METAL-OLEFINCOMPOUNDS 1535
Vol. 3, No. 11, November, 1964 remaining double bonds are not significantly different from 1.34 k. The average value of all the single bonds is 1.475 8., in reasonable agreement with the average value found for cyclooctatetraene by electron diffraction methods, 1.462 k9 The distances are significantly shorter than the normal single bond distance of 1.54 8.
Acknowledgment.-This research work was supported by a grant from the Army Research Office (Durham), DA-ARO(D)-31-124-G26. The authors are indebted to Dr. H. L. Haight for the preparation of the crystal specimens and to Messrs. Mark and Phillip Richards for the estimates of the intensities.
(8) N. C. Baenziger, J. R. Doyle, G . F. Richards, and C. L. Carpenter, “Advances in the Chemistry of the Coordination Compounds,” The Macmillan Company, New Y o r k , N. Y . , 1961, p. 131.
(9) 0.Bastiansen, L. Hedberg, and K. Hedberg, J . Chem. Phys., 27, 1311 (1957).
CONTRIBUTION FROM THE DEPARTMENT OF CHEMISTRY, THESTATE UNIVERSITY O F IOWA,IOWA CITY, IOWA
Metal-Olefin Compounds. VII. The Crystal and Molecular Structure of Cyclo-tetra-p-chloro- tetrakis[bicyclo[2.2.1]hepta-2~,5-dienecopper(I)] BY N. C. BAENZIGER, H. L. HAIGHT,
AND
J. R. DOYLE
Received April 27, 1964 A crystal structure determination of the compound formed by the reaction of copper(1) chloride and bicyclo[2.2.1]hepta2,5-diene (norbornadiene) shows that the complex exists as a tetramer, (CTH&!uCl)a, in the solid state with 3 symmetry. The copper and chlorine atoms form an eight-membered tube-shaped ring with one double bond of the olefin coordinated to the copper atom and lying in the plane defined by the copper atom and adjacent chlorine atoms, The copper atom is coordinated to the olefin in an ex0 configuration; one double bond of the olefin is not coordinated. The distorted trigonal planar coordination about copper is similar to that found for potassium dicyanocuprate( I), cyclooctatetraenecopper( I ) chloride, and 2-butynecopper(I ) chloride,
Introduction
Experimental
The compound dichloro(norbornadiene)palladium(11) has been studied crystallographically, and the 1:2 complex of norbornadiene with silver nitrate had been prepared and the structure determination was in progress3 when a method for preparing olefin complexes containing copper(1) chloride was d e ~ e l o p e d . ~ The preparation of norbornadienecopper(1) chloride, hereafter abbreviated as NBD-CuC1, and the subsequent structure determination was made t o add another member t o a series in which the olefin was kept the same, but the metal to which i t was coordinated was varied. The structure determination reveals an interesting coordination arrangement for copper(1) which is very similar to that reported for 2-butynecopper(1) chloride by Carter and Hughes.6 The companion paper6 in this series contains a summary of other earlier work and a report on the structure determination of cyclooctatetraenecopper(1) chloride (COT-CuCl) +
Preparation of Crystals.-Crystals of norbornadienecopper(I) chloride were made by reducing an ethanol solution of copper(I1) chloride and the olefin with sulfur dioxide. The crystals which precipitated were separated by filtration and washed with methanol containing a small amount of norbornadiene. The crystals used for X-ray diffraction measurements were mounted in two different ways. For the early work on the structure determination, the crystals were coated with a polystyrene-alkyd copolymer resin immediately after being glued to the glass fiber support. A thin-walled glass capillary was then mounted over the glass fiber and crystal and cemented t9 the