Theoretical and physical investigations of group 9-14 metal complexes containing the diphenylmethylenethiophosphinate (MTP) ligand : effect of metal proximity on physical properties

Abstract

A trimetallic complex, [Hg2Pt(CH2P(S)Ph2)4]X2 (X = BPh4-, PF6-, 1a , b), was obtained from the reaction of Hg(MTP)2 (MTP = CH2P(S)Ph2-) with one equivalent of Pt[S(CH2CH3)2]2Cl2, in CH2Cl, in the presence of either NaBPh4 or TIPF6. The X-ray crystal structures of 1a , b show the ylide ligand bridging the three metals with an average Hg...Pt distance of 3.0243 (1) A and 3.136 (2) A. respectively. In contrast to the linear, isoelectronic Au2Pt(MTP)4 complex previously reported,2 the trimetallic units are both non - linear, with an angle of 166.3 (1) ° for 1a and 149.1 (1) ° for 1b. Fenske - Hall molecular orbital (FHMO) calculations were carried out on models of 1. Au2 Pt(MTP)4 , and models of this complex at the angle of 1b . These calculations indicate a platinum - sulfur k antibonding interaction in the HOMO and metal interactions in the LUMO of 1, while calculations on Au2Pt(MTP)4 show a HOMO that is antibonding between metal orbitals, but a LUMO that is bonding between metal orbitals. Similar calculations on Au2(MTP)2 give the same results as for Au2Pt(MTP)4 . The series Au2(MTP)2X2 and Au2Pt(MTP)4X2 (X = Cl, Br, I) were calculated and found to have bonding HOMOs and antibonding LUMOs. FHMO calculations were also performed on the complexes AuTl(MTP)2 and Au2Pb(MTP)4 and compared with the results of Wang, et al.[^3,4] Raman spectroscopic data were collected for the above complexes at 20K in the solid state. All show very complex patterns which appear to progress from one or more low - frequency metal - metal stretching vibrations. The oxidized Au2(MTP)2X2 complexes were found to give Raman spectra with well - defined Au-Au and Au-X stretching frequencies...