SYNTHESIS, STRUCTURE AND REACTIVITY OF BIS(N-ARYL-IMINOPHOSPHORANYL)METHANES. X-RAY CRYSTAL STRUCTURES OF (4-CH3-C6H4-N˭PPh2)2CH2 AND (4-NO2-C6H4-N˭PPh2)2CH2

The synthesis of novel bis(N-aryl-imino-phosphoranyl)methanes of the type CH2(PR2˭N-Ar)2 has been accomplished by reaction of methylene-bisphosphines with arylazides. These compounds have been fully characterized by 1H, 31P and 13C NMR, IR spectroscopy, Field Desorption Mass Spectroscopy (˭ FDMS) and elemental analysis. Variable temperature NMR experiments and single crystal X-ray structure determinations of CH2(PPh2˭N-C6H4-CH3-4)2 (la) and CH2(PMe2˭N-C6H4-NO2-4)2 (1f) reveal that bis(N-aryl-imino-phosphorany1)methane occurs as tautomer 1. Crystals of la are orthorhombic, space group Pcab, with a = 26.602(2), b = 20.521(1), c = 11.8859(7) Å and V = 6488.5(7) Å3 (2 = 8, R = 0.045 and Rw = 0.066). The crystals of lf are monoclinic, space group C/2c, with a = 20.153(4), b = 5.952(1), c = 16.930(5) Å, β = 106.24(3)° and V = 1949.6(6) Å3 (Z = 4, molecular symmetry C2, Rw = 0.051 and R, = 0.079). Both molecules consist of 2 iminophosphoranyl units bridged by a methylene group. The P˭N bond distances of 1.568(2) and 1.566(2) Å for la and 1.580(4) Å for lf represent normal values for iminophosphoranyl compounds. The N-C bond lengths of 1.386(2) and 1.390(2) A (la) or 1.372(5) A for If indicate that some electron delocalisation over the N-aryl moiety takes place. In la the electron delocalisation takes place separately in each iminophosphoranyl entity, while in lf electron delocalisation occurs only in the N-aryl-NO2 moiety. Compound la is easily deprotonated using lithium-diisopropylamide or NaH and shows typical iminophosphoranyl chemistry, since with CO2 an aza-Wittig reaction has been found and with HX (X˭CI, Br) protonation of both imide nitrogen atoms has been observed.