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The crystal structure of primary zinc(II) dithizonate
J. inorg,nucl.Chem., 1972,Vol. 34, pp. 109-115. PergamonPress. Printedin Great Britain
THE CRYSTAL STRUCTURE OF PRIMARY ZINC(II) DITHIZONATE A N N E M A W B Y and H. M. N. H. I R V I N G Department of Inorganic and Structural Chemistry, The University of Leeds, Leeds LS2 9JT, England
(Received 15 April 1971) A b s t r a c t - T h e crystal structure of primary zinc dithizonate, Zn(HDz)2, (where H2Dz = 3-mercapto1,5-diphenylformazan) has been determined by single crystal X-ray analysis and solved in the space group P21/a. The molecule consists of two bidentate dithizone residues coordinated tetrahedrally to zinc through sulphur and nitrogen. Significant differences between the geometry of the two chelate rings are shown to be compatible with the conflicting requirements of coplanarity with the phenylazo groups attached to each of them and the packing of adjacent molecules. INTRODUCTION
DESPITE the important role that dithizone (3-mercapto-l,5-diphenyl formazan, P h N H . N H . C S . N : N P h , H2Dz) plays in trace metal analysis the only reported X-ray structures of its metal complexes are either results from projection data (e.g. Hg(HDz)2 [ 1], Cu(HDz)2 [2], Ni(HDz)2 [3]) or for Ni(HDz)2.bipy [4] which contains a mixture of ligands. Measurement of the stability constants in 50% aqueous dioxan of complexes of zinc and nickel with dithizone and several of its derivatives has shown that an ortho-methyl substituent reduces the stability of 1 : 1-complexes in the case of zinc but increases the stability of nickel complexes relative to that for dithizone itself: on the other hand a para-methyl substituent enhances the stability of complexes with both metals [5]. The X-ray structure of Zn(HDz)2 was undertaken to ascertain to what extent steric hindrance is a significant factor in determining the differences in stability of the compounds mentioned above. EXPERIMENTAL Characterization of the compound Fine grey-green needles with a metallic reflex were obtained by recrystallization of a pure sample of the complex from chloroform. [Found: C, 54.0; H, 3.9; N, 19.4; S, l 1.25; Zn, 11,3%. C2~H22NsS~Zn requires: C, 54.2; H, 3.85; N, 19.45; S, t 1.1, Zn, 11.4%].
Crystal data Crystals of C2sH22NaS2Zn are monoclinic, space group P2~/a (No. 14, C~n) with a = 15.21 _ 0.02 ,~, b = 22.25 _ 0.03/~, c = 7.84 _ 0.01 ~,/3 = 91.4 -+ 0.2 °, Z = 4.
Intensity data Data were collected from a needle shaped crystal of thickness 0.03 mm mounted about the needle axis: 994 independent reflections from hk0 to hk6 were collected by the equi-inclination Weissenberg technique with nickel filtered copper radiation. I. 2. 3. 4. 5.
M. Harding, J. chem. Soc. 4136 (1958). R. F. Bryan and P. M. Knopf, Proc. chem. Soc. 203 (1961). M. Lalng and P. A. Alsop, Talanta 17, 243 (1970). K. S. Math and H. Freiser, Chem. Commun. 1 l0 (1970). K. S. Math, Q. Fernando and H. Freiser,/tnalyt. Chem. 36, 1762 (1964). 109
110
ANNE MAWBY and H. M. N. H. IRVING
Table 1. Final parameterswith e.s.d.'s in units ofthe last place in parentheses x/a
Zn S(1) N(1) N(2) N(3) N(4) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) S(1)' N(1)' N(2)' N(3)' N(4)' C(1)' C(2)' C(3)' C(4)' C(5)' C(6)' C(7)' C(8)' C(9)' C(10)' C(ll)' C(12)' C(13)'
0.17789(32) 0.11564(66) 0.2389(17) 0.2208(16) 0.1673(16) 0.1166(17) 0.1685(20) 0.1050(20) 0.1361(21) 0.1258(22) 0.0821(22) 0.0565(23) 0.0638(21) 0.2932(22) 0.3298(29) 0.3804(26) 0.4037(27) 0.3674(24) 0.3119(21) 0.11770(65) 0.2706(18) 0.2749(16) 0.2119(16) 0.1502(18) 0.2054(19) 0.1597(23) 0.2246(22) 0.2300(25) 0.1695(25) 0.1084(28) 0.0967(22) 0.3410(24) 0.4108(28) 0.4829(29) 0.4776(29) 0.4088(27) 0.3414(24)
y/b
z/c
0.00953(16) 0.03576(34) 0.0944(10) 0.1251(10) 0.1432(10) 0.1270(10) 0.1046(12) 0.1687(12) 0.2256(13) 0.2648(14) 0.2449(14) 0.1854(14) 0.1465(12) 0.1178(15) 0.1764(17) 0.1964(16) 0.1636(17) 0.1057(16) 0.0814(13) -0.02609(30) -0.0557(11) -0.0867(10) -0.1089(10) -0.1021(11) -0.0752(11) -0.1394(15) -0.1839(13) -0.2176(15) -0.2053(14) -0.1663(17) -0.1256(13) -0.0650(16) -0.1083(18) -0.1164(19) -0.0892(18) -0.0555(17) -0.0368(16)
*The anisotropic vibration parameters Zn 0.0507(36) 0.0045(21) 0.0259(24) S(I) 0.0678(85) 0.0174(47) 0.0288(52) S(I)' 0.0683(85) 0.0018(44) 0.0280(51)
