Cationic Group 4 Complexes (M = Ti, Zr, Hf): Modifications and Limitations in the Design of Tridentate Cp, O, P‐Ligand Frameworks Built Directly in the Coordination Sphere of the Metal. Issue 48 (13th November 2018)

• Record Type: Journal Article
• Authors: Fischer, Malte; Jaugstetter, Maximilian; Schaper, Raoul; Schmidtmann, Marc; Beckhaus, Rüdiger
• Is Part Of: European journal of inorganic chemistry. Issue 48(2018)
• Page Start: 5146
• Page End: 5159
• Publication Date: 2018-11-13
• Subjects: Cations -- Metallacycles -- Titanium -- Zirconium -- Hafnium; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201801016
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : The reactions of monopentafulvene complexesTi1, Zr1, andHf1 with bidentate O, P ‐ligand precursorsL1 –L3 to form the corresponding cationic complexes employing an established three‐step synthetic protocol [insertion, methylation, activation with B(C6 F5 )3 ] are investigated. LigandsL1 –L3 are designed to have different sized spacers between the carbonyl and diphenylphosphine functional groups. The attempts to reactTi1, Zr1, andHf1 with acetyldiphenylphosphine (L1 ) proved to yield undesired products at various steps in the synthetic sequence. WhenTi1 is used, Ti2 is formed and diphenylphosphine is released at the same time. CompoundTi2, with the exocyclic double bond, is the formal product of insertion of the smallest ketene (H2 C=C=O) into the Ti–Cexo bond. Starting withZr1 results in isolation of the insertion productZr2 without loss of diphenylphosphine, but a byproduct is formed during the reaction withL1 . Subsequent methylation with methyllithium yields a complex reaction mixture.Hf1 reacts cleanly withL1 to the insertion productHf2 . Also, the methylation reaction selectively yieldsHf3 as the result of chloride/methyl exchange, but final activation with B(C6 F5 )3 causes decomposition and release of diphenylphosphine. The use of the ligand precursorsL2 andL3 with two methylene groups or an aryl group as linkers between the functional groups selectively provides the desired cationic complexesTi6, Zr6, Hf6, andTi9 in good to excellent overall yields. Abstract : Reactions of π ‐η 5 : σ ‐η 1 ‐monopentafulvene complexes to prepare cationic d 0 complexes of each group 4 metal with tridentate Cp, O, P ‐ligands by a convenient three‐step synthetic pathway [insertion of bidentate O, P ‐ligand precursors, subsequent methylation, activation with B(C6 F5 )3 ] are reported. With acetylphosphine as the ligand precursor, side reactions are initiated, depending on the group 4 metal.