The Crystal and Molecular Structure of 2-Formylpyridine Selenosemicarbazone

3464 CRYSTAL STRUCTURE OF MAGNESIUM CHLOROPHOSPHATE Table 4. Bond distances, polyhedral edge lengths, and bond angles for the phosphate tetrahedron Numbers in parentheses are estimated standard deviations in last significant figure. (i) Interatomic distances P-O(I) 1.536 (2) ,A, 0(1)-0(2) 2.535 (3) ,~ P-O(2) 1-521 (3) 0(1)-0(3) 2.445 (3) P-O(3) 1.564 (3) 0(1)-0(4) 2-519 (3) P-O(4) 1-537 (2) 0(2)-0(3) 2.580 (4) 0(2)-0(4) 2.542 (3) 0(3)-0(4) 2-445 (3) (ii) Angles O(1)-P-O(2) 112.0 (1) ° O(I)-P-O(3) 104.1 (1) O(1)-P-O(4) 110.1 (1) O(2)-P-O(3) 113.5 (1) O(2)-P-O(4) 112.4 (1) O(3)-P-O(4) 104"1 (1) This work was supported in part by the Advanced Research Projects Agency through the Materials Science Center, Cornell University. References BUSING, W. R., MARTIN, K. O. & LEVY, H. A. (1962). ORFLS. Report ORNL-TM-305, Oak Ridge National Laboratory, Oak Ridge, Tennessee. BUSING, W. R., MARTIN, K. O. & LEVY, H. A. (1964). ORFFE. Report ORNL-TM-306, Oak Ridge National Laboratory, Oak Ridge, Tennessee. CROMER, D. T. & MANN, J. B. (1968). Acta Cryst. A24, 321. HAMILTON, W. (1965). Acta Cryst. 18, 502. KLEMENT, R. & HASELBECK, H. (1965). Z. anorg, allgem. Chem. 336, 113. REA, J. R. & KOSTINER, E. (1972a). Acta Cryst. B28, 2505. REA, J. R. & KOSTINER, E. (1972b). Acta Cryst. B28, 2525. SHANNON, R. D. t~ PREWITT, C. Z. (1964). Acta Cryst. B25, 925. ZACHARIASEN, W. H. (1967). ,4cta Cryst. 23, 558. Aeta Cryst. (1972). B28, 3464 The Crystal and Molecular Structure of 2-Formylpyridine Selenosemicarbazone BY A. CONDE, A. LOPEZ-CASTRO AND R.M.~,RQUEZ Departamento de Optica, Secci6n de Fisica del Centro de Investigaciones Fisicas y Quimicas del C.S.L C Universidad de Sevilla, Spain (Received 14 July 1972) The structure of 2-formylpyridine selenosemicarbazone, SeN4CTH8, has been determined from threedimensional X-ray photographic data. The crystals are monoclinic, space group P2t/e, with unit-cell dimensions a=9.320, b=6-524 and c= 16-275 ,&, fl=90.53 °. There are four formula units in the cell. The structure was solved by the two-dimensional minimum Patterson function and the heavy atom method. It was refined by a full-matrix least-squares method to a final residual R value of0.11 for 1180 observed reflexions. The Se-C bond length of 1.83 ,~ possesses only partial double-bond character. The molecules are linked by N-H...Se hydrogen bonds to form dimer-like units, which are held together by N-H...N hydrogen bonds. Introduction In recent years, several organic compounds of selenium have been investigated. The molecular structures of different selenosemicarbazones have been studied by Gingras, Suprunchuk & Bayley (1965); they described their infrared spectra with particular emphasis on the Se-C vibration and they have studied the antifugal properties of selenosemicarbazones that were found to be generally more active than the corresponding thiosemicarbazones. French & Blanz (1966) have studied various thiosemicarbazones and have found that all the tumour inhibitors are potentially capable of acting as tridentate N-N-S type ligands. Mathew & Palenik (1969) reported the crystal structure of bis-(1-formyl-isoquinolinethiosemicarbazonato)nickel(I