NEUTRAL 4-COORDINATE (SELENOLATO)IRON(II) COMPLEXES - SYNTHESES AND STRUCTURES OF FE(SE-2,6-I-PR2CS6H3)(2)(PME(2)PH)(2) AND FE(SE-2,6-I-PR2C6H(3))(2)(ET(2)PCH(2)CH(2)PET(2))

The first neutral four-coordinate selenolato iron(II) complexes, Fe(Se -2,6-i-Pr2C6H3)(2)(PMe(2)Ph)(2), 1, and Fe(Se-2,6-i-Pr2C6H3)(2)(Et(2)P CH(2)CH(2)PEt(2)), 2, are prepared by metathesis of chloride ligands o f iron(II) chloride with selenolate in the presence of 2 equiv of dime thylphenylphosphine or 1 equiv of 1,2-bis(diethylphosphino)ethane, res pectively. The room temperature magnetic moment of both 1 and 2 is abo ut 5 mu(B) as determined both in the solid state and in solution. The proton NMR spectra exhibit paramagnetic shifts and broadening associat ed with the unpaired electron density at the metal center. The spectra were completely assigned using integration and linewidth information. Cyclic voltammetry and electronic spectra of 1 and 2 and the Mossbaue r spectrum of 1 are also reported. Single crystal X-ray diffraction st udies at 296 K revealed a crystallographically imposed C-2 symmetry fo r 1. The coordination geometry about the iron centers is distorted tet rahedral for both complexes. The Se-Fe-Se angle is much larger than te trahedral with a value of about 130 degrees for both complexes. Fe(Se- 2,6-i-Pr2C6H3)(2)(PMe(2)Ph)(2), 1, crystallizes in the monoclinic spac e group C2/c with a = 22.330(4), b = 12.485(2), c = 16.667(3) Angstrom , beta = 118.03(3)degrees, Z = 4, V = 4101.6(12) Angstrom(3), d(calc) = 1.316 g cm(-3), R = 0.0431, R(w) = 0.0551. Fe(Se-2,6-i-Pr2C6H3)(2)(d epe), 2, crystallizes in the monoclinic space group P2(1)/n with a = 9 .418(1), b = 19.484(4), c = 20.631(3) Angstrom, beta = 93.79(1)degrees , Z = 4, V = 3777.5(13) Angstrom(3), d(calc) = 1.306 g cm(-3), R = 0.0 529, R(w) = 0.0626.