brass pin base. By maintaining the crystal a t -10’ continuously throughout all the exposures (dry air stream cooled by a Dry Ice-acetone bath) crystal decomposition was retarded. For the measurements made with the G.E. single crystal orienter, an uncoated crystal was mounted in a thin-walled capillary, containing a small amount of norbornadiene, in a drybox, and the capillary was sealed off with a glass seal. Crystals mounted in this fashion did not decompose a t room temperature during the approximately 2week period needed to obtain the intensity data. The crystal used to obtain all of the intensity data was a tetragonal rod, 0.17 X 0.17 X 0.80 mm., bounded by 1,1,0 faces. Crystal Data.-The cell dimensions were determined from the settings needed for the single crystal orienter. Norbornadienecopger(1) chloride has a tetragonal unit cell with a = 12.27 f 0.03 A., c = 9.62 i 0.02 A. a t room temperature. Cell dimensions obtained from precession camera films a t -10” are a = 12.21 f 0.05 A., c = 9.58 f 0.04 A. From precession films, (h01) through (h61), and Weissenberg films, (hkO) through ( h k 5 ) , the systematic extinctions, (hhl)present only when 1 = 2n, (hOO) present only when h = 2n, lead to the unique space group P221c. The early work on the structure used visually estimated film
l p 2
(1) N. C. Baenziger, J. R. Doyle, and C. L. Carpenter, A c f a Cvyst., 14, 303 (1961). (2) N. C. Baenziger, J. R. Doyle, G . F. Richards, and C. L. Carpenter, “Advances in the Chemistry of the Coordination Compounds,” The Macmillan Company, New Y o r k , N. Y., 1961, pp. 131-138. (3) H.L. Haight, Dissertation, University of Iowa, Feb., 1963. (4) H. L. Haight, J. R. Doyle, N. C. Baenziger, and G . F. Richards, Znorg. Chem., a, 1301 (1963). (5) F. L. Carter and E. W. Hughes, Acta Cvyst., 10, 801 (1957). (6) N. C. Baenziger, G . F . Richards and J. R. Doyle, Znovg. Chem., 3, 1529 (1984).
N. C. BAENZIGER, H. L. HAIGHT,AND J. R. DOYLE
Inorganic Chemistry
TABLE I ATOMICPARAMETERS FOR [ C ~ H ~ C U C ~ ] ~ s(x)
Y s (5,)
s(XY 0.1391 0.00009 0.0011 0.1692 0.00015 0.0018 0.3462 0.0006 0.007 0.3624 0.0007 0.008 0.2926 0.0007 0.008 0.2243 0.0006 0.008 0.1604 0,0006 0.008 0.2345 0.0007 0.008 0.3171 0.0006 0.008
0,0189 0.00009 0.0010 0.9719 0.00016 0.0019 0.9754 0 .0007 0,008 0,9514 0.0007 0.008 0.0108 0.0007 0.009 0.0757 0.0006 0,008 0.9880 0.0007 0,009 0.9272 0.0006 0.008 0.0960 0,0007 0.009
0.0010 0.8938 0.00018 0.0017 0.2882 0.0008 0.007 0.4436 0.0007 0.007 0,5150 0.0006 0,006 0.4023 0.0009 0.008 0.3269 0.0008 0.007 0.2594 0.0008 0.007 0.2986 0.0008 0.007
0.41 0.42 0.27 0.19 0.10 0.20 0.28 0.39
0.96 0.89 0.01 0.15 0.94 0.86 0.10 0.13
0.22 0.50 0.62 0.44 0.38 0.20 0.21 0.36
X
2
s (2)
s(Wb
0.1192
698
986 11
- 260
8
869 10
-62
0 IO001
13
18
743 13
832 15
1021 17
-116 22
54 27
-40
606 56
1095 82
961 74
226 118
152 102
- 71 128
726 57
897 64
1031 76
172 110
-205 116
26 126
769 62
915 70
917 67
7.
106
- 180 106
- 260 128
786 56
747 55
1542 105
249 94
-250 153
547 54
950 70
1314 82
- 16 97
- 204
111
702 138
927 64
697 54
869 70
-202 102
-209 119
-22 103
726 56
1148
974 75
-620 119
-48 116
- 127
80
ia
152 18
29
-343 147
131
Ba
5.00 5.00 5.00 5 00 5 00 5 00 5 00 5 00
data. The final refinement of the structure used only the data obtained by means of the single crystal orienter with Cu K a radiation and a proportional counter. All accessible reflections with 28 less than 147.5' were measured in one octant of the reciprocal lattice and the equivalent reflections were averaged. Intensities were measured using the 20 scan; Lorentz, polarization, and absorption corrections (assuming an equivalent cylinder) were made.
