Dinuclear Cp* Cobalt Complexes of the 1,2,4,5-Benzenetetrathiolate Bischelating Ligand

Abstract

The dinuclear Cp*Co dithiolene complex [Cp*Co(btt)CoCp*] ( 1) is prepared in high yield from the reaction of the bis(dibutyltin) complex of 1,2,4,5-benzenetetrathiolate (btt) with 2 equiv of [Cp*Co(CO)I 2]. Mononuclear complexes are also obtained from 1,2,4,5-tetrakis(isopropylthio)benzene ( 2) and sodium in pyridine, from benzo[1,2- d;4,5- d ']bis(1,3-dithiolane-2,6-dione) ( 3) and ( t )BuOK in tetrahydrofuran, or from benzo[ d]-1,3-dithiolane-2-one ( 7) and ( t )BuOK to afford respectively 4a, 4b, and [Cp*Co(bdt)] ( 6), while [Cp*Co(dmit)] ( 8) is obtained by literature methods. The X-ray structures of the dinuclear complex 1 and the mononuclear complexes 4a and 6 were determined. They are all characterized by Cp* . . . btt face-to-face intermolecular interactions, leading to a recurrent 4-fold symmetry motif. The cyclic voltammograms of the [Cp*Co(dithiolene)] complexes performed in CH 2Cl 2 show reversible Co (III) to Co (II) reduction but irreversible oxidation waves. The large potential difference between the two reduction waves of the bimetallic complex 1 (269 mV) indicates a stable mixed-valence Co (III)-Co (II) state for the reduced [Cp*Co(btt)CoCp*] (-) anion. Upon trimethyl phosphite addition, the mono-P(OMe) 3 adduct [ 1.P(OMe) 3] exhibits a red shift of the low-energy absorption band to the IR region (856 nm, = 13 000 M (-1).cm (-1)), while [ 8.P(OMe) 3] exhibits a 150 nm blue shift. The stability constants of these P(OMe) 3 adducts were determined from UV-vis spectroscopic titration experiments, with, for example, log( K/mol (-1).dm (3)) values of 3.1 and 0.52 for the mono- and bis-adduct of 1, respectively. The electrochemical investigation of 1 and 8 in excess phosphite shows a strong current enhancement upon oxidation, attributable to the catalytic generation of the radical cation P(OMe) 3 (*+).

Hydrogen bonding interaction of CpCo(Dithiolene) complex with monocyclic 2-pyridonyl substituent and unexpected formation of dithiolene-fused tricyclic pyridone derivative

“…Most [CpCo(dithiolene)] complexes prepared in this work showed k max around 560-610 nm in dichloromethane solution in visible region, except for 6. These k max results are similar to those of typical [CpCo(dithiolene)] [31,32] and [Cp * Co(dithiolene)] (Cp * = g 5 -pentamethylcyclopentadienyl) [33] complexes previously reported. On the other hand, 6 resulted in the k max at 668 nm ( Table 2).…”

“…1). 5 and 8 have intramolecular OHÁ Á ÁN( 2 Py) hydrogen bondings whose distances are 1.958 (33) and 1.830(3) Å, and 11 has an intermolecular OHÁ Á ÁN( 4-Py) one whose distance is 1.856(3) Å. Those hydrogen bondings result in difference of dihedral angle between cobaltadithiolene and pyridyl rings.…”

Radical CpNi(dithiolene) and CpNi(diselenolene) complexes: Synthetic routes and molecular properties

“…For example, titanium, tin, antimony and zinc dithiolene complexes such as [Cp 2 Ti(dithiolene)] [37], [Bu 2 Sn(dithiolene)] [38], [PhSb(dithiolene)] [39] or (NR 4 ) 2 [Zn(dithiolene) 2 ] [40] have been reported for that purpose. In these complexes, the dithiolene ligand is present as 1,2-dithiolate(2−) form.…”

“…These reactions should be performed in a non-polar solvent (CH 2 Cl 2 , benzene and toluene) because both reactants are neutral. The neutral [Ni(dithiolene) 2 ] complexes with soluble substituents (Ph, Me) on the dithiolene ligand react with 1 at room temperature to afford [CpNi(dphedt)], [CpNi(phedt)] and [CpNi(dmedt)] in moderate yields (50-62%, entries[38][39][40][41][42][43]. On the other hand, the use of Pd and Pt complexes of dphedt resulted in lower yields (entries[44][45][46] than with the corresponding Ni complexes.…”

Two near-UV and visible chromophores of CpCo(Dithiolene) complexes with pyridinium-dicyanomethylide group

“…The dinuclear [Cp* 2 M 2 (btt)] (l max ¼ 677 nm (Co), 586 nm (Rh), 474 nm (Ir); btt ¼ 1,2,4,5-benzenetetrathiolate) [28,29] and trinuclear [Cp* 3 M 3 (bht)] (l max ¼ 704 nm (Co), 590 nm (Rh), 499 nm (Ir); bht ¼ benzenehexathiolate) [30] complexes have shown strong visible absorption based on the LMCT in dichloromethane solution (e > 30,000 M À1 cm À1 ). Gray and Donahue group have reported that multimetallic complexes with the btt ligand (M ¼ group 10 metals) exhibiting strong near-IR absorption (1159e1177 nm, e ¼ 12,400e16,000 M À1 cm À1 ) [31].…”