A General Concept for the Electronic and Steric Modification of 1-Metallacyclobuta-2,3-dienes: A Case Study of Group 4 Metallocene Complexes

We present the synthesis of two Ph substituted dilithiated ligand precursors for the preparation of four new 1-metallacyclobuta-2,3-dienes [rac-(ebthi)M] (M=Ti, Zr; ebthi=1,2-ethylene-1,10-bis(η5-tetrahydroindenyl)). The organolithium compounds [Li2(RC3Ph)] (1b: R = Ph, 1c: R = SiMe3) as well as the metallacycles of the general formula [rac-(ebthi)M(R1C3R2)] (2b: M=Ti, R1=R2=Ph, 2c: M=Ti, R1=Ph, R2=SiMe3; 3b: M=Zr, R1=R2=Ph; 3c: M=Zr, R1=Ph, R2=SiMe3) were fully characterised. Single crystal X-ray diffraction and quantum chemical bond analysis of the Ti and Zr complexes reveal ligand influence on the biradicaloid character of the titanocene complexes. X-band EPR spectroscopy of structurally similar Ti complexes [rac-(ebthi)Ti(Me3SiC3SiMe3)] (2a), 2b, and 2c was carried out to evaluate the accessibility of an EPR active triplet state. Cyclic voltammetry shows that introduction of Ph groups renders the complexes easier to reduce. 13C CPMAS NMR analysis provides insights into the cause of the low field shift of the resonances of metal-bonded carbon atoms and provides evidence of the absence of the β-C-Ti interaction.PMID:38529695 | DOI:10.1002/chem.202400708

Source: Chemistry - March 26, 2024 Category: Chemistry Authors: Sihan Li Mirjam Schr öder Adrian Prudlik Xinzhe Shi Anke Spannenberg Jabor Rabeah Robert Francke Bj örn Corzilius Fabian Rei ß Torsten Beweries Source Type: research