Site preferences in hetero-metallic [Fe9−xNix] clusters: a combined crystallographic, spectroscopic and theoretical analysisElectronic supplementary information (ESI) available: (1) Calibration curve for the X-ray fluorescence experiment (2) discussion of the Mössbauer data and (3) total energies and cartesian coordinates of all computed structures. CCDC 1033941-1033944. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7dt02930f

• Main Authors: Georgopoulou, Anastasia N, Al-Ameed, Karrar, Boudalis, Athanassios K, Anagnostopoulos, Dimitrios F, Psycharis, Vassilis, McGrady, John E, Sanakis, Yiannis, Raptopoulou, Catherine P
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c7dt02930f

The reaction of mixtures of Fe(O 2 CMe) 2 ·2H 2 O and Ni(O 2 CMe) 2 ·4H 2 O of various compositions with di-2-pyridyl ketone (py 2 CO, dpk) in MeCN under an inert atmosphere afforded a family of hetero-metallic enneanuclear clusters with general formula [Fe 9− x Ni x (μ 4 -OH) 2 (O 2 CMe) 8 (py 2 CO 2 ) 4 ] ( 2 , x = 1.00; 3 : x = 6.02; 4 , x = 7.46; 5 , x = 7.81). Clusters 2-5 are isomorphous to the homo-metallic [Fe 9 ] cluster ( 1 ) previously reported by some of us, and also isostructural to the known homo-metallic [Ni 9 ] cluster. All four clusters contain a central M II ion in an unusual 8-coordinate site and eight peripheral M II ions in distorted octahedral environments. The distribution of Fe II and Ni II ions over these two distinct coordination sites in 2-5 can be established through a combination of X-ray fluorescence and Mössbauer spectroscopies, which show that Fe II preferentially occupies the unique 8-coordinate metal site while Ni II accumulates in the octahedral holes. Density functional theory indicates that the distribution of ions across the two sites arises not from any intrinsic preference of the Fe II ions for the 8-coordinate sites, but rather because of the large ligand field stabilization energy available to Ni II in octahedral coordination. The distribution of Fe( ii ) and Ni( ii ) over two distinct metal sites in [Fe 9− x Ni x ] clusters is studied by X-ray crystallography, Mössbauer and XRF spectroscopies, and DFT calculations.