I) monohydrate and confirmed the ability of the ligand to act as a tridentate chelate. However, the compound 2-formylthiophene thiosemicarbazone (Mathew & Palenik, 1971) shows no tumour inhibition although the posibility of an N-N-S type chelate exists. On the other hand, French & Blanz (1966) reported that 4-formylpyridine thiosemicarbazone shows no carcinostatic activity, whereas they found that 2-formylpyridine thiosemicarbazone is a tumour inhibitor. Apparently the position of the thiosemicarbazone group on the pyridine nucleus dictates the biological activity of formylpyridine thiosemicarbazones. A knowledge of the conformation and bond lengths is essential for a final explanation of the requirements for biological activity in these compounds. Therefore, a crystal structure analysis of 2-formylpyridine selenosemicarbazone was carried out to correlate the molecular structure with the thiosemicarbazone analogues. A. CONDE, A. LOPEZ-CASTRO AND R. MARQUEZ 3465 Experimental 0 Crystals of 2-formylpyridine selenosemicarbazone used in this work were prepared and kindly supplied by Dr J. M. Cano of this University. They are brown, needleshaped prisms, elongated along the b axis and belonging to the monoclinic system. Cell dimensions were measured from Weissenberg photographs of th2 three zero levels, upon which Debye-Scherrer diagrams with aluminum powder as standard were superimposed. The crystal data obtained are" a = 9.320 + 0.008 .,~ b = 6.524 + 0.005 c = 16.275 + 0.014 fl =90.53 +0.05 ° Z=4. Dml'48 + 0.02 g.cm -3 Dx = 1"51 /z (Cu Kc0 = 49 cmi F(000) = 112 Systematic absences were consistent with space group P21/c. Two series of equi-inclination Weissenberg photographs were taken with Cu K0c radiation about the a axis up to the third layer, and about the b axis up to the fourth layer. The multiple-film technique was used and 1180 independent reflexions were collected. The intensities were estimated visually with a standard film strip and were converted to Fo(hkl) by applying the usual Lorentz, polarization and spot-shape corrections. No correction was made for either absorption or extinction. One of the crystals used for the a axis rotation had a cross section of 0.10 × 0.11 mm, and ¢2 ¢= U • slnB 0 al 2 sinfl / Se ~_- // Fig. 1. The minimum function M2(x,z). Fig.2. A projection of the structure along the b axis. that for the b axis rotation a cross section of 0.07 x 0.06 mm. The two series of intensity data were correlated and reduced to a common scale by a least-squares method. The data were brought to the absolute scale by comparison with the calculated values at a later stage. Structure determination and refinement The structure was solved by combining two-dimensional Patterson superposition methods and threedimensional Fourier syntheses. The two-dimensional Patterson syntheses P(v, w) and P(u, w) showed outstanding maxima which were attributed to seleniumselenium vectors. The minimum functions M2(y, z) and M2(x, z) (Buerger, 1951) were then calculated using the vectors Se-Se through the symmetry centre. The M2(x, z) function (Fig. 1) shows good resolution and led to the location of the possible positions for all the light atoms. However, the relative position of the molecule makes the interpretation of the other projection difficult. It proved necessary to use three-dimensional methods to obtain the y coordinates for the light atoms. 