Reactions of [Ti(η⁵-C₅Me₄SiMe₂Cl)Cl₃] with Diamines, a Suitable Approach to Prepare Mono- and Dinuclear Cyclopentadienyl-silyl-amido Titanium Complexes with Constrained and Unstrained Structures

Abstract

Complex [Ti(η5-C5Me4SiMe2Cl)Cl3] (1) reacts with NH2(CH2) n NH2 (n = 3, 4), under appropriate reaction conditions, to yield the corresponding di- and mononuclear constrained-geometry cyclopentadienyl-silyl-amido complexes [Ti{η5-C5Me4SiMe2-κ-N(CH2) n/2}Cl2-]2 (n = 3, 2a; 4, 2b) and [Ti{η5-C5Me4SiMe2-κ-N(CH2) n NH2}Cl2] (n = 3, 3a; 4, 3b). Complexes 2a and 2b are obtained as pure compounds when the reaction is carried out in a 1(Ti):1.5(diamine) molar ratio, while the derivatives 3 cannot be selectively prepared. Treatment of 1 with NH2(CH2)5NH2 gives the dinuclear derivative [Ti{η5-C5Me4SiMe2-κ-N(CH2)2.5-}Cl2]2 (2c) as a single complex, regardless of the reaction stoichiometry. On monitoring these reactions by NMR spectroscopy, the formation of the transient asymmetrical dinuclear complexes [TiCl2{η5-C5Me4SiMe2-κ-N(CH2) n NH-η5-C5Me4SiMe2}TiCl3] (n = 3, 4a; 4, 4b; 5, 4c) is observed. The analogue dinuclear complex [TiCl2{η5-C5Me4SiMe2-κ-N(CH2)3NMe-η5-C5Me4SiMe2}TiCl3] (6) is synthesized, on a preparative scale, by treatment of 1 with an equimolar amount of N-methylpropylenediamine, which is transformed into the mononuclear derivative [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NHMe}Cl2] (7) upon addition of a further equivalent of the diamine. However, treatment of 1 with 1 equiv of N-methylpropylenediamine proceeds with the formation of the mononuclear constrained-geometry compound [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NHMe·HCl}Cl2] (5). The reaction of 1 with 2 equiv of NH2(CH2)3NMe2 or NHMe(CH2)3NMe2 specifically affords, respectively, a mononuclear cyclopentadienyl-silyl-amido derivative with constrained geometry, [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NMe2}Cl2] (8), or unconstrained geometry, [Ti{η5-C5Me4SiMe2NMe(CH2)3-κ-NMe}Cl2] (9). When the reaction with NHMe(CH2)3NHMe is monitored by NMR spectroscopy, the mononuclear intermediate [Ti{η5-C5Me4SiMe2NMe(CH2)3NHMe}Cl3] (11) and the dinuclear complex [Ti{η5-C5Me4SiMe2NMe(CH2)1.5-}Cl3]2 (12) are observed. The dinuclear complex [Ti{η5-C5Me4SiMe2NMe(CH2)3-}Cl3]2 (13) is synthesized by treatment of 1 with 1 equiv of NHMe(CH2)6NHMe. All the reported compounds were characterized by the usual analytical and spectroscopic methods, and the crystal structure of 9 has been determined by X-ray diffraction methods.

Stereospecific Synthesis of Chiral Titanium Complexes Bearing a Bifunctionalized Cyclopentadienyl-Terpenoid Ligand Derived from α-Pinene

“…The synthesis of this new family of chiral compounds was achieved following the strategy described above, consisting of the protonolysis of Ti–Cl and/or Si–Cl bonds in monocyclopentadienyl complexes bearing a SiMe 2 Cl group on the Cp ring, such as [Ti­(η 5 -C 5 H 4 SiMe 2 Cl)­Cl 3 ] and [Ti­{η 5 -C 5 H 3 (SiMe 3 )­(SiMe 2 Cl)}­Cl 3 ]. , …”

“…28,29 The synthesis of this new family of chiral compounds was achieved following the strategy described above, consisting of the protonolysis of Ti−Cl and/or Si−Cl bonds in monocyclopentadienyl complexes bearing a SiMe 2 Cl group on the Cp ring, such as [Ti(η 5 -C 5 H 4 SiMe 2 Cl)Cl 3 ] and [Ti{η 5 -C 5 H 3 (SiMe 3 )(SiMe 2 Cl)}Cl 3 ]. 30,31 Thereafter, reactions of the complexes [Ti(η 5 -C 5 H 4 SiMe 2 Cl)Cl 3 ] and [Ti{η 5 -C 5 H 3 (SiMe 3 )(SiMe 2 Cl)}Cl 3 ] with 1 equiv of the terpenoid preligand C 7 H 6 Me 3 (OH)-(NCH 2 CH 2 NH 2 ) in dichloromethane, at room temperature, and in the presence of 3 equiv of NEt 3 yielded the new constrained-geometry complexes [Ti{(η 5…”

Titanium, zirconium, hafnium

“…Calculations on [Cp 2 Zr(C 2 H 5 )(C 2 H 4 )] + [CH 3 B(C 6 F 5 ) 3 ]indicate that the stabilisation of the a-agostic configuration by the counteranion is of the order of 1 kcal mol -1 . 76 80 Dimeric dinitrogen complexes continue to be a fertile area of new reactions. CySiH 3 combines with the new complex [{(Z 5 -C 5 H 2 -1,2,4-Me 3 ) 2 Hf} 2 (m 2 ,Z 2 ,Z 2 -N 2 )] with the formation of N-Si and Hf-H bonds and the generation of a silyldiazenido ligand, which undergoes N-N scission at 75 1C.…”

Suitable Approach to Prepare N‐Substituted Niobium Complexes – Study of the Factors Controlling the Process

“…In this field, one of our ongoing research lines is focused on the development of an alternative and efficient synthetic strategy for transition‐metal complexes bearing polydentate ligands consisting of a cyclopentadienyl ring that incorporates appended donor substituents , , . Such an approach is based on the protonolysis reactions of the Si–Cl and M–Cl bonds of the chlorosilyl‐substituted cyclopentadienyl compounds [M(η 5 ‐C 5 H 4 SiMe 2 Cl)Cl n ] (M = Ti, n = 3; M = Nb, n = 4) , …”