Transition metals squarate complexes

The structures of transition-metal squarate complexes consist of one-dimensional metal squarate chains interlinked by hydrogen bonding. These complexes could be possible precursors to low dimensional polymeric electrical conductors... 

The decompositions of selected transition metal squarates (MC4O4) were identified as being of interest because they contain a fiirther organic anion that, like the oxalates and mellitates, contains no hydrogen, so decreasing the complexity of product mixtures and secondary reactions. 

Squarate Complexes of Heavier Transition Metals and Lanthanides The Squarate Ion as a Linking Group Spectroscopy of Squarate Complexes Luminescence Studies Electrochemistry... 

Fig. 13. The simple /i-1,3-bridging by the squarate ion of a pair of transition metal complexes in the structure of [(/a2-squarato-0,0 )-bis(aqua-bromo-(2,2 -bipyridyl-i JV )-copper(II)] 44).

E. Squarate Complexes of Heavier Transition Metals and Lanthanides... 

Although there are several examples of lanthanide complexes with the squarate ion 42, 55, 57), only a few squarate complexes of second-and third-row transition metals have been reported. The platinum and... 

Infrared and UV/vis data have been used by several authors to identify the C=C, C=0, and M—O stretches in the complexes synthesized 15, 18-21, 37, 38, 41, 44, 50, 54, 56, 58, 59, 64-66, 69, 74, 78, 80, 82, 103). Except in the initial research on first-row transition metal complexes of squaric acid, where these data were used in proposing structures, IR and UV/vis analysis have been used as supporting evidence for the particular coordination mode of the ligand 19,21,22, 45, 52, 59, 65). Infrared spectroscopy has also been utilized in the study of mixed oxalate/squarate complexes 118), although not to the same extent as in complexes of the oxalate ion. For example, Scott et al. studied the IR properties of Co(III) oxalate complexes with the hgand in a variety of chelating/bridging situations 119). 

Squarate compounds with transition metal ions are rarely described in the chemical literature. For example, the crystal structure of cis-bis(dicyanomethylene) squarate 27 in a complex with Cu(I) has been reported [48b]. Galibert and collaborators synthesized a complex of Cu(II) with fraws-bis(dicyanomethylene) squarate 26 [86]. The pseudo-oxocarbon ring in this complex was found to be planar. However, a significant deviation of the cyano groups from the best plane formed by the ring contributes to the diminished planarity of the complex, a phenomenon that is also reflected by the loss of Jt-delocalization in the ring. 

Copper is the only transition metal cited in the literature that has been utilized for the complexation with trans- and cis-dianions, 26 and 27, respectively. In a study by our research group, two more crystal structures of new complexes with transition metals have been synthesized. The structures of these new complexes were characterized by various spectroscopic techniques and by single-crystal X-ray diffraction [84]. Figure 5.9 shows the crystal structures of the coordination compounds of tr s-bis(dicyanemethylene) squarate 26 with the Zn(II) and Co(II) metals, respectively. The zinc complex belongs to the P2 c spatial monoclinic group [86, 87]. The zinc complex is isostructural with the... 

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