Dinuclear and Mononuclear Chromium Acetylide Complexes

Abstract

Abstract Reaction of trans ‐Cl 2 Cr(dmpe) 2 ( 1 ) [dmpe = 1,2‐bis(dimethylphosphanyl)ethane] with 0.5 equiv. of Me 3 Sn–C≡C–C≡C–SnMe 3 or Me 3 Sn–C≡C–C 6 H 4 –C≡C–SnMe 3 afforded the dinuclear complexes trans ‐[Cl(dmpe) 2 Cr≡C–C≡C–C≡Cr(dmpe) 2 Cl] ( 2 ), trans ‐[Cl(dmpe) 2 Cr–C≡C–C≡C–Cr(dmpe) 2 Cl][SnMe 3 Cl 2 ] 2 ( 2 [SnMe 3 Cl 2 ] 2 ), and trans ‐[Cl(dmpe) 2 Cr–C≡C–C 6 H 4 –C≡C–Cr(dmpe) 2 Cl][SnMe 3 Cl 2 ] 2 ( 3 [SnMe 3 Cl 2 ] 2 ), which could be transformed to the 2 [PF 6 ] 2 and 3 [BPh 4 ] 2 salts. Substitutions of the chloride groups in 2 were carried out to achieve the corresponding iodo ( 4 ) and (trimethylsilyl)alkynyl ( 5 ) complexes. Utilizing similar reactions and treatment with only 1 equiv. of the corresponding alkynyl ligand [Me 3 Sn–C≡C–R (R = –SnMe 3 , –C 6 H 5 ), Me 3 Sn–C≡C–C≡C–R (R = –SiMe 3 , –SnMe 3 ), and Me 3 Sn–C≡C–C 6 H 4 –C≡C–SnMe 3 ] allowed us to prepare a series of mononuclear monoacetylide complexes: trans ‐[Cl(dmpe) 2 Cr–C≡C–R] [R = –SnMe 3 ( 6 ),–C 6 H 5 ( 7 )], trans ‐[Cl(dmpe) 2 Cr–C≡C–C≡C–R] [R = –SiMe 3 ( 8 ),–SnMe 3 ( 9 )], and trans ‐[Cl(dmpe) 2 Cr–C≡C–C 6 H 4 –C≡C–SnMe 3 ] ( 10 ), respectively. The complexes 2 , 2 [SnMe 3 Cl 2 ] 2 , 2 [PF 6 ] 2 , 3 [SnMe 3 Cl 2 ] 2 , 3 [BPh 4 ] 2 , and 6 – 10 displayed paramagnetic behavior. Electrochemical studies performed on the dinuclear complexes ( 2 ), ( 2 [SnMe 3 Cl 2 ] 2 ), ( 3 [SnMe 3 Cl 2 ] 2 ), and ( 5 ) showed one two‐electron redox wave revealing a class‐I type behavior based on the Robin–Day classification, which is untypical for dinuclear complexes bridged by a butadiyne ligand. The complexes were characterized by NMR, ESI–MS, cyclic voltammetry, EPR spectroscopy, magnetic measurements, and exemplary single‐crystal X‐ray diffraction studies for 2 , 2 [SnMe 3 Cl 2 ] 2 , 8 , 9 , and 10 .