Structural Evidence for Lewis Acid Triggered Nitrosyl Bending in Rhenium(-I) Chloro Catalysts for Alkene Hydrogenation Reactions

• Published in: European journal of inorganic chemistry Vol. 2014; no. 1; pp. 140 - 147
• Main Authors: Jiang, Yanfeng, Huang, Wenjing, Schmalle, Helmut W., Blacque, Olivier, Fox, Thomas, Berke, Heinz
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.01.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Bending; Catalysis; Catalysts; Derivatives; Homogeneous catalysis; Hydrogenation; Lewis acid; Lewis acids; Ligands; Nitrosyls; Rhenium; Structure elucidation
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201301174

The “catalytic nitrosyl effect” operating in reversible nitrosyl bending governs the performance of NO‐functionalized chlororhenium derivatives as catalysts in 1‐hexene hydrogenation reactions. Structural support for a Lewis acid (LA) induced bending at the NNO atom was provided by terminal attachment of a Lewis acid to one of the nitrosyl ligands in the [ReCl(PR3)2(NO)2] complexes (2: R = iPr a, R = Cy b) to give the products [ReCl(PR3)2(NO)(NO‐LA)][Z] {3: LA = B(C6F5)3; 4: LA = Et+; Z = [B(C6F5)4]–; 5a: LA = SiEt3+, Z = [HB(C6F5)3]–; R = iPr a, Cy b}. X‐ray diffraction studies revealed a moderately bent nitrosyl ligand in the nonderivatized complex 2a [159.3(5)°] and fully bent NO‐LA groups in 3a [131.4(3)°] and 4b [132.7(3)°]. The catalytic activities of the chloro dinitrosyl complexes in the hydrogenation of prototypical 1‐hexene were investigated. The NO‐LA bent complexes 3b and 4b furnished excellent TONs of up to 1.0 × 104 and high TOFs of up to 5.4 × 104 h–1 when the Lewis acids were present as co‐catalysts. Structural evidence for Lewis acid enabled nitrosyl bending is evident in chloro dinitrosyl bis‐phosphine complexes, which themselves can be “made” catalytic for the hydrogenation of alkenes.