H. Winter

Fluorinated cyclothiaphosphazenes: Synthesis, structure and reactivity

Reaction of chlorocyclothiaphosphazenes NPCl2(NSOX)(2) (X = Cl, Ph) and (NPCl2)(2)NSOX (X = Cl, F, Ph) with KSO2F in bulk leads to fluorination at the phosphorus centers. The substitution reaction follows a geminal pattern. Reactions of trans-NPF2(NSOPh)(2) with Grignard reagents RMgX (R = Me, (t)Bu) show substitution of fluorine by alkyl groups to be a slow process. The more reactive PhMgBr gives an acceptable reaction rate and good yields. Organolithium reagents offer organo-substituted cyclothiaphosphazenes in low to moderate yields, depending on the reagent used. Crystals of cis-NPF2(NSOPh)(2) are monoclinic, space group P2(1)/n, with a = 13.665(7) Angstrom, b = 10.676(1) Angstrom, c = 9.897(3) Angstrom, beta = 90.55(3)degrees, V = 1443.8(9) Angstrom(3), and Z = 4. The final R and wR values are 0.034 and 0.043, respectively. The PN and SN bond lengths vary from 1.571(2) to 1.590(2) Angstrom.

Reactivity of a cyclothiaphosphazene towards Grignard reagents. Crystal structure of the 1 : 1 adduct of the Bi(cyclothiaphosphazene)[NPMe(NSOPh)2]2 and benzene

Reactions of the ring system trans-NPCl2(NSOPh)2(1) with MgMeCl and an excess of propan-2-ol in tetrahydrofuran show that chlorine substitution occurs both along a nucleophilic substitution pattern and a metal–halogen exchange process, the latter giving rise to the formation of bicyclic compounds. For reactions of this ring system with MgButCl or the organosilyl Grignard reagents Mg(CH2SiMe3)Cl and Mg[CH(SiMe3)2]Cl nucleophilic substitution appears to be the preferential process. Application of the copper-assisted Grignard reagents MgRCl–[{Cul(PBu3n)}4](R = alkyl) and alkyl iodides, allyl bromide, or propan-2-ol leads to the formation of dialkyl, alkylallyl, or alkylhydrido derivatives, according to an initial metal–halogen exchange process. The crystal and molecular structure of the bicyclic compound [NPMe(NSOPh)2]2·C6H6 has been determined. Crystals are triclinic, space group P, a= 8.063(1), b= 8.979(1), c= 12.712(3)A, α= 71.38(1), β= 74.13(1), γ= 86.57(1)°, and Z= 1. The basic structure consists of two six-membered N3PS2 rings coupled by a P–P bond [2.211 6(9)A] with the methyl groups in trans position. Mean bond lengths are N–P 1.614(2), N–S 1.565(5), 1.585(1), S–0 1.436(1 ), S–C 1.768(1), and C–C (phenyl) 1.388(1)A. The endocyclic angles at P and S are 114.6(1) and 113.3(4)°(average), respectively, and those at N range from 121.3(1) to 124.8(1)°.

Reactivity of cyclothiaphosphazenes towards alkyl-lithium reagents

Reactions of (NPCl2)n(NSOPh)3 –n(n= 1 or 2) with 1 and 2 equivalents of LiMe or LiBut and an excess of 2-propanol in tetrahydrofuran lead to complex reaction mixtures, containing the hydridoisopropoxycyclothiaphosphazenes NPH(OPri)(NPCl2)n(NSOPh)2 –n(n= 0 or 1) and several alkyl-substituted ring systems (based on 31P and 1H n.m.r. spectrometry). The structural characterization of the reaction products is described together with the appropriate reaction pathways, based on an initial metal–halogen exchange process. Reactions of the cyclothiaphosphazenes with alkyl-lithium reagents show a tendency to afford lower yields of cyclic derivatives than those previously reported for (NPCl2)3. This different behaviour is ascribed to competition between the metal-halogen exchange process and nucleophilic substitution, which is supposed to induce ring cleavage.

REACTIVITY OF HEXACHLOROCYCLOTRIPHOSPHAZENE TOWARDS ALKYL-LITHIUM REAGENTS

Reactions of (NPCl2)3 with LiMe or LiBut and an excess of propan-2-ol at –60 °C in tetrahydrofuran lead to complex reaction mixtures containing cyclic derivatives in 80–90% yield. The composition of each reaction mixture has been analyzed by 1H and 31P n.m.r. spectrometry. The n.m.r. data thus obtained indicate the presence of a novel cyclophosphazene, viz. NP(H)OPri(NPCl2)2 and several alkyl-substituted cyclophosphazenes. Typical compounds were isolated and characterized as their 2,2,2-trifluoroethoxy-substituted derivatives. The structural characterizations of the reaction products are described together with the appropriate reaction pathways, based on an initial metalhalogen exchange process.