3466 STRUCTURE OF 2-FORMYLPYRIDINE SELENOSEMICARBAZONE Using only the phases the selenium atom, all the light atoms excepting hydrogen were located after one cycle of structure-factor calculations and a threedimensional electron-density synthesis. A structurefactor calculation with the set of coordinates obtained gave an R index of 0.21. A Fourier synthesis was calculated and the R value dropped to 0.17 for all observed reflexions. Isotropic temperature factors, exp(-2.5 sin-' 0/22), were used in calculating structure factors. The refinement by means of six least-squares cycles, of which the last three were with anisotropic thermal factors, were sufficient to reduce the discrepancy index to 0.11. A full-matrix program written by Busing, Martin & Levy (1962) was used, in which the weighting scheme was that of Hughes (1941). In the anisotropic refinement complex scattering factors were introduced for the correction of the anomalous dispersion, which was expected to be significant for the Se atom (Af'= - 1.0, Af"= 1.1). With the above calculations, inter-and intramolecular distances and bond angles were obtained as a test of the improvement in the structure. The Fo and final F~ values are given in Table 1, and the final atomic parameters and their corresponding standard deviations in Tables 2 and 3. Description of the structure A projection of the structure along the [010] direction is shown in Fig. 2. Bond distances and angles in the 2formylpyridine selenosemicarbazone molecule are listed in Table 4 and shown in Fig. 3. The observed value of 1.83 A, for the Se-C distance is intermediate between the Se-C single-bond distance of 1.92 A and the Se-C double-bond value of 1.71 ~. Thus, the Se-C bond in this selenosemicarbazone possesses only partial double-bond character in agreement with the canonical forms: / / Se- - C Se = C \ \ N.~ / N~ The C(2)-N(3) bond of 1.29 .~ should be a double bond. The corresponding C(1)-N(1) bond distance of 1.37 A and the C(I)-N(2) bond distance of 1.35 A are ~a.s -,~.~ 08 *0,3 "~o3 i "3,Z .s** I: ......... Xl.3 -:'.5 *,.c -v).o ,c.3 -,.o. ~ ,I.a o-O., *'6.Z -I|.3 ,;:; ..... ~,~.~ s,.~ s~.~ -~o.s ~, ~.: ~,.~ i i aa.5 ,.1 ~,.:* .~,.~. 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Io ........ 15.~ Z~.~ ao., -3X.: , :~., -o.~ 1o., X3.S *.,. -1~.~ - b s~.6 o,..o z, Z~oe -e.~, °I: ........ - :g ......... x 13., -s,.1 o~ :3".Z :5','. :.: 2:: ::::~ --:a 3:.e ~o.: = ~.i -~,.: ~,.~ .~,,., z~.: :9.~ g ....... .o ~,.e -~.~ ~s :i., 1:., ~, i,.~ :6.: :~ ~::: -*::; -s ~,.o z6.6 ;~ -., .,., z3..z -3z.~ x-za ~., -,,.s z-x) zo.s 16.X x-xs 31*S ze.o ~-:6 i,.~ 16.~ :-z9 zo., -i~.o r l~.z 1o.1 1 3Z., -51.S z ~s.,. ,).1 i,.o ~6.1 6 ,z,~ -~,.o )~., .~e..~ zz sl.~ -~.., ~3 zo.5 ~,.: :9 ~z.o -:5.~ -1 tox.s -°3.' z -z zc.t ze.~ z -5 'C.3 ?z.i a -~. e.c ;:.~ z-, z -* ~z.c -~5.5 a-x,, ~s.z -H.,, z-:5 ~s.i zs.1 o ~,o.~ -se., x ~0.6 5"*Z *,..z ,a.~ , ,i.z s~.z 3 Z",'~ -3Z.# s.e 1".6 ~0.~ -ZZ.' lO 'O.Z -~.~' :z x,.z o.o ~3 ~o.e xe.s x, z~.s xe.s ) -~ l~.z -,.5 -,. ,,s.o ,o., :,' ~,':~ ..... ,..o 1-:~ :Z*9 -:o.- s-~ xz.~ -:x.~ 3-;3 Z3." -Z~.3 : I ........ -" I °'° "'" o.e, -6.o sz.1 -~.,.~. ~,,3 3),° Table 1 Observed and ca/cu/ated structure factors The columns are in the order h, k, l, Fo and F~. • is Q.5 -:~.l , -3 '::l "3::I • -, 33.~ -53., -~ ;~.e -;~.~ • -, ~3.I X6*Z • -io 5,..5 ~o.e ,-:: ~o.a -xs.: 3~.6 -30.3 z#.~ -,., 36.5 ]~.Z 13 Z~.~ -~.~ 16 1o.~. -6.S o) zo.l -z,.~ -,. ~,.z -z,.e -, , .... .., -9 t~., zz.', s 3~.~ -~.3 zs.s ~.o :; ;,:: ;l:~ : :I :'" i,., : :l ..o ..... at.a -~,.~ -s Z5.3 -x1.~. -o :'.9 H.~ • , x3.~ -H.- • -) :3 3 :~., -s ~:o :6.: e o xz.e, -I~., s a zl.s -Z3.* s ~ s,, ~,.,. o a ~.(.., z zo.,~ e, le,.o -p.- o s s,.o -~5.a e~ zo ~,..e -ti.5 o ~a ac.6 x*.x z, 36.Z ~**g ~e a~.~ -a~.~ o -z ~,.z -6O.: o -,. ,z.~ --~.~ o -s ,,.s -~.,. o-lo x ;,..~ -:-.: i ~ xs., i:,,~ z ~*., -~.~, I i lz,.o ~z:.~ i ,5., -io., ~.5 -'.3.C x ~1.1 -a,.5 • ,.,,, 5;.) -~ ',e*~ -IZ.S :':i z3., ~a.z • ^., .~., • ,z.~ -,-., -~ ,,.,~ -~3,i z-;z ,.s -,.~ Z-15 z,., *~.e z-l~ ~,.6 zo.e a~.s -,., a ,e.~ ,i., i ,,.o -5Z.~ ~, I~.t -tS.~ • a,.l -zo..~ ~'.6 Z'.' lo 15.* Is.* ~t 1,.~ -13.S it, is., -is.6 iv ,.~, 13.e -3 5~.S 5~.., -5 ~3., -a,.o -6 51.0 -a~.Z -,~ s,.o -s.., -e ~.o 3a.1 3-:X 3Z.~ S~.6 )*z, zo.6 -re., l:ll ......... : I ......... 3 Ze." -*., ,. • x~.e xc.c ,. -> S6*~ S'~.6 • -s zv.s so.,. z*.* sz.z • -xs x~.s -~,.s o 3*.S -,o.) z ~6*S -e., 3~.~ -~,~. s s ,,., ~s.1 a~,.5 ,.z.~ xo z:., -~.e, i~ :;.~ ~,.~ -3 ~z.~ ;~.3 -,. ~o.~ ~,., -, ~3.~ -~3.'. ~-zo zz.z .zz.,~ 1-z I P.c ;~.i x,.c -;,.- -~ ~-.~ .~,.: .'~ ~.e ~., ;3.~ *~.* • ~ ~.,, ~.~ :,., -;z.* -~ zs:, la.c i i 9., IZ*O : -; I~:~ -11:: g : ......... 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'-'i ',!!i :ii!! - :~ ~.~ ~.~ ~.: -,:.~ 7~ ........ ~,~.~ ,~.~ ~s.. ,~.e - , ~-.~ -~,~.~ • ~.~ .~,.~ o -, ~,6 r -e~ • ,,.~ ~,., ~6., i a.., as.~ i:~ a~.~ -~,.~ ~ ,o.? 66.6 e -e ,q.z -~s., -to ~',.: -~)., o-;a V'.3 ;'.9 ~,.'~ ~e.o o , ]~.9 ~.s o ~ I a 15., |Tel .z ~o.~ -~.c i i ......... z*., o-:o i~.'~ -~o.~ e-:, ,~.~ -,~.z i z ~,.'~ ~).o 6 Z6.,~ --~).6 ,.g ..... s :).6 g ,o ........ -e., 1 , ........... °'" i ~I:I "~.~ "~.~ -:,.~ ~ : .~ ~e.~ e.o - ~ ~-~o ~,.o -,e.~ A. CONDE, A. LOPEZ-CASTRO AND R. MARQUEZ 3467 Table ~I ~ :: '::~ ..... 11.o z~.o -,., i-i~ e.l I J ......... i -6 i.) -la.s -14 ,., -1o.o i ]I I~Io l]le~ i -I Ii.I *iiii i-Ii ~iiI II., i-I I Ii.$ 1OoO I-ii io.s -Iio, • i.~ 41,+ • 5+., -b**! sl,o -,I.o 11.1 .v.! Ii.I -ii.I I O 16'6 ~,.~ ao.o is.+ I: ........ I -I "9.' .5+.? :| ,,., .,., ,.z -s,.? • ,+ s+.+ *s~.l s ,., *9 Ps., -~,.+ l )x.~ -,=.- : ~+., *~+.6 : :+.,..:,.+ : i ~. :~.x :~.~ I I, ~ .1 z t i, e.+ -xl.-. : -: ,~ .... ~.. : *~ x~.+ -:x.s i -~ 1),, i+.+ : -+, ++-., .++.. i -- ~.~ :~.. lJ ........ I : ......... 1 8 Q*I IP*I :x., -:~.~ I -1 ~.~ ~.- i -Z I".6 +3.1 t -b i+.~ Is.: i -~ ~..- -,~.~ ' ;i!+ .... ~i .... )~.) ~-:e :l.s -0.+ 1..1 i.i .-~: 11.: +1°, 1-io ,**i ,1.1 l-l+ :+.: :t.* I-ii ll.l -19*$ :? ¢ 16.+ -ll*O x-x, zl.. -at., :x.~ -:~.+ 1-1s 9.5 1.~ I116 -1o.o gs., -+z.+ t , ~,.z -::,~ :k I I ......... i; I : ........ la zl.s - "6*S "1.~ tt 1 :+ ....... ..... :0 !! s,.o -ss,t ii z..l *as.! I *8 +7.1 -11.1 1-9 15.9 1111 :*x0 16.e -15., 1-11 16.0 ~0.~ l-t/ 19.+ ll.z x-t, ao.8 z,.. t-ll 19.I -14.1 I-I~ 6.~ -$.( : x6.* -x~.l a,.o -~z.