Solution and Solid-State Dynamics of Metal-Coordinated White Phosphorus

The dynamic behavior in solution of eight mono-hapto tetraphosphorus transition metal-complexes, trans-[Ru(dppm)(2)(H)(eta(1)-P-4)]BF4 ([1]BF4), trans-[Ru(dppe)(2)(H) (eta(1)-P-4)] BF4 ([2]BF4), [CpRu(PPh3)(2)(eta(1)-P-4)] PF6 ([3]PF6), [CpOs(PPh3)(2)(eta(1)-P-4)] PF6 ([4]PF6), [Cp*Ru(PPh3)(2)(eta(1)-P-4)] PF6 ([5]PF6), [Cp*Ru(dppe) (eta(1)-P-4)] PF6 ([6]PF6), [Cp*Fe(dppe) (eta(1)-P-4)] PF6 ([7]PF6), [(triphos) Re(CO)(2)(eta(1)-P-4)] OTf ([8]OTf), and of three bimetallic Ru(mu,eta(1:2)-P-4)Pt species [{Ru-(dppm)(2)(H)}(mu,eta(1:2)-P-4){Pt(PPh3)(2)}]BF4 ([1-Pt]BF4), [{Ru(dppe)(2)(H)}(mu,eta(1:2)-P-4){Pt(PPh3)(2)}]BF4 ([2-Pt] BF4), [{CpRu (PPh3)(2))}(mu,eta(1:2)-P-4){Pt(PPh3)(2)}]BF4 ([3-Pt]BF4), [dppm=bis(diphenylphosphanyl) methane; dppe=1,2-bis(diphenylphosphanyl) ethane; triphos=1,1,1-tris (diphenylphosphanylmethyl)ethane; Cp=eta(5)-C5H5; Cp*=eta(5)-C5Me5] was studied by variable-temperature (VT) NMR and P-31{H-1} exchange spectroscopy (EXSY). For most of the mononuclear species, NMR spectroscopy allowed to ascertain that the metal-coordinated P-4 molecule experiences a dynamic process consisting, apart from the free rotation about the M-P-4 axis, in a tumbling movement of the P-4 cage while remaining chemically coordinated to the central metal. EXSY and VT 31P NMR experiments showed that also the binuclear complex cations [1-Pt](+) -[3-Pt](+) are subjected to molecular motions featured by the shift of each metal from one P to an adjacent one of the P-4 moiety. The relative mobility of the metal fragments (Ru vs. Pt) was found to depend on the co-ligands of the binuclear complexes. For complexes [2]BF4 and [3]PF6, MAS, P-31 NMR experiments revealed that the dynamic processes observed in solution (i.e., rotation and tumbling) may take place also in the solid state. The activation parameters for the dynamic processes of complexes 1(+), 2(+), 3(+), 4(+), 6(+), 8(+) in solution, as well as the X-ray structures of 2(+), 3(+), 5(+), 6(+) are also reported. The data collected suggest that metal-coordinated P-4 should not be considered as a static ligand in solution and in the solid state.