The yttrium, cerium and magnesium bis(trimethylsilyl)methyls [Ln{CH(SiMe3)2}3]
[Ln = Y (1), Ce (2)], and the known compound Mg[CH(SiMe3)2]2
(C) and [Mg(μ-Br){CH(SiMe3)2}(OEt2)]2
(D) formed the crystalline nitrile adducts [1(NCBut)2]
(5), [2(NCPh)]
(6), [C(NCR)2]
[R = But
(8), Ph (9), C6H3Me2-2,6 (10)] and [Mg(μ-Br){CH(SiMe3)2}(NCR)]2
[R = But
(11), Ph (12), C6H3Me2-2,6 (13)], rather than β-diketiminato–metal insertion products. The β-diketiminato–cerium complex [Ce{(N(SiMe3)C(C6H4But-4))2CH}{N(SiMe3)2}2]
(16) was obtained from [Ce{N(SiMe3)2}3] and the β-diketimine H[{N(SiMe3)C(C6H4But-4)}2CH]]. The cerium alkyl 2 and [Ln{CH(SiMe3)(SiMe2OMe)}3]
[Ln = Y (3), Ce (4)] were obtained from the appropriate lithium alkyl precursor and [Ce(OC6H2But2-2,6-Me-4)3] or LnCl3, respectively. Heating complex 3 with benzonitrile in toluene afforded 2,2-dimethyl-4,6-diphenyl-5-trimethylsilyl-1,3-diaza-2-silahexa-1,3-diene (7), a member of a new class of heterocycles. The X-ray structures of the crystalline compounds 1–7, D, [Mg{CH(SiMe3)2}2(OEt2)2], the known [Ce(Cl){(N(SiMe3)C(Ph))2CH}2]
(E) and 16 are reported. The cerium alkyl 2
(like 1) has one close Ce⋯C contact for each ligand, attributed to a γ-C–Ce agostic interaction. The Ln alkyls 3 and 4 have a trigonal prismatic arrangement of the chelating ligands (each of the same chirality at Cα) around the metal. In an arene solution at 313 K 3 exists as two isomers, as evident from detailed NMR spectroscopic experiments.