Mercury complexes, with selenourea

As observed previously for soft donor ligands such as thioethers and phosphines, mercury(n) reacts with selenoethers and telluroethers to form complexes of the general type HgLX2, where X is a halide or pseudohahde. In addition, mercury(II) forms complexes with various Se-donor ligands such as diethylselenocarbamate and selenourea. 

Selenourea is less stable than urea or thiourea, as it is sensitive to air and light, particularly in solution, and tends to dimerize in certain systems. In general, the donor properties of selenourea are similar to those of thiourea,2.3 and complexes with cobalt(II),4,5 palladium(II), platinum(n), zinc, cadmium, and mercury acceptors can be obtained by appropriate modification of the methods used for the preparation of the analogous thiourea derivatives. 

Complexes of thiourea with mercury(II) halides have been known for almost a century, and compounds containing one, two, three, or four molecules of coordinated thiourea can be isolated from aqueous solution. With selenourea in acetone, it is possible to prepare 1 2 complexes Hg[(NH2)2CSe]2X2 (X = C, Br, I) and a dimeric 1 1 complex [Hg (NH2)2CSe Cl2]2 in excellent yields. 

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