Pentacoordination for pincer and related terdentate coordination compounds: Revisiting structural properties and trends for d 8 transition metal systems

An investigation of ethylene rotational barriers for 5-coordinate d 8 metal bis-ethylene complexes

“…Axial ethylene coordination in TBP complexes is quite rare: equatorial coordination is normally preferred due to enhanced backbonding available in the trigonal plane [19,26]. In all reported asymmetric bis ethylene d 8 Ir(I) TBP complexes ( CF3 PCP)Ir(C 2 H 4 ) 2 , ( [9]aneS 3 [27]. One general conclusion, in accord with earlier predictions [26], was that hydrocarbyl ligands strongly prefer axial TBP coordination sites.…”

Crystal structure and DFT analyses of a pentacoordinated PCP pincer nickel(II) complex

“…The majority of pentacoordinated Ni II complexes containing pincer-like terdentate ligands adopts SPy geometries, which is mainly due to steric factors (Roddick & Zargarian, 2014). DuBois, Wiedner, Bullock and co-workers have reported the synthesis of pentacoordianted Ni II hydride complexes from square-planar Ni II complexes containing four -acceptor phosphane donors upon reaction with H 2 in the presence of bases (Curtis et al, 2003;Wilson et al, 2006;Klug et al, 2017;Yang et al, 2013).…”

Unexpected reactivity of a PONNOP ‘expanded pincer’ ligand

“…The nickel atom exhibits a slightly distorted square pyramidal geometry with a Br atom in the apical position. Nickel(II) pentacoordination is uncommon in pincer chemistry 16 22 A rare example of a related pentacoordinated Ni(PNNNP) pincer complex with an anionic phosphinite instead of a basal Br ligand, showed an significantly shorter apical Ni-Br bond of 2.535(4) Å. 23 The intraligand bond metrics are distinctly different from those in complex 1 (Table S6, ESI †).…”