Carboxylate-malonate bridge

The structural complexity in these compounds (nuclearity ranging from discrete entities to ID" or 3D compounds" is associated with different carboxylato-bridging modes of mal and different structural functions of water molecules. Most of these complexes have been magnetically characterized, and they exhibit ferromagnetic coupling through the carboxylate-malonate bridge. " ... 

Malonate and the dianions of the other aliphatic dicarboxylic acids H02 C(CH2 ) CO,H (n = 1-8) have been isolated as crystalline hydrates, and some of these have been dehydrated.293 X-Ray structural analyses have been reported for the malonate dihydrate,294 which has trans H2Os and bridging malonates of type (110), and for the succinate tetrahydrate and adipate dihydrate 295 the succinate reputedly has a trans- fAn02 (H2 0)4 ] polyhedron with bridging dicarboxylate, presumably as in (109). The monoanion of maleic acid (111) is only unidentate in crystalline [Mn(H-maleate)2-(H20)4] 296 but the equivalent compound of phthalic acid is a bis-chelated octahedral [Mn(0,0)2 (H2 0)2] species.297 Clearly other interactions in the solids, as well as the bonding interactions with Mn", define structure in the carboxylate compounds. 

Tin(II) carboxylates M2Sn(C204)2 H20 (M = NH4, Na, K, Rb, Cs = 0, 1) all exhibit distorted square planar geometry as determined by Mossbauer spectroscopy. The molecular structure of K2[Sn(02C)2CH2)3] H20 is polymeric with malonates that bridge tin centers (124).33" Partial oxidation of (CF3C02)2Sn allows isolation of the mixed oxidation state pentanuclear assembly Sn s7 0)3(CF3C02)8. ... 

Fig. 5.15 Homology models of PedC and PedD showing the arrangement of the active site residues around the malonate unit. The active site schematics to the tight simphfy the interactions identified between the protein and the malonate. The major difference between the two domains is the presence of an arginine residue in PedD at the rear of the pocket, which is hypothesised to participate in a bidentate salt bridge with the carboxyl region of the malonate. In contrast, PedC has a glutamine at this position which is unable to provide the cationic species for the salt bridge...

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