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Feb 14, 2002 - phosphiniminocyclotrithiazene. J. Srinivas,(1)* G. Sreenivasa Murthy,(1) U. Swarnalatha,(2) and M.N. Sudheendra Rao(2). Received March 6 ...

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Journal of Chemical Crystallography (JOCC)

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February 14, 2002

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C 2002) Journal of Chemical Crystallography, Vol. 31, No. 5, May 2001 (°

Crystal structure of trismorpholino phosphiniminocyclotrithiazene J. Srinivas,(1) * G. Sreenivasa Murthy,(1) U. Swarnalatha,(2) and M.N. Sudheendra Rao(2) Received March 6, 2001

The title compound (OC4 H8 N)3 P == N ---- S3 N3 crystallizes in a monoclinic crystal system ˚ β= with unit cell parameters a = 8.9996(3), b = 17.2895(7), and c = 12.3648(9) A, 90.63(5)◦ , Z = 4, and space group P21 /n. Strikingly the exocylic S1 ---- N4 bond length ˚ and is accompanied by the largest angle at P ---- N4 ---- S1 as 131.2(2)◦ . The is 1.545(3) A tricoordinated sulfur atom of the cyclotrithiazene ring deviates from the mean plane of other ˚ five atoms by 0.654(1) A. KEY WORDS: Cyclotrithiazene; arylaminophosphine; crystal structure.

symmetric and asymmetric environment around the phosphorus atom have been synthesized, and a few crystal structures have been reported in recent years.6−14 Among these in only one compound is the phosphorus atom surrounded by like atoms.8 The crystal structure of the title compound (abbreviated as TRIMPC) has been determined in order to find the changes, if any, in the bonding pattern of the cyclotrithazene ring and in the exocyclic P ---- N ---- S moiety, when the phosphorus atom is bonded to four nitrogen atoms. The salient features have been compared with the reported crystal structures.

Introduction Phosphiniminocyclotrithiazenes are stable examples of 8π inorganic heterocycle systems and provide ample scope to analyze experimentally the effect of various substituents attached to the phosphorus atom on the bonding and conformation of the cyclotrithiazene ring.1−4 The crystal structure of Ph3 P == N ---- S3 N3 5 is the first to be reported among this class by Holt and Holt in 1974. Since then attempts have been made to determine the bonding pattern in the S3 N3 ring with different substituents attached to the phosphorus atom as the presence of polar exocyclic groups may allow donation of electrons to the ring and influence the conformation of the ring. Phosphiniminocyclotrithiazenes having both

Experimental The compound was prepared from the phosphine (OC4 H8 N)3 P by reaction with S4 N4 in acetonitrile medium at room temperature.6 Dark red parallelepiped crystals were obtained by slow evaporation from a mixture of CH2 Cl2 ---- CH3 CN (1:2) at 22◦ C. A crystal of dimensions 0.12 × 0.13 × 0.32 mm was selected for data collection. The intensity data were collected at room

(1)

Department of Physics, Indian Institute of Technology, Madras, Chennai 600 036, India. (2) Department of Chemistry, Indian Institute of Technology, Madras, Chennai 600 036, India. * To whom correspondence should be addressed at Whistler Center for Carbohydrate Research, 1160 Food Science Bldg., Purdue University, West Lafayette, Indiana 47907; e-mail: [email protected] foodsci.purdue.edu.

267 C 2002 Plenum Publishing Corporation 1074-1542/01/0500-0267/0 °

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268

Srinivas, Murthy, Swarnalatha, and Rao

temperature in ω–2θ scan mode on an EnrafNonius CAD-4 diffractometer using graphite ˚ radiation. monochromated Mo Kα (0.71069 A) The intensities were corrected for Lorentz and polarization effects. The structure was solved by direct methods, using SHELX-86,15 and refined by full-matrix least squares methods, using SHELXL-97.16 All the non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms located from the difference electron density maps during the intermediate stages of refinement have been refined with isotropic displacement parameters. The crystal data along with the details of structure refinement are listed in Table 1.