0.29196(47) 0.53407(95) 0.3053(26) 0.4354(25) 0.6755(25) 0.8010(27) 0.5507(31) 0.9353(32) 0.9163(35) 1.0622(37) 1.2059(36) 1.2155(37) 1.0827(32) 0.1803(37) 0.2055(47) 0.0794(43) -0.0664(45) -0.0852(40) 0.0430(33) 0.04142(93) 0.2701(29) 0.1327(26) -0.1224(27) -0.2449(30) 0.0160(29) -0.3914(37) -0.4002(36) -0.5505(41) -0.6847(40) -0.6792(45) -0.5271(34) 0.3905(39) 0.3541(45) 0.4806(47) 0.6439(48) 0.6711(44) 0.5515(40)
U(,~ 2) * * 0.0282(66) 0.0243(65) 0.0200(61) 0.0303(68) 0.0177(74) 0.0216(78) 0.0302(86) 0.0358(88) 0.0351(88) 0-0398(93) 0.0214(76) 0.0442(98) 0.072(12) 0.060(11) 0.067(12) 0.053(11) 0.0258(79) * 0.0384(72) 0.0228(62) 0.0303(66) 0.0424(76) 0.0121(69) 0.0421(97) 0.0330(86) 0.053(11) 0.048(10) 0.068(12) 0.0295(84) 0.051(10) 0.070(12) 0.080(13) 0.079(13) 0.068(12) 0.053(10)
are -0.0193(36) 0.0121(43) 0.0090(50) -0.0113(77) 0.0301(96) -0-022(11) -0.0117(69) 0.0079(95) 0.0206(92)
The isotropic temperature factor is exp [-8rr2U(Sin 0IX)~] where U is the mean square amplitude of vibration. The anisotropic temperature factor is exp [--2~-z × (Ullh2a,2 + U~21db,2 + U~l~c , 2 + 2U~aklb*c* + 2U31lhc*a* + 2U12hka*b*)].
The crystal structure of primary zinc(II) dithizonate
111
Structure determination The intensities were estimated visually by comparison with a calibrated intensity strip. Lorentz and polarization factors were applied but no correction was made for absorption or extinction. The coordinates of the zinc atom were obtained from the three dimensional Patterson function and a structure factor calculation gave an R factor of 57%. The remaining 36 atoms were located from two successive Fobs electron density maps and the coordinates of all 37 atoms were improved by the calculation of three more electron density maps. The R factor at this point was 20 per cent. The structure was refined by the least squares method in its block diagonal approximation, with anisotropic temperature parameters for the zinc and sulphur atoms and isotropic temperature parameters for the remaining light atoms together with seven layer scale factors. Scattering factors for all atoms and f ' corrections for the zinc and sulphur atoms were taken from International Tables[6]. A satisfactory weighting scheme was found to be w~ = (36 + IFo~[ + 0.011Fo, Iz)-1 and the R factor at the end of the anisotropic refinement was 12.2% when the parameter shifts were less than one tenth of their standard deviations. A difference map computed at this stage did not show any peaks greater than 0.5e A,-~ and this indicates that the final structure is substantially correct. The final parameters and estimated standard deviations are given in Table 1 and a complete list of the observed and calculated structure factors has been deposited at the address given below.*
DISCUSSION
The molecule contains two almost planar dithizonate groups, acting as bidentate ligands, tetrahedrally coordinated to the zinc atom through sulphur and nitrogen (Fig. 1). Bond lengths and angles in the molecule are given in Table 2. cot)
c(lo)~c(i
/~-.C~ '°) c (9)'C'~
T C( l \\ "%¢ ",~ c(o),~__...,.//
C(I~)~'--'~C(SI. , / ~
c' (6r-----x.r~
~
~
)~'..
t)"
/\
C( 13)"
r-
"-... ",,
",
",,..
-J2,Ni2) - . . . . -'-,.'~T ~ -
",~
,/'--',-r cx~,
.I"
C(7)
C(6)
Fig. 1. A molecular unit of primary zinc(lI) dithizonate viewed down the b axis. Portions of adjacent molecules with the zinc atoms centred at (x, y, - 1 + z) and (x, y, 1 + z) are shown by full lines and broken lines respectively.
One phenyl group (A) of each ligand is associated with a chelate ring whereas the other phenyl group (B) is extended as far as possible from the central atom with two intervening nitrogen atoms that hold it in the trans-configuration. All the light atom-light atom bonds contain some degree of double bond character and this effectively maintains the phenyl ring (B) coplanar with the planar chelate ring to which it is attached through N(3) and N(4). This coplanarity also extends to the phenyl group (A) attached through N(1) to the chelate ring so that the molecule as a whole can be envisaged as two planes through A-zinc-B and A'*The Professor of Inorganic & Structural Chemistry, The University of Leeds, Leeds LS2 9JT.
