Magnesium Cyanide or Isocyanide?

Abstract

Preference for the binding mode of the CN À ligand to Mg (Mg À CN vs.Mg À NC) is investigated. Amonomeric Mg complex with at erminal CN ligand was prepared using the dipyrromethene ligand Mes DPM which successfully blocks dimerization. While reaction of ( Mes DPM)MgN(SiMe 3 ) 2 with Me 3 SiCN gave the coordination complex ( Mes DPM)MgN-(SiMe 3 ) 2 ·NCSiMe 3 ,r eaction with ( Mes DPM)Mg(nBu) led to ( Mes DPM)MgNC·(THF) 2 .AM g À NC/Mg À CN ratio of % 95:5 was established by crystal-structure determination and DFT calculations.IRstudies show absorbances for CN stretching at 2085 cm À1 (MgÀNC) and 2162 cm À1 (MgÀCN) as confirmed by 13 Clabeling.Insolution and in the solid state,the CN ligand rotates within the pocket. The calculated isomerization barrier is only 12.0 kcal mol À1 and the 13 CNMR signal for CN decoalesces at À85 8 8C( Mg À NC:1 75.9 ppm, Mg À CN: 144.3 ppm). Experiment and theory both indicate that Mg complexes with the CN À ligand should not be named cyanides but are more properly defined as isocyanides.

Metal‐Metal Charge Transfer Properties of a Series of Trinuclear Fe2Ru and Corresponding Pentanuclear Fe2Ru2Ag Cyanido‐Bridged Complexes

“…The single‐crystal X‐ray structural analyses showed that from the trinuclear N to the pentanuclear M , the cyanide bridge between silver and ruthenium turned around, namely the backbone is Fe‐(μ‐NC)‐Ru‐(μ‐NC)‐Ag‐(μ‐CN)‐Ru‐(μ‐CN)‐Fe not Fe‐(μ‐NC)‐Ru‐(μ‐CN)‐Ag‐(μ‐NC)‐Ru‐(μ‐CN)‐Fe, confirmed by their IR spectra and the following fact: during solving the single crystal structure, if the orientation of the bridging cyanide coordinated to ruthenium remained unchanged, the refinement would give much higher w R2 and R1 values, with unrealistically displacement parameter for both the C and N atoms. The similar phenomenon for this alternative cyanide connectivity was also reported by Harder et al [13] . This fact will be further discussed in the following section of Crystal structures.…”

“…confirmed by their IR spectra and the following fact: during solving the single crystal structure, if the orientation of the bridging cyanide coordinated to ruthenium remained unchanged, the refinement would give much higher wR2 and R1 values, with unrealistically displacement parameter for both the C and N atoms. The similar phenomenon for this alternative cyanide connectivity was also reported by Harder et al [13] This fact will be further discussed in the following section of Crystal structures.…”