The crystal and molecular structure of K[Al₂(CH₃)₆SCN], a compound which contains an S,N-bridging thiocyanate ligand

The crystal structure of K[Al₂(CH₃)₆SCN] has been determined from single-crystal X-ray diffraction data collected by counter methods. The compound crystallizes in the monoclinic space group C2/m with unit cell parameters a 18.579(8), b 8.168(5), c 11.753(6) Å, β 126.80(4)°, and ρ{variant}_calc 1.12 g cm^-3 for Z = 4. Least-squares refinement gave a final R value of 0.028 for 722 independent observed reflections. The anion exhibits an S,N-bridging thiocyanate. The SCN is linear, and the CNAl angle is 173.4(4)°. The AlN bond is normal, 1.951(5) Å, but the AlS bond length, 2.489(2) Å, implies a rather weak interaction. A distance of ca. 2.35 Å would have been expected. The sulfur atom appears to be using p-orbitals in its bonding scheme, since the AlSC bond angle is 97.3(2)°.