6. International Tables for X-ray Crystallography Vol. III. Kynoch Press, Birmingham (1962).
112
ANNE MAWBY and H. M. N. H. IRVING
Table 2. Bond lengths* in Angstr6ms and angles* in degrees in the molecule Zn(HDz)2 with e.s.d.'s in parentheses in units of the last figure Zn-N(1) Zn-S(1) S(1)-C(I) C(1)-N(2) N(2)-N(I) N(1)-C(8) C(I)-N(3) N(3)-N(4) N(4)-C(2) S(1)-Zn-N(I) Zn-N(I)-N(2) Zn-N(I)-C(8) N(2)-N(1)-C(8) N(1)-N(2)-C(1) N(2)-C(1)-S(I) N(2)-C(1)-N(3) S(1)-C(1)-N(3) C(1)-S(1)-Zn C(1)-N(3)-N(4) N(3)-N(4)-C(2)
2.11(2) 2.220(9) 1.73(3) 1.30(3) 1.26(3) 1.40(4) 1.30(3) 1.32(3) 1.42(3)
2.03(3) 2.288(9) 1.74(3) 1.40(3) 1.28(3) 1.43(4) 1.32(3) 1.34(3) 1.43(4)
85-3(6) 115(2) 125(2) 121(2) 121(2) 123(2) 108(2) 129(2) 95"2(9) 114(2) 118(2)
S(1)-Zn-S(I)'
N(1)-Zn-N(I)'
86.8(7) 120(2) 124(2) 115(3) 113(2) 127(2) 111(2) 121(2) 91.4(9) 117(2) 116(3) 130.9(4) ll0(1)
C(2)-C(3) C(3)-C(4) C(4)-C(5) C(5)-C(6) C(6)-C(7) C(7)-C(2) C(2)-C(3)-C(4) C(3)-C(4)-C(5) C(4)-C(5)-C(6) C(5)-C(6)-C(7) C(6)-C(7)-C(2) C(7)-C(2)-C(3) N(4)-C(2)-C(3) N(4)-C(2)-C(7)
1.36(4) 1.45(4) 1.39(4) 1.38(4) 1.36(4) 1.42(4) 115(3) 121(3) 119(3) 123(3) 117(3) 125(2) 118(2) 116(2)
1.40(5) 1.40(4) 1.41(5) 1.27(5) 1.51(5) 1.45(4) 118(3) 118(3) 125(3) 122(3) 111(3) 125(3) 122(3) 113(3)
C(8)-C(9) C(9)-C(10) C(10)-C(11) C(11)-C(12) C(12)-C(13) C(13)-C(8)
1.43(5) 1.34(5) 1.41(5) 1.41(5) 1.43(4) 1.38(4)
1.47(5) 1.47(6) 1.42(5) 1.31(6) 1.43(5) 1.41(5)
C(8)-C(9)-C(10) C(9)-C(10)-C(I 1) C(10)-C(I 1)-C(12) C(I 1)-C(12)-C(13) C(12)-C(13)-C(8) C(13)-C(8)-C(9) N(1)-C(8)-C(9) N(1)-C(8)-C(13)
115(3) 126(3) 117(3) 121(3) 117(3) 124(3) 119(3) 118(3)
119(3) 120(4) 117(4) 128(3) 116(3) 119(3) 120(3) 121(3)
*Where two values are given, the first refers to the quantity in the (HDz)- ligand with rings labelled A, B and C and the second to the (HDz)- ligand with rings labelled A', B' and C' (see Fig. 1).
zinc-B' intersecting at about 85 °, an angle which deviates little from the ideal ofg0 °. Coplanarity in the dithizonate ligand of the three ring systems A, B, C, (see Fig. 1) is also found in Hg(HDz)z[1, 7] but not of course in Ni(HDz)~[3, 7] or Ni(HDz)z.bipy [4] where coplanarity of the phenyl ring directly bonded to the chelate ring is sterically impossible with square planar and octahedrally coordinated nickel respectively. Some dihedral angles in Zn(HDz)z are given in Table 3. The effect of ortho-subsfituents on the phenyl rings A and A' in Zn(HDz)z Table 3. Dihedral angles in degrees in Zn(HDz)2 where for example C'/C represents the angle between the ring systems C and C' (see Fig. 1) C'/B' C/B
6 12
7. P.A. Alsop, Personal Communication.
C'/C C'/A' C/A
85 8 3
A'/B' A/B
8 10
113
The crystal structure of primary zinc(lI) dithizonate
would be to increase the angles A/C and A'/C' in order to leave reasonable distances between the ortho-substituents and the chelate rings C' and C respectively. In Table 4 various bond lengths in Zn(HDz)~ are compared with the corresponding features in other dithizonates for which structure analyses have been completed. The most interesting conclusion is that the bond lengths in the chelated rings of the two nickel and the zinc complexes are essentially unchanged by the nature of the central metal. The changes in the mercury complex are consistent with adjustments caused by the appreciably longer bond from metal to nitrogen. The two chelate rings are significantly different and probably the most striking difference is that between the Zn-S bond lengths which differ by 0.07 ,~, i.e. 5tr. The differences in the two chelate rings can be explained in terms of the packing of individual molecules in the crystal lattice and a list of relevant intermolecular distances is given in Table 5. The two main factors determining the geometry of Table 4. Comparison of bond lengths (A) in the H D z - moiety in various metal complexes Zn(HDz)2* S(1)-C(1) C(1)-N(2) N(2)-N(1) C(1)-N(3) N(3)-N(4) N(4)-C(2) N(1)-C(8)
1.73 1.30 1.26 1.30 1.32 1.42 1.40
1.74 1.40 i.28 1.32 1.34 1.43 1.43
Ni(HDz)2'bipyt 1.71 1.37 1-33 i.36 1.33 1.48
1.74 1.38 1.16 1.31 1.33 1.39
Ni(HDz)~*
Hg(HDz)2*
1.72 1.35 1.30 !.31 1.33 1.40 1.43
1.64 1.41 1.25 1.36 1.25 1.44 1.42
*This work. tRef. [4]. *Ref. [7]. Table 5. Some inter-molecular distances (in AngstriSms) given in the form A...-B or A....B*. The zinc atom coordinates of the molecules containing atoms A, B and B* are (x, y, z), (x, y, 1 + z) and (x, y, 2 + z) respectively C(6)....N(2) C(7)....N(I) N(2) ..... C(5)' N(2) ..... C(6)' C(6)....N(1) C(1) ..... C(6)' N(1) ..... C(7)' N(I)'....C(6)' Zn-.-.C(7)' S(I)-..-N(4)' C(6)....C(1) C(2)--..C(8) C(8) ..... C(3)' C(7)---.C(8) C(13) ..... C(2)' S(1)....C(7)' N(4).-.-C(13)
