Cyclotriphosphazanes and Bicyclic Tetraphosphapentazanes

Abstract

An unusual ring contraction-rearrangement occurs in the reactions of trifluoroethoxy/aryloxy λ³-cyclotriphosphazanes and the bicyclic phosphazane, (EtN)₅P₄(OPh)₂ (L) with tetrachloro-1,2-benzoquinone (TCB) to give λ⁵-cyclodiphosphazanes. The bicyclic phosphazane monoxide, (EtN)₅P₄(O)(OPh)₂ (L′) undergoes oxidative addition with TCB with retention of the P₄N₅ ring. Treatment of bicyclic phosphazane L and its monoxide L′ with [Mo(CO)₄(NBD)] (NBD = norbornadiene) gives the chelate complexes [Mo(CO)₄(P-P)] (P-P = L or L′). The structures of the products have been elucidated by high field ³¹P NMR and X-ray crystallographic studies.

Keywords::

• cyclotriphosphazanes
• bicyclic tetraphosphapentazanes
• P-N ring conformation
• negative hyperconjugation