~ + Is.? SO.5 s Is,, Is,~ 19.1 I110 ~'*! -Z?,S !.9 10.1 tz x,.? is.s 11 ..... ,., ;:+ o+ 6,,1 061,$ -I +.! o,e -$ $114 ll.l al.e x*.~ 1-IO II.6 *ii., i*I~ ls.~ -l).o t-~z ao.l -~o.l l-IS ~..~ +0.6 l-ls :1., xl.s 1-16 1~.I 1o.o )s.i sl., -1 :e.* -+.b -z :+.l -x+.r -s z~.+ ze.s -~ zs., +s.s -, If./ -I~*.9 -~ x...z -X'*6 i q'~ q': 15.0 -Z6.~ Z ,.s -it.+ 1 Iz,e -:P.,~ ;z,, -::.* -'P e,, 11.0 Z-14 6*1 -716 t ~., It.4 z-lo 9.1 -11.1 o +5.1 -/?°S ll.b s.s I ,.+ -,.z + ;+.v -:s., s hi.6 -b~., Ii tb,e +l~.o xs xs., -1,.~ I -s ++., -,e., + -+ *.+ -s.s + *s +,?.. -,z.o z-lo Is. +, ;s.o z-l+ 1*.: z:.) 1-11 11.2 ic,| ~-:s l.~.+ -z,.o +-Is te.~ -,.s x +a., -z,.~ I I ......... 1 (cont.) :,, ::., ~.~ -z :s., s.~ -1 sz.+ +e.~ -+ ,.1 -v.s *s x,** x/.+ z-l+ +.~ -,.t a.~.s z+.o :.+.o z-xs iI.b ~I.~ 1-1 + le., -11.1 a bo.l ,:.~ :t'.'5 ,.o a~.~ ~..x Sl.,. -i).+ z 11 ll*& 1~'06 1) :Z.b l,.o :~ ;t:: ..... +:; ,,., -,6., ,,+., ,.,+i + -, as.s z+.+ 2-II 1~*6 -10,6 l-as to.e -io.s z-ls l:.s ll., o 11.1 o.v t ss., ,o.~ lz./ -'P., $1 .~. -1116 , X6.: -as.+ + x~,9 zs,++ :l a~.s l,.o I -i 18.? lb*l -) is.a -1,.1 z -s ~s.t -s~..e + -.+ ~o.s lz.6 z-lt Zb.~ Ib., 1*x, ",.s -.~.9 :~ o 6.'. -).s z ) zs., -Z'.6 • 16,$ ~zlz 2 *$ 3,*8 3106 ; :: .... .,::: is.,. o,.,. 13 ' : ........ Is,* -Z~.9 1o z -1 a,.o -a:,., -s I,,s IS.'P io 2 *? 18*1 +o.~ $~+ z z 16° ? ~1o°1 I| ? s l-.o -15,3 xl ~ -1 1,.+. xe,+ l: ~ -~ ~,,c, -le,e ii i -$ 16°~ -20.2 ) i~ 6,6 e.,. If; ....... s-z+ t/., -*.s i/.I -9.0 Xb tl.~ -1,./ + ,.o -l.+ 2O ~6.'r S+.Z 16,6 z+..e +) ~9.~ -sl.s • zt,* -l~,o s +,. :, *~,.s 19.1 161Z lb." IS.* 1 s+.s +,.+ 13 +~., -1~.1 1~ ,., *e.s -1 .s.s ~a.~ Table 2. Fractional coordinates (× 10 4) deviations (x 10 4) 2 I;:: .... -n ll.e -~.$ -, ~1.6 -,.o -e S2.1 ~e., -p 18,. -19.. 1-i1 1/,i |b*4 l-l) l~*l I~,$ ~-I 0 1106 -1~,1 2b.+ -e.v : 1,.i -ss,a z ~,., -2s.I s +,.i sl..l . is,+ -+*,, + s+.. ++.t + :+.s -2..o lz .;.1 -t2°+ zs lo,o l+.e 16 ,.9 s.,l *: s6.l *I.i.5 -z ~+.. zs.. -s bO*+ )+,s 1,.* lb.+ -i +1.s -t.~.+ -+ /z.s -zz., s-ll 1,., -i+..+ $-11 ii.I 161S s-Is ll.s t+.,. +'~.1 lhl 1,.' lb., 1.,,+ zb.2 lJ*l -/PI6 1o1+ -?111 ls 6.~ "** -+ 11.e -Is.0 -s t4.+ -is.s *~ 1b.6 +6*5 is.o :+.s -9 IS.e ~6.V s-l+ ., +.1 ++-i,~ ... -le.t o 16.* :,..; 3 1,,1 -+s., 6 1~.1 -~s,I 9 20." iii,$ :o ls.e 1,.+ zl.~ zz.. .1 Zl,1 16,+, -,. re.) *Iv.o sz.., -)o.1 s-l+ s.+ s-ls Is.) ~+.~ o '.6 -).1 x+.l -XS*6 o 1~** -is., S 1,.1 ll.S v n iz., :'.o v 1,1oi -i,.~ ! ;I ...... -~ 13.* i+.o -, l~.e t,., + -e It.9 -:S.'I "' 'l:+' ..... + s-to -..b xo Io.~ ~.~ :s e.,t S*6 I+ xl.t +.~ lO 11..~ i$. I, '+- 1117 -Ib*2 :o Ib.~ -l?.e :: ~ ~ -~.+ -t0.l Lz .... :' -:~., !++ -b ~c ^ -+.6 -s l+~+ -1+.+ :++ -+ ~x., ~b.s :- -+ + ..... x:.o x+., :," :i ::I ,,.,'" with standard x/a y/b z/c Se 6610 (2) -3630 (3) 4013 (1) N(1) 3950 (15) -2280 (25) 4614 (9) N(2) 5008 (14) - 192 (24) 3634 (9) N(3) 3788 (15) 1067 (23) 3692 (9) N(4) 2835 (16) 5649 (25) 2649 (9) C(1) 5053 (17) -1942 (26) 4081 (10) C(2) 3856 (18) 2626 (30) 3208 (11) C(3) 2697 (16) 4169 (32) 3199 (11) C(4) 1523 (20) 4045 (38) 3750 (11) C(5) 519 (20) 5564 (38) 3716 (12) C(6) 631 (21) 7103 (37) 3142 (14) C(7) 1847 (22) 7049 (41) 2618 (13) indicative of some double-bond character, in agreement with the above resonance forms. The N(2)-N(3) bond distance of 1.41 A agrees well