Inorganic Chemistry, Vol.33, No.10, 2090-2102, 1994
Synthesis and Structures of (P-Halogenophenoxy)Phosphazenes - Comparison of the Structures of Cyclic and Linear Short-Chain Species
The crystal structures of OP(OR)2NP(OR)3, where OR = O-C6H4F-p, O-C6H4Cl-p, and O-C6H4Br-p, and [NP(OR)2]3, where OR = O-C6H4F-p, O-C6H4Cl-p, O-C6H4Br-p and O-C6H4I-p, were determined by X-ray crystallography. These small molecule phosphazenes are structural models for the corresponding high polymers, and their structures provide insight into the conformation and nature of bonding in the polymeric species. Crystals of OP(O-C6H4F-p)2NP(O-C6H4F-p)3 are triclinic with cell dimensions of a = 8.394(2) angstrom, b = 10.690(3) angstrom, c = 16.760(4) angstrom, alpha = 86.99(2)-degrees, beta = 84.82(2)-degrees, gamma = 69.66(2)-degrees, space group P1BAR, Z = 2. Crystals of OP(O-C6H4Cl-p)2NP(O-C6H4Cl-p)3 are triclinic with cell dimension of a = 10.513(6) angstrom, b = 12.574(3) angstrom, c = 13.359(5) angstrom, alpha = 91.83(3)-degrees, beta = 106.76(4)-degrees, gamma = 104.68(3)-degrees, space group P1BAR, and Z - 2. Crystals of OP(O-C6H4Br-p)2NP(O-C6H4Br-p) are triclinic with cell dimension of a = 9.839(2) angstrom, b - 12.373(4) angstrom, c = 14.286(3) angstrom, alpha = 103.74(2)-degrees, beta = 91.76(2)-degrees, gamma = 100.89(2)-degrees, space group P1BAR, and Z = 2. Crystals of the cyclic species are monoclinic. The unit cell dimensions are as follows : [NP(O-C6H4F-P)2]3, a = 20.860(5) angstrom, b - 8.085(12) angstrom, c = 21.813(5) angstrom, beta = 104.62(3)-degrees, space group P2(1)/n, Z = 4; [NP(O-C6H4Cl-p)2]3, a = 17.746(9) angstrom, b = 7.623(7) angstrom, c = 27.856(10) angstrom, beta = 91.76(12)-degrees, space group P2(1)/c, Z = 4; [NP(O-C6H4Br-P)2]3, a = 13.680(5) angstrom, b = 31.316(7) angstrom, c - 9.289(3) angstrom, beta = 90.70(3)-degrees, space group P2(1)/n, Z = 4; [NP(O-C6H4I-P)2]3, a = 13.700(6) angstrom, b - 9.381(11) angstrom, c = 32.675(16) angstrom, beta = 95.72(4)-degrees, space group P2(1)/c, Z = 4. The results show that the P-N bond lengths in both the short-chain and cyclic species are very similar, with an average value of 1.55 angstrom. Evidence for side group stacking can be detected in the crystal lattice of both the cyclic and linear oligomers, and these arrangements are analogous to those expected in polymer microcrystallites.