2748
Inorg. Chem. 1994, 33, 2748-2757
Molecular Cleft Reactivity and Conformational Properties of Skeletally Stabilized Triphosphazanes Susan M. Young, Abbas Tarassoli,'. Josepb M. Barendt,lb Cbristopber A. Squiers,lC Francoise Bartbelemy, Riley Scbaeffer, R. Curtis Haltiwanger, and Arlan D. Norman' Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 Received December 17, 19936 Regioselective reactivity, molecular cleft selectivity, and conformational properties have been examined in the skeletally stabilized triphosphazanes C ~ H ~ N Z [ P ( N E ~ ~ ) (31, ~ ] ~C6H4N2[P(S)(NEt2)212PNEtz PNE~~ (41, C6H4N2[P(S)(NEt2)2]2PCl(5), and C~H~N~[P(S)(NE~~)~]~P(S)NE~Z ( 9 ) and in a series of new derivatives. 3 is oxidized/ coordinated regioselectively by 0 3 , Se, PhN3, and BH3 to C~H~N~[P(O)(NE~~)~]ZPNE~~ (10) and C6H4N2[P(O)(NEt2)212P(O)NEt2 (111, C~H~NZ[P(S~)(NE~~)~~~PNE~~ (12), C6H4N2[P(NPh)(NEt2)212PNEt2 (131, and C6H4N2[P(BH3)(NEt2)2]2PNEt2 (14), respectively. 4 reacts selectively with HBF4, CF,C02H, and H3P04to form the endo-phosphorus-substituted C6H4N2[P( S)(NEt2)21 2PF (18), CaH4N2[P(S)(NEB) 21 2POC (0)CF3 (19), and C6H4N2[P(S)(NEt2)2]2POP(0)(OH)2 (20). Quantitative Me1 quaternization or BH3 coordination of 4 yields {C6H4N2[P(S)(NEt2)2]2P(CH3)NEt~)I (16) or CsH4N2[P(S)(NEt2)2]2P(BHp)NEt2(15). 5 reacts selectively with alcohols MeOH, EtOH, and i-PrOH (but is inert toward t-BuOH) to form C ~ H ~ N Z [ P ( S ) ( N E ~ ~ ) ~[R ] ~=P Me OR (21), Et (22), i-Pr (23)] and withBH3 toformC6H4N2[P(S)(NEt2)2]2PH(25) anditsadduct C6H4N2[P(S)(NEt2)2]2PH(BH3) (24). New triphosphazanes 1&16 and 18-25 are characterized by spectral data. Structures of 9, 12, and 16 are determined by X-ray crystallography: 9, orthorhombic, Aba2, a = 23.1 1l(4) A, b = 21.324(5) A, c = 14.609(3)A, V = 7200(2) AS,Z = 8, R = 0.042, R, = 0.045; 12,orthorhombic,Pbca, a = 14.975(6)A, b = 18.894(7) A, c = 24.524(8) A, V = 6939(3) A3, Z = 8, R = 0.053, R, = 0.058; 16, orthorhombic, C2221, a = 10.885(4) A, b = 20.78(2) A, c = 36.31(2) A, V = 8214(9) A3,Z = 8, R = 0.048, R, = 0.050. Variable-temperature 3lP{lH) NMR spectra of 3-5, 10, 11, 15, 16, and 20 and of the known CsH4N2[P(S)(NEt2)2]2PNH2(a), C6H4N2[P(S)(NEt2)2]2PN3 (7), and C6H4N2[P(S)(NEt2)2]2P(O)H (8) show that rotation around skeletal exo P-N bonds is unrestricted to below -90 OC; only 9 and 11freeze to unsymmetrical conformationsat low temperatures. Rotation of the endo (CH3CH2)2N- group in the molecular cleft of 3 is unrestricted to -90 OC; in 16 the group freezes to an unsymmetrical conformation below -40 OC. Potential impacts of the observed reaction selectivity and conformational properties on oligomeric/polymeric phosphazane structure and reactivity are discussed.