3.29 3.36 3.42 3.45 3.49 3.49 3.49 3.51 3.56 3.56 3.58 3.59 3.60 3.61 3.62 3.63 3.63
N(3)....C(12) C(7)....N(2) C(13) ..... N(3)' C(12) ..... N(3)' C(13) ..... N(4)' N(4) ..... C(7) N(4) ..... C(6) C(7)'....C(6)* C(8) ..... C(2)' N(I) ..... C(2)' N(I) ..... C(5)' C(13)'...C(3)' C(9) ..... C(4)' C(I) ..... C(5)' C(2)-.--C(13) S(1) ..... C(6)' C(3)....C(9)
3.63 3.64 3.64 3.64 3.65 3-65 3.66 3.67 3.67 3-69 3.69 3-75 3.76 3-77 3-78 3.82 3.83
114
A N N E M A W B Y and H. M. N. H. I R V I N G
the molecule appear to be (i) that the coordination of the zinc atom should be as nearly tetrahedral as possible and (ii) that the dithizonate ligands should deviate as little from planarity as possible. The angle of 85 ° between the two ring systems is obviously a compromise from the ideal angle of 90° induced by considerations of packing for it can be seen from the data in Table 5 that any attempt to increase it would further decrease a number of short intermolecular distances. The slight divergences from planarity of the dithizonate ligands are almost entirely due to changes in geometry effected to minimise repulsion between neighbouring atoms in the adjacent molecules shown in Fig. 1. The chelate rings in particular are very restricted in position by the phenyl group B' of the adjacent molecule indicated by broken lines. Any readjustment of these ring systems would further diminish some already short interatomic distances and this crowded situation has been relieved by S(1) moving inwards towards the central zinc atom. The main effects of S(1) moving inwards are to lengthen Zn-N(1) relative to ZnN(1)' and to increase C(1)-S(I~')-Zn relative to C(1)'-S(I')'-Zn. There appear to be no considerations connected with packing alone which should determine the coplanarity of the phenyl rings A (or A') and the chelate ring to which each is attached and there appears to be adequate freedom for outof-plane rotation about C(8)-N(1) (or C(8)'-N(1)'). This situation is in complete contrast to that in the nickel complex where steric factors dictate that these phenyl rings cannot be coplanar with, and indeed are considerably out of the plane of, the chelate rings to which they are directly attached. As a direct consequence we can see why the presence of an ortho-methyl substituent must cause a distortion of the zinc dithizonate structure but need not do so for the nickel complex. Provided the respective complexes retain the same structures in solution as they are now shown to have in the solid state (and assuming no major differences in the solvation energies of the relevant cations and anions by dioxan and water) the variation in formation constants reported[5] are now readily explicable. The relative bond lengths in each dithizonate residue indicate that the two hydrogen atoms are bonded to N(4) and N(4)'. The interatomic distances N(4)S(1) and N(4)'-S(1)' are both 2.9 A. The N - H bond length is normally about 1 ,A, and the H atom will presumably be situated such that N(3)-N(4"-~-H and N(3)'-N---'~'-H' are about 120° thus giving H~-.S(1) and H'...S(I)' distances of about 2.4A and N(4)'-H'-S(1)' and N(4)-H-S(1) values of about 110°. This geometry is such that a lone pair on the sulphur atom points approximately towards the hydrogen atom and the sum of the distances N - H and H - S is - 3.4 A, i.e. about the sum of the Van der Waals radii of nitrogen and sulphur. It is probable that N - H . . . S hydrogen bonding is occurring here. The H " "S distance of 2.4 .A, is the same as that found in xanthane hydride [8] where the hydrogen atoms were located approximately and the presence of an almost linear N - H " ' S hydrogen bond reported. The rather small angle N - H . . . S in Zn(HDz)2 can be compared with that of 119° in (NH4)~SO419] found for an N - H . . . O type bond where the H position was located by neutron diffraction. The apparently similar geometry of the dithizonate ligands, excluding the 8. R. H. Stanford, Jr.,Acta crystallogr. 16, 1157 (1963). 9. E. O. Schlemper and W. C. Harnilton, J. chem. Phys. 44, 4498 (1966).
The crystal structure of primary zinc(II) dithizonate
115
attachment of the phenyl group to the chelate ring, in Ni(HDz)2, Hg(HDz)2 and Ni(HDz)~.bipy suggests that N-H...S intra-molecular hydrogen bonds are also present in these solid compounds. We are currently examining the structure of the zinc complex of o-tolyldithizone to study directly how the ortho-methyl substituent has changed the comformation of zinc dithizonate. The analytical implications of the present work have been reported elsewhere [ 10]. 10. Anne Mawby and H. M. N. H. lrving, Analytica. Chim.Acta 55,269 (1971).
