Synthesis and structural properties of ylidenemalonatoplatinum(II) complexes

Subtle Ring Size Effects on Bonding Mode. Structures and Properties of Platinum(II) Complexes Involving Sulfur-Containing Dicarboxylate Ligands S−(CH2)n−S−CC(COO-)2 (n = 2, 3, 4)

“…All reactions were carried out under the same conditions. Only a single O,O′-chelate was obtained for the DTOYM in our previous work 11 and only a single O,S-chelate for DTAYM even prior to recrystallization. However, for the DTEYM complexes, (DACH)Pt(DTEYM) and (NH 3 ) 2 Pt(DTEYM), an isomeric mixture of O,S-and S,S′-chelates was afforded in the approximate mole ratios of 1:9 and 1:1, respectively, at the beginning of the preparative reaction, but the O,S-chelate isomerizes to the thermodynamically more stable S,S′-chelate on standing, which will be published separately.…”

“…A series of ylidenemalonates containing sulfur atoms have been used as fascinating multidentate ligands for platinum complexes in our laboratory. , These malonate-derivative ligands containing dithioether rings may coordinate to a platinum atom via one of three distinct modes of O,O‘-, O,S-, or S,S‘-chelation. Such a variety of chelation modes has stimulated our interest in understanding the coordination chemistry of platinum complexes.…”

The Layered Planar Structure of Barium 1,3-Dithiepan-2-ylidenemalonate

“…The two carboxylate groups of the present DTEYM ligand characteristically bond with five barium atoms in the following fashion: The dihedral angle between the two carboxylate planes in a DTEYM ligand is 74.6(6)°, presumably due to an electrostatic repulsion between the two adjacent anionic carboxylate groups. Such a conformation of the two carboxylate groups seems to exclude the resonance of an α,β-unsaturated system containing sulfur atoms: the CC bond length (1.337(12) Å) is very similar to that of a normal double bond (1.33−1.34 Å), but it is prominently shorter than the corresponding bond (1.374(9) Å) of (DACH)Pt(DTOYM), which exhibits a significant resonance in the system . In particular, such unique chelating and bridging coordination modes for each carboxylate group in the title complex seem to hamper the intramolecular S···O interaction which is favored in (DACH)Pt(DTOYM): the shortest S···O distance of the present compound (2.86 Å) is explicitly longer than that of (DACH)Pt(DTOYM) (2.53 Å) …”

“…Such a conformation of the two carboxylate groups seems to exclude the resonance of an α,β-unsaturated system containing sulfur atoms: the CC bond length (1.337(12) Å) is very similar to that of a normal double bond (1.33−1.34 Å), but it is prominently shorter than the corresponding bond (1.374(9) Å) of (DACH)Pt(DTOYM), which exhibits a significant resonance in the system . In particular, such unique chelating and bridging coordination modes for each carboxylate group in the title complex seem to hamper the intramolecular S···O interaction which is favored in (DACH)Pt(DTOYM): the shortest S···O distance of the present compound (2.86 Å) is explicitly longer than that of (DACH)Pt(DTOYM) (2.53 Å) 1 Perspective view of the compound as a PLUTON drawing including the unit cell, viewed along the z axis.…”

“…The coordination properties of dicarboxylate ligands are extraordinarily versatile, including the ability to form polymeric species via bridging modes . Among the dicarboxylate derivatives, the following ylidenemalonate ligands containing a dithioether ring are noninnocent systems: they can coordinate to a platinum atom via one of three distinct modes (O,O‘-, O,S-, and S,S‘-chelation) depending on the dithioether ring size. , For this system, in addition, the close proximity of two carboxylate groups linked to an sp 2 carbon can facilely enable them to act as an intermetallic chelating ligand. In an effort to expand this coordination chemistry to alkaline earth metals, we report herein the synthesis and structural properties of barium 1,3-dithiepan-2-ylidenemalonate ( n = 4).

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