Synthesis, Characterization, and Crystal Structure of a (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Hexapyridine Ligand, 1,2-Bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane. The First Example of a Discrete (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Ligand

A mononucleating tripyridine ligand, 2-(bis(2-pyridyl)methyl)-6-methylpyridine (L(1)), and a dinucleating hexapyridine ligand, 1,2-bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane (L(2)), have been prepared. The reaction of a carbanion of 2,6-lutidine with 2-bromopyridine affords L(1) which is converted to L(2) quantitatively by treating with tert-butyllithium and 1,2-dibromoethane. (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) complexes [Fe(2)(O)(OAc)(2)(L(1))(2)](ClO(4))(2) (1) and [Fe(2)(O)(OAc)(2)L(2)](ClO(4))(2) (2) have been synthesized and characterized by means of infrared, UV/vis, mass, and M?ssbauer spectroscopies and by measuring magnetic susceptibility and cyclic voltammograms. All the spectral data are consistent with the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure in both 1 and 2. A relatively strong molecular ion peak at m/z 865 corresponding to [{Fe(2)O(OAc)(2)L(2)}(ClO(4))](+) in a FAB mass spectrum of 2 suggests the stabilization of the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure by L(2) in a solution state. The compound 2.DMF.2-PrOH.H(2)O, chemical formula C(44)Cl(2)Fe(2)H(51)N(7)O(16), crystallizes in the monoclinic space group C2/c with a = 22.034(6) ?, b = 12.595(5) ?, c = 20.651(7) ?, beta = 121.49(2) degrees, and Z = 4. The cation has 2-fold symmetry with the bridging oxygen atom on the 2-fold axis: Fe-(&mgr;-O) = 1.782(5) ?, Fe-O-Fe = 123.6(6) degrees, and Fe.Fe = 3.142(3) ?. The diiron(III) core structure of 2 seems to be stabilized by encapsulation of the ligand. Compound 2 is the first example of a discrete (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) complex with a dinucleating ligand.     

Model Compounds for Iron Proteins. Structures and Magnetic, Spectroscopic, and Redox Properties of Fe(III)M(II) and [Co(III)Fe(III)](2)O Complexes with (&mgr;-Carboxylato)bis(&mgr;-phenoxo)dimetalate and (&mgr;-Oxo)diiron(III) Cores

A series of heterobimetallic complexes of the type [Fe(III)M(II)L(&mgr;-OAc)(OAc)(H(2)O)](ClO(4)).nH(2)O (2-5) and [{Fe(III)Co(III)L(&mgr;-OAc)(OAc)}(2)(&mgr;-O)](ClO(4))(2).3H(2)O (6) where H(2)L is a tetraaminodiphenol macrocyclic ligand and M(II) = Zn(2), Ni(3), Co(4), and Mn(5) have been synthesized and characterized. The (1)H NMR spectrum of 6 exhibits all the resonances between 1 and 12 ppm. The IR and UV-vis spectra of 2-5 indicate that in all the cases the metal ions have similar coordination environments. A disordered crystal structure determined for 3 reveals the presence of a (&mgr;-acetate)bis(&mgr;-phenoxide)-Ni(II)Fe(III) core, in which the two metal ions have 6-fold coordination geometry and each have two amino nitrogens and two phenolate oxygens as the in-plane donors; aside from the axial bridging acetate, the sixth coordination site of nickel(II) is occupied by the unidentate acetate and that of iron(III) by a water molecule. The crystal structure determination of 6 shows that the two heterobinuclear Co(III)Fe(III) units are bound by an Fe-O-Fe linkage. 6 crystallizes in the orthorhombic space group Ibca with a = 17.577(4) ?, b = 27.282(7) ?, c = 28.647(6) ?, and Z = 8. The two iron(III) centers in 6 are strongly antiferromagnetically coupled, J = -100 cm(-1) (H = -2JS(1).S(2)), whereas the other two S(1) = S(2) = (5)/(2) systems, viz. [Fe(2)(III)(HL)(2)(&mgr;-OH)(2)](ClO(4))(2) (1) and the Fe(III)Mn(II) complex (5), exhibit weak antiferromagnetic exchange coupling with J = -4.5 cm(-1) (1) and -1.8 cm(-1) (5). The Fe(III)Ni(II) (3) and Fe(III)Co(II) (4) systems, however, exhibit weak ferromagnetic behavior with J = 1.7 cm(-1) (3) and 4.2 cm(-1) (4). The iron(III) center in 2-5 exhibits quasi-reversible redox behavior between -0.44 and -0.48 V vs Ag/AgCl associated with reduction to iron(II). The oxidation of cobalt(II) in 4 occurs quasi-reversibly at 0.74 V, while both nickel(II) and manganese(II) in 3 and 5 undergo irreversible oxidation at 0.85 V. The electrochemical reduction of 6 leads to the generation of 4.     

