engleski

Synthesis and Structures of Ammonium and Tetraphenylphosphonium salts of mu-Oxo-diaquadioxalatotetraoxodimolybdenum(VI). An interesting example of intramolecular hydrogen bonds within the dimeric anion.

The reaction of molybdenum(VI) oxide with oxalic acid and RCl where R = NH_4 (1) and (C_6H_5)_4P (2), results in the formation of molybdenum(VI) oxalate complexes of the general formula R_2[Mo_2O_5(C_2O_4)_2(H_2O)_2]. As determined by X-ray structure analysis both salts are built up of the dimeric anions containing Mo_2O_5 core. Molybdenum atoms exhibit distorted octahedral coordination. Whereas in the ammonium salt the Mo-O-Mo bridge is linear, that one in the corresponding tetraphenylphosphonium salt is angular with an angle of 162.42(15)^o at the oxygen atom. This angular structure of 2 is also caused by additional strong intramolecular hydrogen bonds [2.719(4) and 2.661(4) A] between coordinated water molecules and oxalato-oxygens. Both complexes were characterized by chemical analysis, thermogravimetry, UV and IR spectroscopy as well as by conductivity measurements.

molybdenum(VI) complexes; oxalate; crystal structure; hydrogen bonding

nije evidentirano