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Alkali Metal (Li+,Cs+) Salts with Hexafluorochromate(V), Hexafluorochromate(IV), Pentafluorochromate(IV), and Undecafluorodichromate(IV) Anions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2008
Zoran Mazej
Abstract The compounds ACrF6 (A = Li,Cs) were prepared by photochemical reactions of AF/CrF3 mixtures in anhydrous HF with elemental F2 at ambient temperature. The crystal structures of compounds ACrF6 (A = K,Cs) are analogous to that of KOsF6, and NaCrF6 exhibits polymorphism. The trigonal phase (II) can be classified to have the well-known LiSbF6 type of structure, while the crystal structure of the orthorhombic modification (I) appears to be a new structure-type. Thermal decomposition of the ACrF6 salts produce ACrF5(A = Rb, Cs), ACrF5/A2CrF6 (A = K), or A2CrF6 (A = Li, Na). These compounds undergo partial solvolysis in anhydrous HF with precipitation of CrF4. From the remaining solutions of the [CrF6]2, anions and dissolved AF (A = Li,Cs), single crystals of ACrF5 (A = K,Cs), A2CrF6·2HF (A = Na, K), A2CrF6·4HF (A = Rb, Cs), Li2CrF6, and K3Cr2F11·2HF were grown, and their crystal structures determined. The main structural feature of the ACrF5 compounds is the infinite zig-zag [CrF5]nn, chain of distorted [CrF6] octahedra joined by cis vertices. The crystal structures of A2CrF6·2HF (A = Na, K) and A2CrF6·4HF (A = Rb, Cs) consist of distorted [CrF6]2, octahedra involved in moderate to strong hydrogen bonding with HF molecules, while two A+ cations compensate the negative charge of each octahedron. In Na2CrF6·2HF, two neighboring HF molecules are involved in moderate to strong hydrogen bonding with each other. (HF)2 dimers with a parallelogram structure are formed. The mutual interactions in the crystal structure of K2CrF6·2HF differ from those found in Na2CrF6·2HF. In the former, each HF molecule interacts with the [CrF6]2, anion and three K+ cations. A2CrF6·4HF compounds of Rb and Cs are isostructural. Their structures consist of A+ cations and [CrF6]2, anions involved in hydrogen bonding with two sets of HF molecules in the trans position. The crystal structure of K3Cr2F11·2HF reveals a rare case of the [M2F11]3, anion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Oxovanadium(IV) Complexes with Pyrazinecarboxylic Acids:The Coordinating Properties of Ligands with the (Naromatic, COO,) Donor Set

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2006
Eugenio Garribba
Abstract Complex formation between the VIVO ion and four pyrazine derivatives, 2-pyrazinecarboxylic acid (pzc), 5-methyl-2-pyrazinecarboxylic acid (5-Mepzc), 2,3-pyrazinedicarboxylic acid (3-COOHpzc) and 5-hydroxy-2-pyrazinecarboxylic acid (5-OHpzc), was studied in aqueous solution and in the solid state through the combined application of potentiometric and spectroscopic (EPR and FT-IR) techniques. The results indicate that in acidic and neutral aqueous solution all theligands form mono(chelated), bis(chelated) and dinuclear species of composition VOL, VOL2 and (VO)2L2H,2. Hexacoordinated VOL2 complexes are characterised by a cis/trans isomerism, where cis and trans are the species with a water molecule bound in the cis or trans position with respect to the V=O group. The trans arrangement is favoured over the cis arrangement. Three solid derivatives, [VO(5-Mepzc)2] (1), cis -[VO(pzc)2(H2O)] (2) and cis -[VO(3-COOHpzc)2(H2O)] (3), were isolated and characterised. Based on the experimental results and on the data in the literature, the stability of cis and trans isomers in aqueous solution and in the solid state has been discussed, showing that with ligands of comparable basicity and size of the chelate ring the hydrophilicity favours the cis species and determines the relative amount of the two isomers. The analysis of the magnetic properties of the hydroxo-bridged VIVO dimers suggests that for the (VO)2L2H,2 species the anti -coplanar arrangement is realised. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Configuration of Octahedral Metal Compounds , Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms Ligands

