The reaction of TiCl 4 and CpTiCl 3 with tridentate triaminosilyl ligands. crystal and molecular structure of a titanibicycloheptane with an unusual Si-N-Li-Cl-Ti chain

Abstract

The reaction of lithiated triaminosilanes RSi(NLiR′) 3 (R = Me, t-Bu, Ph; R′ = t-Bu, SiMe 3) with TiCl 4 and CpTiCl 3 gives, in poor yields, the novel spiro- and monocyclic sila-titana-diazacyclobutane derivatives Ti[(NR′) 2Si(Me)(NHR′)] 2 (R′ = SiMe 3 (VII)), R′NH(Ph)S iNR′TiX 1X 2N R′ (R′ = SiMe 3, X 1 = X 2 = Cl (VIII), R′ =t-Bu, X 1 = X 2 = Cl (X) and R′ = SiMe 3, X 1 = Cl, X 2 = Cp (XIII)). Cleavage of VII with TiCl 4 yields R′NH(Me) SiNr′TiCl 2N R′ (R′ = SiMe 3), while Me 2SiNR′-TiCl 2NR′ (R′ = SiMe 3 (XI) and t-Bu (XII) were obtained with Me 2Si(NHSiMe 3) 2 and Me 2Si(NH-t-Bu) 2. If the synthesis of XIII is performed at −30°C, the moholithiated cyclic titanium amide R′(Li)N(Ph)SiNR′Ti(Cl)(Cp)NR′ (R′ = SiMe 3 (XIV)) is isolated as diethyletherate. It crystallizes in the monoclinic space group P2 1/ n with a 11.033(1), b 17.504(2), c 18.001(2) Å, β 98.21(2)°, Z = 4, D x 1.151 g cm −3 and R = 0.045 for 4277 observed reflections. The structure contains an unusual heteronuclear bicyclo[3.1.1]heptane system with CpTi and PhSi groups at the bridge-heads. The main bridge contains the Ti-bonded Cl atom, a Li·O(C 2H 5) 2 moiety and an NSiMe 3 Fragment whereas NSiMe 3 groups are found in the other two bridges. Important bond distances are LiCl (2.455(7) Å), TiCl (2.364(1) Å) and TiN (1.859(6) Å).