Isolation and Electronic Structures of Lanthanide(II) Bis(trimethylsilyl)phosphide Complexes.

While lanthanide (Ln) silylamide chemistry is mature, the corresponding silylphosphide chemistry is underdeveloped, with [Sm{P(SiMe 3 ) 2 }{μ-P(SiMe 3 ) 2 } 3 Sm(THF) 3 ] being the sole example of a structurally authenticated Ln(II) silylphosphide complex. Here, we expand the Ln(II) {P(SiMe 3 ) 2 } chemistry through the synthesis and characterization of nine complexes. The dinuclear "ate" salt-occluded complexes [{Ln[P(SiMe 3 ) 2 ] 3 (THF)} 2 (μ-I)K 3 (THF)] ( 1-Ln ; Ln = Sm, Eu) and polymeric "ate" complex [KYb{P(SiMe 3 ) 2 } 3 {μ-K[P(SiMe 3 ) 2 ]} 2 ] ∞ ( 2-Yb ) were prepared by the respective salt metathesis reactions of parent [LnI 2 (THF) 2 ] (Ln = Sm, Eu, Yb) with 2 or 3 equiv of K{P(SiMe 3 ) 2 } in diethyl ether. The separate treatment of these complexes with either pyridine or 18-crown-6 led to the formation of the mononuclear solvated adducts trans -[Ln{P(SiMe 3 ) 2 } 2 (py) 4 ] ( 3-Ln ; Ln = Sm, Eu, Yb) and [Ln{P(SiMe 3 ) 2 } 2 (18-crown-6)] ( 4-Ln ; Ln = Sm, Eu, Yb), with concomitant loss of K{P(SiMe 3 ) 2 }. The complexes were characterized by a combination of NMR, electron paramagnetic resonance (EPR), attenuated total reflectance infrared (ATR-IR), electronic absorption and emission spectroscopies, elemental analysis, SQUID magnetometry, and single crystal X-ray diffraction. We find that these complexes contrast with those of related Ln(II) bis(silyl)amide complexes due to differences in ligand donor atom hardness and ligand steric requirements from Ln-P bonds being longer than Ln-N bonds. This leads to higher coordination numbers, shorter luminescence lifetimes, and smaller eas y -axis magnetic anisotropy parameters.