THE CRYSTAL STRUCTURE OF PRIMARY ZINC(II) DITHIZONATE A N N E M A W B Y and H. M. N. H. I R V I N G Department of Inorganic and Structural Chemistry, The University of Leeds, Leeds LS2 9JT, England
(Received 15 April 1971) A b s t r a c t - T h e crystal structure of primary zinc dithizonate, Zn(HDz)2, (where H2Dz = 3-mercapto1,5-diphenylformazan) has been determined by single crystal X-ray analysis and solved in the space group P21/a. The molecule consists of two bidentate dithizone residues coordinated tetrahedrally to zinc through sulphur and nitrogen. Significant differences between the geometry of the two chelate rings are shown to be compatible with the conflicting requirements of coplanarity with the phenylazo groups attached to each of them and the packing of adjacent molecules. INTRODUCTION
DESPITE the important role that dithizone (3-mercapto-l,5-diphenyl formazan, P h N H . N H . C S . N : N P h , H2Dz) plays in trace metal analysis the only reported X-ray structures of its metal complexes are either results from projection data (e.g. Hg(HDz)2 [ 1], Cu(HDz)2 [2], Ni(HDz)2 [3]) or for Ni(HDz)2.bipy [4] which contains a mixture of ligands. Measurement of the stability constants in 50% aqueous dioxan of complexes of zinc and nickel with dithizone and several of its derivatives has shown that an ortho-methyl substituent reduces the stability of 1 : 1-complexes in the case of zinc but increases the stability of nickel complexes relative to that for dithizone itself: on the other hand a para-methyl substituent enhances the stability of complexes with both metals [5]. The X-ray structure of Zn(HDz)2 was undertaken to ascertain to what extent steric hindrance is a significant factor in determining the differences in stability of the compounds mentioned above. EXPERIMENTAL Characterization of the compound Fine grey-green needles with a metallic reflex were obtained by recrystallization of a pure sample of the complex from chloroform. [Found: C, 54.0; H, 3.9; N, 19.4; S, l 1.25; Zn, 11,3%. C2~H22NsS~Zn requires: C, 54.2; H, 3.85; N, 19.45; S, t 1.1, Zn, 11.4%].
Crystal data Crystals of C2sH22NaS2Zn are monoclinic, space group P2~/a (No. 14, C~n) with a = 15.21 _ 0.02 ,~, b = 22.25 _ 0.03/~, c = 7.84 _ 0.01 ~,/3 = 91.4 -+ 0.2 °, Z = 4.
Intensity data Data were collected from a needle shaped crystal of thickness 0.03 mm mounted about the needle axis: 994 independent reflections from hk0 to hk6 were collected by the equi-inclination Weissenberg technique with nickel filtered copper radiation. I. 2. 3. 4. 5.
M. Harding, J. chem. Soc. 4136 (1958). R. F. Bryan and P. M. Knopf, Proc. chem. Soc. 203 (1961). M. Lalng and P. A. Alsop, Talanta 17, 243 (1970). K. S. Math and H. Freiser, Chem. Commun. 1 l0 (1970). K. S. Math, Q. Fernando and H. Freiser,/tnalyt. Chem. 36, 1762 (1964). 109
110
ANNE MAWBY and H. M. N. H. IRVING
Table 1. Final parameterswith e.s.d.'s in units ofthe last place in parentheses x/a
Zn S(1) N(1) N(2) N(3) N(4) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) S(1)' N(1)' N(2)' N(3)' N(4)' C(1)' C(2)' C(3)' C(4)' C(5)' C(6)' C(7)' C(8)' C(9)' C(10)' C(ll)' C(12)' C(13)'
0.17789(32) 0.11564(66) 0.2389(17) 0.2208(16) 0.1673(16) 0.1166(17) 0.1685(20) 0.1050(20) 0.1361(21) 0.1258(22) 0.0821(22) 0.0565(23) 0.0638(21) 0.2932(22) 0.3298(29) 0.3804(26) 0.4037(27) 0.3674(24) 0.3119(21) 0.11770(65) 0.2706(18) 0.2749(16) 0.2119(16) 0.1502(18) 0.2054(19) 0.1597(23) 0.2246(22) 0.2300(25) 0.1695(25) 0.1084(28) 0.0967(22) 0.3410(24) 0.4108(28) 0.4829(29) 0.4776(29) 0.4088(27) 0.3414(24)
y/b
z/c
0.00953(16) 0.03576(34) 0.0944(10) 0.1251(10) 0.1432(10) 0.1270(10) 0.1046(12) 0.1687(12) 0.2256(13) 0.2648(14) 0.2449(14) 0.1854(14) 0.1465(12) 0.1178(15) 0.1764(17) 0.1964(16) 0.1636(17) 0.1057(16) 0.0814(13) -0.02609(30) -0.0557(11) -0.0867(10) -0.1089(10) -0.1021(11) -0.0752(11) -0.1394(15) -0.1839(13) -0.2176(15) -0.2053(14) -0.1663(17) -0.1256(13) -0.0650(16) -0.1083(18) -0.1164(19) -0.0892(18) -0.0555(17) -0.0368(16)
*The anisotropic vibration parameters Zn 0.0507(36) 0.0045(21) 0.0259(24) S(I) 0.0678(85) 0.0174(47) 0.0288(52) S(I)' 0.0683(85) 0.0018(44) 0.0280(51)