Table 1. Crystal Data and Summary of Intensity Data Collection and Structure Refinement Compound CCDC No. Color/shape Crystal dimensions (mm) Melting point (◦ C) Data collected at (◦ C) Crystal system Space group Unit cell dimensions

˚3 Cell volume, A Formula units/unit cell Dcalc , g/cm3 F(000) Diffractometer/scan Radiation employed µcalc (mm−1 ) Standard reflections Decay of standards Reflections measured 2θ range, deg Range of hkl Reflections observed [I ≥ 3σ (I)] Number of unique reflections Number of parameters refined R1 wR2 Goodness of fit on F2 Maximum shift/esd. ˚ −3 ) Largest peak and hole (e/A

C12 H24 O3 N7 S3 P CCDC-1003/6049 Red/parallelopiped 0.12 × 0.13 × 0.32 165 25 Monoclinic P21 /n ˚ a = 8.9996(3) A ˚ b = 17.2895(7) A ˚ c = 12.3648(9) A β = 90.63(5)◦ 1923.8(2) 4 1.524 928 Enraf-Nonius/ω–2θ ˚ Mo Kα (λ = 0.71069 A) 0.50 (122) (213) 2% 3423 4 ≤ 2θ ≤ 50 ±10, +20, +14 2678 2505 (Rmerg = 0.0337) 331 0.0382 0.1014 1.088 0.01 0.52 and −0.29

Results and discussion The crystal structure of (C5 H10 N)3 P == N ---- S3 N3 8 (abbreviated as TRIPPC) is the first among the reported phosphiminimocyclotrithiazene structures, in which the phosphorus atom is surrounded by four nitrogen atoms. The title compound, (OC4 H8 N)3 P == N ---- S3 N3 , is the second in the series. The fractional coordinates of all non-hydrogen atoms along with their equivalent displacement parameters are given in Table 2. The ORTEP17 of the molecule along with the numbering scheme is shown in Fig. 1. The observed bond distances in the S3 N3 ring are in between the sulfur–nitrogen double bond distance of 1.55 ˚ 19 ˚ 18 and the single bond distance of 1.76 A. A As observed in other reported phosphiniminocyclotrithiazenes these S ---- N bond distances can be Table 2. Atomic Fractional Coordinates (×104 ) and Isotropic ˚ 2 ) of all Non-Hydrogen Atoms Displacement Parameters (×103 A With Their esd’s in Parentheses Atom P S1 S2 S3 N1 N2 N3 N4 N5 N6 N7 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 O1 O2 O3 aU eq

x

y

z

Ueq a

426(1) 1587(1) 4311(1) 4173(1) 2627(3) 5030(3) 2622(3) 353(3) 1112(3) −1296(3) 1394(2) 837(4) 2120(6) 2623(4) 1341(4) −2598(3) −3560(4) −2771(4) −1763(4) 924(4) 1382(4) 3397(4) 3008(3) 2355(3) −4026(2) 2943(2)

4306(1) 5849(1) 5983(1) 6125(1) 5674(2) 6206(2) 5663(2) 5227(1) 3858(1) 4093(1) 3940(1) 4154(2) 3936(2) 2847(2) 3017(2) 4580(2) 4204(3) 2971(2) 3306(2) 4048(2) 3346(2) 3109(2) 3810(2) 3124(1) 3452(2) 3208(2)

7266(1) 7516(1) 6463(1) 8699(1) 6454(2) 7568(3) 8607(2) 7483(2) 8332(2) 6949(2) 6275(2) 9428(2) 10151(3) 9124(3) 8375(3) 7159(3) 7998(4) 7484(4) 6647(3) 5136(2) 4502(3) 5671(3) 6340(3) 10181(2) 7671(2) 4577(2)

28(1) 42(1) 59(1) 67(1) 53(1) 63(1) 61(1) 38(1) 34(1) 35(1) 31(1) 45(1) 60(1) 49(1) 39(1) 42(1) 59(1) 53(1) 42(1) 41(1) 50(1) 46(1) 38(1) 60(1) 58(1) 55(1)

= one third of the trace of the orthogonalised Ui j tensor.