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004
Aminou Mohamadou
Abstract Two new nickel(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X-ray crystallography and ligand-field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position; all Ni,N and Ni,O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni,N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Synthesis and Structure of the First Non-Metallocene TiIII Fluoride Complex LTiF2·2Me3SnCl Supported by a ,-Diketiminato Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2003
Grigori B. Nikiforov
Abstract The TiIII dichloride complex LTiCl2 (1) and the first non-metallocene TiIII fluoride complex LTiF2·2Me3SnCl (2) supported by the ,-diketiminato ligand 2-{[2-(diethylamino)ethyl]amino}-4-{[2-(diethylamino)ethyl]imino}pent-2-ene have been synthesized. Elemental analysis, mass spectrometry and X-ray structural analysis show that 1 is monomeric, neutral, and free of solvent and lithium salt. The complex adopts a pseudo-octahedral geometry with the two chlorine atoms arranged in trans position to each other. Compound 1 is soluble in common organic solvents and thermally surprisingly robust. Complex 2 was prepared using Me3SnF as a fluorinating agent. X-ray structural analysis revealed that complex 2 consists of the LTiF2 unit and two molecules of Me3SnCl coordinated through a fluorine bridge to the titanium center. The fluorine atoms in 2 are located in trans positions to each other and the geometry around the titanium atom is distorted octahedral. Elemental analysis and mass spectrometry proved that 2 releases the coordinated Me3SnCl under vacuum or during sublimation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

15N NMR coordination shifts in Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with pyridine, 2,2,-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2,-biquinoline, 2,2,:6,, 2,-terpyridine and their alkyl or aryl derivatives

MAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2008
Leszek Pazderski
Abstract The 15N NMR data for 105 complexes of Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with simple azines such as pyridine, 2,2,-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2,-biquinoline, 2,2':6', 2"-terpyridine and their alkyl or aryl derivatives have been reviewed. The 15N NMR coordination shifts, i.e. the differences between the 15N chemical shifts of the same nitrogen in the molecules of the complex and the ligand (,15Ncoord = ,15Ncompl , ,15Nlig), have been related to some structural features of the reviewed coordination compounds, like the type of the central ion and the character of auxiliary ligands (mainly in trans position). These ,15Ncoord parameters are negative, their absolute magnitudes (ca 30,150 ppm) generally increasing in the metal order Au(III) < Pd(II) < Pt(II) and Rh(III) < Co(III) < Pt(IV) < Ir(III), as well as with the enhanced trans influence of the other donor atoms (H, C , Cl < N). Copyright © 2008 John Wiley & Sons, Ltd. [source]

Analysis of quinazoline and pyrido[2,3- d]pyrimidine N9,C10 reversed-bridge antifolates in complex with NADP+ and Pneumocystis carinii dihydrofolate reductase

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2002
Vivian Cody
Structural studies of two ternary complexes of Pneumocystis carinii dihydrofolate reductase (pcDHFR) with the cofactor NADP+ and potent antifolates, the N9,C10 reversed-bridge inhibitor 2,4-diamino-6-[N -(2,,5,-dimethoxybenzyl)- N -methyl­amino]quinazoline (1) and its 3,,5,-dimethoxypyrido[2,3- d]pyrimidine analog (2), were carried out. Data for the monoclinic crystals were refined to 1.90,Å resolution for the complex with (1) (R = 0.178) and to 2.1,Å resolution for the complex with (2) (R = 0.193). The effect of the N9,C10 reversed-bridge geometry is to distort the bridge from coplanarity with the pyrido[2,3- d]pyrimidine or quinazoline ring system and to twist the C10 methylene conformation toward a gauche conformation. This change also influences the conformation of the methoxybenzyl ring, moving it away from a trans position. This change places the 5,-methoxy group deeper within the hydrophobic pocket made by Ile65, Pro66 and Phe69 of the pcDHFR active site. These results also revealed the first observation of an unusual conformation for the reversed-bridge geometry (C5,C6,N9,C10 torsion angle) in antifolate (2). The electron density is consistent with the presence of two models (conformers 2-1 and 2-2) that result from inversion of the geometry at N9. The four examples of N9,C10 reversed-bridge antifolates cluster in two conformations, with the structure of quinazoline (1) similar to that previously reported for its 2,,5,-dimethoxypyrido[2,3- d]pyrimidine analog (3). The two conformers of (2) differ from these and each other by a twisted-bridge geometry that results in the dimethoxybenzyl ring occupying the same conformational space. Conformer 2-2 also has the N9,C10 reversed bridge perpendicular to the pyrido[2,3- d]pyrimidine plane, in contrast to the gauche,trans conformation normally observed. As a result of these changes, the N9 methyl probes conformational space in the active site not normally occupied by antifolate structures. The N9 methyl of conformer 2-2 makes close contacts to the conserved Leu25 as well as the hydroxyl O atoms of the nicotinamide ribose and Ser64, whereas the other three reversed-bridge conformers make weak hydrophobic contacts with Ile123, Thr61 and Ile65. These antifolates are ten times more selective for pcDHFR than the C9,N10 bridge parent trimetrexate. However, pyrido[2,3- d]pyrimidines (2) and (3) are three times more selective for pcDHFR than quinazoline (1) is for rat liver DHFR. These data suggest that the loss of hydrogen-bonding interactions with N8 is more important to potency than the interactions of the methoxybenzyl substituents. [source]