Structure Determination From the film data the copper and chlorine positions were easily found from a three-dimensional Patterson function. An indication of the position of the olefinic portion of the molecule was obtained from an electron density projection on the 001 plane. ,4 model of the complex was constructed to correspond to this projection, and a least-squares refinement starting with this model gave an R value of 0.19 for all data. The copper and chlorine atoms formed an eightmembered tub-shaped ring. The copper atom was coordinated to one double bond of the norbornadiene molecule, the other double bond lying much further away in an endo configuration. Minor variations in this arrangement, including a more nearly tetrahedral configuration, always led to essentially the same ar-
rangement upon least-squares refinement Since several crystals had been used in obtaining the intensity data, and some crystal decomposition had been noted to occur, it was felt that the poor agreement might be due t o the intensity data rather than an incorrect structure. Thus, a t this stage new intensity data were obtained by use of the proportional counter. A continuation of the refinement with the new intensity data did not lead to any significant reduction in the discrepancy factor. By altering the positions of three of the carbon atoms the configuration of the copper atom with respect to the olefin was changed from endo to exo. The double bond coordinated to the copper atom remained the same, but the other double bond no longer was in the vicinity of the copper atom. This arrangement refined rapidly to R = 0.11. At this point, seven reflections which appeared to be strongly influenced by extinction (1, 0, 1; 2 , 0, 0; I,1,0; 2 , 2, 0 ; 3, 3, 0;4, 4, 0;3, 3, 10) were removed from the refinement. The R value decreased to 0.098. Individual anisotropic temperature factors were then refined and hydrogen atoms were included a t fixed positions and not allowed to refine. The R value decreased to 0.056. Removal of about a half-dozen
1/02. 3, N o . 11, November, 1964
METAL-OLEFINCOMPOUNDS1537
TABLE I1 INTERATOMIC DISTANCES AND ANGLESFOR [ C ~ H ~ C U C ~ ] ~ Distance,
A.
Std. dev.,
A. 0,002 0.002 0,002 0,008 0.007 0,008 0,010 0,011 0.012 0,011 0.011 0.011 0.011 0,011 0.011 0,010 0.011 0.010 0.011 0.012 0.010 0.011 0.011
cu-Cl 2.296 cu-C1' 2.275 cu-C1" 3.091 cU-( c&=c6)01.971 cu-c5 2,051 CU-cS 2.111 c1-C? 1.537 c1-c6 1.518 Cl-C? 1,526 c 2 & 3 1.317 c3-c4 1.587 CrC7 1 534 c 4 4 5 1.516 c5-c6 1.345 c2-G 2.386 c 3 & 6 2.448 c 2 & 7 2.324 CrC7 2.350 C6-G 2.353 C6-cl 2.338 Ci-Ca 2.321 CZ-c4 2.314 C&6 2.286 cs-c1 2.316 0.111 C1-G 2.226 0.011 Cl-CI' 3.611 0.003 I
Angle, deg.
Cl-CU-Cl' Cl-CU-( C5=Cs)o Cl'-cU-( c6=c6)0 CZ-CI-Ce Cs-CrCs c7-c1-c2
CrCrC3 C?-Cl-C6 C~-C~-C.G Ci-Cz-C3 C2-Ca-G C4-C5-C6 C6-Cs-C1 C1-C7-C4 CU-C1-CU'
104.4 124.7 130.9 102.7 104.1 98.7 97.6 100.2 100.9 108.6 105.3 105.9 107.8 93.3 94.1
Std. dev., deg.
0.1 0.2 0.2 0.7 0.4 0.7 0.4 0.6 0.5 0.8 0.4 0.3
0.6 0.6 0.1
W
W
Fig. 1.-Projection of the structure of [ C ~ H ~ C U C onI ](001). ~ The small spheres are carbon atoms; the largest spheres are chlorine atoms.
