Crystal structure of diaqua-bis(pyridine)-μ2-squarato(1,3)-nickel(II), Ni(C4O4)(C5H5N)2(H2O)2

Abstract

C14H14N2NiO6, orthorhombic, Pbca (No. 61), a = 7.914(1) Å, b = 12.020(2) Å, c = 15.718(3) Å, V = 1495.3 Å3, Z = 4, Rgt(F) = 0.026, wRref(F2) = 0.062, T = 293 K.

μ‐1,3‐ (trans) and μ‐1,2‐ (cis) Bonding in Squarato‐Bridged Dinuclear Copper(II) and Nickel(II) Complexes Derived from Polypyridyl Amines

“…The presence of four donor oxygen atoms and the richness of the electron density on the squarate dianion enhance its capability to simultaneously bind more than one metal ion, hence acting as a bridging ligand. The bridging squarato ligand affords three types of coordination modes known as µ-1,3-(trans), [2][3][4]6,16,22] µ-1,2-(cis), [2,5,8,9,13,14,16,18] and µ- ronment in 2 is achieved by the three N-atoms of the MeDPA ligand, by an oxygen atom of a bridging squarato ligand and, at longest distances, by two oxygen atoms from coordinated water molecules. In the nickel complex 3, the geometry is attained by the four N-atoms of TPA and by two oxygen atoms supplied by a coordinated water molecule and by a bridging squarato ligand.…”

Synthesis and Spectrothermal Studies of Thermochromic Diamine Complexes of Cobalt(III), Nickel(II) and Copper(II) Squarate. Crystal Structure of [Co(en)3](sq)1.5 · 6H2O

“…Squaric acid, H 2 C 4 O 4 [3,4-dihydroxycyclobut-3-ene-1,2-dione, sq, Figure 1a], has been of much interest because of its cyclic structure, and possible aromaticity and coordination chemistry of the squarate ligand has been investigated in some detail [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], which suggests that it may act as a monodentate or bridging ligand, since, the squarate anion has a very good ligating property and in some transition metal complexes, squaric acid acts as a counter ion [50][51][52][53][54][55]. Solid state thermal studies of several metal squarate and mixed ligand-metal squarate complexes have been reported, indicating a high thermal stability of the squarate moiety [10,[26][27][28]56].…”

A novel 1-D coordination Cu(II) polymer with alternating μ1,3-squarato and binucleating polypyridylamine bridges

“…The coordination geometry around the Cu(II) centers is a five-coordinate with a slightly distorted square pyramidal environment which is achieved by the three N-donor atoms of each arm of the ligand L, an oxygen atom of the bridging squarato moiety and by an oxygen atom of the ClO À 4 anion. The complex shows antiferromagnetic coupling between the squarato-bridged Cu(II) ions with J = À6.3 cm À1 .Ó 2009 Elsevier B.V. All rights reserved.The squarate dianion, C 4 O 2À 4 (3,4-dihydroxycyclobut-3-ene-1,2-dionate) is a very well known ligand that is capable of binding more than one metal ion at the same time leading to a variety of coordination modes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] where four types were recognized known as l-1,3-(trans) [1,3-6], l-1,2-(cis) [1,3,7-11], l-1,2,3-and l-1,2,3,4- [2,[12][13][14]. It has been pointed out that the ligand does not generally act as a bis-bidentate linker for the first raw divalent transition metal ions because of its very large bite angle relative to that observed in the oxalate dianion [15].…”

“…It has been pointed out that the ligand does not generally act as a bis-bidentate linker for the first raw divalent transition metal ions because of its very large bite angle relative to that observed in the oxalate dianion [15]. The geometrical and the structural nature of the coligands coordinated to the central metal ion are considered to be the major factors that determine the bonding modes in the squarato-bridged-M II complexes where the intradimer distances between the metal centers vary from ca 5 Å A 0 in the cis, l-1,2-bonding to 8 Å A 0 in the trans, l-1,3-bonding [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In general, the dinuclear squarato-bridged Cu(II) complexes exhibit weak antiferromagnetic interaction with the singlet-triplet exchange constant, |J| values in the range 0-26 cm À1 .…”

“…In general, the dinuclear squarato-bridged Cu(II) complexes exhibit weak antiferromagnetic interaction with the singlet-triplet exchange constant, |J| values in the range 0-26 cm À1 . The failure of the squarato dianion to promote more significant magnetic coupling in these complexes was attributed to the stabilization of the ligand orbitals by the large p-delocalization associated with the squarate ring [20].Polymeric structures via bridged-squarato l-1,2-and l-1,3-coordination have also been reported but the number of these compounds is very small compared to the corresponding dinuclear species [6,8,[16][17][18][19]5,21,22]. It has been noticed that most of the squarato coordination polymers required the incorporation of another bridging ligand such as pyrazine [21], 4,4 0 -bipyridine [22], imidazole [16] or oxalate [18].…”