Scandium chloride, alkyl and phenyl complexes of diamido-donor ligands

Abstract

Reactions of the lithiated diamido-pyridine and -amine ligands Li2N2TMSNpy or Li2N2NC2,TMS with ScCl3 in tetrahydrofuran (THF) afforded the five-coordinate scandium chloride derivatives [Sc(N2TMSNpy)Cl(THF)] 1 and [Sc(N2NC2,TMS)Cl(THF)] 2 where N2TMSNpy = MeC(2-C5H4N)(CH2NSiMe3)2 and N2NC2,TMS = Me3SiN(CH2CH2NSiMe3)2. The corresponding reactions of ScCl3 with the dilithium salts of the amino N-methylated two-carbon analogue N2NC2,Me (N2NC2,Me = MeN(CH2CH2NSiMe3)2) or of the amino N-silylated three-carbon chain analogue N2NC3,TMS (N2NC3,TMS = Me3SiN(CH2CH2CH2NSiMe3)2) afforded no tractable products. In contrast, reaction of ScCl3with the homologous N-methylated three-carbon chain species Li2N2NC3,Me (N2NC3,Me = MeN(CH2CH2CH2NSiMe3)2) cleanly gave the THF-free dinuclear, chloride-bridged compound [Sc2(N2NC3,Me)2(μ-Cl)2] 3. The compounds 1–3 have been crystallographically characterised. Organometallic analogues of 1 and 2 have been prepared by protonolysis reactions of H2N2R′Npy (N2R′Npy = MeC(2-C5H4N)(CH2NR′)2 where R′ = SiMe3, Tol (4-C6H4Me) or Mes (2,4,6-C6H2Me3)) and H2N2NC2,R′ (R′ = Me or SiMe3) with [ScR3(THF)2] (R = CH2SiMe3 or Ph) in benzene which gave the five-coordinate alkyl or phenyl compounds [Sc(N2R′Npy)R(THF)] (R = CH2SiMe3, R′ = SiMe3 4, Tol 5 or Mes 6; R = Ph, R′ = SiMe3 7) and [Sc(N2NC2,R′)(CH2SiMe3)(THF)] (R′ = Me 8 or SiMe3 9). The compound 4 can also be prepared by the reaction of 1 with LiCH2SiMe3. Reaction of [Sc(CH2SiMe3)3(THF)2] with H2N2NC3,Me afforded no tractable product, and with H2N2NC3,TMS in deuterobenzene the labile compound [Sc(N2NC3,TMS)(CH2SiMe3)(THF)] 10 was observed by 1H NMR spectroscopy but could not be isolated. On one occasion the THF-free dimeric alkyl species [Sc2(N2TolNpy)2(CH2SiMe3)2] 11 was obtained. This compound possesses one bridging and one terminal amido nitrogen per N2TolNpy ligand. The X-ray crystal structures of 6 and 11 have been determined. The monomeric compounds 1, 2 and 6 all have trigonal bipyramidal Sc centres in the solid state; the neutral donors take up the axial sites, and the amido nitrogens and either Cl or CH2SiMe3 occupy the equatorial ones.