Four-coordinate and pseudo five-coordinate Hg(II) complexes of a new bidentate phosphorus ylide: X-ray crystal structure and spectral characterization

Abstract

The reaction of Ph 2PCH 2PPh 2 (dppm) with BrCH 2C(O)C 6H 4NO 2 in chloroform produces the new phosphonium salt [Ph 2PCH 2PPh 2CH 2C(O)C 6H 4NO 2]Br ( 1). Further, by reacting the phosphonium salt with appropriate base the bidentate phosphorus ylide, Ph 2PCH 2PPh 2 C(H)C(O)C 6H 4NO 2 ( 2) was obtained. The reaction of ligand 2 with mercury(II) halides in dry methanol led to the formation of the P, C-coordinated mononuclear complexes [HgX 2(Ph 2PCH 2PPh 2C(H)C(O)C 6H 4NO 2)] [X = Cl ( 3), Br ( 4), I ( 5)]. Characterization of the obtained compounds was performed by elemental analysis, IR, 1H, 31P, and 13C NMR. The X-ray crystal structure of 5 as well as the complex derived from crystallization of 4 in DMSO, [HgBr 2(Ph 2PCH 2PPh 2C(H)C(O)C 6H 4NO 2)(DMSO)] ( 6), is reported. In both complexes 5 and 6 the title ylide is coordinated through the ylidic carbon and the phosphine atom. However, in compound 6 the Hg–C bond length is considerably weakened due to coordination of DMSO molecule to the metal ion and locating of ylidic carbon atom in the axial position of the resulting trigonal bipyramidal complex. Theoretical studies on ligand and all complexes at DFT (B3LYP) level of theory are also reported. The results show that the addition of DMSO molecule to the compound 4 and formation of compound 6 is energetically favored.