Nitrogen-Phosphorus V Rings

Ph2P(NSiMe3)(NHSiMe3) + 1/2S4N4 Ph2PN3S2 + (Me3Si)2NH (5) 

The diphosphadithiatetrazocines 110 (E=S) and 111 (E=S) contain one more R2PN unit in the ring than 109. The structure of the orange-red 1,3-isomer (110, E=S, R=Ph) consists of an essentially planar N3S2 unit with the two phosphorus atoms located on opposite sides of the plane. The 1,5-isomers 111 

The P2N4S2 ring in 111 is readily susceptible to nucleophilic attack at sulfur. Reactions with organolithium reagents give monolithium derivatives 

Li[Ph4P2N4S2R].274 Alkali-metal derivatives of the dianion [Ph4P2N4S2]2 are prepared by treatment of 111 (E=S, R=Ph) with alkali-metal superhydrides M[Et3BH] (M=Li, Na].275 The methylene bridge between the two sulfur atoms in 116 is introduced by the addition of diiodomethane to 

The combination of hard (N) and soft (S or Se) donor sites in the 1,5-P2N4E2 ring system leads to a diversity of coordination modes in complexes with transition metals.277 A versatile approach is the oxidative addition of the neutral ligand 111 to the metal centre (Equation 6).278,279 

NMR chemical shifts of 111 are ca. 80-100 ppm downfield eompared to other P-N-S rings or cyclophosphazenes.  

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If two additional sources of structural diversity, namely, variable oxidation state and double bond incorporation, in the ring are taken into account, the variety of four-membered ring systems increases greatly. This is illustrated by the phosphorus nitrogen pair. In this case, the coordination number varies from two to three for phosphorus(III), from three to six for phosphorus(V) and two to four for nitrogen (Scheme 25). 

Behrens C, Cichon MK, Grolle F, Hennecke U, Carell T (2004) Excess Electron Transfer in Defined Donor-Nucleobase and Donor-DNA-Acceptor Systems. 236 187-204 Bertrand G, Bourissou D (2002) Diphosphorus-Containing Unsaturated Three-Menbered Rings Comparison of Carbon, Nitrogen, and Phosphorus Chemistry. 220 1-25 Betzemeier B, Knochel P (1999) Perfluorinated Solvents - a Novel Reaction Medium in Organic Chemistry. 206 61-78 Bibette J, see Schmitt V (2003) 227 195-215 Blais J-C, see Astruc D (2000) 210 229-259 Bogar F, see Pipek J (1999) 203 43-61 Bohme DK, see Petrie S (2003) 225 35-73 Bourissou D, see Bertrand G (2002) 220 1-25 Bowers MT, see Wyttenbach T (2003) 225 201-226 Brand SC, see Haley MM (1999) 201 81-129... 

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