Synthesis, Characterization and Electrochemical Properties of 4,5‐Diazafluoren‐9‐yl or Fluoren‐9‐yl Terminated Homobimetallic Ruthenium and Osmium Allenylidene, Alkynyl‐Allenylidene Complexes

Abstract

AbstractA variety of rigid ruthenium and osmium allenylidene [M1Cl(PΛP)2 = C = C(4,5‐diazafluoren‐9‐yl){M2(CHC(PPh3)CHC(PPh3)Cl2(PPh3)2}][PF6]3 (4a: M1=Os, M2=Os, PΛP=dppm; 4b: M1=Os, M2=Ru, PΛP=dppm; 4c: M1=Ru, M2=Os, PΛP=dppe; 4d: M1=Ru, M2=Ru, PΛP=dppe), ruthenium alkynyl‐allenylidene complexes trans‐[(dppe)2Ru(C≡CPh)Ru = C = C(R)][PF6] (6a: R = fluoren‐9‐yl; 6b: R = 4,5‐diazafluoren‐9‐yl), trans‐{(dppe)2[=C = C(fluoren‐9‐yl)]Ru(C ≡ C‐R‐C ≡ C)Ru[(=C = C(fluoren‐9‐yl)(dppe)2]} [PF6]2 (8a, R = 1,4‐phenylene; 8b, R = 1,3‐phenylene) terminated by 4,5‐diazafluoren‐9‐yl and fluoren‐9‐yl group have been prepared. These allenylidene complexes were derived from 9‐ethynyl‐9‐fluorenol and 9‐hydroxy‐9‐ethynyl‐4,5‐diazafluorene in the presence of cis‐OsCl2(dppm)2 and cis‐RuCl2(dppe)2. The respective products have been fully characterized by 1H, 13C, 31P NMR spectrometry, IR spectrometry, elemental analysis, and UV/Vis spectrophotometry. Moreover, electrochemical studies reveal that the dinuclear complexes display a quasi‐reversible redox behavior and a moderate electronic communication between the two metal centers in 8a. UV–vis studies show a remarkable absorption in the region (λmax = 300‐700 nm) for these complexes.