One-dimensional metal string complexes

Recent developments in the d-block metallo-supramolecular chemistry of polypyridyls

In previous reports, the extension of dinuclear metal complexes10-12 to metal string complexes supported by oligoRpyridylamino ligands was focused on the trinuclear [M 3(μ3dpa)4X2] (M ) Cr,2 Co,3,4 Ni,5 Cu,6 Rh,7 Ru;7 dpa) dipyridylamido anion) and pentanuclear [M 5(μ5-tpda)4X2] (M ) Co, Ni)8,9 complexes. Here we report two new types of metal string complexes; one contains an even number of the metal in a string of ligand I [Ni 4(μ4-phdpda) 4], and the other is an extension of the triand pentanickel(II) complexes to at this time the longest metal string of ligandIIb [Ni 7(μ7-teptra)4Cl2]. Ligand I was synthesized by the palladium-catalyzed crosscoupling1,13 of (6-bromo-2-pyridyl)(2′-pyridyl)amine and aniline with high yield.14 I was characterized on the basis of 1H and13C NMR spectroscopy and mass spectrometry. The nickel string complex of ligandI was synthesized by treating equimolar amounts of NiCl 2 andI in refluxing naphthalene and addingtBuOK as a base. The crude product was obtained by extraction using acetone and characterized by mass spectrometry (FAB) and X-ray diffraction. 15 The structure of [Ni 4(μ4phdpda) 4], obtained by X-ray single-crystal diffraction study, shows several features as shown in Figure 1. First, the tetranickel metal chain is helically wrapped by four syn-syn-syn type phdpda2ligands, with two phenyl groups positioned in cis conformation on one side and the other two cis phenyl groups positioned on the other side. Each of the four nickel(II) ions is bonded by two cis Npyridine and two cis Namido atoms. This arrangement may be the contributing factor to the stronger trans influence by Namido than that by Npyridine. Second, the four Ni(II) ions are collinear. The angles of Ni -Ni-Ni are nearly 180 °. The Ni-Ni distances are 2.3269(6), 2.3010(6), and 2.3280(6) Å, which are comparable with the inner Ni -Ni distance ( ∼2.30 Å) in [Ni5(μ5-tpda)4X2] complexes. 8,9 Third, the average Ni -N bonds are 1.924(4) Å for Ni(1) -N, 1.915(3) Å for Ni(2)-N, 1.913(3) Å for Ni(3)-N, and 1.927(4) Å for Ni(4) -N, comparable to the Ni-N distance found in the low-spin square-planar Ni(II) configuration and consistent with the diamagnetic behavior. 16

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Metal String Complexes: Synthesis and Crystal Structure of [Ni4(μ4-phdpda)4] and [Ni7(μ7-teptra)4Cl2] (H2phdpda = N-Phenyldipyridyldiamine and H3teptra = Tetrapyridyltriamine)

The synthesis and X-ray crystal structure of a linear unsymmetrical trinuclear cobalt(II) complex with a syn–syn bis(2-pyridyl)amido ligand, possessing a short, localized CoII–CoII bond and a spin crossover square-pyramidal CoII ion, is described.

Structure of a linear unsymmetrical trinuclear cobalt(II) complex with a localized COII–COII bond: dichlorotetrakis[µ3-bis(2-pyridyl)amido]tricobalt(II)

The synthesis, crystal structures, and magnetic properties of linear pentanuclear complexes, [Ni5(μ5-tpda)4X2]n+ [tpdaH2 = tripyridyldiamine, with different axial ligands X = Cl- (1), CN- (2), N3- (3), and NCS- (4) (n = 0) and CH3CN (5) (n = 2)], are reported. All of the [Ni5(tpda)4]2+ moieties are isostructral and involve a Ni5 linear chain unit with all of the ∠Ni−Ni−Ni being nearly 180°, terminated by the two axial ligands. The pentanuclear linear metal chain is helically wrapped by four syn−syn−syn−syn type tpda2- ligands. There are two types of Ni−Ni distances existing in these complexes. The terminal Ni−Ni distances bonded with the axial ligand are longer (2.35−2.40 A) and affected by various axial ligands. The inner Ni−Ni distances are very short and remain constant (∼2.30 A). The relationship between terminal Ni−Ni distances and properties of the axial ligands on 1−5 will be discussed. Two terminal Ni(II) ions bonded with the axial ligands are in a square-pyramidal (NiN4X) environment and exhibit ...

Synthesis, Crystal Structures, and Magnetic Properties of a Series of Linear Pentanickel(II) Complexes: [Ni(5)(m(5)-tpda)(4)X(2)] (X = Cl(-), CN(-), N(3)(-), NCS(-)) and [Ni(5)(m(5)-tpda)(4)(CH(3)CN)(2)]- (PF(6))(2) (tpda(2-) = the Tripyridyldiamido Dianion).

The crystal structure of [Ni3(bipyam–H)4Cl2]·023H2O·05(CH3)2CO 1[bipyam–H = bis(2-pyridyl)-amide] has been determined using X-ray diffractometer data; C415H355Cl2N12Ni3O075, monoclinic, space group C2/c, with a= 37525(7), b= 16237(3), c= 22550(6)A, β= 11012(2), Z= 12; 5778 measured and 5519 unique reflections gave a final R value of 0051 The structure involves two independent Ni3(bipyam–H)4Cl2 units, (1) and (2)[(1) occupies a general position and (2) is on a C2 axis], one non-co-ordinated water molecule [site occupation factor (sof) 023], and one acetone molecule (sof 05) The Ni3N12Cl2 chromophores of (1) and (2) involve a nearly linear Ni3 unit, mean Ni–Ni–Ni angle 1784(1)°, terminated by the two chloride anions The four separate bipyam–H ligands act as tridentate ligands, involving co-ordination to three separate nickel(II) ions with Ni–Ni distances 2443(1)(twice) and 2431(1)A for units (1) and (2), respectively If the Ni–Ni separations are ignored the central Ni atom in both units involves a four-co-ordinate rhombic coplanar NiN4 chromophore, generated by the four central amido nitrogens of the bipyam–H ligands The two terminal Ni atoms involve a square-based pyramidal NiN4Cl chromophore, involving the four pyridine nitrogens of the bipyam–H ligands and an axial Cl atom A dihedral angle of ca 54° is involved between the planes of the individual pyridine rings of each bipyam–H ligand and results in a spiral configuration in the Ni3(bipyam–H)4Cl2 unit The room-temperature magnetic moment µeff of compound 1 is 246, consistent with a diamagnetic central NiN4 chromophore and two paramagnetic terminal NiN4Cl chromophores The electronic spectrum involves a low-energy peak at 6500 cm–1, an intense peak at 17 700 cm–1, and a low-intensity shoulder at 10 800 cm–1, consistent with the two nickel(II) stereochemistries present

Sujittra Aduldecha

Papers

Crystal structure and electronic properties of tetrakis[µ3-bis(2-pyridyl)amido]dichlorotrinickel(II)–water–acetone (1/0.23/0.5)