Synthesis, NMR Study, and Reactivity of Isomeric Early-Late Heterobimetallic Dihydrides. X-ray Crystal Structure of (PPh(3))HRu(&mgr;-H)(&mgr;-PMe(2)C(5)Me(4))(2)(&mgr;-Cl)ZrCl

The new isomeric ruthenium/zirconium dihydrides of the formula (PPh(3))HRuH(&mgr;-PMe(2)Cp)(2)ClZrCl (1, 2) (Cp = C(5)Me(4)) have been characterized by elemental analysis and NMR ((1)H, (31)P and (1)H relaxation data). Complex 1, stabilized by Cl and H bridges, has been isolated from the room temperature reaction between RuH(2)(H(2))(PPh(3))(3) and (PMe(2)Cp)(2)ZrCl(2). The X-ray crystallographic study of 1 revealed a bimetallic complex. The six-coordinate Ru atom and the five-coordinate Zr atom are held together by two bifunctional phosphinocyclopentadienyl ligands and by H and Cl bridges. Crystal data for 1: monoclinic space group P2(1)/c, a = 13.901(2) ?, b = 18.205(6) ?, c = 16.633(3) ?, beta = 92.43(1) degrees, V = 4206 ?(3), Z = 4, d(calc) = 1.472 g cm(-)(3), R(F) = 0.056, R(w)(F) = 0.058. Complex 2 with two H bridges and terminal Cl ligands at Ru and Zr has been obtained by an irreversible isomerization of 1 in the presence of HNEt(3)BPh(4). This transformation has been proposed to occur through slow protonation of one of the phosphorus ligands with the five-coordinate Ru center formed by undergoing rapid pseudorotation. Complexes 1 and 2 do not react with H(2), N(2), or 3,3-dimethyl-but-1-ene. Treatment of 1 with 1 equiv of NaHBEt(3) in C(6)D(6) gives a mixture of new trihydrides (PPh(3))HRu(&mgr;-Cl)(&mgr;-H)(&mgr;-PMe(2)Cp)(2)ZrH (3) and (PPh(3))HRu(&mgr;-H)(2)(&mgr;-PMe(2)Cp)(2)ZrCl (4). Complex 3 transforms to 4 upon standing in solution for a period of several days. Under the same conditions, complex 2 leads smoothly to trihydride 4. Both trihydrides are new and have been characterized by (1)H, (31)P NMR, and (1)H NMR relaxation data. Complexes 1 and 4 are fluxional in solution at room temperature, showing hydride exchange between the terminal and bridging positions. The variable-temperature (1)H NMR spectra allowed determinations of the DeltaG() values of 16.4 (313 K, THF-d(8)) and 13.5 kcal/mol (295 K, toluene-d(8)) for the exchange in complexes 1 and 4, respectively. Possible exchange mechanisms have been discussed. Complex 2 is rigid on the NMR time scale.     

