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JOURNALOFTHE CHEMICAL SOCIETY~- ~~PERKIN TRANSACTIONS IIPhysical Organic ChemistryBonding in I ,2,4-Triazolesm Part 11.l Crystal Structure of 3,4,5-Tri-amino-l,2,4-triazole Hydrobromide (Guanazine Hydrobromide)By R. C. Seccombe and C. H. L. Kennard,' Department of Chemistry, University of Queensland, Brisbane,Queensland 4067, AustraliaThe crystal structure of the title compound was determined from diffractometer data by Patterson and Fouriermethods. Crystals are monoclinic, space group C2/c, with Z = 8 in a unit cell of dimensions: a = 686.9(1),b = 1069-3(2), c = 1855*0(2) pm, p = 95.66(3)". The structure was refined by least-squares to an R 0.036for 91 5 observed reflections. The molecule is planar. Interatomic distances (each ~k0.5 pm) : N-N(ring) 140.8,N-N(side-chain) 139-3, C-N(ring) 129.8 and 131 .I, and C-N(side-chain) 134.8 and 131.2.DICKINSON and Jacobsen 2 have found a reliable anal- effect the sulphur group has in influencing the propertiesytical procedure to detect the thioureido-group (or of the triazole ring.precursors of such a group) irrespective of the remainderof the molecule, through a reaction with hydrazine to DISCUSS1oNgive readily isolable and recognizable 4-amino-3- The arrangement of the atoms in the molecule is shownhydrazino-5-mercapto-1,2,4-triazole (1).in Figure 1. The interatomic distances for N-N in thetriazole ring and the side chain are intermediate betweenthat of 135.0 pm in 1,2,4-triazole and the single-bondvalue of 147.0 pm.Results indicate that substitution on C(3) and C(5) hasA\ /N\ N-N little influence on the bond lengths of the triazole ringsexcept the N(4)-C(5) bond when sulphur replaces theNH2 NH2 I I 1" F S - N 2"Lo r - HsyNYNH I ,y( 1 1hydcogen atom .of 1,2,4-triazole in (1) and (2) .3 There(1) and 3-hydrazino-5-mercapto-l,2,4-triazole (2) C(5), i.e.the sulphur atom has an effect on the delocalised have interatomic distances which differ from the normal Replacement of thefound in 1,2,4-triazole itself. The structure of the other substituents decreases the aromaticity of theDerivatives Of (l) have been found to be is also a decrease in the aromaticity of the triazole ringfor compounds containing a sulphur atom bonded to in tests for The structures Oforbital system of the triazole ring.sing1e- and lengths and from those hydrogen atoms on C(3) and C(5) in 1,2,4-triazole byhydrobromide of 3,4,5-triamino-1,2,4-triazole (3) wasundertaken to obtain more information on the nature ofthe 1,2,4-triazole ring and in particular to observe whatl N.W. Isaacs and C. H. L. Kennard, J . Chem. SOC. (B), 1971,1270 is regarded as Part I.R. G. Dickinson and N. W. Jacobsen, Analyt. Chem., 1969,41, 3124.triazole ring, this decrease being greatest for (2). Thevarious substituent groups attached to the triazole ringhave little effect with this bond length. There is remark-able similarity between the bond lengths obtained for (3)and (1). The results indicate that replacing the aminegroup on C(3) with the hydrazino-group produces nochange in the N(2)-C(3) and C(3)-N(4) bond lengths.The only significant change is in the N(4)-C(5) bondlength where replacement of the amine group on C(5)with the sulphur atom produces a lowering of the yoM.E. Senko and D. H. Templeton, Acta Cryst., 1968, 11,808. * P. Goldstein, J . Ladell, and G. Abowitz, Acta Cryst., 1969,B, 25, 1362 J.C.S. Perkin I1been removal of electron density from the H(l)-N(l)bond leaving the hydrogen atom H(l) positively charged.The electron density is then transmitted through thedelocalised x orbital system to reside in the C(5)-N(6)bond thus resulting in the formation of a stronger bond.Since the N(9) atom is more basic than the tertiarynitrogen atoms