additional reflections which appeared t o have some extinction errors did not further decrease the R value ) ~5%. The atom but did decrease the sum Z W ( A F ~by parameters did not change significantly. The final R value is 0.057. The refinement continued until the changes in the parameters were less than 1 in the fifth decimal place, on the average. The atom parameters TABLE I11 EQUATIONS OF IMPORTANT PLANE? AND VECTORS( I N NORMAL FORM WITH COMPONENTS IN A,) FOR [C7H8CUC1]4 0 . 8 0 5 0 ~ 0 . 5 9 2 9 ~(CU, c1, Cl') 0.02042 = 1.488 0 . 7 8 0 6 ~ 0 . 6 2 4 2 ~(CU, c1, c1', c5, c6) 0.03142 = 1.474 Dev. from plane (k) -0.03, -0.04, 0.06, -0.13, 0.14 -0.0907~: 0 . 5 9 6 0 ~(c1, c6, c5, C4) 0.79792 = -2.780 Dev.fromplane(i%.) -0.003,0.005, -0.004,0.003 - 0 . 6 6 0 2 ~ - 0 . 7 4 9 4 ~(Cl, c2, cs, C4) 0.50212 = -2.713 0.005, -0.009, 0.008, -0.005 Dev. from plane ( b . ) 0.1627i - 0.25363 - 0.9535k Cu+C1 vector - 0.59301 0,80333 - 0.0544k CU-tCl' 0.3635i - 0.38173 0.8498k cU-t(Cj=cS center) 0,67691 - 0,55493' - 0,4835k cs+cs 0.9745k 0.1271i - 0.18483 CUC '5 0.55471 - 0.53293 0.6390k c U d c 6 0.6619j 0.5520k -0.5071i (CU, C1, Cl', C5, c6) and (CI, cs, c6, c4) plane intersection -4ngle between ( c u , c1, el', (25, c6) and (CI, c6, C6, Ca) plane normals = 70.9" Angle between ( c l , c6, C5, c4) and (Cl, Cg, C3, C,) plane normals = 89.2' = 87.3" Angle between c u e ( C6=C6 center) and c6-&6 Angle between C5+c6 and ( c u , c1, c1', c5, c6) and (C,, C6, Cb,C4) plane intersection = 12.2'
+ +
+
+
-
+
+
+ +
are listed in Table I. Interatomic distances and bond angles are given in Table I1 together with their standard deviations. The equations of pertinent planes and vectors are given in Table 111. The calculated and observed structure factors are summarized in Table IV. The anisotropic thermal vibrational parameters were analyzed by the method of Cruickshank7 into translational and torsional motions of the tetramer unit. The assumption that intramolecular vibrations can be neglected appears to be reasonable for this molecule a t room temperature. The translational and torsional tensors are 5.53 f 0 51
T X lo2 (in A . 2 ) 0 00 f 0 45 5 53 f 0 51 (in deg.z) 0 00 f 0.85 0 08iO.98
0 00 f 0 38
0 00 0 38 4 99 dz 0 45
w
0.08
0.98
0.00 f 0.62 0.00 f 0 92 4 08f1.3
The full matrix least-squares program used in the refinement was developed for the IBM 7040 in our laboratory. The program minimizes 2w(Fo2 - FO2)2 and is sufficiently flexible to allow any coordinate or temperature parameter to be held fixed or allowed to vary. Individual anisotropic or isotropic temperature factors may be intermixed. Both real and imaginary dispersion corrections may be included for any atom but only the real corrections were made for the copper and chlorine in this refinement Uncorrected atom scattering factors are obtained by interpolation from the tabulated values in the International Tables for Crystallography, Vol. 3.
Discussion of the Structure The structure consists of a tetrameric unit (C7HsCuC1)d with 7 symmetry. The copper and chlorine atoms form an eight-membered tub-shaped ring. A projection of the structure is shown in Fig. 1. One of the double bonds of the norbornadiene molecule (7) D. W. J. Cruickshank, Acta Cryst., 9, 754, 787 (1956).
1538
Inorganic Claemistry
N.C. BAENZIGER, H. L. HAIGHT, AND J. R.DOYLE TABLE IV CALCULATED AXD OBSERVED STRUCTURE FACTORS FOR [ C~118CuCl]ra
h k
I
Fobid.