Leucine Side-Chain Conformation and Dynamics in Proteins from 13C NMR Chemical Shifts

CHEMBIOCHEM, Issue 9 2009
Frans A. A. Mulder Dr.
Abstract Look to the left: The carbon nucleus of a substituent in the gauche position about a subtending dihedral angle experiences an NMR chemical shift of about 5 ppm relative to the same chemical group present in the trans position. We demonstrate that this ",-gauche effect" can be utilized to determine the conformation and extent of rotameric averaging for leucine amino acid side chains in the protein calbindin D9k. The success of this approach suggests that rules can be established to define the orientation of other side chains in proteins as well, offering an easy gauge of protein side-chain flexibility, as well as avenues to advance protein structure determination by using side-chain chemical shifts. [source]

Pincer-Type Heck Catalysts and Mechanisms Based on PdIV Intermediates: A Computational Study

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2010
Olivier Blacque Dr.
Abstract Pincer-type palladium complexes are among the most active Heck catalysts. Due to their exceptionally high thermal stability and the fact that they contain PdII centers, controversial PdII/PdIV cycles have been often proposed as potential catalytic mechanisms. However, pincer-type PdIV intermediates have never been experimentally observed, and computational studies to support the proposed PdII/PdIV mechanisms with pincer-type catalysts have never been carried out. In this computational study the feasibility of potential catalytic cycles involving PdIV intermediates was explored. Density functional calculations were performed on experimentally applied aminophosphine-, phosphine-, and phosphite-based pincer-type Heck catalysts with styrene and phenyl bromide as substrates and (E)-stilbene as coupling product. The potential-energy surfaces were calculated in dimethylformamide (DMF) as solvent and demonstrate that PdII/PdIV mechanisms are thermally accessible and thus a true alternative to formation of palladium nanoparticles. Initial reaction steps of the lowest energy path of the catalytic cycle of the Heck reaction include dissociation of the chloride ligands from the neutral pincer complexes [{2,6-C6H3(XPR2)2}Pd(Cl)] [X=NH, R=piperidinyl (1,a); X=O, R=piperidinyl (1,b); X=O, R=iPr (1,c); X=CH2, R=iPr (1,d)] to yield cationic, three-coordinate, T-shaped 14e, palladium intermediates of type [{2,6-C6H3(XPR2)2}Pd]+ (2). An alternative reaction path to generate complexes of type 2 (relevant for electron-poor pincer complexes) includes initial coordination of styrene to 1 to yield styrene adducts [{2,6-C6H3(XPR2)2}Pd(Cl)(CH2CHPh)] (4) and consecutive dissociation of the chloride ligand to yield cationic square-planar styrene complexes [{2,6-C6H3(XPR2)2}Pd(CH2CHPh)]+ (6) and styrene. Cationic styrene adducts of type 6 were additionally found to be the resting states of the catalytic reaction. However, oxidative addition of phenyl bromide to 2 result in pentacoordinate PdIV complexes of type [{2,6-C6H3(XPR2)2}Pd(Br)(C6H5)]+ (11), which subsequently coordinate styrene (in trans position relative to the phenyl unit of the pincer cores) to yield hexacoordinate phenyl styrene complexes [{2,6-C6H3(XPR2)2}Pd(Br)(C6H5)(CH2CHPh)]+ (12). Migration of the phenyl ligand to the olefinic bond gives cationic, pentacoordinate phenylethenyl complexes [{2,6-C6H3(XPR2)2}Pd(Br)(CHPhCH2Ph)]+ (13). Subsequent ,-hydride elimination induces direct HBr liberation to yield cationic, square-planar (E)-stilbene complexes with general formula [{2,6-C6H3(XPR2)2}Pd(CHPhCHPh)]+ (14). Subsequent liberation of (E)-stilbene closes the catalytic cycle. [source]

