Bradley W. Smucker

Reactivity studies of 2,3,5,6-Tetra(2-pyridyl) pyrazine (tppz) with first-row transition metal ions

Reactions of 2,3,5,6-tetra(2-pyridyl) pyrazine (tppz) with [ML 6 ][X] 2 (L = CH 3 CN, H 2 O; X = [BF 4 ] - , [ClO 4 ] - , [NO 3 ] - [BArF] - (BArF - B[3.5-C 6 H 3 (CF 3 ) 2 ] 4 ) lead to the high-yield formation of mononuclear [M(tppz) 2 ] 2 + , (M = Mn I I , Fe I I , Co I I , and Ni I I ) and dinuclear [Ni 2 (tppz)(CH 3 CN) 6 ] 4 + species. The new compounds were fully characterized by X-ray crystallographic, spectroscopic, and magnetic susceptibility measurements. Surprisingly, the 2:1 M:tppz reactions did not lead to isolation of the dinuclear species except in the case of Ni(II). It was further noted that even in the case of the Ni reactions, the nuclearity of the product depends on the choice of anions and the reaction conditions. Magnetic measurements of the mononuclear species [Co(tppz) 2 ] 2 + revealed thermally induced spin-crossover behavior from a high-spin S = 3/2 at higher temperatures to a low-spin S = ½ complex at lower temperatures. The dinuclear compound [Ni 2 (tppz)(CH 3 CN) 6 ] 4 + exhibits a weak antiferromagnetic interaction through the bridging tppz ligand.

Tetra­pyrazine­platinum(II) bis­(tetra­fluoro­borate) acetonitrile hemisolvate

The improved synthesis and characterization of tetrapyrazineplatinum(II) bis(tetrafluoroborate) acetonitrile hemisolvate, [Pt(C4H4N2)4](BF4)2·0.5CH3CN, is reported. The unit cell contains a half equivalent of an acetonitrile solvent molecule per tetrapyrazineplatinum(II) ion. The coordination geometry of the PtII ion is almost square-planar, with the Pt atom residing on an inversion center. The BF4 − counter-anion, located at a general position, has an idealized tetrahedral geometry and an acetonitrile solvent molecule, the methyl group of which is disordered over two equal positions, sits on a twofold rotation axis.

Crystal structure of bis­(aceto­nitrile-κN)(4,4′-di-tert-butyl-2,2′-bi­pyridine-κ2N,N′)platinum(II) bis­(tetra­fluorido­borate) packing as head-to-head dimers

The bulky tert-butyl groups of the dbbpy ligand do not preclude the formation of head-to-head dimers in the crystal structure of bis(acetonitrile)(4,4′-di-tert-butyl-2,2′-bipyridine)platinum(II) tetrafluoridoborate.

trans-Dichloridotetra­pyrazine­ruthenium(II) dichloro­methane disolvate

In the title compound, [RuCl2(C4H4N2)4]·2CH2Cl2, the RuII atom occupies a position of 222 symmetry and the C atom of the solvent molecule occupies a site with twofold symmetry. The RuII atom has a slightly distorted octahedral geometry. The pyrazine rings are propeller-like and rotated 45.1 (1)° from the RuN4 plane. In the crystal, the complex and solvent molecules are bridged by weak C—H⋯N hydrogen bonds along the c axis. Weak intermolecular C—H⋯Cl contacts link the complexes in the ab plane, forming a network.

Chlorido(4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine)platinum(II) chloride toluene monosolvate

In the title compound, [PtCl(C27H35N3)]Cl·C7H8, the PtII atom is coordinated in a pseudo-square-planar fashion by the N atoms of a 4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridine (tbtrpy) ligand and a Cl atom. The Pt—N distance of the N atom on the central pyridine is 1.941 (4) Å, while the peripheral N atoms have Pt—N distances of 2.015 (4) and 2.013 (4) Å. The Pt—Cl bond distance is 2.3070 (10) Å. The cations pack as dimers in a head-to-tail orientation with an intermolecular Pt⋯Pt distance of 3.2774 (3) Å and Pt⋯N distances of 3.599 (4), 3.791 (4) and 4.115 (4) Å. The solvent molecule is disordered and occupies two positions with a ratio of 0.553 (6):0.447 (6).

Chlorido(4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridine)­platinum(II) tetra­fluorido­borate

In the title compound, [PtCl(C27H35N3)]BF4, the PtII atom is in a pseudo-square-planar coordination, which is typical of Pt–terpyridine complexes. The Pt—Cl bond distance is 2.2998 (7) Å. The Pt—N distance of the N atom on the central pyridine is 1.931 (2) Å, while the peripheral N atoms have Pt—N distances of 2.018 (2) and 2.022 (2) Å. The cations pack as dimers in a head-to-tail orientation with an intermolecular Pt⋯Pt distance of 3.5214 (2) Å and Pt⋯N distances of 3.527 (2), 3.873 (2) and 4.532 (2) Å. In the crystal, cations and anions are linked by weak C—H⋯F hydrogen-bonding interactions.

A new ‘hybrid’ molecular square composed of alternating multiply-bonded dinuclear and mononuclear corners

The incorporation of both dinuclear (M2) and mononuclear (M′) units into molecular squares has been achieved by reacting a triply bonded Re2(II,II) complex that possesses two cis isonicotinate donor ligands with Pt(II) molecules that contain substitutionally labile cis triflate groups.