The reactions of Cl3P=N-P(O)Cl-2 (1) with Sodium 2,4,6-tert-butylphenoxide and sodium 2,6-di-tert-butyl-4-methylphenoxide give geminal bis products (2) and (3), respectively. Compounds (2) and (3) have been characterised by elemental analysis, IR, H-1-, C-13 and P-31-NMR and the structure of compound (2) has been examined crystallographically. It crystallizes in the monoclinic space group P2(1)/n with a = 10.056(1), b = 25.986(1), c = 15.533(1)Angstrom, beta = 95.9(1)degrees, V = 4037.6(1)Angstrom(3), Z = 4 and D-x = 1.19 g cm(-3). The bulky substituents are instrumental in determining the molecular geometry. The P-N bonds have neither single-nor double-bond character and are substantially shorter than the ideal P-N single bond. The P=O double bond is abnormally long and it has a single bond character. The P-N-P angle [158.0(3)degrees] is the largest one for the reported acyclic phosphazene derivatives in the literature. (C) 2000 Elsevier Science B.V. All rights reserved.