45(2)°, V = 3016(2) Å3, Z = 2.