Synthesis, Structures, and Properties of 1,2,4,5-Benzenetetrathiolate Linked Group 10 Metal Complexes

Abstract

Dimetallic compounds [(P-P)M(S(2)C(6)H(2)S(2))M(P-P)] (M = Ni, Pd; P-P = chelating bis(phosphine), 3a-3f) are prepared from O=CS(2)C(6)H(2)S(2)C=O or (n)Bu(2)SnS(2)C(6)H(2)S(2)Sn(n)Bu(2), which are protected forms of 1,2,4,5-benzenetetrathiolate. Selective monodeprotections of O=CS(2)C(6)H(2)S(2)C=O or (n)Bu(2)SnS(2)C(6)H(2)S(2)Sn(n)Bu(2) lead to [(P-P)Ni(S(2)C(6)H(2)S(2)C=O)] or [(P-P)Ni(S(2)C(6)H(2)S(2)Sn(n)Bu(2))]; the former is used to prepare trimetallic compounds [(dcpe)Ni(S(2)C(6)H(2)S(2))M(S(2)C(6)H(2)S(2))Ni(dcpe)] (M = Ni (6a) or Pt (6b); dcpe = 1,2-bis(dicyclohexylphosphino)ethane). Compounds 3a-3f are redox active and display two oxidation processes, of which the first is generally reversible. Dinickel compound [(dcpe)Ni(S(2)C(6)H(2)S(2))Ni(dcpe)] (3d) reveals two reversible oxidation waves with DeltaE(1/2) = 0.66 V, corresponding to K(c) of 1.6 x 10(11) for the mixed valence species. Electrochemical behavior is unstable to repeated scanning in the presence of [Bu(4)N][PF(6)] electrolyte but indefinitely stable with Na[BArF(24)] (BArF(24) = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate), suggesting that the radical cation generated by oxidation is vulnerable to reaction with PF(6)(-). Chemical oxidation of 3d with [Cp(2)Fe][BArF(24)] leads to formation of [3d][BArF(24)]. Structural identification of [3d][BArF(24)] reveals appreciable shortening and lengthening of C-S and C-C bond distances, respectively, within the tetrathioarene fragment compared to charge-neutral 3d, indicating this to be the redox active moiety. Attempted oxidation of [(dppb)Ni(S(2)C(6)H(2)S(2))Ni(dppb)] (3c) (dppb = 1,2-bis(diphenylphosphino)benzene) with AgBArF(24) produces [[(dppb)Ni(S(2)C(6)H(2)S(2))Ni(dppb)](2)(mu-Ag(2))][BArF(24)](2), [4c][BArF(24)](2), in which no redox chemistry has occurred. Crystal structures of bis(disulfide)-linked compounds [(P-P)Ni(S(2)C(6)H(2)(mu-S(2))(2)C(6)H(2)S(2))Ni(P-P)] are reported. Near IR spectroscopy upon cationic [3d](+) and neutral 6a reveals multiple intense absorptions in the 950-1400 nm region. Time-dependent density functional theory (DFT) calculations on a 6a model compound indicate that these absorptions are transitions between ligand-based pi-type orbitals that have significant contributions from the sulfur p orbitals.

Polydentate chalcogen reagents for the facile preparation of Pd2 and Pd4 complexes

“…The non co-planar nature of the 2 × Pd 2 units contrasts with planar, conjugated structures prepared from group 10 metals and arenetetrathiolate ligands. 29 The NMR data for [3]X 4 are not reported due to its poor solubility in common organic solvents. Attempts at improving the yield of [3] 4+ by repeating the synthesis with the more soluble [ n Bu 4 N]Br did not result in the formation of pure material as shown by ESI-MS and elemental analysis.…”

Group 10 Metal Dithiolene Bis(isonitrile) Complexes: Synthesis, Structures, Properties, and Reactivity

“…19 (Table 2, Scheme 1) remain consistent with ene-1,2-dithiolate formulation of the ligand and indicate that electron transfer did not occur. Rather, the Ag + ions have simply been ensconced between the soft thiolate 20 and other complexes featuring the Ag2 2+ unit in an environment of sulfur donor atoms have been described. [21][22] Triarylaminium cations such as [N(C6H4-p-Br)3] + are both more potent oxidizing agents and disposed at an angle of 74.3°.…”

Nickel, palladium and platinum

“…10 Bi-and tri-metallic arrays, {(P 2 )M[(S 2 C 6 H 2 S 2 )M] 1or2 (P 2 )}, were prepared directly from the reaction of the tetrathiolate precursor 8 and group 10 metals (where P 2 = chelating diphosphine). 11 Adsorption of Ni(II) porphyrin complexes onto EPG electrodes followed by oxidation in 0.5 M H 2 SO 4 results in a new redox-active, pH-dependent modified electrode. 12 The structure of ''amorphous nickel sulfide'' has been determined as a hydrated nanoparticulate material with an approximate formula NiSÁ1.5H 2 O.…”