Premium
Ternary Alkali Metal Transition Metal Acetylides A 2 MC 2 (A=Na, K; M=Pd, Pt)
Author(s) -
Hemmersbach Sabine,
Zibrowius Bodo,
Kockelmann Winfried,
Ruschewitz Uwe
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010504)7:9<1952::aid-chem1952>3.0.co;2-c
Subject(s) - acetylide , alkali metal , ternary operation , chemistry , transition metal , palladium , raman spectroscopy , acetylene , crystallography , platinum , metal , crystal structure , neutron diffraction , catalysis , stereochemistry , organic chemistry , physics , computer science , optics , programming language
Ternary transition metal acetylides A 2 MC 2 (A=Na, K; M=Pd, Pt) can be synthesised by reaction of the respective alkali metal acetylide A 2 C 2 with palladium or platinum in an inert atmosphere at about 350 °C. The crystal structures are characterised by $\rm{^{1}_{\infty }}$ [M(C 2 ) $\rm{^{2-}_{2/2}}$ ] chains, which are separated by the alkali metals ( P $\bar 3$ m 1, Z =1). The refinement of neutron powder diffraction data gave C−C=1.263(3) Å for Na 2 PdC 2 (Na 2 PtC 2 : 1.289(4) Å), which is distinctively longer than the expected value for a C−C triple bond (1.20 Å). On the basis of band‐structure calculations this can be attributed to a strong backbonding from the metal into the antibonding orbitals of the C 2 unit. This was further confirmed by Raman spectroscopic investigations, which showed that the wavenumbers of the C–C stretching vibrations in Na 2 PdC 2 and Na 2 PtC 2 are about 100 cm −1 smaller than in acetylene. 13 C MAS‐NMR spectra demonstrated that the acetylenic C 2 units in the title compounds are very different from those in acetylene. Electrical conductivity measurements and band‐structure calculations showed that the black title compounds are semiconductors with a small indirect band gap (approximately 0.2 eV).