The first three anisotropy constants of nickel

The technique of ferromagnetic resonance at 23 GHz has been used to determine the first three anisotropy constants of pure Ni down to 4.2K. A temperature and orientation dependent linewidth has also been observed.     

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

Abstract

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) ų (2 = 8, R = 0.045 and R_w = 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) ų (Z = 4, molecular symmetry C₂, R_w = 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.