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Crystal structure of (OC4 H8 N)3 P == N ---- S3 N3

Fig. 1. The ORTEP of (OC4 H8 N)3 P == N S3 N3 . The thermal ellipsoids are at 50% probability level.

categorized broadly into three groups (i) 1.662(3), 1.648(3); (ii) 1.611(3), 1.610(4), 1.608(3); and ˚ The bond lengths and angles in the (iii) 1.586(4) A. present heterocycle are listed in Table 3. An examination of the endocyclic bond lengths and angles reveals that the tricoordinated sulfur atom is associated with long bonds and the smallest angle, whereas the N2 atom is involved in the smallest bond and the largest angle observed in the ring. ˚ Bond Angles (deg), and Table 3. Selected Bond Lengths (A), Torsion Angles (deg) With esd’s in Parentheses Bond lengths S1 N1 S1 N3 S2 N1 S2 N2 S3 N2 S3 N3

1.648(3) 1.662(3) 1.608(3) 1.586(4) 1.610(4) 1.611(3)

P N4 P N6 P N5 P N7 S1 N4 P· · ·S1

Bond angles N1 S1 N3 S1 N1 S2 N1 S2 N2 S2 N2 S3 N2 S3 N3 S3 N3 S1 P N4 S1

107.1(2) 119.7(2) 116.3(2) 123.5(2) 113.9(2) 116.1(2) 131.2(2)

N4 N4 N5 N4 N5 N6

Torsion angles S1 N1 S2 N1 S2 N2 S2 N2 S3 N2 S3 N3 S3 N3 S1 N3 S1 N1

N2 S3 N3 S1 N1 S2

18.6(3) −0.9(3) 9.9(3) −40.0(3) 56.0(3) −44.9(2)

P P P P P P

1.616(2) 1.636(2) 1.644(2) 1.639(2) 1.545(3) 2.879(7) N5 N6 N6 N7 N7 N7

110.3(1) 102.8(1) 115.7(1) 121.9(1) 102.6(1) 104.1(1)

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269 Further the S ---- N bond distances are longer in the present compound and have a larger spread when compared to TRIPPC. The larger spread in the S ---- N bond lengths might be due to more uneven occurrence of π-bonds over the ring skeleton. The tricoordinated sulfur atom (S1) in the present compound is found with approximately tetrahedral angles (N1 ---- S1 ---- N3 = 107.1(2)◦ ; N1 ---- S1 ---- N4 = 105.4(1)◦ ; N3 ---- S1 ---- N4 = 106.4(2)◦ ) as in the other reported iminocyclotrithiazenes. The angles N1 ---- S1 ---- N3 (107.1(2)◦ in TRIMPC and 107.2(2)◦ in TRIPPC) and S2 ---- N2 ---- S3 (123.5(2)◦ in TRIMPC and 123.2(2)◦ in TRIPPC) agree with the corresponding ones in both the compounds. The tricoordinated sulfur atom (S1) deviates from the mean plane of N1, S2, N2, ˚ A similar value S3, and N3 by 0.654(1) A. ˚ has also been observed in TRIPPC (0.65 A). From the signs of the torsion angles it can be inferred that the folding of S3 N3 ring is toward a distorted chair conformation. In the series Ph[(C6 H11 )2 N](R)P == N ---- S3 N3 20 ,where R is an alicyclic or aliphatic amino group, the angle at N2 and the deviation of S1 from the mean plane of other five skeletal atoms have shown some dependence on the nature of the substituent R, but this is not the case in the present series. Appreciable changes have been observed in the bond lengths and angles of the exocyclic P ---- N4 ---- S1 fragment. The S1 ---- N4 bond dis˚ in TRIMPC against 1.574(3) tance is 1.545(3) A ˚ in TRIPPC, whereas P ---- N4 bond distance is A ˚ There has been an 1.616(2) against 1.595(3) A. increase in the P ---- N4 ---- S1 angle from 120.0(2)◦ in TRIPPC to 131.2(2)◦ in TRIMPC. This has resulted in a longer P· · ·S nonbonded distance ˚ (2.745(8) A ˚ in TRIPPC). The bond 2.879(7) A 2 angle opening at sp hybridized nitrogen atom and the observed bond shortening in S1 ---- N4 could be due to the back donation of nitrogen lone pair into the empty orbitals of phosphorus or the sulfur atoms.21,22 In general the interaction of 3d orbitals of sulfur or phosphorus atom with 2p orbitals of nitrogen atom depends on the ligand effects of shrinking the 3d orbitals sufficiently for an effective overlap.23 It seems in the present case back