Introduction Skeletally stabilized phosphazane oligomers and polymers containing alternating skeletal phosphorus and nitrogen atoms bridged at adjacent nitrogen atoms by l,2-C6H4 groups have been the subject of several recent studies.2-' From 1,2(NH2)2C6H4/RPC12 (R = Me, Ph) condensationq-6 or 1,2(NH2)2CbH4/RP(NEt2)2 (R = Me, Et, Ph) transamination" reactions, polymers (l), linear oligomers, and cyclic crown type cyclo dimers (1; n = 2)c6,8 and trimers (1; n = 3)s are formed. These new skeletally stabilized extended phosphazanes lead to basic questions about reactivity and molecular structure. Since *Abstract published in Advance ACS Abstracfs, June 1, 1994. (1) Present address: (a) Department of Chemistry, Shahid Chamran University, Ahwaz, Iran. (b) Callery Chemical Co., P.O. Box 429,
Pittsburgh, PA 15230.(c) Smithkline Beechum, P.O. Box 1539,L-950, King of Prussia, PA 19406. (2) (a) Barendt, J. M.; Haltiwanger, R. C.; Norman, A. D. J . Am. Chem. Soc. 1986,108,3127.(b) Barendt, J. M.; Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1989, 28, 2334. (c) Bent, E. G.; Schseffer, R.; Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1990, 29, 2608. (3) (a) Barendt, J. M.; Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1986,25,4323.(b) Barendt, J. M.; Haltiwanger, R. C.; Squier, C. A.; Norman, A. D. Inorg. Chem. 1991, 30,2342. (4) Bent. E. G.;Barendt, J. M.;Haltiwanger,R. C.;Norman,A. D. Inorganic and Organometallic Polymers; ACS Symposium Series 360;American Chemical Society: Washington, DC, 1988;p 303. ( 5 ) (a) Barendt, J. M.; Bent, E. G.; Haltiwanger, R. C.; Norman, A. D. J. Am. Chem.Soc. 1989,111,6883.(b) Barendt, J. M.;Bent,E.G.;Young, S.M.; Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1991,30,325. (6) N0rman.A. D.;Bent, E.G.;Haltiwanger, R.C.;Prout,T.R.Phosphorur Sulfur, 1989,41, 63. (7) Bent, E. G.; Haltiwanger, R. C.;Norman, A. D. Inorg. Chem. 1990.29, 4310. ( 8 ) Young, S.M.; Imiolczyk, T. M.; Haltiwanger, R. C.; Norman, A. D. Submitted for publication.
0020-1669/94/ 1333-2748304.50/0
1
3 (X = Et2N, E = lone pair) 4 (X I EtpN. E = S) 5 ( E = S, X = Cl)
it is known that diphosphazanecondensation reactions can m u r with a high degree of stereoselectivity? it is possible that higher phosphazanes can also form stereoregularly. Second, although diphosphazane conformational properties have been examined,l@m little is known about conformations in higher phosphazanes. (9) (a) Hill. T.G.; Haltiwanger. R. C.; Norman, A. D. Inorg. Chem. 1985, 24,3499.(b) Prout, T.R.; Imiolczyk, T.W.; Haltiwanger, R. C.; Hill, T.G.; Norman, A. D. Inorg. Chem. 1992,31,215. (IO) Keat, R. Top. Curr. Chem. 1982, 102,89. (11) Prout, T. R.; Imiolczyk, T. W.; Barthelemy, F.; Young, S. M.; Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1994,33,1783. (12) Keat, R.; Manoj1ovic'-Muir, L.;Muir, K. W.; Rycroft, D. S.J. Chem. Soc., Dalton Trans. 1981,2192 and references cited therein. (13) Cross, R.J.; Green, T. H. Keat, R. J. Chem. SOC.,Dalfon Trans. 1976, 1424. (14) Colquhoun, I. J.; McFarlane, W. J. Chem. Soc., Dalton Trans. 1977, 1674. (15) Harvey, D. A.; Keat, R.; Keith, A. N.; Muir. K. W.; Rycroft, D. S. Inorg. Chim. Acta 1979.34, L201. (16) Rudolph, R. W.; Newmark, R. A. J. Am. Chem. Soc. 1970,92,1195. (17) (a) Ebsworth, E. A. V.;Rankin, D. W. H.; Wright, J. G. J, Chem. Soc., Dalton Trans. 1977,2348.(b) Ebsworth, E. A. V.; Rankin, D. W. H.; Wright, J. G. J. Chem. Soc., Dalfon Trans. 1979, 1065. (18) HHgele, G.; Harris, R. K.; Wazeer, M. I. M.; Keat, R. J. Chem. Soc., Dalton Trans. 1986,1974.
