Sterically encumbered acyclic diphosphazanes: synthesis, conformations and coordination behavior

Abstract

The reaction between lambda(3)-diphosphazane [EtN(PCl2)(2)] and the sodium salts of substituted phenols affords sterically encumbered diphosphazanes [EtN{P(OR)(2)}(2)] (R= -(C6H3Pr2)-Pr-i-2,6 (1), -C6H3Me2-2,6 (2) and -C6H2Me3-2,4,6 (3)). When the same reaction was carried out with bulky sodium 2,4-di-tert-butyl-4-methylphenoxide, only a monosubstitution takes place to result in the formation of [EtN{PCl(OR)}(2)] (R= -(C6H2Bu2)-Bu-t-2,6-Me-4) (4). Further reaction of 2 with [Mo(CO)(4)(NBD)] produces cis-[(EtN{P(OC6H3Me2-2,6)(2)}(2)) Mo(CO)(4)] (5). Diphosphazanes 1-4 and the metal derivative 5 have been characterized by means of their analytical data and EI-MS, IR and multinuclear NMR (H-1 and P-31) spectral data. The solid-state structure of the diphosphazanes 1, 2 and 4, and the molybdenum complex 5 have been determined by X-ray diffraction studies. Irrespective of the size of substituent, the bulky groups on the phosphorus and nitrogen are on the same side of the P-N-P skeleton with a local C-2v symmetry. The central nitrogen remains almost trigonal planar in all the compounds.