| Abstract
| - New precursors to potentially conductivenoninteger oxidation state (NIOS) compounds based on metal complexes[ML2]n- (M = Ni,Pd, Pt; L = dddt2-,dtdt2-, and dmit2-;n = 2, 1, 0) have been investigated. Thesingle-crystal conductivity at room temperature of(SMeEt2)[Pd(dmit)2]2 is100 S cm-1. The crystal and electronictight-binding band structures of this compound have been determined,and the possible origin of the metal-insulator transition at 150 K isdiscussed.
- New precursors to potentially conductive noninteger oxidationstate (NIOS) compounds based on metal complexes[ML2]n- [M = Ni,Pd, Pt; L = 5,6-dihydro-1,4-dithiin-2,3-dithiolato(dddt2-),5,7-dihydro-1,4,6-trithiin-2,3-dithiolato (dtdt2-), and2-thioxo-1,3-dithiole-4,5-dithiolato(dmit2-); n = 2, 1, 0] havebeen investigated. Complexesof the series (NR4)[ML2] (R = Me, Et,Bu; L = dddt2-,dtdt2-) have been isolated and characterized,and thecrystal structure of(NBu4)[Pt(dtdt)2] (1)has been determined {1 =C24H44NPtS10, a =12.064(2) Å, b = 17.201(3) Å, c = 16.878(2) Å, β = 102.22(2)°,V = 3423(1) Å3, monoclinic,P21/n, Z = 4}. Oxidation ofthese complexesaffords the corresponding neutral species[ML2]0. Another series of generalformula (cation)n[M(dmit)2][cation= PPN+, BTP+, and(SMeyEt3-y)+with y = 0, 1, 2, and 3, n = 2, 1, M = Ni,Pd] has also been studied. All ofthese (cation)n[M(dmit)2]complexes have been isolated and characterized [with the exception of(cation)[Pd(dmit)2] for cation =(SMeyEt3-y)+].The crystal structures of(PPN)[Ni(dmit)2]·(CH3)2CO(2) and (SMeEt2)[Ni(dmit)2] (3) have been determined{2 =C45H36NNiS10P2O,a = 12.310(2) Å, b = 13.328(3) Å,c = 15.850(3)Å, α = 108.19(3)°, β = 96.64(2)°, γ =99.67(2)°, V = 2373(1) Å3,triclinic, P1̄, Z = 2; 3 =C11H13NiS11, a=7.171(9) Å, b = 17.802(3) Å, c =16.251(3) Å, β = 94.39(4)°, V =2068(2) Å3, monoclinic,P21/n, Z = 4}NIOSsalts derived from the preceding precursors were obtained byelectrochemical oxidation. Electrochemical studiesof the [M(dddt)2] complexes show that they may be usedfor the preparation of NIOS radical cation salts and[M(dddt)2][M‘(dmit)2]xcompounds, but not for the preparation of(cation)[M(dddt)2]z NIOSradical anion salts.The electrochemical oxidation of the[M(dtdt)2]- complexes always yields theneutral [M(dtdt)2]0 species.Thecrystal structure of[Pt(dddt)2][Ni(dmit)2]2(4) has been determined and is consistent with the lowcompactionpowder conductivity (5 × 10-5 Scm-1 at room temperature) {4 =C20H8Ni2PtS28,a = 20.336(4) Å, b =7.189(2) Å, c = 14.181(2) Å, β = 97.16(2)°,V = 2057(1) Å3, monoclinic,C2/m, Z = 2}. The crystalstructures ofthe semiconducting NIOS compounds(BTP)[Ni(dmit)2]3 (5)and (SMe3)[Ni(dmit)2]2(6) have been determined{5 =C43H22PNi3S30,a = 11.927(2) Å, b = 24.919(2) Å,c = 11.829(3) Å, α = 93.11(1)°, β =110.22(1)°, γ =83.94(1)°, V = 3284(1) Å3,triclinic, P1̄, Z = 2; 6 =C15H9Ni2S21,a = 7.882(1) Å, b = 11.603(2) Å,c =17.731(2) Å, α = 77.44(1)°, β = 94.39(1)°,γ = 81.27(1)°, V = 1563(1)Å3, triclinic, P1̄, Z = 2}.The parentcompound(SEt3)[Ni(dmit)2]z(unknown stoichiometry) is also a semiconductor with a single-crystalconductivityat room temperature of 10 S cm-1. Bycontrast, the single-crystal conductivity at room temperature of(SMeEt2)[Pd(dmit)2]2 (7) is ratherhigh (100 S cm-1). 7 behavesas a pseudometal down to 150 K and undergoes anirreversible metal−insulator transition below this temperature.The crystal structure of 7 has been determined{7= C17H13NPd2S21,a = 7.804(4) Å, b = 36.171(18) Å,c = 6.284(2) Å, α = 91.68(4)°, β =112.08(4)°, γ =88.79(5)°, V = 1643(1) Å3,triclinic, P1̄, Z = 2}. Theelectronic structure of(SMeEt2)[Pd(dmit)2]2(7) and thepossible origin of the metal−insulator transition at 150 K arediscussed on the basis of tight-binding band structurecalculations.
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