Sulfido-bridged 1,2-bis(diphenylphosphino)ethane (dppe) appended trinuclear nickel(II) clusters: Crystallographic and computational analyses

The cluster compounds are still gaining considerable attention due to their peculiar behaviour and M−M bonding or M···M interactions. In this report, two sufido-bridged, 1,2-bis-(diphenylphosphino)ethane (dppe) appended trinuclear Ni(II) clusters having formula [Ni₃S₂(dppe)₃].2BPh₄ (Ni₃S₂-1) and [Ni₃S₂(dppe)₂(4-pyCH₂OH)₂].2PF₆ (Ni₃S₂-2) are reported. These clusters are synthesized from the same starting reactants the xanthate ligand 4-PyCH₂OCS₂Na, Ni(II) and dppe employing two different reaction pathways. The obtained compounds have been characterized by microanalyses, FTIR, UV–Vis, ¹H, ¹³C and ³¹P NMR spectroscopy as well as by single crystal X-ray diffraction technique. The X-ray analyses revealed that in both compounds three Ni(II) centers are coordinated to two sulfido and dppe ligands. In Ni₃S₂-1 three dppe and two sulfido ligands are stabilising the trinuclar cluster cation while in Ni₃S₂-2 along with two sulfido and two dppe ligands, two 4-pyCH₂OH are also coordinating with one of the Ni(II) center. Both Ni₃S₂-1 and Ni₃S₂-2 display different non-covalent interactions along with the Ni···Ni interactions. The nature of these interactions has been addressed with the aid of Hirshfeld surface analysis, density functional theory and quantum theory of atoms-in-molecules (QTAIM) analyses. The occurrence of such non-covalent intermolecular interactions is also well supported by the non-covalent interactions reduced density gradient (NCI-RDG) approaches. Also, the Wiberg bond index, Mayer bond order and delocalization indices have been calculated to assess the nature of Ni···Ni interactions.