Synthesis and Structures of Lithium and Potassium Complexes of Phosphanyl-Substituted Bis[1,3-bis(trimethylsilyl)cyclopentadienyl]yttriates

The metathesis reaction of [(THF)4Li][Cp‘ ‘2Li] (1) (Cp‘ ‘ = 1,3-(Me3Si)2C5H3) with yttrium
trichloride yields bis(tetrahydrofuran)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl]dichloroyttriate (2). The metathesis reaction of 2 with potassium (triisopropylsilyl)phosphanide in toluene gives a stepwise exchange of the chloride ligands with the
phosphanide substituents. In contrast to bis(tetrahydrofuran)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl][(triisopropylsilyl)phosphanyl]chloroyttriate (3), which appears as an
intermediate observable by NMR spectroscopy, (tetrahydrofuran)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl][bis(triisopropylsilyl)phosphanyl]yttriate (4) is isolated as a
colorless crystalline material with a YP2Li cycle and Y−P bond lengths of 2.840 Å. In solution
a dissociation is observed into lithium (triisopropylsilyl)phosphanide and the THF complex
of bis[1,3-bis(trimethylsilyl)cyclopentadienyl][(triisopropylsilyl)phosphanyl]yttrium (5). The
reaction of either 2 or 4 with potassium (triisopropylsilyl)phosphanide in benzene yields
(η6-benzene)potassium bis[1,3-bis(trimethylsilyl)cyclopentadienyl][bis(triisopropylsilyl)phosphanyl]yttriate (6) with a YP2K cycle and Y−P distances of 2.846 Å. The metathesis
reaction of 2 with (DME)LiPH2 gives (1,2-dimethoxyethane)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl]bis(phosphanyl)yttriate, which reacts with TMEDA to give colorless bis[(TMEDA)lithium] bis[1,3-bis(trimethylsilyl)cyclopentadienyl]bis(phosphanyl)yttriate chloride
(7). The central YP2Li2Cl cycle is nearly planar with Y−P bond lengths of 2.849 Å.