of the triazole ring, the N(4)-N(9) bondis a weaker bond than N(l)-N(2).The bond lengthsobtained for the triazole ring in (3) indicate that themolecule can still be considered as having aromaticcharacter but the amount of aromaticity has beendecreased from that found in 1,2,4-triazole. In (3), thereare two C-N distances within the triazole ring, C(3)-N(4)and N(4)-C(5) joined at a common nitrogen atom N(4) ata mean distance of 136.2 pm, and two external C-Ndistances, C(3)-N(7) and C(5)-N(6), mean 133.0 pm.These distances indicate that the external C-N bondshave more double-bond character than the internal C-Nbonds within the triazole ring. However, these meanslie in between the recorded values for pure single (147-0pm) and double (126.5 pm) bonds. Analysis of double-bond character indicate that it is difficult to describe thestructure in terms of any one of the possible canonicalforms, but is probably best described by a combinationof canonical forms (A) and (B).yH2 yH2double-bond character for this bond.The replacementof substituents appears to affect only the bond lengths inthe immediate vicinity of the replacement and is notapparently transmitted over the triazole nucleus. Forexample, in the case just mentioned, there is little changein the N(l)-N(2) and C(3)-N(4) bond lengths.H(71IFIGURE 1 Stereochemical arrangement of 3,4,6-triamino-1,2,4-triazole hydrobromide; Q: for bond distances 0.6 pm, forbond angles 0.4"; including hydrogen: distances 6.0 pm,angles 0.8"In (3), the C(5)-N(6) bond is considerably shorter thanthe C(3)-N(7) bond.This may be explained by the factthat since the molecule is positively charged, there hasH2N,$N H 2\ /H 2 h y N y NH 2+/N-N N-NN-N/H (C 1Packing of the molecule in the unit cell is shown inFigure 2. The closest distances between the negativelyI \FIGURE 2 Packing of the unit cel1973 3charged bromine atom and the atoms of the triazole ringare: Br - . - H(6) 285.7, Br - H(71) 275.7, Br - - - H(7)267.6, and Br - - H(l) 22343 pm, last one being thestrongest interaction. This is further evidence forthe observation that the positive charge is residing onH(l) and not distributed throughout the molecule as itwould be in a resonance structure. This short Br * * - H(l)distance can be partly responsible for the lengthening ofthe H(1)-N(l) bond by removal of electron density fromthe bond to reside on the hydrogen atom.The moleculeis planar except for atoms H(9) (-28.4), H(91) (20.6),and H(7) (-13.1 pm) which are displaced from the plane.EXPERIMENTALCrystaZData.-C,H,BrN,, M = 195.027. Monoclinic, a =686.9 (l), b = 1069.3 (2), G = 1855.0 (2) pm, p = 95-66' (3),U = 1.355 nm3, D, = 1.89 (by flotation), 2 = 8, D, = 1.91,F(000) =L768. Mo-&radiation, A = 71-07 pm; p(Mo-K, =63.47 cm-1. Space group, C2/c (C&, No. 15) or CG (C:,Counter data, from a crystal mounted about the b axis,were used to obtain accurate unit-cell dimensions by a least-squares procedure. A total of 915 out of 1240 independentreflections were observed from a crystal measuring 0.40 x0.24 x 0.06 mm on a Hilger and Watts computer-controlledfour-circle diffractometer by the 8-a step scan up to 0 26O.Data were collected a t a constant scan rate of 0.01' s-l andwere considered observed when I was >2.5a ( I ) and scan-width 1.4'.During data collection, a complete sphere ofdata were collected and (h,k,Z,) and (h,h,l) were corrected forLorentz and polarization factors and then averaged. Anabsorption correction was applied by use of a Gaussianintegration method with a grid size of 14 x 24 x 4 witha transmission coefficient of maximum 0-686 and minimum0.236.St, ztcture Determination and Refinement.