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270 donation takes place to phosphorus as well as sulfur atoms and when interactions with phosphorus atom are not favorable donation to sulfur atom becomes more so, resulting in a short S ---- N distance. The phosphorus atom has a distorted tetrahedral geometry. The observed P ---- N bond distances in the present compound are longer than those of TRIPPC and are shorter than the expected ˚ 24 Probably P(sp3 ) ---- N(sp2 ) bond length 1.77 A. the π-electron delocalization around the phosphorus atom is more extensive in the present compound. The three morpholino rings adopt a chair conformation. No short contacts are observed and the molecules are held together by van der Waals forces. Acknowledgments The intensity data have been collected at RSIC, IIT Madras, India. The first author is thankful to Dr Babu Varghese and Sri M.V. Rao for their encouragement and helpful discussions.

References 1. Chivers, T.; Oakley, R.T.; Cordes, A.W.; Pennington, W.T. J. Chem. Soc., Chem. Commun. 1981, 1214.

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Srinivas, Murthy, Swarnalatha, and Rao 2. Holt, E.M.; Holt S.L.; Watson, K.J. J. Chem. Soc., Dalton Trans. 1977, 514. 3. Spang, C.; Edelmann, F.T.; Noltemeyer, M.; Roesky, H.W. Chem. Ber. 1989, 122, 1247. 4. Thomas, C.J.; Cea-Olivares, R.; Espinosa-Perez, G.; Turner, R.W. J. Organometal. Chem. 1995, 493, 101. 5. Holt, E.M.; Holt, S.L. J. Chem. Soc., Dalton Trans. 1974, 1990. 6. Mohan, T. PhD thesis; Indian Institute of Technology, Madras, India, 1990. 7. Thomas, C.J.; Bhandary, K.K.; Thomas, L.M.; Senadhi, S.E.; VijayKumar, S. Bull. Chem. Soc. Jpn. 1993, 66, 1830. 8. Elias, A.J.; Rao, M.N.S.; Babu, V. Polyhedron 1990, 9, 1433. 9. Srinivas, J.; Murthy, G.S.; Mohan, T.; Rao, M.N.S. Acta Crystallogr., Sect. C 1996, 52, 1250. 10. Srinivas, J.; Murthy, G.S.; Thomas, C.J.; Rao, M.N.S. J. Chem. Crystallogr. 1996, 26(6), 403. 11. Srinivas, J.; Murthy, G.S.; Mohan, T.; Rao, M.N.S. Z. Krist-New Cryst. St. 1997, 212, 323. 12. Gopalakrishnan, J.; Rao, M.N.S.; Srinivas, J.; Murthy, G.S. Polyhedron 1997, 16(7), 1089. 13. Gopalakrishnan, J.; Srinivas, J.; Murthy, G.S.; Rao, M.N.S. P. Indian As-Chem. Sci. 1998, 110(2), 89. 14. Gopalakrishnan, J.; Srinivas, J.; Murthy, G.S.; Rao, M.N.S. Indian J. Chem. 1998, A37(12), 1052. 15. Sheldrick, G.M. SHELXS-86, Program for Solution of Crystal Structures; University. of G¨ottingen: Germany, 1985. 16. Sheldrick, G.M. SHELXL-97, Crystal Structure Refinement-PC version; University of G¨ottingen: Germany, 1997. 17. Johnson, C.K. ORTEPII, Report ORBNL-5138; Oak Ridge National Laboratory: Oak Ridge, TN, 1976. 18. Bats, J.W.; Coppens, P.; Koetzle, T.P. Acta Crystallogr., Sect. B 1977, B33, 37. 19. Sass, R.L. Acta Cryst. 1960, 13, 320. 20. Janaswamy, S. Ph.D. thesis, Indian Institute of Technology, Madras, India, 1997. 21. Coulson, C.A. Nature 1969, 221, 1106. 22. Craig, D.P.; Paddock, N.L. J. Chem. Soc. 1962, 4118. 23. Craig, D.P.; Zauli, C. J. Chem. Phy. 1962, 37(3), 601. 24. Cruickshank, D.W.J. Acta Cryst. 1964, 17, 671.

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