Charge-Transfer Salts of Ferrocene Derivatives with Bis(maleonitriledithiolato)metallate(III) Complexes ([M(mnt)2]−, M=Ni, Pt): A Ground-State High-Spin [(Ni(mnt)2)2]2− Dimer

Abstract

New hexamethylated ferrocene derivatives containing thioether moieties (1,1′‐bis[(tert‐butyl)thio]‐2,2′,3,3′,4,4′‐hexamethylferrocene (3a,b)) or fused S‐heteropolycyclic substituents (rac‐1‐[(1,3‐benzodithiol‐ 2‐yliden)methyl]‐2,2′,3,3′,4,4′‐hexamethylferrocene (5) and rac‐1‐[1,2‐bis(1,3‐benzodithiol‐2‐yliden)ethyl]‐2,2′,3,3′,4,4′‐hexamethylferrocene (14)), as well as a series of ferrocene‐substituted vinylogous tetrathiafulvalenes (1,1′‐bis[1,2‐bis(1,3‐benzodithiol‐2‐yliden)ethyl]ferrocene (6a), 1,1′‐bis[1‐(1,3‐benzodithiol‐2‐yliden)‐2‐(5,6‐dihydro‐1,3‐dithiolo[4,5‐b] [1,4]dithiin‐2‐yliden)ethyl]ferrocene (6b), [1,2‐bis(1,3‐benzodithiol‐2‐yliden)ethyl]ferrocene (21a), [1‐(1,3‐benzodithiol‐2‐yliden)‐2‐(5,6‐dihydro‐1,3‐dithiolo[4,5‐b] [1,4]dithiin‐2‐yliden)ethyl]ferrocene (21b), [1,2‐bis(5,6‐dihydro‐1,3‐dithiolo[4,5‐b] [1,4]dithiin‐2‐yliden)ethyl]ferrocene (21c), [1‐(5,6‐dihydro‐1,3‐dithiolo[4,5‐b] [1,4]dithiin‐2‐yliden)‐2‐(1,3‐benzodithiol‐2‐yliden)ethyl]ferrocene (21d)) were prepared and fully characterized. Their redox properties show that some of them are easily oxidized and undergo transformation to paramagnetic salts containing bis(maleonitriledithiolato)‐metallate(III) anions [M(mnt)2]− (M=Ni, Pt; bis[2,3‐dimercapto‐κS)but‐2‐enedinitrilato(2−)]nickelate (1−) or ‐platinate (1−). The derivatives [3a] [Ni(mnt)2] (26), [3a] [Pt(mnt)2] (27), [Fe{(η5‐C5Me4S)2S}] [Ni(Mnt)2] (28), [Fe{(η5‐C5Me4S)2S}] [Pt(mnt)2] (29), [5] [Ni(mnt)2]⋅ClCH2CH2Cl (30), [6a] [Ni(mnt)2] (31), [6a] [Ni(mnt)2]⋅ClCH2CH2Cl (31a), [6a] [Pt(mnt)2] [32), and [6b] [Ni(mnt)2] (33) were prepared and fully characterized, including by SQUID (superconducting quantum interference device) susceptibility measurements. X‐Ray crystal‐structural studies of the neutral ferrocene derivatives 6a,b, 21c,d, and 1,1′‐bis[1‐(1,3‐benzodithiol‐2‐yliden)‐2‐oxoethyl]ferrocene (23), as well as of the charge‐transfer salts 26 – 28, 30, and 31a, are reported. The salts 28 and 30 display both a D+A−A−D+ structural motif, however, with a different relative arrangement of the [{Ni(mnt)2}2]2− dimers, thus giving rise to different but strong antiferromagnetic couplings. Salt 26 exhibits isolated ferromagnetically coupled [{Ni(mnt)2}2]2− dimers. Salt 27 displays a D+A−D+A− structural motif in all three space dimensions, and a week ferromagnetic ordering at low temperature. Salt 31a, on the contrary, shows segregated stacks of cations and anions. The cations are connected with each other in two dimensions, and the anions are separated by a 1,2‐dichloroethane molecule.

Oligomeric and Polymeric Systems with a Cross-conjugated π-Framework

“…Bryce and co-workers have thoroughly explored this topic through the synthesis of dendralenes terminated with ferrocenyl groups (56)(57)(58)(59) and the subsequent analysis of their electrochemical and electronic absorption characteristics. 53,58 Analogous cross-conjugated systems built around a ferrocene core 60 have also been reported.…”

“…53,58 Analogous cross-conjugated systems built around a ferrocene core 60 have also been reported. 58,59 The two-dimensional polymer 61 based on the crossconjugated vinylogous TTF subunit was synthesized using electrochemical polymerization (Scheme 16). 60 As a result of the meta-linkages of the aryl rings, the redox activity of the polymer was limited to the segment shown in bold, and upon p-doping the polymer undergoes a significant conformational change in order to planarize the vinylogous TTF units.…”

Heteroligand Metal Complexes with Extended Redox Properties Based on Redox-Active Chelating Ligands of o-Quinone Type and Ferrocene

“…Pierpont et al [70] have shown that the interaction of cobaltocene and nickel(II) bis-o-benzosemiquinone complexes Ni II In contrast to these complexes, salts [L 1 ] + [Ni(mnt) 2 ] − and [L 1 ] + [Pt(mnt) 2 ] − demonstrate structural ordering D + A − D + A − and ferromagnetic nature of the exchange between [{Ni(mnt) 2 } 2 ] 2− dimers at low temperature. Throughout the CT complexes series, the contribution of the magnetic exchange interaction between the donor (D + ) and acceptor (A − ) does not significantly affect the magnetic susceptibility of these ionic systems [68].…”

Structural, electronic and magnetic properties of Cu(ii) complexes of 2-substituted tropones bearing a ferrocenyl group at 5-position

“…Upon cooling from 300 K, c M T slightly decreases until around 150 K, and then gradually increases, reaching a maximum of 3.2 emu K mol -1 at 4.8 K, and finally rapidly decreases to 2 K. The slight decrease of c M T at high temperatures is owing to the temperature independent paramagnetism (TIP) arisen from the ferrocenium ion moiety as seen in the related compounds reported previously. 18 Therefore, the increase of c M T indicates that ferromagnetic exchange coupling is dominant among constituting magnetic centers in the wide range of temperature. Considering ESR data measured in solid and solution media, this dominant coupling should be for the intramolecular coupling between Cu(II) and Fe(III) centers via the aminotroponato and cyclopentadienyl moieties.…”

“…Unfortunately, we still do not have an adequate reason to explain this point. Considering that related compounds with ferrocenium units have given similar large values (g ª 2.6-2.9), 18 such large values might be essential. Taking the results of the packing structure of 3 2+ into consideration, it is quite interesting that the intramolecular coupling is dominant despite being a longer Fe(III)-Cu(II) intramolecular distance (8.77 A ˚) than the intermolecular distance (5.17 A ˚).…”