Znorg. Chem. 1988, 27, 1911-1915
1911
Contribution from AT&T Bell Laboratories, Murray Hill, New Jersey 07974
Phenalene-Phosphazene Complexes: Effect of Exocyclic Charge Densities on the Cyclotriphosphazene Ring System R. C. Haddon,* S. V. Chichester-Hicks, and S.L. Mayo Received October 27, 1987
The synthesis and properties of a new series of 1,9-diamino-substitutedphenalene complexes of the cyclotriphosphazenering system i s described. One of the compounds is shown to be amphoteric, and this behavior allows an examination of the response of the phosphazene linkage to variations in exocyclic charge density at the spiro center in a plane perpendicular to the cyclotriphosphazene ring system. 'lP NMR spectroscopy indicates that substituent lone pairs with this orientation are not effective in long-range delocalization within the phosphazene linkage (in accord with our theoretical model of spiro delocalization). An X-ray crystal structure of one compound (7) identifies the presence of clathrated molecules of chloroform together with doubly hydrogen-bonded monoclinic space group pairs of the phenalene-phosphazene complexes in the lattice. Crystal data for 7 (CI3H8CI4N5P3.CHCI3): P2,/c,,a = 12.401 (4) A, b = 28.404 (6) A,c = 12.962 (3) A,0 = 91.76 ( 2 ) O , V = 4564 (2) A', Z = 8, R = 0.050 for 4525 reflections. The chemistry of the cyclo- and polyphosphazenes is currently receiving a great deal of attention.' While a large number of derivatives have now been synthesized and the electronic structure of these compounds is not well ~ n d e r s t o o d . Although ~~ the phosphazenes are conjugated systems, the cyclic compounds do not exhibit aromatic character, and the polyphosphazene backbone does not appear to support charge transport. As a result most polyphosphazenes are insulators.'-' Recently it has proved possible to induce electrical conductivity in polyphosphazenes by introduction of substituents that can supply a conducting pathway (outrigger polymer~).~3"'~Nevertheless, the question of electronic spin and/or charge mobility in the polyphosphazene linkage still presents a daunting challenge and contrasts with the behavior exhibited by other classes of conjugated polymers. The cyclophosphazenes provide useful model compounds for their polymeric a n a l o g ~ e s and , ~ ~to ~ this end we have studied the bonding in these compound^.^ This led to the development of a theoretically based mechanism for injection of 7r-electron spin density from a spiro substituent into a phosphazene linkage via the phosphorus d orbitals.I2 A phenalene-phosphazene complex based on this theoretical model provided the first evidence for the injection of electron spin density into a segment of a phosphazene linkage.I2 In this work, we report new phenalene-phosphazene complexes designed to probe the electronic structure of the phosphazene linkage via alteration of the exocyclic charge density at the spiro center in a plane perpendicular to the cyclotriphosphazene ring system.
Results and Discussion Preparation of Phenalene-Phosphazene Complexes. We have previously reported the synthesis of the monosubstituted phenalene-phosphazene complexes 1 and 2.12 Replacement of the remaining halide in these compounds by reaction with sodium trifluoroethoxide gave rise to different modes of substitution, as
demonstrated by the isolation of compounds 3 and 4; the former molecule allowed the preparation of compounds 5' and 6'.
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