Jane Hanna Welch

Structural Characterization of bis(arylimino)isoindoline Complexes of Dimolybdenum

Abstract The complexes [Mo2(OAc)3(BAII)], where BAII is either bis(pyridylimino) isoindoline or bis(4,6-dimethylpyridylimino)isoindoline, have been synthesized. A detailed interpretation of their 1H NMR spectra has been made. The structure of the bis(pyridylimino)isoindoline derivative has been determined by X-ray analysis to facilitate the assignment of the resonance lines in the NMR spectra. The complex is triclinic belonging to the space group P1 with a = 8.241(3), b = 12.274(4), c = 15.390(6) A, V = 1490.1(9) A3 and Dcalc = 1.66 g cm−3. The final R value was 0.058. The structure consists of a quadruply bonded dimolybdenum unit which is bound to three bridging acetates and one bridging BAII ligand. The BAII ligand is bound to one molybdenum by an imino nitrogen and to the other molybdenum by the isoindoline nitrogen and a pyridyl nitrogen. The pyridyl nitrogen is bound in a position approximately co-axial with the metal-metal bond. The MoMo bond distance is 2.109(1) A.

Synthesis and characterization of tetraalkylammonium salts of bis(5,6-dihydro-1,4-dithiin-2,3-dithiolato)cobaltate(III). Crystal structure of [(C4H9)4N]2[Co(DDDT)2]2

Abstract The reaction between CoCl2·6H2O and K2DDDT (the potassium salt of 1,2-dithiolene 5,6-dihydro-1,4- dithiin-2,3-dithiolate) under an argon atmosphere yields a dimeric dianion which can be isolated as a tetraalkylammonium salt. Constant potential electrolysis of the formally Co(III) product yields a Co(II) species. Both complexes are extremely sensitive to air in solution. The solid Co(III) product, however, is sufficiently air stable to allow a structural analysis of the tetrabutylammonium salt. The crystal belongs to the monoclinic space group C2/c with unit cell dimensions of a=23.626(3), b=16.915(3), c= 16.294(2) A, β=101.62(1)°, Z=8. The coordination around the cobalt atom is best described as square pyramid with an average basal CoS bond length of 2.197(1) A and an apical CoS distance of 2.328(1) A. The dimeric structure allows for S…S contacts in the crystal lattice as short as 3.22 A. The structure refined to R=0.037 and Rw=0.053. The frozen glass ESR spectrum of the Co(II) complex exhibits three sets of eight lines with g1=1.933, g2=2.067 and g3=2.860. A cyclic voltammogram contains a two-electron reversible wave, a quasi-reversible one- electron wave and a reversible one-electron wave indicating a four-member electrochemical series: [Co- (DDDT)2]2o[Co(DDDT)2]2− ⇄[Co(DDDT)2]22−⇄2Co(DDDT)22−. The solid-state 13C NMR spectrum shows different resonances for carbons in the double bonds of the ligand, consistent with splitting of the C=C stretch in the IR spectrum.

Effect of cation on the structures, magnetic properties and specific heats of salts of bis(5,6-dihydro-1,4-dithiin-2,3-dithiolato)nickelate(III): the crystal structure of[(CH-3)4N] [Ni(DDDT)2]

Abstract The structure of the tetramethylammonium salt of Ni(DDDT)2- (DDDT2-=5,6-lihydro-l,4-dithiin-2,3-dithiolate) has been determined by X-ray crystallography. The crystal belongs to the orthorhombic space group Pbca with unit cell dimensions a=0.543(2), b=13.937(5), c=27.518(7) A, Z=8. The NiS4 core exhibits square planar coordination with an average NiS bond length 2.146(2) A. The crystal packing can be described as interlocking colums consisting of alternating cations and anions. The columns form a zigzag pattern when viewed down the y axis. The shortest S···S contact is 3.57 A with a total of four contacts less than 3.8 A. The X-ray powder diffraction spectrum of this salt showed the presence of only one crystallographic species, while that of the tetrabutylammonium salt indicated the possibility of a third polymorph. Magnetic susceptibility data for [(CH3)4N] [Ni(DDDT)2] were fit to the Curie-Weiss law by expanding the Weiss constant as an infinite series. The specific heats of the [(CH3)4N]+, [(C2H5)4N]+ and [(C4H9)4N]+ salts of Ni(DDDT)2− were measured between 1 and 25 K. Similar specific heats were observed above 4 K but the values differed significantly below this temperature.