Compressed Octahedral Coordination in Chain Compounds Containing Divalent Copper: Structure and Magnetic Properties of CuFAsF6 and CsCuAlF6

CHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2004
Zoran Mazej Dr.
Abstract Crystal structures and magnetic investigations of CuFAsF6 and CsCuAlF6 are reported. Together with KCuAlF6, these appear to be the only examples of Jahn,Teller pure CuII compounds containing only one type of ligand that exhibits a compressed octahedral coordination geometry. The Rietveld method has been used for refining the CsCuAlF6 structure based on neutron powder diffraction data at 4 K. The compound crystallizes in space group Pnma (no. 62) with a=7.055(1), b=7.112(1), c=10.153(1) Å and Z=4 at 4 K. The structure is built from infinite [CuF5]n3n, chains of [CuF6]4, octahedra running along the [1,0,0] direction and (AlF6)3, octahedra connected by corners in the trans position, thus giving rise to chains oriented along the [0,1,0] direction. Single crystals of CuFAsF6 were prepared under solvothermal conditions in AsF5 above its critical temperature. The structure was determined from single-crystal data. CuFAsF6 crystallises in the orthorhombic space group Imma (No. 74) with a=10.732(5), b=6.941(3), c=6.814(3) Å and Z=4 at 200 K. The structure can also be described in terms of one-dimensional infinite [CuF5]n3n, chains of tilted [CuF6]4, octahedra linked by trans -vertices running along the b axis. The [CuF5]n3n, chains are connected through [AsF6], units sharing joint vertices. The compressed octahedral coordination of CuII atoms in CuFAsF6 and CsCuAlF6 compounds at room temperature is confirmed by Cu K-edge EXAFS (extended x-ray absorption fine structure) analysis. For both compounds strong antiferromagnetic interactions within the [CuF5]n3n, chains were observed (,p=,290±10 K and ,p=,390±10 K for CuFAsF6 and CsCuAlF6, respectively). The peculiar magnetic behaviour of chain compounds containing divalent copper at low temperature could be related to uncompensated magnetic moments in the one-dimensional network. [source]

Configuration of Octahedral Metal Compounds , Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms Ligands

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004
Aminou Mohamadou
Abstract Two new nickel(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X-ray crystallography and ligand-field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position; all Ni,N and Ni,O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni,N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Synthesis and Structure of the First Non-Metallocene TiIII Fluoride Complex LTiF2·2Me3SnCl Supported by a ,-Diketiminato Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2003
Grigori B. Nikiforov
Abstract The TiIII dichloride complex LTiCl2 (1) and the first non-metallocene TiIII fluoride complex LTiF2·2Me3SnCl (2) supported by the ,-diketiminato ligand 2-{[2-(diethylamino)ethyl]amino}-4-{[2-(diethylamino)ethyl]imino}pent-2-ene have been synthesized. Elemental analysis, mass spectrometry and X-ray structural analysis show that 1 is monomeric, neutral, and free of solvent and lithium salt. The complex adopts a pseudo-octahedral geometry with the two chlorine atoms arranged in trans position to each other. Compound 1 is soluble in common organic solvents and thermally surprisingly robust. Complex 2 was prepared using Me3SnF as a fluorinating agent. X-ray structural analysis revealed that complex 2 consists of the LTiF2 unit and two molecules of Me3SnCl coordinated through a fluorine bridge to the titanium center. The fluorine atoms in 2 are located in trans positions to each other and the geometry around the titanium atom is distorted octahedral. Elemental analysis and mass spectrometry proved that 2 releases the coordinated Me3SnCl under vacuum or during sublimation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

