RESUMEN
Reactions of 3,4-dimethyl-3',4'-bis(diphenylphosphino)tetrathiafulvalene, o-P2, with [BF(4)](-) salts of Fe(ii), Co(ii), Ni(II), Pd(II), and Pt(II) yield complexes of general formula [M(o-P2)(2)][BF(4)](2). Similar reactions between o-P2 and AgSbF(6) or AgPF(6) produced the salts [Ag(o-P2)(2)][X] where X = [SbF(6)](-) or [PF(6)](-). The resulting compounds were fully characterized by (1)H and (31)P{(1)H} NMR, infrared and electronic absorption spectroscopies, cyclic voltammetry, FAB-MS and single-crystal X-ray diffraction. The paramagnetic Co(II) compound exhibits an S = 3/2 state with large spin-orbit coupling contribution at higher temperatures and an effective S' = 1/2 state below 20 K. Electrochemical studies of the compounds indicate that the two functionalized TTF ligands are not in electronic communication and that they essentially behave as isolated redox centers.
RESUMEN
Reaction of [(n-Bu)(4)N](2)[Re(2)Cl(8)] with the tetrathiafulvalene phosphine ligand o-{P(C(6)H(5))(2)}(2)(CH(3))(2)TTF (o-P2) in refluxing ethanol produces the mixed-nuclearity salt [ReCl(2)(o-P2)(2)][Re(2)Cl(6)(o-P2)] (1.2), composed of the mononuclear Re(III) complex (1) and the mixed-valence Re(II)-Re(III) dinuclear anion (2). The complex crystallizes as a CH(2)Cl(2) solvate in the triclinic space group P&onemacr;, a = 13.4559(1) Å, b = 20.4015(3) Å, c = 21.5538(1) Å, alpha = 88.261(1) degrees, beta = 72.987(1) degrees, gamma = 84.933(1) degrees, and Z = 2. The molecular cation consists of two trans o-P2 ligands in the equatorial plane and axial chloride ligands. The dinuclear anion adopts an eclipsed geometry with an unsymmetrical coordination environment for the two metal atoms; one Re(II) center is coordinated to a chelating o-P2 ligand and two chlorides while the other Re atom is coordinated to four chloride ligands. The dinuclear portion of the salt is a monoanion which leads to a formal bond order assignment of 3.5, based on the fact that the molecule possesses an Re(2)(5+) core. The salt was further characterized by infrared and electronic spectroscopies, electrochemistry, and variable temperature magnetic susceptibility; the presence of the individual ions in bulk samples was verified by positive and negative FAB mass spectrometry. Isolation of the two separate ions was achieved by treatment of the salt with Co(C(5)H(5))(2), which reduces the Re(III) cation to the Re(II) complex ReCl(2)(o-P2)(2) (3). This neutral compound was separated from the byproduct salt [Co(C(5)H(5))(2)][Re(2)Cl(6)(o-P2)] and reoxidized with CCl(4)/CH(2)Cl(2) or NOBF(4) to produce [ReCl(2)(o-P2)(2)][Cl] (1.[Cl]) and [ReCl(2)(o-P2)(2)][BF(4)] (1.[BF(4)]), respectively. Compounds 3, 1.[Cl], and 1.[BF(4)] were identified by a combination of infrared spectroscopy, mass spectrometry, and cyclic voltammetric measurements. Variable temperature dc susceptibility studies of [ReCl(2)(o-P2)(2)][Re(2)Cl(6)(o-P2)] (1.2) revealed classical Curie paramagnetic behavior (with a Curie constant equal to 0.395) and a large temperature independent paramagnetic contribution (chi(TIP) = 9.64 x 10(-)(3) emu/mol). The EPR spectrum of 1.2 consists of a broad, complex signal due to hyperfine interactions to both isotopes (185,187)Re (I = (5)/(2)) and (31)P (I = (1)/(2)) which is typical for paramagnetic metal-metal bonded dirhenium phosphine compounds.