Bimetallic rare-earth-metal imide complexes Ln 2 (μ 2 -Ndipp)(μ 3 -Ndipp)[(μ 2 -Me) 2 AlMe](AlMe 4 ) 2 (3-Ln; Ln = Y, La, Ce, Nd; dipp = 2,6-diisopropylphenyl) have been obtained from the reaction of Ln(AlMe 4 ) 3 (1-Ln) with Li(NHdipp) (2). X-ray diffraction studies of toluene-soluble 3-Ln revealed an unusual Ln[{(μ 2 -Me) 2 AlMe}(μ 3 -Ndipp)]Ln moiety as the most striking feature. Facile salt-metathetical exchange of the tetramethylaluminato ligands in 3-Ln with K(L) (L = N(SiMe 3 ) 2 , Cp′) allowed for the isolation of Ln 2 (Ndipp) 2 [N(SiMe 3 ) 2 ] 2 (AlMe 3 ) (4-La), partially exchanged Ln 2 (Ndipp) 2 (Cp′)(AlMe 4 )(AlMe 3 ) (5-La, Cp′ = C 5 Me 4 SiMe 3 ), and Ln 2 (Ndipp) 2 (Cp′) 2 (AlMe 3 ) (6-La). Attempted cleavage of the AlMe 3 moiety in 3-Ln with THF led to C−H bond activation of one of the isopropyl methine moieties to produce Ln 2 (μ 2 -Ndipp)[(μ 3 -NC 6 H 3 -2-CMe 2 -6-iPr)Al(μ 2 -Me) 2 ](AlMe 4 ) 2 (7-La). Selective cleavage of the bridging AlMe 3 "cap" was achieved by addition of DMAP (DMAP = 4-dimethylaminopyridine) to produce [Ln(μ 2 -Ndipp)(AlMe 4 )(DMAP)] n (8-Ln; Ln = La, Ce) and concomitantly DMAP•AlMe 3 . The organoaluminum-free compounds [Ln(μ 2 -Ndipp){N(SiMe 3 ) 2 }(DMAP)] 2 (9-Ln; Ln = La, Ce), [Ln(μ 2 -Ndipp)(Cp′)(DMAP)] 2 (10-La), and [Ln(μ 2 -Ndipp)(OAr)(DMAP)] 2 (11-Ln; Ln = La, Ce; Ar = 2,6-di-tert-butyl-4-methylphenyl) were obtained via reactions of 8-Ln with K(L) (L = Cp′, N(SiMe 3 ) 2 , OAr). In the presence of activators [Ph 3 C][B(C 6 F 5 ) 4 ] and [PhNMe 2 H][B(C 6 F 5 ) 4 ], AlEt 2 Cl complexes 3-Ln, 5-Ln, and 7-Ln initiate the polymerization of isoprene to yield PIPs with narrow molecular weight distributions, involving new imido-supported bimetallic catalysts.

The reactivity of alkylaluminum hydrides HAlMe2, HAl­(CH2SiMe3)2, and H2AlMes* (Mes* = C6H2 tBu3-2,4,6) toward yttrium methyl complexes was assessed. From the reaction with [Cp2YMe]2 the corresponding methylated alkylaluminum compounds could be isolated and characterized along with [Cp2Y­(thf)­(μ-H)]2, obtained upon workup in thf (Cp = C5H5 = cyclopentadienyl). Structurally characterized complexes Cp14Y6H3Cl and Cp15Y6H3 represent side-products of the transformation. The reactions of [YMe3] n and [(C5Me5)­YMe2]3 indicated occurrence of hydrido transfer for H2AlMes* and led to product mixtures for HAl­(CH2SiMe3)2. Following the reaction of HAlMe2 with these compounds as well as the half-sandwich derivatives (C5Me4R)­Y­(AlMe4)2 (R = Me, SiMe3) indicated reversible hydrido binding, leading ultimately to the formation of insoluble hydride clusters. The organoaluminum compounds [HAl­(CH2SiMe3)2]3, [(μ-H)­(Me)­AlMes*]2, and Me2AlMes* were analyzed by X-ray crystallography.

The synthesis of homoleptic gallium(III) bis(dimethylsilyl)amide Ga[N(SiHMe 2 ) 2 ] 3 was attempted via different pathways. A transsilylamination protocol using Ga[N(SiMe 3 ) 2 ] 3 and HN(SiHMe 2 ) 2 was unsuccessfully applied. An unexpected side product, MeGa[N(SiMe 3 ) SiMe 2 N(SiMe 3 ) 2 ] 2 , could be obtained from the synthesis of homoleptic gallium(III) bis(trimethylsilyl)amide via GaCl 3 and LiN(SiMe 3 ) 2 . Alkane elimination from Me 3 Ga or Et 3 Ga and HN(SiHMe 2 ) 2 did not lead to the isolation of Ga[N(SiHMe 2 ) 2 ] 3 either. When a salt metathesis route was conducted, reacting GaCl 3 with LiN(SiHMe 2 ) 2 , the silylamido-bridged dimeric hydride complex {H 2 Ga[μ-N(SiHMe 2 ) 2 ]} 2 was obtained. Its further reaction with N,N,N′,N′-tetramethylethylendiamine (tmeda) gave the dinuclear, tmeda-bridged {[H 2 GaN(SiHMe 2 ) 2 ] 2 (μ-tmeda)}.