0.29196(47) 0.53407(95) 0.3053(26) 0.4354(25) 0.6755(25) 0.8010(27) 0.5507(31) 0.9353(32) 0.9163(35) 1.0622(37) 1.2059(36) 1.2155(37) 1.0827(32) 0.1803(37) 0.2055(47) 0.0794(43) -0.0664(45) -0.0852(40) 0.0430(33) 0.04142(93) 0.2701(29) 0.1327(26) -0.1224(27) -0.2449(30) 0.0160(29) -0.3914(37) -0.4002(36) -0.5505(41) -0.6847(40) -0.6792(45) -0.5271(34) 0.3905(39) 0.3541(45) 0.4806(47) 0.6439(48) 0.6711(44) 0.5515(40)
U(,~ 2) * * 0.0282(66) 0.0243(65) 0.0200(61) 0.0303(68) 0.0177(74) 0.0216(78) 0.0302(86) 0.0358(88) 0.0351(88) 0-0398(93) 0.0214(76) 0.0442(98) 0.072(12) 0.060(11) 0.067(12) 0.053(11) 0.0258(79) * 0.0384(72) 0.0228(62) 0.0303(66) 0.0424(76) 0.0121(69) 0.0421(97) 0.0330(86) 0.053(11) 0.048(10) 0.068(12) 0.0295(84) 0.051(10) 0.070(12) 0.080(13) 0.079(13) 0.068(12) 0.053(10)
are -0.0193(36) 0.0121(43) 0.0090(50) -0.0113(77) 0.0301(96) -0-022(11) -0.0117(69) 0.0079(95) 0.0206(92)
The isotropic temperature factor is exp [-8rr2U(Sin 0IX)~] where U is the mean square amplitude of vibration. The anisotropic temperature factor is exp [--2~-z × (Ullh2a,2 + U~21db,2 + U~l~c , 2 + 2U~aklb*c* + 2U31lhc*a* + 2U12hka*b*)].
The crystal structure of primary zinc(II) dithizonate
111
Structure determination The intensities were estimated visually by comparison with a calibrated intensity strip. Lorentz and polarization factors were applied but no correction was made for absorption or extinction. The coordinates of the zinc atom were obtained from the three dimensional Patterson function and a structure factor calculation gave an R factor of 57%. The remaining 36 atoms were located from two successive Fobs electron density maps and the coordinates of all 37 atoms were improved by the calculation of three more electron density maps. The R factor at this point was 20 per cent. The structure was refined by the least squares method in its block diagonal approximation, with anisotropic temperature parameters for the zinc and sulphur atoms and isotropic temperature parameters for the remaining light atoms together with seven layer scale factors. Scattering factors for all atoms and f ' corrections for the zinc and sulphur atoms were taken from International Tables[6]. A satisfactory weighting scheme was found to be w~ = (36 + IFo~[ + 0.011Fo, Iz)-1 and the R factor at the end of the anisotropic refinement was 12.2% when the parameter shifts were less than one tenth of their standard deviations. A difference map computed at this stage did not show any peaks greater than 0.5e A,-~ and this indicates that the final structure is substantially correct. The final parameters and estimated standard deviations are given in Table 1 and a complete list of the observed and calculated structure factors has been deposited at the address given below.*
DISCUSSION
The molecule contains two almost planar dithizonate groups, acting as bidentate ligands, tetrahedrally coordinated to the zinc atom through sulphur and nitrogen (Fig. 1). Bond lengths and angles in the molecule are given in Table 2. cot)
c(lo)~c(i
/~-.C~ '°) c (9)'C'~
T C( l \\ "%¢ ",~ c(o),~__...,.//
C(I~)~'--'~C(SI. , / ~
c' (6r-----x.r~
~
~
)~'..
t)"
/\
C( 13)"
r-
"-... ",,
",
",,..
-J2,Ni2) - . . . . -'-,.'~T ~ -
",~
,/'--',-r cx~,
.I"
C(7)
C(6)
Fig. 1. A molecular unit of primary zinc(lI) dithizonate viewed down the b axis. Portions of adjacent molecules with the zinc atoms centred at (x, y, - 1 + z) and (x, y, 1 + z) are shown by full lines and broken lines respectively.
One phenyl group (A) of each ligand is associated with a chelate ring whereas the other phenyl group (B) is extended as far as possible from the central atom with two intervening nitrogen atoms that hold it in the trans-configuration. All the light atom-light atom bonds contain some degree of double bond character and this effectively maintains the phenyl ring (B) coplanar with the planar chelate ring to which it is attached through N(3) and N(4). This coplanarity also extends to the phenyl group (A) attached through N(1) to the chelate ring so that the molecule as a whole can be envisaged as two planes through A-zinc-B and A'*The Professor of Inorganic & Structural Chemistry, The University of Leeds, Leeds LS2 9JT.
