Reversal of polarization in amidophosphines: neutral- and anionic-κP coordination vs. anionic-κP,N coordination and the formation of nickelaazaphosphiranes

Abstract

Nickel(II) chloride reacts with the bis(tert-butylamino)diazadiphosphetidine {Bu^t(H)NP(μ-NBu^t)₂PN(H)Bu^t} to form trans-[{Bu^t(H)NP(μ-NBu^t)₂PN(H)Bu^t}₂NiCl₂]. In solution and the solid-state each heterocyclic ligand coordinates nickel through one phosphorus atom only. For comparison the solid-state structure of the known trans-[NiCl₂(PEt₃)₂] was also determined and it was found that the two complexes have almost identical bond parameters about nickel. The nickel–amidophosphine complexes [{Bu^tOP(μ-NBu^t)₂PNBu^t}NiCl(PBuⁿ₃)], [(PBuⁿ₃)ClNi{Bu^tNP(μ-NBu^t)₂PNBu^t}NiCl(PBuⁿ₃)], and [{Me₂Si(μ-NBu^t)₂PNBu^t}NiCl(PBuⁿ₃)] were synthesized and X-ray structurally characterized. In these mono- and di-nuclear nickel complexes the nickel ions are coordinated in pseudo square-planar fashions, by one trialkylphosphine ligand, one chloride ligand and one κP,N-coordinated amidophosphine moiety from tert-butylamido-substituted heterocycles. Attempts to create nickel complexes chelated in a κ²P fashion by the o-phenylenediamine-tethered mono- and di-anionic 1-{Me₂Si(μ-NBu^t)₂PN} 2-{Me₂Si(μ-NBu^t)₂PNH}C₆H₄ and 1,2-{Me₂Si(μ-NBu^t)₂PN}C₆H₄, respectively, afforded instead [1,2-{Me₂Si(μ-NBu^t)₂PN}{Me₂Si(μ-NBu^t)₂PN}C₆H₄NiCl] and [1,2-{Me₂Si(μ-NBu^t)₂PN}{Me₂Si(μ-NBu^t)₂PN}C₆H₄Ni{PEt₃}], each complex having κP,N and κP coordinated amidophosphine ligands.