Metal-metal bonding in tetracyanometalates (M = Pt-II, Pd-II, Ni-II) of monovalent thallium. Crystallographic and spectroscopic characterization of the new compounds Tl2Ni(CN)(4) and Tl2Pd(CN)(4)
2007 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, no 11, 4642-4653 p.Article in journal (Refereed) Published
The new crystalline compounds Tl2Ni(CN)(4) and Tl2Pd(CN)(4) were synthesized by several procedures. The structures of the compounds were determined by single-crystal X-ray diffraction. The compounds are isostructural with the previously reported platinum analogue, Tl2Pt(CN)(4). A new synthetic route to the latter compound is also suggested. In contrast to the usual infinite columnar stacking of [M(CN)(4)](2-) ions with short intrachain M-M separations, characteristic of salts of tetracyanometalates of Ni-II, Pd-II, and Pt-II, the structure of the thallium compounds is noncolumnar with the two Tl-I ions occupying axial vertices of a distorted pseudo-octahedron of the transition metal, [MTl2C4]. The Tl-M distances in the compounds are 3.0560(6), 3.1733(7), and 3.140(1) A for Ni-II, Pd-II, and Pt-II, respectively. The short Tl-Ni distance in Tl2Ni(CN)(4) is the first example of metal-metal bonding between these two metals. The strength of the metal-metal bonds in this series of compounds was assessed by means of vibrational spectroscopy. Rigorous calculations, performed on the molecules in D-4h point group symmetry, provide force constants for the Tl-M stretching vibration constants of 146.2, 139.6, and 156.2 N/m for the Ni-II, Pd-II, and Pt-II compounds, respectively, showing the strongest metal-metal bonding in the case of the Tl-Pt compound. Amsterdam density-functional calculations for isolated Tl2M(CN)(4) molecules give Tl-M geometry-optimized distances of 2.67, 2.80, and 2.84 A for M = Ni-II, Pd-II, and Pt-II, respectively. These distances are all substantially shorter than the experimental values, most likely because of intermolecular Tl-N interactions in the solid compounds. Time-dependent density-functional theory calculations reveal a low-energy, allowed transition in all three compounds that involves excitation from an a(1g) orbital of mixed Tl 6p(z)-M nd(z)(2) character to an a(2u) orbital of dominant Tl 6p(z) character.
Place, publisher, year, edition, pages
2007. Vol. 46, no 11, 4642-4653 p.
crystal-structure, structural-characterization, aqueous-solution, molecular-structure, solid-state, complexes, platinum, spectra, chalcogenides, tl2pt(cn)4
IdentifiersURN: urn:nbn:se:kth:diva-16643DOI: 10.1021/ic062092kISI: 000246581500039ScopusID: 2-s2.0-34250701639OAI: oai:DiVA.org:kth-16643DiVA: diva2:334685
QC 201005252010-08-052010-08-05Bibliographically approved