6. International Tables for X-ray Crystallography Vol. III. Kynoch Press, Birmingham (1962).
112
ANNE MAWBY and H. M. N. H. IRVING
Table 2. Bond lengths* in Angstr6ms and angles* in degrees in the molecule Zn(HDz)2 with e.s.d.'s in parentheses in units of the last figure Zn-N(1) Zn-S(1) S(1)-C(I) C(1)-N(2) N(2)-N(I) N(1)-C(8) C(I)-N(3) N(3)-N(4) N(4)-C(2) S(1)-Zn-N(I) Zn-N(I)-N(2) Zn-N(I)-C(8) N(2)-N(1)-C(8) N(1)-N(2)-C(1) N(2)-C(1)-S(I) N(2)-C(1)-N(3) S(1)-C(1)-N(3) C(1)-S(1)-Zn C(1)-N(3)-N(4) N(3)-N(4)-C(2)
2.11(2) 2.220(9) 1.73(3) 1.30(3) 1.26(3) 1.40(4) 1.30(3) 1.32(3) 1.42(3)
2.03(3) 2.288(9) 1.74(3) 1.40(3) 1.28(3) 1.43(4) 1.32(3) 1.34(3) 1.43(4)
85-3(6) 115(2) 125(2) 121(2) 121(2) 123(2) 108(2) 129(2) 95"2(9) 114(2) 118(2)
S(1)-Zn-S(I)'
N(1)-Zn-N(I)'
86.8(7) 120(2) 124(2) 115(3) 113(2) 127(2) 111(2) 121(2) 91.4(9) 117(2) 116(3) 130.9(4) ll0(1)
C(2)-C(3) C(3)-C(4) C(4)-C(5) C(5)-C(6) C(6)-C(7) C(7)-C(2) C(2)-C(3)-C(4) C(3)-C(4)-C(5) C(4)-C(5)-C(6) C(5)-C(6)-C(7) C(6)-C(7)-C(2) C(7)-C(2)-C(3) N(4)-C(2)-C(3) N(4)-C(2)-C(7)
1.36(4) 1.45(4) 1.39(4) 1.38(4) 1.36(4) 1.42(4) 115(3) 121(3) 119(3) 123(3) 117(3) 125(2) 118(2) 116(2)
1.40(5) 1.40(4) 1.41(5) 1.27(5) 1.51(5) 1.45(4) 118(3) 118(3) 125(3) 122(3) 111(3) 125(3) 122(3) 113(3)
C(8)-C(9) C(9)-C(10) C(10)-C(11) C(11)-C(12) C(12)-C(13) C(13)-C(8)
1.43(5) 1.34(5) 1.41(5) 1.41(5) 1.43(4) 1.38(4)
1.47(5) 1.47(6) 1.42(5) 1.31(6) 1.43(5) 1.41(5)
C(8)-C(9)-C(10) C(9)-C(10)-C(I 1) C(10)-C(I 1)-C(12) C(I 1)-C(12)-C(13) C(12)-C(13)-C(8) C(13)-C(8)-C(9) N(1)-C(8)-C(9) N(1)-C(8)-C(13)
115(3) 126(3) 117(3) 121(3) 117(3) 124(3) 119(3) 118(3)
119(3) 120(4) 117(4) 128(3) 116(3) 119(3) 120(3) 121(3)
*Where two values are given, the first refers to the quantity in the (HDz)- ligand with rings labelled A, B and C and the second to the (HDz)- ligand with rings labelled A', B' and C' (see Fig. 1).
zinc-B' intersecting at about 85 °, an angle which deviates little from the ideal ofg0 °. Coplanarity in the dithizonate ligand of the three ring systems A, B, C, (see Fig. 1) is also found in Hg(HDz)z[1, 7] but not of course in Ni(HDz)~[3, 7] or Ni(HDz)z.bipy [4] where coplanarity of the phenyl ring directly bonded to the chelate ring is sterically impossible with square planar and octahedrally coordinated nickel respectively. Some dihedral angles in Zn(HDz)z are given in Table 3. The effect of ortho-subsfituents on the phenyl rings A and A' in Zn(HDz)z Table 3. Dihedral angles in degrees in Zn(HDz)2 where for example C'/C represents the angle between the ring systems C and C' (see Fig. 1) C'/B' C/B
6 12
7. P.A. Alsop, Personal Communication.
C'/C C'/A' C/A
85 8 3
A'/B' A/B
8 10
113
The crystal structure of primary zinc(lI) dithizonate
would be to increase the angles A/C and A'/C' in order to leave reasonable distances between the ortho-substituents and the chelate rings C' and C respectively. In Table 4 various bond lengths in Zn(HDz)~ are compared with the corresponding features in other dithizonates for which structure analyses have been completed. The most interesting conclusion is that the bond lengths in the chelated rings of the two nickel and the zinc complexes are essentially unchanged by the nature of the central metal. The changes in the mercury complex are consistent with adjustments caused by the appreciably longer bond from metal to nitrogen. The two chelate rings are significantly different and probably the most striking difference is that between the Zn-S bond lengths which differ by 0.07 ,~, i.e. 5tr. The differences in the two chelate rings can be explained in terms of the packing of individual molecules in the crystal lattice and a list of relevant intermolecular distances is given in Table 5. The two main factors determining the geometry of Table 4. Comparison of bond lengths (A) in the H D z - moiety in various metal complexes Zn(HDz)2* S(1)-C(1) C(1)-N(2) N(2)-N(1) C(1)-N(3) N(3)-N(4) N(4)-C(2) N(1)-C(8)
1.73 1.30 1.26 1.30 1.32 1.42 1.40
1.74 1.40 i.28 1.32 1.34 1.43 1.43
Ni(HDz)2'bipyt 1.71 1.37 1-33 i.36 1.33 1.48
1.74 1.38 1.16 1.31 1.33 1.39
Ni(HDz)~*
Hg(HDz)2*
1.72 1.35 1.30 !.31 1.33 1.40 1.43
1.64 1.41 1.25 1.36 1.25 1.44 1.42
*This work. tRef. [4]. *Ref. [7]. Table 5. Some inter-molecular distances (in AngstriSms) given in the form A...-B or A....B*. The zinc atom coordinates of the molecules containing atoms A, B and B* are (x, y, z), (x, y, 1 + z) and (x, y, 2 + z) respectively C(6)....N(2) C(7)....N(I) N(2) ..... C(5)' N(2) ..... C(6)' C(6)....N(1) C(1) ..... C(6)' N(1) ..... C(7)' N(I)'....C(6)' Zn-.-.C(7)' S(I)-..-N(4)' C(6)....C(1) C(2)--..C(8) C(8) ..... C(3)' C(7)---.C(8) C(13) ..... C(2)' S(1)....C(7)' N(4).-.-C(13)