Structure of trans-5-isopropyl-1,3-diphenyl-5-propyl-1λ6,3λ6,2,4,6,5λ5-dithiatriazaphosphorine 1,3-dioxide

C18H24N302PS2, Mr=409.5 , monoclinic, P21/n, a = 13.432 (6), b = 16.727 (4), c = 9.602 (2) A, fl=110.21(3) ° , V=2025(1)A 3, Z=4, Dx= 1.343 gcm -3, 2(Mo K~) = 0.71073 A, /L = 3.5 cm -~, F(000) = 864, T- 295 K, R = 0.053 for 1628 observed reflections. The inorganic ring possesses a twistboat conformation with the phenyl substituents in trans positions. Mean bond lengths are N-P = 1.608 (3), N-S (from segment SNS)= 1.568 (4), N-S (from segment PNS)= 1.544 (3)A. The average endocyclic angles at S and N are 114.3 (2) and 124.4(5) ° respectively. The endocyclic angle at P amounts to 113.0(2) ° .

Structure of cis-5,5-dichloro-1,3-diphenyl-1λ6,3λ6,2,4,6,5λ5-dithiatriazaphosphorine 1,3-dioxide

C12H10C12N302PS2, Mr=394.22, triclinic, P1, a = 9.8757 (4), b= 9.9319 (4), c= 17.219 (1)A, ct= 96.183 (4), fl= 96.283 (4), y= 76.525 (3) °, V= 1626.6(1)A 3, Z=4, Dx=1.610gcm -3, 2(MoKtx) = 0.71073 A, p = 7.5 cm -1, F(000) = 800, T= 295 K, R = 0.042 for 4018 observed reflections. The unit cell contains two independent molecules, both with a skew-boat conformation of the inorganic ring. Phenyl substituents are in cis positions. Mean bond lengths are N-P = 1.573 (3), N-S = 1.575 (3), S-O = 1.428 (1), S-C = 1.761 (2), P-Cl= 1.981 (2) and C-C = 1.374 (2) A. The average endocyclic angles at P and S are 118.4 (2) and 112.3 (1) ° respectively. The endocyclic angles at N range from 121.2 (2) to 122.6 (2) °.

Structure of trans-5-iodo-5-iso­propyl-1,3-di­phenyl-1λ6,3λ6,2,4,6,5λ5-di­thiatri­aza­phosphorine 1,3-dioxide

C15HITIN302PS2, Mr= 493.33, orthorhombic, Pna2,, a= 16.895 (1), b= 10.589 (1), c= 10-513(1),(, V= 1880.8(3)A 3, Z=4, Dx= 1-742 g cm -3, Mo Ka, ,;I, = 0.71073 A, ~t = 19.9 cm -~, F(000)=976, T= 295 K, R =0.036 for 1363 observed reflections with I > 2.5a(I). The inorganic ring skeleton possesses a twist-boat conformation with the phenyl substituents in trans positions. The endocyclic bond lengths reflect double-bond character caused by d~-p~ overlap [S(1)-N(2) 1.602(6), N(2)-S(2) 1.580 (6), S(2)-N(3) 1.554 (5), N(3)-P 1.608 (6), P-N(1) 1.610 (6), N(1)--S(1)1.558 (5) A].

Controlled hydrolysis of hexachlorocyclotriphosphazene and related, sulphur-containing ring systems

Reactions of the ring systems (NPCl2)3, (NPCl2)2NSOX, and NPCl2(NSOX)2(X = Cl or Ph) with water in acetonitrile in the presence of AsPh4Cl or KCl–C12H24O6(1,4,7,10,13,16-hexaoxacyclooctadecane) afford salts derived from hydroxy derivatives of these rings. In all compounds the introduced oxygen ligands are exclusively attached to phosphorus atoms. In addition to monosubstituted derivatives some disubstituted ones can also be isolated. For (NPCl2)3 a non-geminal structure for the two isomeric disubstituted derivatives was established, whereas the derivative of (NPCl2)2NSOCl appears to have a geminal structure. The difference in reaction behaviour of these two ring systems is rationalized in terms of the different base strengths of the rings. The 31P n.m.r. spectra of the salts are briefly discussed.