Q 1994 American Chemical Society
Skeletally Stabilized Triphosphazanes Finally, there is insufficient information to assess the reactivity and/or accessibility of nonterminal skeletal phosphorus centers to P-X substituent replacement, Lewis acid coordination, or oxidation [e.g. P(II1) to P(V)]. The latter question is further complicated by the fact that these skeletally stabilized systems contain two types of phosphorus environments, bridge RP and phosphadiazole RP units, which could possess significantly different reactivities. A triphosphazane unit, such as 2A or 2B, is a minimum-sized phosphazane that can yield representative information about extended skeletal phosphazaneconformationalproperties around,
Inorganic Chemistry, Vol. 33, No. 13, 1994 2749
P40lo. Silica gel (EM Science), KBr (Baker, Oven dried), Se (laboratory supply), HBF4 (85% in Et20 complex, Aldrich), BH3.THF (1.0 M in THF, Aldrich), petroleum ether, ethyl acetate, and deuterated solvents were used as received. PhIO (Aldrich) and Me3NO (Aldrich) were sublimed before use. B2H6,U PhN3,ZSC ~ H ~ N Z [ P ( N E ~ Z ) Z ] Z(3),2b PNE~Z (4)IZb C~HINZ[P(S)(NE~Z)~IZPCI (5)?b C~H~NZ[P(S)(NE~~)ZI~PNH~ (6),2bC ~ H ~ N Z [ P ( S ) ( N E ~ ~ )(7)?b ~IZPN~ C~HINZ[P(S)(NE~~)Z~~P(O)H (8),2band CsH,N2[P(S)PhzlzP(S)NEt2 (9)zb were prepared as described previously. R=ctionsof~P(NEt2)2bPNEtz(3). (A) WithC H r [P(O)(NEt2)2bPNEQ (10) .ndCdWdP(O)(NEt2)2bp(O)N& (11). To C , ~ H ~ N Z [ P ( N E ~ ~ ) ~ (3) ] ~(20 P Nmmol) E ~ ~ in 120 mL of CH2C12 in a Schlenk tube at 10-12 OC was added 0 3 as 0 3 / 0 2 at 8 psi. Samples were taken every 3 min for ,IP NMR analysis. After 42 min, resonances were present at 6 13.7 (d, area 2, V p ~ = p 51.3 Hz] and 97.9 (t, area 1) and at 6 11.3 (d, area 2, z J p ~ p= 16.5 Hz) and 19.2 (t, area 1) due to 1 0 and 11, respectively (1011 = 2:l). Attempts to separate the mixture by crystallizationor column chromatography failed. No distinguishable change in the mixture composition was observed after 2 weeks at 25 OC. Conditions under which 1 0 formed without 11 were not found. 2A 28 Addition of 0 3 to 3 in CHzClz at 10-12 OC (as above) for 100 min yielded 11 quantitatively. 11 crystallized from CHlClz (mp 109-1 11 or reactivity at, the RP centers. From recent studies, one such OC, yield 97%). MS: M+ m/e 605. IR (KBr, cm-I): 2978 (s), 2935 triphosphazane is available, C ~ H ~ N Z [ P ( N E ~ & ] ~(3, P NXE=~ ~ (s), 2875 (s), 1680 (w), 1593 (s), 1488 (vs), 1465 (m), 1382 (m), 1360 EtZN), a species which could model a central phosphadiazole (w), 1332 (w), 1302 (w), 1255 (w), 1232 (s), 1211 (s), 1192 (s), 1170 (w), 1120 (vs), 1100 (m), 1065 (m), 1035 (w), 1008 (w), 962 (vs), 942type triphosphazane (2B).2b3 In preliminary studies, 3exhibited (w), 918 (m), 908 (vs), 794 (vs), 755 (vs), 735 (m), 716 (vs), 694 (vs), highlyregioselectiveoxidationby SSat theexovs endo phosphorus 668 (s), 562 (w), 532 (m), 502 (m), 460 (m). Mol wt: calcd for atom^.