Stereoselective Synthesis of Hexacoordinated Mononuclear Cyclometalated Rhodium(III) Complexes − Transfer of Chirality from the Metal Center to the Ligand

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

“…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…”

“…Such a process involves not only the rupture of the Ti−N bond and the aperture of the constrained structure but also the decoordination of the imino nitrogen, as inferred from an 15 N NMR analysis, giving rise to new strain-free ansa-cyclopentadienyl-alkoxide or -thiolate complexes. Thus, the reaction of 4 with 1 equiv of isopropanol yields the formation of the corresponding strain-free alkoxide-methyl derivative [Ti{(η 5 6), while treatment with an equimolar amount of a thiol renders the related thiolate-methyl derivative [Ti{(η 5…”

“…The thermal transformation of 7 and 8 goes through abstraction of the silylamino proton SiNH with evolution of methane and a simultaneous regeneration of the original constrained-geometry system observed for 4, exchanging the initial methyl group by a thiolate ligand. Thus, complexes 7 and 8 thermally decompose to afford the corresponding constrained-geometry thiolate derivatives [Ti{(η 5 The regeneration of the constrained geometry in complexes 9 and 10 made them excellent starting materials to perform a second opening reaction by using different protonic reagents.…”

“…In order to prove this, complex 10 was treated with a further 1 equiv of p-Me-C 6 H 4 SH, specifically giving the corresponding open-structure bis-thiophenolate complex [Ti{(η 5 Complexes 9−11 were synthesized on an NMR tube scale, and though none of them were isolated, their molecular structures were certainly established by multinuclear NMR spectroscopy ( 1 H, 13 C, 19 Si, and 15 N). The spectroscopic behavior of these complexes follows the same trend as those analyzed above for complexes featuring similar molecular structures.…”

“…1−4 In this sense, one of the most promising and rational approaches to achieve asymmetric synthesis within a complex is through the transmission of chiral information from one enantiopure ligand to the metal center. 5,6 Cyclopentadienyl complexes have been extensively used as catalysts for a wide range of processes, most notably polymerization 7−11 and oxidation catalysis. 12,13 Among the transition metals, titanium highly stands out as one of the most employed metals for catalytic transformations due to its Earth abundance, cheapness, nontoxicity, and catalytic properties.…”