The layered compound poly[,2 -4,4,-bipyridyl-di-,2 -chlorido-mercury(II)]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2007
Yi-Ming Xie
The title compound, [HgCl2(C10H8N2)]n, features two-dimensional [HgCl2(4,4,-bipy)]n neutral networks (4,4,-bipy is 4,4,-bipyridine), based on an octahedral Hg atom coordinated by four ,2 -Cl atoms and two ,2 -4,4,-bipy ligands in trans positions, yielding a HgCl4N2 octahedron. The structure has mmm symmetry about the Hg atoms, with most of the atoms on at least one mirror plane, but the unsubstituted C atoms of the 4,4,-bipy rings are disordered across a mirror plane. Photoluminescent investigations reveal that the title compound displays a strong emission in the green region, which probably originates from a ligand-to-ligand charge-transfer transition. [source]

One-dimensional structure of catena -poly[tetra­ethyl­ammonium [tetra­cyano­iron(III)-,-cyano-[bis­(ethyl­ene­diamine)­cadmium(II)]-,-cyano] tetra­hydrate]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2006
Werner Massa
The title compound, {(C8H20N)[CdFe(CN)6(C2H8N2)2]·4H2O}n, was isolated from the aqueous system Cd2+/ethyl­ene­diamine (en)/[Fe(CN)6]3, in the presence of [Et4N]Br. The crystal structure is dominated by a one-dimensional motif, viz. a negatively charged 2,2-CT (cis,trans) [,Cd(en)2,NC,Fe(CN)4,CN,]nn, chain. The Cd and Fe atoms of the anion and the N atom of the cation all lie on twofold axes. The ethyl groups of the cation are equally disordered over two orientations. The cationic building block of the chain consists of a CdII atom coordinated by two chelating en ligands, and the distorted octa­hedral coordination is completed by two bridging cyano ligands in cis positions. The anionic building block is an [Fe(CN)6]3, anion in which the FeIII atom is octa­hedrally coordinated by six cyano ligands; two of the cyano ligands, in trans positions, are bridging. The uncoordinated water mol­ecules link neighbouring chains through O,H,N and N,H,O hydrogen bonds. [source]

Crystallographic report: A synthetic precursor for hetero-binuclear metal complexes, [Ru(bpy)(dppy)2(CO)2](PF6)2 (bpy = 2,2,-bipyridine, dppy = 2-(diphenylphosphino)pyridine)

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2004
Dai Ooyama
Abstract In the title complex, [Ru(bpy)(dppy)2(CO)2](PF6)2 (bpy = 2,2,-bipyridine, dppy = 2-(diphenylphosphino)pyridine), the ruthenium atom exhibits a slightly distorted octahedral coordination with the carbonyl ligands in cis positions. In addition, two dppy ligands coordinate to the ruthenium center through the phosphorus atoms in mutually trans positions and two pyridyl nitrogen atoms of the dppy direct toward two carbonyl ligands. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Ni(bipy)2Ni(CN)4, a new type of one-dimensional square tetra­cyano complex

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2000
Juraj, ernák
The one-dimensional structure of catena -poly­[[bis(2,2,-bi­pyri­dyl-1,2N,N,)-,-cyano-1:2,2N:C -di­cyano-2,2C -di­nickel(II)]-,-cyano- C:N], [Ni2(CN)4(C10H8N2)2]n, consists of infinite zigzag chains running parallel to the c axis. The chains are composed of paramagnetic [Ni(bipy)2]2+ cations (bricks; nickel on a twofold axis) linked by diamagnetic [Ni(CN)4]2, anions (mortar; nickel on an inversion center) via bridging cyano groups. The bridging cyano groups occupy cis positions in the cation and trans positions in the anion, giving rise to a new previously unknown CT-type chain (i.e. cis,trans -type) among square tetra­cyano complexes. The coordination polyhedron of the paramagnetic Ni atom (twofold symmetry) is a slightly deformed octahedron with the two Ni,N(bipy) bonds in cis positions being somewhat longer [2.112,(3),Å] than the remaining four Ni,N bonds with a mean value of 2.065,(6),Å. The bond distances and angles in the anion have typical values. [source]