^ Further, thedisulfide C~H~N~[P(S)(NE~~)Z]~PNE~Z (4) C%H&Jfi,P3,605.357 94;found(exactmassMS),605.35788. Because and chloro-substitutedderivativeC~H~NZ[P(S)(NE~Z)~] zPCI(5) samples were routinely contaminated with traces of H20 which we were showed restricted reactivity at the endo phosphorus, which was unable to remove completely, satisfactory chemical elemental analyses attributed to the existence of a protective molecular cleft at the were not obtained. 31P(1H)NMR (toluene-ds, 27 OC): A X 2 pattern,26 central (endo) phosphorus site. We have now extended our studies 6 10.5 [d, area 2, 2Jpp = 14.7 Hz; P(l), P(3)], 19.0 [t, area 1, P(2)]. of triphosphazanes in this series; the results are described below. 31P(lH)NMR (EtOH), 27 OC): 6 11.0 (d, area 2, J = 17.1 Hz), 18.6 (t, area 1). IH NMR (toluene-ds): a 7.23-6.92 (m, area 4; C&), Experimental Section 3.26-2.84 (m, area 20; CHI), 1.00 (m, area 30; CH3). 11 reacted slowly with HzO, during 6 h, to form a mixture of soApparatusand Materials. Phosphorus-3 1, IIB, and I9FNMR spectra far-uncharacterized products. were obtained on a Varian Gemini or a VXR300S spectrometerat 121.4, (B) With Otber [O] Oxidants. 3 with excess PhIO or Me3NO in 96.2, and 292.2 Hz, respectively. ,IP NMR spectra were also obtained refluxing benzene for 20 h showed no reaction. with JEOL FX-90Q and Bruker WM-250 spectrometers at 36.5 and 101.2 MHz. IH NMR spectra were obtained on JEOL FX30Q (90 (C) WithSelenium. C&NP(Se)(NEt2)2bpNEt~(12). 3andexcess MHz) and Varian Gemini-300 or VXR300S (300 MHz) NMR Se in toluene were refluxed for 12 h. 31PNMR spectral analysis showed only 12. Recrystallization from toluene yielded 1 2 (mp 128-129 OC, spectrometers. 3lP, IH, IlB, and '9Fchemical shiftsdownfieldfrom 85% H J P O (external), ~ Me& (internal), BF3OEtz (external), and CF3COzH yield >90%). ''P('H) NMR (C6H6, 27 "c): 6 99.7 [d, area 2, 2 J p =~ (external), respectively, are reported as positive (+6). IR spectra (400068.4 Hz; P(l), P(3)], 63.0 [t, area 1; P(l)]; Jpsc = 391 Hz. 3IP(lH)VT NMR (toluene-d8): V p ~ p Hz , (temp, "C): 68.4 (25), 68.2 (OO), 68.1 400 cm-I) were obtained using a Beckman 4250 or an IBM IR/32 Type (-30),68.3 (-6O), 68.0 (-90). IHNMR (C6D6): 6 7.54 (m, area ZC6H4 9132 spectrometer. Mass spectra were obtained at 70 eV with a Varian MAT-CH5 or a VG Analytical 7070 EQ-HFspcctrometer. Massspectral ortho),6.86 (m,area2;C6H4ortho), 3.40(m,area 4;exoCH2CH3), 3.13 data refer to the major peak of the respective envelope. Chemical (m, area 12; exo CHZCH~), 2.82 (m, area 4;endo CHZCH~), 0.9-1.2 (m, area 30; CH3). IR (KBr, cm-I): 2924 (m), 1586 (s), 1482 (vs), 1377 ionization (CI+ and CI-) was achieved using isobutane as the ionizing gas. Exact mass analyses were referenced to perfluorokerosene. (vs), 1331 (w), 1293 (w), 1250(vs), 1200(s), 1165 (vs), 1115 (w), 1061 (vs), 945 (vs), 883 (vs), 794 (vs), 