with the single N-N bond and with the value reported by Andreetti, Domiano, Gasparri, Nardelli & Sgarabotto (1970) in thiosemicarbazide. In this paper, the most striking evidence for the single-bond character of N(2)-N(3) is the tetrahedral configuration for N(2). On the other haiad, in the structure of 4-formylpyridine thiosemicarbazone, the N-N bond is 1.375 A, which suggests that other canonical forms may be important (Restivo & Palenik, 1970). However, there is no evidence for the existence of these forms in this structure. A slight shortening of the C(4)-C(5) and C(5)-C(6) bond lengths, is noted, which may indicate the presence of resonance forms involving the pyridine ring. Regarding the bond angles, one finds that the angle N(2)- N(3)-C(2) is 112.1 ° and the C(2)-C(3)-N(4)is 115.4 °, which are below the corresponding values observed in 4-formylpyridine thiosemicarbazone. These significant deformations occur in the part of the molecule that is engaged in the shortest intermolecular contact. A comparison with other structural studies of similar thioand selenosemicarbazones may help to explain some of the observed values. The complete molecule is nearly planar, as illustrated in Table 5. The maximum deviations from the mean plane are for N(1) at 0.064, N(2) at 0.054 and C(5) at 0.049 A; the first below and the other two above the plane. The pyridine ring is planar as expected, the maximum deviation from the ring plane involving C(5) at 0.012 +~ above the plane. In Table 6 the shorter intermolecular contacts are listed. The structure includes three intermolecular hydrogen bonds which link the molecules. There are dimer-like molecules formed by two N-H. • • Se hydrogen bonds across a centre of symmetry; these N-H... Se hydrogen bonds are rather weak since the N...Se distance is 3-52 A. The dimer-like units are linked into a three-dimensional network by a strong N-H-..N hydrogen bond. The N...N distance of 2.96 ~ is shorter than most of the -NHz-..ring-N distances reported by Fuller (1959), which average 3.06 /~. The molecular packing is analogous to that found in the structural analysis of 4-formylpyridine thiosemicarbazone. Table 3. Anisotropic thermal parameters (x 10 4) with estimated standard deviations (x 10 4) The form of the temperature factor is : exp [- (B1~h z + B22k 2 + B33/2 + 2Bx2hk + 2B~3hl+ 2B23kl)]. BI 1 B22 B33 B12 Bl 3 B23 Se 71 (2) 151 (5) 31 (1) -39 (4) 7 (1) -16 (2) N(1) 85 (18) 167 (40) 37 (6) 11 (26) 20 (8) 20 (14) N(2) 62 (15) 157 (42) 30 (6) 23 (25) 1 (7) 2 (13) N(3) 80 (17) 103 (41) 31 (6) 24 (26) -3 (8) 0 (13) N(4) 80 (18) 144 (37) 30 (6) 24 (27) 5 (8) 17 (13) C(1) 77 (18) 85 (40) 23 (6) 18 (27) -1 (8) - 8 (13) C(2) 74 (19) 157 (49) 32 (7) 44 (30) -5 (9) - 4 (16) C(3) 46 (17) 227 (60) 33 (7) 15 (31) -4 (9) - 4 (17) C(4) 95 (23) 349 (81) 30 (7) - 1 (40) 10 (10) 12 (19) C(5) 88 (22) 277 (65) 39 (8) 59 (38) -3 (11) 0 (20) C(6) 91 (24) 262 (63) 51 (11) 80 (38) 1 (12) -17 (22) C(7) 121 (25) 302 (75) 42 (9) 58 (41) 16 (13) 1 (22) 3468 STRUCTURE OF 2-FORMYLPYRIDINE SELENOSEMICARBAZONE Table 4. Bond lengths and angles with e.s.d.'s in parentheses (a) Bond lengths (A) Se---C(1) 1.83 (2) C(3)-C(4) 1.42 (3) C(1)-N(1) 1.37 (2) C(4)-C(5) 1-36 (3) C(1)-N(2) 1.35 (2) C(5)-C(6) 1.38 (3) N(2)-N(3) 1.41 (2) C(6)-C(7) 1.42 (3) N(3)-C(2) 1.29 (2) C(7)-N(4) 1.32 (3) C(2)-C(3) 1.48 (3) N(4)-C(3) 1.32 (3) (b) Bond angles (°) Se---C(1)-N(1) 122.9 (2.4) C(2)-C(3)-N(4) 115.4 (3.0) Se---C(I)-N(2) 119.8 (2.3) C(3)-C(4)-C(5) 121.4 (3.4) N(1)-C(1)-N(2) 117-2 (2.8) C(4)-C(5)-C(6) 120.1 (4.3) C(1)-N(2)-N(3) 118.5 (2.8) C(5)-C(6)-C(7) 118.0 (3.8) N(2)-N(3)-C(2) 112.1 (2.7) C(6)-C(7)-N(4) 122.6 (4.0) N(3)-C(2)-C(3) 120.3 (3.3) C(7)-N(4)-C(3) 118-4 (3.9) C(2)-C(3)-C(4) 121.4 (3.4) N(4)-C(3)-C(4) 123.2 (3-5) Table 5. Deviations of the atoms from least-squares Table 6. Interatomic distances less than 4 ~, planes Symmetry code The planes are expressed as AX+BY+CZ+D=O, where i 1-x -1-y 1-z v 1-x -y 1-z X, ¥ and Z are referred to orthogonal axes. The atoms inii 1-x -½+y ½-z vi x 1 +y z dicated with asterisks were omitted from the calculations of iii x -1 +y z vii 1-x ½+y ½-z the least-squares planes, iv 1 +x - 1 +y z viii -x -½+y ½-z Plane Description A B C D Distances Se---N(1 t) 3.52 A N(2)-C(2") 3.49 /~ I Through all atoms 0.497 0.528 0.688 6.245 Se__N(4ti) 3.92 N(2)-C(3 ji) 3.70 II Through pyridine Se---C(2 "t) 3.77 N(2)-C(7 "l) 3.80 ring atoms 0.513 0.541 0.666 6.204 Se---C(2") 3.73 N(2)-C(7") 3.88 Se---C(5 ~v) 3-72 N(3)-C( 1 v) 3.86 I II N(1)-N(I v) 3.77 N(3)-N(4 ~) 3.82 Se 0.034 -0.005* N(1)-N(2 v) 3.41 N(3)-C(7 "l) 3.60 N(1) -0.064 -0.152" N(1)-N(3 v) 3.55 N(4)-C(1 v~) 3-55 N(2) 0"054 0"035* N(1)-N(4 "~) 3"62 N(4)-C(1 ~") 3.64 N(3) -0.013 -0.040* N(1)-C(1 ~) 3"60 N(4)-C(2 v") 3"63 N(4) -0"037 -0"001 N(1)-C(3 m) 3.46 C(1)-C(1 v) 3-97 C(1) -0.030 -0.080* N(I)-C(4 m) 3.58 C(1)-C(2 m) 3.97 C(2) 0.017 0.021" N(1)-C(5 "~) 3-78 C(1)-C(2 'i) 3.82 C(3) 0.002 0.003 N(I)-C(6 m) 3-92 C(1)-C(3 m) 3-64 C(4) 0-028 -0.008 N(1)-C(7 "i) 3"80 C(1)-C(7 "t) 3"86 C(5) 0.049 0.012 N(2)-N(4 m) 3"74 C(4)-C(6 ~"l) 3"87 C(6) - 0"008 - 0"009 N(2)-N(4") 2"96 C(5)-C(6 v"t) 3"92 C(7) -0.031 0.004 N(2)-C(1 v) 3-97 C(5)-C(7 ~"~) 3.82 c(7)------- N(4) 122.G 1~6.4°~ 115.4 ° C(E) 118 .00 123"2° C~3)~C(2) .~\.~e_ s¶ c(s)------.- c(4) cO)~" ", 112 7 122.9 e ".,. • N(1) "', • ,, "N(1) """ s, ~....~...~c1'~¢:.,. c(4) 1.3s c(s) ~(2) ~.4...~..--s c(3) c(6) N(4) ~71 Fig. 3. Arrangement of a dimer-like unit. Bond distances and angles. A. CONDE, A. LOPEZ-CASTRO AND R. M/kRQUEZ 3469 Apart from the hydrogen bonds there are some intermolccular distances shorter than the van der Waals contacts. At Se there are two carbon contacts close to 3.72 &, which is only slightly below the sum of the van der Waals radii, 3.85 A. There is also a carbon-carbon intermolecular contact of 3.64 A, which is slightly below the sum of the van der Waals radii for carbon (3.70 A). The authors wish to thank Dr J. M. Cano, University of Seville, for supplying the crystals; Professor S. Martinez-Carrera, of the Instituto Rocasolano del C.S.I.C. Madrid, for making available the crystallographic programs for the Univac 1108 and also for help in running them; and Dr M. Laing of Natal University (Durban) for sending the programs for the IBM 1130. We also thank the E.T.S. de Ingenieros Industriales de Sevilla for the computing facilities on the IBM 1130. The present work forms part of the Doctoral Thesis of one of us (A.C.A.), who acknowledges the research grant of Formaci6n de Personal Investigador given by the Ministerio de Educaci6n y Ciencia. References ANDREETTI, G., DOMIANO, P., GASPARRI, G., NARDELLI, M. SGARABOTTO, P. (1970). Acta Cryst. B26, 1005. BUERGER, M. J. (1951). Acta Cryst. 