IFcalcd)h
k
I
Fobid 21.13
0
0
0 0
0 0
0
0
I
O
1.37 16.02 3.51
1
0
43.3v .b2
I
I I I
2. 7.27 Ib
O O O O
0
0
10.17 2.65
0 0
2
0c
10.28 2V.39 9V.VI 111.36 6.22 75.v7 €.e7
2
II I O 2
0
3
0
3
0
1 1 1
3 0 3 0 3 0 3 0 3 0 33 0 3
c
4 U
0 O
43
(14.3b 4.82 lV.17 17.02 1V l b
1
b 5
1
7
1
v8
I2.b3 10.17
1 10
11.10 5.30 32.53
II l Ol
0
k
1 2
1 1
1 2
kPb.52 0.73
1
93
P2.51 47.~7
4
0
P
O
Y4
0 O
1
9
0
I
B
I4.bb
*
O
I
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21.81
1I
65
7
1 1 I O1
P4 0 O P O
1
01
5
0
1
2
5
0
11
93
5 5
0 0
1
5
5 5
0 0
5 5 b5
0 0 0
U.08 b.59 2b.8b lb.lU
0.3k 5.01 25.23 17.33
42.Vb .00
Q.0b 5.I5
b
o
b
o
1b.VP 20.Yb
6
0
83.30
6 B
0 O
b
0
14.73 a.e7 1V.117 26.00
b
A
O
1.05
0.18
15.5U 1V.05
7V.12 lV.4b
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55.58
3.08
7
0
7 7 7 7 7 7 7 7
0 0 0 0 0 0 0 0
*
70.2U 5.V1 1.v1 1.85 28.13 3 . 0 ~
a o a o a 8
40.98 21.b3 3.vii
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0
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0 0
9 v 9 P
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9 V P P
0 O O O
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0
10
0 0 0 0 0 0 0
v o
IO IO 10
IO 10 10 IO 11 11 11 I 1I 1
7l .. 3 V 9l
0
0
0 0 0 0
*
17.01 17.25 b.35 1.17 ).I1 2.22 5.73 8.01 I.Vl b.72 8.bV 2.39 7.52 24.71 2b.bB 5.92 17.07 lb,7b
111.15 1.34 10.29 3.bU 2.0v lI.*b 32.Vb
a.bv 14.11
2.v0
1I 1
0
1V.00 7.21
11 12 12 12
0
u.ei 5.42 15.10 7.116
0 0 0
8 9 1 10 1 11 0 1
I
2
3
1
9
1
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l b 1 7 1 8 1 v I IO 1 I1
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0.Vb 7C.65 4.92 I.7V I.bB
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2e.18
1
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1 1101 I I
i.es 10.33 17.C3
1.lV
7 1 7 7
C.75 5.08 7 2.P2 7 ii.50 7 8 . ~ 1 a 1.99 a 7.32 a 7.57 a 2 . 4 ~ a
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21
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27.93 1.13 IU.tO 16.71 10.bP 11.13 10.11
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0.02 0.v2 11.21 IV.10 27.Cb UV.bI 1V.7b
3.04 85.C7 V.52 b1.81 12.e2 1e.w 17.80 17.3Y 10.45 13.39 10.51 7.20 3b.78 38.51 97.25 41.4v 97.17 52.22 22.01 1b.Vb I4.V5 22.8b
a.?u 7.77 21.2b 2e.e3 58.V7
33.63 22. I 9 31.e~ 44.51 1v.tu 7.52 l0.VO 17.71 8.11 *o.vu li2.VB
4l.OU 37.03 40.88
32.33 22.4Y 2C.b5 9.70 V.82
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ll.tO 0.v3 b7.11 21.37 52.16
0.50
20.09 b4.39 23.23 20.V5 10.41 29.88 2.OV v.73 7.11 2V.20 32.b5 38.14 15.03 6.22 16.88 28.17 7.82 12.b3
5. 30 5.73 I1.V5 Ub.02
72.7" 10.84
8.39 27.32 1l.bO 2V.lb
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7. 70 5.73 br53 Il.b4
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12.51 5.73 18.53
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21.63 22.L.v 2.71
27.18 53.68 32.b5 17.28 lb,C3 3I.b2 ia.72 1l.bV
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The asterisk denotes reflections which were unobserved.
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10
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21.63 lb.57
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The value of F, for these reflections is the minimum value observable.