-The position ofthe bromine atom was found from a Patterson synthesis.A subsequent structure-factor calculation gave R 0.680.By use of refined bromine co-ordinates, a difference Fouriersynthesis revealed all the remaining non-hydrogen atompositions. Two cycles of full-matrix isotropic least-squares refinement reduced Ii to 0.116.Least squaresrefinement with anisotropic temperature factors lowered R to0.054 arid a difference electron-density map revealed sevenhydrogen atom positions. During the refinement, thehydrogen atoms were assigned temperature factors equi-valent to the refined isotropic temperature factor of theatom to which they were bonded. A final full-matrix least-squares refinement varying all parameters and with isotropictemperature factors for the hydrogen atoms gave R 0.036and R' 0.032 {R' = Cw(lFol - ~Fc~)2//cwJFo[2]*].A final difference-Fourier synthesis revealed no prominentfeatures.A weighting scheme using the standard deviations* For details see Notice to Authors No. 7 in J. Chenz. SOC.A), 1970, Issue No. 20 (items less than 10 pp. are sent as full sizecopies)..E, ' International Tables for X-Ray Crystallography,' vol. 111,Iiynoch Press, Birmingham, 1962.R. F. Stewart, E. R. Davidson, and W. T. Simpson, J .Chew. Phys., 1965, 42, 3175.No. 9).calculated from counting statistics was used during thelest-squares refinement. The standard deviation of anobservation of unit weight given by ([Cw(lFol - IFcl)2]/(n - m))i, where n is the number of observations and nz isthe number of variables, was 1.14 indicating that theweighting scheme used was adequate. The final atomicparameters are listed in the Table.A list of observed andcalculated amplitudes appears in Suppementary PublicationNo. 20509 (4 pp., 1 microfiche).* The atomic scatteringfactors used throughout for carbon, nitrogen, bromine weretaken from ref. 5, and for hydrogen from ref. 6, and that forbromine corrected for anomalous dispersion.6 No correc-tions were made for extinction, since a plot of Ic/Io vs. I cshowed no reflections which were seriously affected byextinction.(a) Atomic positions (fractional co-ordinates) and temperaturefactors with estimated standard deviations in parenthesesxla0-1324( 1)0*1444( 6)0.1927 (6)0-2340(5)0.2 02 7 (5)0.1 359 (4)0.201 9( 8)0.1 07 1 (6)0.081 1 (7)0-236(7)0.1 64( 6)1 -234 (7)O-OOS( 7)0.LOO( 5)0*447( 7)0*144( 6)Ylb0*1923( 1)0.7 893 (3)0.6068 (4)0- 6963 ( 3)0*8141(3)0-66 18( 3)0*4842(4)0*8704(4)0*5947(4)0.189( 5)0.442 (4)0.453 ( 5 )0.865 (4)0*938(4)0- 11 6 (5)0.6 19 (4)ZIC0.0993( 1)0.1260(2)0.1776(2)0.2250( 2)0*1932(2)0.1 141 (2)0*1864(3)0.0707 (2)0.06 10( 2)0.21 8( 3)0.1 64(2)0*216(3)0.037 (3)0.077 (2)0*037( 3)0.023(3)(b) Anisotropic temperature factors ( x lo4) *Atom P11 Pz2 P33 P l Z P13C(3) 153(9) 36(4) 18(1) -6(4) -4(3)Br 202(1) 58(1) 16(1) O(1) --6(1)C(5) 166(9) 44(4) 15(1) O(5) O(4) -10(3)-3(N(l) 251(9) 51(3) 14(1)N(2) 233(9) 45(3) 16(1) -5(5) -9(2)N(4) 164(7) 41(3) ll(1) -3(4) -l0(2)-23(4) i!:! -21(3)441(16) 16(1)287(121 ~~~~~ 18111Calculations.-All computations * tl-ere made on an IBM360/44 a t the University of Canterbury, Christchurch, NewZealand.We thank Professor B. Penfold for making available thediffractometer, Dr. W. Robinson for assistance during datacollection and structure solution, and Dr. N. W. Jacobsenand R. G. Dickinson for preparing the crystals. R. C. S. isa Commonwealth Postgraduate Scholar.[2/352 Received, 17th February, 19721G. H. Stout and L. H. Jensen, ' X-Ray Structure Deter-mination: A Practical Guide,' Macmillan, New York, 1968, p. 411.IBM 360/44 Programs written by the Canterbury groupplus modifications of FORDAP (A. Zalkin and R. J. Dellaca),ORFLS (R. S. Busing, H. A. Levy, and R. J. Dellaca), andORTEP (C. J. Johnson), used on a CDC 3600 (C.S.I.R.O., Can-berra)

ISSN:1472-779X    

DOI:10.1039/P29730000001

出版商:RSC    

年代:1973

数据来源: RSC