4, 531. BUSING, W., MARTIN, K. & LEVY, H. ORFLS. Report ORNL-TM-305, Oak Ridge National Laboratory, Oak Ridge, Tennessee. FRENCH, F. & BLANZ, E. J. (1966). J. Med. Chem. 9, 585. FULLER, W. (1959). J. Phys. Chem. 63, 1705. GINGRAS, B., SUPRUNCHUK, T. & BAYLEY, C. (1965), Canad. J. Chem. 43, 1650. HUGHES, E. W. (1941). J. Amer. Chem. Soc. 63, 1737. MATHEW, M. & PALENIK, G. (1969). J. Amer. Chem. Soc. 91, 6310. MATHEW, M. & PALENIK, G. (1971). Acta Cryst. B27, 59. RESTIVO, R. & PALENIK. G. (1970). Acta Cryst. B26, 1397. Aeta Cryst. (1972). B28, 3469 The Structure of 7-Uranyl Dihydroxide, UO2(OH)2* BY STANLEY SIEGEL, HENRY R. HOEKSTRA, AND ELIZABETH GEBERT Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, U.S.A. (Received 16 June 1972) 7-Uranyl dihydroxide, UO2(OH)2, is monoclinic, space group P2x/c with a= 5"560 (3), b= 5.522 (3), c= 6.416 (3) .&, and fl= 112.71 (9) °. The observed density is 5-55 g.cm -3 and the computed value is 5"56 g.cm -3 for two formula weights. The structure was solved with 317 independent reflections recorded with an automatic diffractometer utilizing both double filter and 0/20 scan techniques. A least-squares refinement based on Fgave an R value of 6.1%. The configuration about a uranium atom is a distorted octahedron composed of two O(1) (uranyl) and four 0(2) (secondary) oxygen atoms. Each 0(2) atom is shared between two octahedra leading to puckered sheets of secondary oxygen atoms distributed within the bc plane. Each O(1) oxygen atom is associated with only one octahedron within a layer but is hydrogen-bonded to an 0(2) oxygen atom in an adjacent layer. The structure is very similar to the orthorhombic fl-UO2(OH)2. Postulated coordinates for the fl modification at 280°C indicate that the fl and 7 forms can be related by a shear involving one-half of the hydrogen atoms. Grinding experiments demonstrate the existence of a shear effect. Introduction Three crystallographic modifications of uranyl dihydroxide, UO2(OH)2 , have been prepared from the uranium trioxide-water system. The crystal structure of the ~ form was reported by Taylor (1971). Roof, Cromer & Larson (1964) published the structure of the fl modification and subsequently, Bannister & Taylor (1970) reported on the results of a study of the struc- * Work performed under the auspices of the U.S. Atomic Energy Commission. ture and anisotropic thermal expansion offl-UO2(OH)2. A neutron powder diffraction study by Taylor & Hurst (1971) confirmed the hydrogen locations proposed in the fl form by Roof et al. and in the ~ modification by Taylor. The preparation of a third form ofuranyl dihydroxide and the identification of its symmetry and cell dimensions from an X-ray powder pattern has been described by Cordfunke & Debets (1964) who referred to this phase as the e modification. As the existence of only three forms of laranyl dihydrate has been confirmed, the present phase will be regarded as 7-UO2(OH)2. The structure of ),-UOz(OH)z and its relation to fl-UO2(OH)2 will be presented here.