741 (s), 691 (w), 579 (m), 509 (m), Ozonolyses were carried out in a Welsbach Ozonator Model T-408 operating at 90 V. X-ray diffraction data were collected on a Nicolet 475 (m), 428 (w). MS: M+ m / e 717. Anal. Calcd for cz6H~N&Se2: P3/Fautomateddiffractometer equipped withagraphitemonochromator C, 43.64; H, 7.55; N, 13.69. Found: C, 44.64; H, 7.85; N, 13.04. and low-temperature attachment. All manipulations were carried out (D)With PhN, CdWdP(NPh)(NEt2)2hNEtz (13). 3 and PhN3 using standard vacuum-line, glovebag, or Schlenk techniques under dry [(2-3):l moleratio] in toluenewtrecombinedat 25 OC;reactionoccurred Nz." immediately. 31PNMRspectrashowed 13withonlytracesof unidentified Flash chromatography was carried out as described by Still et aLZ3A materials. Removal of toluene in vacuo yielded 13 as an oil (>90%), 650- or 450-mL column was packed (1 5 cm) with silica gel 60 (230-400 which we were unable to purify completely by crystallization or column mesh). Compounds were eluted with the necessary solvent mixture under chromatography. 31P(1H)NMR (C6H6): 6 99.1 [t, area 1, 2 J p ~ =p 47.6 N2 pressure at 5 cm/min. Hz; P(2)], 32.9 [d, area 2; P(l), P(3)I. Elemental analyses were performed by Huffman Laboratories Inc., (E) WithBHyTHF. -fl(BH3)(NEtz)&PNEt2( 14). BH3.THF Golden, CO, and Desert Analytics, Tuscon, AZ. (excess) wasaddedunderNztoasolutionof3inTHFatroomtemperature, lr2-(NHz)2C6H4 (Aldrich) was recrystallized from toluene and and the mixture was stirred overnight. The SIP NMR spectrum showed sublimed. CF3C02H (Aldrich) was stored over 13-A molecular sieves. only 14. The reaction solution was concentratedin vacuo. 14precipitated CH3I wasdistilled from CaHz. Toluene (over Na/benzophenoneor CaHz) upon cooling to 0 OC and was recrystallized from toluene (mp 152-1 54 and CHzCl2 (CaHz) were distilled before use. H3PO4 was dried with OC, yield 92%). 'H NMR (C6D6): 6 7.57 (m, area 2; C6H4 ortho), 6.84 (m, area 2; C6H4 meta), 3.40 (m, area 20; CH~CHI),1.30 (br m, area Bulloch, G.; Keat, R.; Rycroft, D. S.;Thompson, D. G. Org. Magn. 0.93 (t, area 6; PBH3), 1.05 (t, area 12, 3 J = ~7.08~Hz; ex0 CHZCH~), Reson. 1979, 12, 708. 6, 3 J ~ 7.08~HZ; endo CHZCH~), 0.91 (t, area 12, 'JHH 7.08 HZ; Chen, H.-J.; Barcndt, J. M.; Haltiwanger, R.C.; Hill, T. G.; Norman, A. D. Phosphorus Suljur 1986, 26, 155. Moskva, V. V.; Kuliev, A. K.;Akhmedzade. D. A.; Pudovik, M.A.; (24) Norman. A. D.; Jolly, W. L. Inorg. Synthesis 1968, 11, 15. Sakhnovskaya.J. Gen. Chem. USSR (Engl. Tronsl.) 198$,55,834. (25) Lindsay, R.0.;Allen, C. F. H. Organic Syntheses; Wiley: New York, Shriver, D. F.; Drezdzon, M. A. The Manipulotion of Air-Sensitive 1955; Collect. Vol:III, p 710. Compounds, 2nd ed.; McGraw Hill: New York, 1986. (26) Abraham, R . J. The AnolysisofHigh ResolutionNMRSpectro; Elsevier Still, W. C.; Kahn, M.;Mitra, A. J. Org. Chem. 1978.43, 2923. Publishing Co.: New York, 1971.
Young et al.