The first example of a stacked structure containing the 5,6-dihydro-1,4-dithiin-2,3-dithiolate ligand: the crystal structure of [(C2H5)4N][Pt(DDDT)2]

The crystal structure of [(C 2 H 5 ) 4 N][Pt(DDDT) 2 ] where DDDT 2− =5,6-dihydro-1,4-dithiin-2,3-dithiolate belongs to the monoclinic space group C 2/ c with unit cell dimensions a =22.199(6), b =8.206(2), c = 17.698(4) A, β=130.87(1)°, Z =4. The Pt and N atoms lie on an inversion center and a two-fold axis, respectively. The PtS 4 core exhibits square planar coordination with an average PtS bond length of 2.270(6) A. This structure represents the first transition metal complex of the DDDT 2− ligand containing stacks of planar anions. The stacks interlock to form a layer. The molecular packing diagram shows alternating cation and anion layers.

Syntheses, characterization and structural studies of copper complexes of the 1,2-dithiolene ligand, 5,6-dihydro-1,4-dithiin-2,3-dithiolate

Abstract The synthesis and characterization of the Cu(II) and Cu(III) complexes of the ligand 5,6-dihydro-1,4-dithiin-2, 3-dithiolate (DDDT2−) are reported. Cu(DDDT)22− was isolated as the tetraethylammonium salt from the reaction of CuCl2·2H2O with K2DDDT in thoroughly degassed 1/1 ethanol/water under an Ar atmosphere. Cu(DDDT)2− was isolated as both the tetrabutylammonium and trimethylammonium salts from similar reactions in the presence of air. Single crystal structural studies have been carried out on the two formally Cu(III) complexes. Crystals of the tetrabutylammonium salt of Cu(DDDT)2− belong to the monoclinic space group P21/c with a=17.937(2), b=8.806(1), c=21.962(3) A, β=109.8(1)°, R=7.6% for 2984 reflections, and p(calc.) = 1.36, p(obs.) = 1.34 g/cm3 for Z = 4. Crystals of the trimethylammonium salt of Cu(DDDT)2− belong to the orthorhombic space group Pnnm with a=9.211(2), b= 10.114(3), c= 10.956(4) A, R = 6.3% for 443 reflections, and p(calc.) = 1.58, p(obs.)=1.58 g/cm3 for Z=2. While the CuS4 core exhibits the D2h symmetry expected for the trimethylammonium salt, that of the tetrabutylammonium salt is distorted with a twist angle of 29° between the two CuS2 planes. A solution and frozen glass ESR study of Cu(DDDT)22− yielded g value assignments of g∥ = 2.101(1), g⊥ = 2.042(1) and o = 2.069(1) as well as the hyperfine splitting values (in cm−X10−4) of A∥ = 142.3(5), A⊥ = 33.4(5) and o=68.6(5). The electrochemical behavior of Cu(DDDT)2- indicates that material is plating out on the electrode surface at potentials more positive than E 1 2 for the 0 ↔ −1 couple.

Crystal structure of bis(pyrrole-N-carbothioate)bis(triphenylphosphine)nickel(II), C46H38N2S2P2Ni

Abstract The crystal structure of Ni(C4H4NCOS)2[(C6H5)3P]2, Ni(ptc)2(Ph3P)2, has been determined by single crystal X-ray diffraction methods. This species exists as a square planar complex. The structure is monoclinic, P21/n, a=12.759(4), b=10.069(2), c= 16.158(6) A, and β=91.96(3)°. The unit cell contains 2 formula units with an observed density of 1.31 g cm−3 (1.34 calculated). The final R index= 0.047 (Rw=0.038) for 2618 non-zero reflections having I > 3 σ(I).