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

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(η(3)-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(η(3)-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(η(3)-C3H5)Cl, MoO2Cl2(OSMe2)2, MoOCl3, VOF3, WOCl4, and WO2Cl2(CH3CN)2 to produce the corresponding salts, [PPN]2[(P3O9)Mo(CO)2(η(3)-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 κ(3) connectivity.