2750 Inorganic Chemistry, Vol. 33, No. 13, 1994 exo CHzCH3). 3lP(lH) NMR (toluene-d8, 27 "C): 6 100.3 [t, area 1, 2Jp~= p 59.3 Hz; P(NEtz)], 94.0 (br m, area 2; P(BH3)l. 31P(lH)VT NMR (toluene-dg): 70 "C, 6 101.3 [t, area 1, V p ~ = p 61.6 Hz; P(l), P(3)], 95.4 [d of q, area 2, IJpe = 84.9 Hz; P(2)]; -90 "C, 6 98.4 (t, area 1, 2 J p ~ p= 55.1 Hz), 90.0 (br d, area 2). z J ~ pHz , (temp, "C): 59.7 (loo), 60.7 (90), 60.3 (80), 61.0 (70), 60.1 (60), 60.3 (50), 60.1 (40), 59.9 (30), 59.9 (25), 59.5 (0), 59.2 (-20), 58.2 (-4O), 57.6 (do)55.9 , (-80), 55.1 (-90). lIB(IH) NMR (toluene-d8): 6 -33.4 (d, IJep = 87.9 Hz); from IH-coupled spectrum, d of q, 'JBH= 122 Hz. Anal. Calcd for C Z ~ H & N ~ P C, ~ : 53.33; H, 10.26; N, 16.75. Found: C, 53.52; H, 10.48; N, 16.37. MS (CI+), M+ m / e (% re1 int): 585 ( 5 ) . IR (KBr, cm-I): 3426 (w), 3060 (w), 2974 (vs), 2934 (s), 2870 (s), 2390 (vs), 2281 (w), 1586 (w), 1483 (vs), 1380(vs), 1349 (m), 1332 (s), 1291 (m), 1251 (vs), 1202 (vs), 1178 (vs), 1119 (m), 1076 (s), 1028 (vs), 986 (m), 946 (vs), 890 (s), 866 (s), 842 (m), 797 (s), 738 (vs), 691 (s), 674 (m), 603 (w), 505 (m), 481 (m). Reactions of C&NdP(S)(NEtz)&PNEt2 (4). (A) With B3H(and BHyTHF. C&NdP(S)(NEtz)&P(BH3)NEt2 (IS). Bz&(0.13 mmol) was condensed onto 4 (0.065 mmol) in toluene-d8, and the mixture was warmed to 25 "C. The NMR spectrum exhibited resonances from 15 and uncoordinated 4 (mole ratio 1 5 4 = 1.3:l). The llB(lH) NMR spectrum showed singlet resonances from 15 and unreacted B2H6. IlP(IH) NMR (toluene-d8): 6 108 (br s, area 1; PBH3), 66.4 (d, area 2, J p ~ = p 34.0 Hz; P = S ) . IIB{lH) NMR (toluene-ds): 6 -33.8 (br s). Measured quantities of BHyTHF were added under N2 to a solution of 4 in toluene-d8 or THF in mole ratios of (OS-10):l. Solutions were allowed to reach equilibrium at 20 "C (NMR probe temperature), and the 1 5 4 ratios were determined by integration of the OIPNMR spectra. Typical reaction conditionsareasfollows. [BHyTHF], [4], [THF] initial molar concentrations(solvent), 1 5 4 equilibriumratio: (1) 0.121,0.235, 12.3 (THF), 0.14:l; (2) 0.189, 0.161, 12.3 (THF), 0.22:l; (3) 0.343, 0.0850, 4.23 (THF), 1.l:l; (4) 0.857, 0.142, 12.3 (THF), 0.71:l; ( 5 ) 0.814,0.0821, 12.3 (toluene), 0.58:l; (6) 0.471,0.0456, 5.82 (toluene), 1.34:l. The IIB(IH) NMR spectrum showed singlet resonances from unreacted BHyTHF and 15. Removal of solvent and BHyTHF in vacuo resulted in complete conversion of 15 to 4. (B) With CHZ. (C&L+N~P(S)(NE~Z)Z~P(CH~)NE~Z)I (16). CH3I (0.2 mL, 3.2 mmol) was syringed into a solution of 3 (0.974 g, 1.6 mmol) in CHzC12 at 25 "C. Reaction occurred slowly; in 18 h the 3lP(IH}NMR spectrum showed AB2I9pattern resonances assigned to 16 along with those of 3 (16:3 = 2:l). Reaction was complete in 36 h. The solution contained mainly 16 along with minor amounts of 3 and C6&N2[P(S)(NEtz)z]zP(O)H (8) (
