New lanthanide alkynylamidinates and diiminophosphinates

Abstract

This contribution reports the synthesis and structural characterization of several new lithium and lanthanide alkynylamidinate complexes. Treatment of PhC=CLi with N,N'-diorganocarbodiimides, R-N=C=N-R (R = iPr, Cy (cyclohexyl)), in THF or diethyl ether solution afforded the lithium-propiolamidinates Li[Ph-C=C-C(NCy)2] S (1: R = iPr, S = THF; 2: R = Cy, S = THF; 3: R = Cy, S = Et2O). Single-crystal X-ray diffraction studies of 1 and 2 showed the presence of typical ladder-type dimeric structures in the solid state. Reactions of anhydrous LnCl3 (Ln = Ce, Nd, Sm or Ho) with 2 in a 1:3 molar ratio in THF afforded a series of new homoleptic lanthanide tris(propiolamidinate) complexes, [Ph-C=C-C(NCy)2]3Ln (4: Ln = Ce; 5: Ln = Nd; 6: Ln = Sm; 7: Ln = Ho). The products were isolated in moderate to high yields (61%-89%) as brightly colored, crystalline solids. The chloro-functional neodymium(III) bis(cyclopropylethynylamidinate) complex [(c-C3H5-C=C-C(NiPr)2)2Ln(μ-Cl)(THF)]2 (8) was prepared from NdCl3 and two equiv. of Li[c-C3H5-C=C-C(NiPr)2] in THF and structurally characterized. A new monomeric Ce(III)-diiminophosphinate complex, [Ph2P(NSiMe3)2]2Ce(μ-Cl)2Li(THF)2 (9), has also been synthesized in a similar manner from CeCl3 and two equiv. of Li[Ph2P(NSiMe3)2]. Structurally, this complex resembles the well-known "ate" complexes (C5Me5)2Ln(μ-Cl)2Li(THF)2. Attempts to oxidize compound 9 using trityl chloride or phenyliodine(III) dichloride did not lead to an isolable cerium(IV) species.