METAL-COMPLEXES OF DITHIOLATE LIGANDS - 5,6-DIHYDRO-1,4-DITHIIN-2,3-DITHIOLATO (DDDT(2-)), 5,7-DIHYDRO-1,4,6-TRITHIIN-2,3-DITHIOLATO (DTDT(2-)), AND 2-THIOXO-1,3-DITHIOLE-4,5-DITHIOLATO (DMIT(2-)) - SYNTHESIS,ELECTROCHEMICAL STUDIES, CRYSTAL AND ELECTRONIC-STRUCTURES, AND CONDUCTING PROPERTIES

New precursors to potentially conductive noninteger oxidation state (N IOS) compounds based on metal complexes [ML(2)](n-) [M = Ni, Pd, Pt; L = 5,6-dihydro-1,4-dithiin-2,3-dithiolato (dddt(2-)), 5,7-dihydro-1,4, 6-trithiin-2,3-dithiolato (dtdt(2-)), and 2-thioxo-1,3-dithiole-4,5-di thiolato (dmit(2-)); n = 2, 1, 0] have been investigated. Complexes of the series (NR(4))[ML(2)] (R = Me, Et, Bu; L = dddt(2-), dtdt(2-)) ha ve been isolated and characterized, and the crystal structure of (NBu( 4))[Pt(dtdt)(2)] (1) has been determined {1 = C24H44NPtS10, a = 12.064 (2) Angstrom, b = 17.201(3) Angstrom, c = 16.878(2) Angstrom, beta = 1 02.22(2)degrees, V = 3423(1) Angstrom(3), monoclinic, P2(1)/n, Z = 4}. Oxidation of these complexes affords the corresponding neutral specie s [ML(2)](0). Another series of general formula (cation)(n)[M(dmit)(2) ] [cation = PPN+, BTP+, and (SMe(y)Et(3-y))(+) with y = 0, 1, 2, and 3 , n = 2, 1, M = Ni, Pd] has also been studied. All of these (cation)(n )[M(dmit)(2)] complexes have been isolated and characterized [with the exception of (cation)[Pd(dmit)(2)] for cation = (SMe(y)Et(3-y))(+)]. The crystal structures of (PPN)[Ni(dmit)(2)].(CH3)(2)CO (2) and (SMeEt (2))[Ni(dmit)(2)] (3) have been determined {2 = C45H36NNiS10P2O, a = 1 2.310(2) Angstrom, b = 13.328(3) Angstrom, c = 15.850(3) Angstrom, alp ha = 108.19(3)degrees, beta = 96.64(2)degrees, gamma = 99.67(2)degrees , V = 2373(1) Angstrom(3), triclinic, <(P)over bar 1>, Z = 2; 3 = C11H 13NiS11, a = 7.171(9) Angstrom, b = 17.802(3) Angstrom, c = 16.251(3) Angstrom, beta = 94.39(4)degrees, V = 2058(2) Angstrom(3), monoclinic, P2(1)/n, Z = 4} NIOS salts derived from the preceding precursors were obtained by electrochemical oxidation. Electrochemical studies of the [M(dddt)(2)] complexes show that they may be used for the preparation of NIOS radical cation salts and [M(dddt)(2)][M'(dmit)(2)](x) compoun ds, but not for the preparation of (cation)[M(dddt)(2)](z) NIOS radica l anion salts. The electrochemical oxidation of the [M(dtdt)(2)](-) co mplexes always yields the neutral [M(dtdt)(2)](0) species. The crystal structure of [Pt(dddt)(2)][Ni(dmit)(2)](2) (4) has been determined an d is consistent with the low compaction powder conductivity (5 x 10(-5 ) S cm(-1) at room temperature) {4 = C20H8Ni2PtS28, a = 20.336(4) Angs trom, b = 7.189(2) Angstrom, c = 14.181(2) Angstrom, beta = 97.16(2)de grees, V = 2057(1) Angstrom(3), monoclinic, C2/m, Z = 2}. The crystal structures of the semiconducting NIOS compounds (BTP)[Ni(dmit)(2)](3) (5) and (SMe(3))]Ni(dmit)(2)](2) (6) have been determined {5 = C43H22P Ni3S30, a = 11.927(2) Angstrom, b = 24.919(2) Angstrom, c = 11.829(3) Angstrom, alpha = 93.11(1)degrees, beta = 110.22(1)degrees, gamma = 83 .94(1)degrees, V = 3284(1) Angstrom(3), triclinic, <P(1)over bar>, Z = 2; 6 = C15H9Ni2S21, a = 7.882(1) Angstrom, b = 11.603(2) Angstrom, c = 17.731(2) Angstrom, alpha = 77.44(1)degrees, beta = 94.39(1)degrees, gamma = 81. 27(1)degrees, V = 1563(1) Angstrom(3), triclinic, <P(1)ov er bar>, Z = 2}. The parent compound (SEt(3))[Ni(dmit)(2)](z) (unknown stoichiometry) is also a semiconductor with a single-crystal conducti vity at room temperature of 10 S cm(-1). By contrast, the single-cryst al conductivity at room temperature of (SMeEt(2))[Pd(dmit)(2)](2) (7) is rather high (100 S cm(-1)). 7 behaves as a pseudometal down to 150 K and undergoes an irreversible metal-insulator transition below this temperature. The crystal structure of 7 has been determined {7 = C17H1 3NPd2S21, a = 7.804(4) Angstrom, b = 36.171(18) Angstrom, c = 6.284(2) Angstrom, alpha = 91.68(4)degrees, beta = 112.08(4)degrees, gamma = 8 8.79(5)degrees, V = 1643(1) Angstrom(3), triclinic, <P(1)over bar>, Z = 2}. The electronic structure of (SMeEt(2))[Pd(dmit)(2)](2) (7) and t he possible origin of the metal-insulator transition at 150 K are disc ussed on the basis of tight-binding band structure calculations.