Facile synthesis of mononuclear early transition-metal complexes of κ3cyclo-tetrametaphosphate ([P4O12]4−) and cyclo-trimetaphosphate ([P3O9]3−)

Abstract

We herein report the preparation of several mononuclear-metaphosphate complexes using simple techniques and mild conditions with yields ranging from 56% to 78%. Treatment of cyclo-tetrametaphosphate ([TBA]₄[P₄O₁₂]·5H₂O, TBA = tetra-n-butylammonium) with various metal sources including (CH₃CN)₃Mo(CO)₃, (CH₃CN)₂Mo(CO)₂(η³-C₃H₅)Cl, MoO₂Cl₂(OSMe₂)₂, and VOF₃, leads to the clean and rapid formation of [TBA]₄[(P₄O₁₂)Mo(CO)₃]·2H₂O, [TBA]₃[(P₄O₁₂)Mo(CO)₂(η³-C₃H₅)], [TBA]₃[(P₄O₁₂)MoO₂Cl] and [TBA]₃[(P₄O₁₂)VOF₂]·Et₂O salts in isolated yields of 69, 56, 68, and 56% respectively. NMR spectroscopy, NMR simulations and single crystal X-ray studies reveal that the [P₄O₁₂]⁴⁻ anion behaves as a tridentate ligand wherein one of the metaphosphate groups is not directly bound to the metal. cyclo-Trimetaphosphate-metal complexes were prepared using a similar procedure i.e., treatment of [PPN]₃[P₃O₉]·H₂O (PPN = bis(triphenylphosphine)iminium) with the metal sources (CH₃CN)₂Mo(CO)₂(η³-C₃H₅)Cl, MoO₂Cl₂(OSMe₂)₂, MoOCl₃, VOF₃, WOCl₄, and WO₂Cl₂(CH₃CN)₂ to produce the corresponding salts, [PPN]₂[(P₃O₉)Mo(CO)₂(η³-C₃H₅)], [PPN]₂[(P₃O₉)MoO₂Cl], [PPN]₂[(P₃O₉)MoOCl₂], [PPN]₂[(P₃O₉)VOF₂]·2CH₂Cl₂, and [PPN]₂[(P₃O₉)WO₂Cl] in isolated yields of 78, 56, 75, 59, and 77% respectively. NMR spectroscopy, NMR simulations and single-crystal X-ray studies indicate that the trianionic ligand [P₃O₉]³⁻ in these complexes also has κ³ connectivity.