3.29 3.36 3.42 3.45 3.49 3.49 3.49 3.51 3.56 3.56 3.58 3.59 3.60 3.61 3.62 3.63 3.63
N(3)....C(12) C(7)....N(2) C(13) ..... N(3)' C(12) ..... N(3)' C(13) ..... N(4)' N(4) ..... C(7) N(4) ..... C(6) C(7)'....C(6)* C(8) ..... C(2)' N(I) ..... C(2)' N(I) ..... C(5)' C(13)'...C(3)' C(9) ..... C(4)' C(I) ..... C(5)' C(2)-.--C(13) S(1) ..... C(6)' C(3)....C(9)
3.63 3.64 3.64 3.64 3.65 3-65 3.66 3.67 3.67 3-69 3.69 3-75 3.76 3-77 3-78 3.82 3.83
114
A N N E M A W B Y and H. M. N. H. I R V I N G
the molecule appear to be (i) that the coordination of the zinc atom should be as nearly tetrahedral as possible and (ii) that the dithizonate ligands should deviate as little from planarity as possible. The angle of 85 ° between the two ring systems is obviously a compromise from the ideal angle of 90° induced by considerations of packing for it can be seen from the data in Table 5 that any attempt to increase it would further decrease a number of short intermolecular distances. The slight divergences from planarity of the dithizonate ligands are almost entirely due to changes in geometry effected to minimise repulsion between neighbouring atoms in the adjacent molecules shown in Fig. 1. The chelate rings in particular are very restricted in position by the phenyl group B' of the adjacent molecule indicated by broken lines. Any readjustment of these ring systems would further diminish some already short interatomic distances and this crowded situation has been relieved by S(1) moving inwards towards the central zinc atom. The main effects of S(1) moving inwards are to lengthen Zn-N(1) relative to ZnN(1)' and to increase C(1)-S(I~')-Zn relative to C(1)'-S(I')'-Zn. There appear to be no considerations connected with packing alone which should determine the coplanarity of the phenyl rings A (or A') and the chelate ring to which each is attached and there appears to be adequate freedom for outof-plane rotation about C(8)-N(1) (or C(8)'-N(1)'). This situation is in complete contrast to that in the nickel complex where steric factors dictate that these phenyl rings cannot be coplanar with, and indeed are considerably out of the plane of, the chelate rings to which they are directly attached. As a direct consequence we can see why the presence of an ortho-methyl substituent must cause a distortion of the zinc dithizonate structure but need not do so for the nickel complex. Provided the respective complexes retain the same structures in solution as they are now shown to have in the solid state (and assuming no major differences in the solvation energies of the relevant cations and anions by dioxan and water) the variation in formation constants reported[5] are now readily explicable. The relative bond lengths in each dithizonate residue indicate that the two hydrogen atoms are bonded to N(4) and N(4)'. The interatomic distances N(4)S(1) and N(4)'-S(1)' are both 2.9 A. The N - H bond length is normally about 1 ,A, and the H atom will presumably be situated such that N(3)-N(4"-~-H and N(3)'-N---'~'-H' are about 120° thus giving H~-.S(1) and H'...S(I)' distances of about 2.4A and N(4)'-H'-S(1)' and N(4)-H-S(1) values of about 110°. This geometry is such that a lone pair on the sulphur atom points approximately towards the hydrogen atom and the sum of the distances N - H and H - S is - 3.4 A, i.e. about the sum of the Van der Waals radii of nitrogen and sulphur. It is probable that N - H . . . S hydrogen bonding is occurring here. The H " "S distance of 2.4 .A, is the same as that found in xanthane hydride [8] where the hydrogen atoms were located approximately and the presence of an almost linear N - H " ' S hydrogen bond reported. The rather small angle N - H . . . S in Zn(HDz)2 can be compared with that of 119° in (NH4)~SO419] found for an N - H . . . O type bond where the H position was located by neutron diffraction. The apparently similar geometry of the dithizonate ligands, excluding the 8. R. H. Stanford, Jr.,Acta crystallogr. 16, 1157 (1963). 9. E. O. Schlemper and W. C. Harnilton, J. chem. Phys. 44, 4498 (1966).
The crystal structure of primary zinc(II) dithizonate
115
attachment of the phenyl group to the chelate ring, in Ni(HDz)2, Hg(HDz)2 and Ni(HDz)~.bipy suggests that N-H...S intra-molecular hydrogen bonds are also present in these solid compounds. We are currently examining the structure of the zinc complex of o-tolyldithizone to study directly how the ortho-methyl substituent has changed the comformation of zinc dithizonate. The analytical implications of the present work have been reported elsewhere [ 10]. 10. Anne Mawby and H. M. N. H. lrving, Analytica. Chim.Acta 55,269 (1971).