A Nearly Linear Single Hydroxo Bridge. Synthesis, Structure, and Magnetic Susceptibility of (&mgr;-Hydroxo)bis((tetraphenylporphinato)manganese(III)) Perchlorate

The synthesis, X-ray structure, and magnetic susceptibility characterization of a hydroxo-bridged complex, (&mgr;-hydroxo)bis((tetraphenylporphinato)manganese(III)) perchlorate, {[Mn-(TPP)](2)(OH)}ClO(4), are described. The complex is readily prepared by a controlled hydrolysis of monomeric diaquo(tetraphenylporphinato)manganese(III) perchlorate. Interestingly, the bridging hydroxo complex appears to be more stable than the putative &mgr;-oxo complex in halocarbon solvents. The X-ray structure determination shows a complex in which two five-coordinate manganese(III) ions are bridged by a single hydroxo ligand with an average Mn-O distance of 2.026(1) ? and a Mn-O(H)-Mn bridge angle of 160.4(8) degrees. The two porphyrin planes are nearly coplanar, and the two metal ions are separated by 3.993 ?. The average Mn-N(P) distance is 2.008(7) ?. The two manganese ions are displaced by 0.19 and 0.20 ? from their respective 24-atom mean planes. Both of the two porphyrin rings are moderately S(4) ruffled and have a near-staggered orientation (the N-Mn-Mn'-N' dihedral angle is 29.9 degrees ). The four inter-ring pairs of meso-phenyl groups of the binuclear cation are extremely crowded, with a nearly perpendicular orientation for each pair. The solid-state magnetic susceptibility was measured over the temperature range 2-300 K. The observed behavior is typical of an exchange-coupled binuclear complex. The data were fit to the total spin Hamiltonian (H(tot) = H(1) + H(2) - 2J&Svector;(1).&Svector;(2)) of a zero-field-split, high-spin d(4)-d(4) dimer in its actual crystallographic geometry, using numerical techniques. The hydroxide bridge supports a relatively strong antiferromagnetic coupling (2J = -74.0 cm(-1)) between two zero-field-split (D = -10.8 cm(-1)) manganese(III) ions. Crystal data: a = 16.807(7) ?, b = 17.061(6) ?, c = 17.191(5) ?, alpha = 85.64(3) degrees, beta = 79.75(3) degrees, gamma = 61.95(2) degrees, triclinic, space group P&onemacr;, V = 4281(3) ?(3), Z = 2, R(1) = 0.0707 for 14 802 observed data based on F(o) >/= 4.0sigma(F(o)), R(2w) = 0.2007 for 21 696 total unique data, least-squares refinement on F(2) using all data.     

1,2‐Di­cyano‐1,2‐bis­(imidazolidine‐2‐thione)­digold(I) and 2,2‐di­cyano‐1,1‐bis­(di­methyl­thio­urea)­digold(I)

Gold(I) cyanide forms complexes with imidazolidine‐2‐thione (etu) and di­methyl­thio­urea (dmtu) with the formula [Au₂(CN)₂L₂], i.e. the title complexes di­cyano‐1κC,2κC‐bis(imidazolidine‐2‐thione)‐1κS,2κS‐digold(I)(Au—Au), [Au₂(CN)₂(C₃H₆N₂S)₂], and di­cyano‐1κ²C‐bis(N,N′‐di­methyl­thio­urea)‐2κ²S‐digold(I)(Au—Au), [Au₂(CN)₂(C₃H₈N₂S)₂]. In the etu complex, two approximately linear (etu)AuCN groups are held together by a weak homopolar Au—Au bond [3.117 (1) Å], with a torsion angle of 61 (3)° between the two groups. In the dmtu complex, an approximately linear Au(dmtu)₂ group is bound to an approximately linear Au(CN)₂ group by a weak heteropolar Au—Au bond [3.091 (1) Å], with a torsion angle of 83 (5)° between the two groups.     

Diheterocyclic compounds from dithiocarbamates and derivatives thereof. I. 2,2′-(arylenediamino)bisbenzoazoles, 2,2′-(arylenediamino)bis(imidazopyridines) and 8,8′-(arylenediamino)bispurines

A general method for the synthesis of the title compounds 5, 6, 10, 14, 15 and 16 is reported. All of them were prepared in one step from readily available dimethyl N,N'-(arylene)bisdithiocarbamates 1 and red mercury(II) oxide. The superiority of these reagents over the corresponding diisothiocyanates 7 and the synthetic utility of tetramethyl N,N'-(arylene)bisdithiocarbonimidates 2 are also discussed.