lies approximately in the plane of the copper atom and its two adjacent chlorine atoms in a direction giving a distorted trigonal configuration about copper. The plane (Cd, Cj, Cs, C,) which contains the coordinated double bond makes an angle of 109.1' (180 - 70.9) with the plane (Cu, C1, Cl', C6,(26); see Fig. 2. For comparison, the comparable angle in COT-CuC1 is 109.2'. The reason why the angle is not closer to
90' in NBD-CuCI may be because the hydrogen atom, H7, attached to the bridgehead carbon atom, C7, is only 2.18 A. away from the copper atom. The covalent radii sum (1.17 0.30 = 1.47 A,)indicates that the hydrogen and copper atoms are less than a normal van der Waals distance apart. Thus, repulsion of the hydrogen atom by the copper atom may cause the larger angle. In the NBD-CuCl case the second
+
METAL-OLEFIN COMPOUNDS1539
Vol. 3, No. 11, November, 1964 double bond is not near any copper atom. In an additional comparison with the COT-CuCl structure, the distorted trigonal arrangement of ligands about copper is very similar. The C1-Cu-C1 chain angle is 106.0' in COT-CuC1; it is 104.4' in NBD-CuCl. The angles between chlorine, copper, and the C=C bond center are 123.1 and 130.1' in COT-CuC1; in NBD-CuC1 they are 124.7 and 130.9'. The similarity of the latter two angles is surprising. One might have expected the vector from the copper atom to the double bond center to be symmetrically located, with both angles equal to (360 - 104.4)/2 = 127.8'. Packing of the organic portion of the complex might easily cause the asymmetry, but it is unusual to find the asymmetry the same in two different packing arrangements of the complexes. In the COT-CuC1 complex, two double bonds were located in the directions roughly perpendicular to the (Cu, C1, Cl') plane at the apices of a distorted trigonal bipyramid. The ligands were far enough away that their participation in bonding is not certain. In the NBD-CuC1 complex, a chlorine atom a t 3.091 A. lies in one apical direction. Nothing exists in the other apical direction except H,. In another point of similarity between the COT- and NBD-CuC1 complexes, the deviations of the atoms of the coordinated double bond from the (Cu, C1, CI', C=C) plane are similar. In COT-CuC1 they are -0.06 and 0.10 A.; in NBD-CuCl they are -0.13 and 0.14 8. Both deviations are in the direction of a tetrahedral distortion, but this distortion is very small. The norbornadiene molecule itself is compared with the dimensions of the free molecule as determined from electron diffraction data8 and to the dimensions in the NBD-PdCI2 complex9 in Table V. The bond distances and angles which would be equivalent in the free uncomplexed molecule have been averaged for comparison with the electron diffraction data. In most cases, the apparent differences due to complexing are not significant. As can be seen from the tabular comparison, the complexed norbornadiene molecular dimensions are in reasonable agreement with each other and with Schomaker's values. The reliability of Schomaker's values is unknown, so statements of significant agreement or disagreement with those values are not possible. Assuming that free norbornadiene should have double bond distances of 1.34 A. and single bond distances of 1.54 one could not claim that any bond distance in NBD-CuC1, except C&a, is significantly different, using 3.3 X the standard deviation as the criterion. Even as an internal check, the coordinated double bond Cs=Co is not significantly longer than the noncoordinated bond. In the companion structure determination of COTCuC1, the C=C bond length was found to be lengthened significantly. The particular value found, 1.392 A., is probably longer than the true value. Based on the
w.,
(8) C. F. Wilcox, Jr., S. Winstein, and W. H. McMillan, J . A m . Chem. Sac., 82, 6450 (1960). The authors refer t o a private communication from V. Schomaker. (9) G. F. Richards, Ph.D. Dissertation, University of Iowa, Feb., 1964.
4
2
3
Fig. 2.-View of one tetramer of [C7HsCuCI]4. Two C7H8 molecules have been omitted for clarity. The tetramer corresponds to the one a t the lower left in Fig. 1.
shift in the double bond frequencies in the infrared spectrum (about 100 cm.-' toward lower frequencies in both COT-CuC1 and NBD-CuC1) a bond length corresponding to the average of the two distances found, (1.392 1.345)/2 = 1.369 A., would be more compatible. This bond length compares reasonably well with the value 1.366 A. found for the C=C bond in dichloro(norbornadiene)palladium(II),2 in which the change in frequency is about 150 cm.-'. The structure which has been found from the crystallographic studies is compatible with the infrared spectrum and the structure proposed for the complex by Schrauzer and Eichler.'O They observed a band at 1547 cm.-l in the free olefin which they attributed to the double bond stretching frequency. In the norbornadienecopper(1) chloride complex, bands were observed a t 1563 and 1473 cm.-' and attributed to an uncoordinated and a coordinated double bond ; the copper atom was proposed to be in an exo configuration to the coordinated double bond. Spectral measure-
+
(10) G. N. Schrauzer and S.Eichler, Chem. Ber., 96, 260 (1962).
H. L. HAIGHT, AND J. R. DOYLE 1540 N. C. BAENZIGER,
COMPARISON
Inorganic Chemistry
TABLE V DIMENSIONS WITH
O F NORBORNADIENE
OTHER W O R K
Distance,
1. c1-c2
c4-c3
h-BD-CuC1
Av .
1.537 (0,010) 1,587(0.011)
NBD-PdClsS
1.539 C1-ce
c4-c5 c1-c7
c 4 - 4 7
C2=CP
c5=cs
1.518(0,011) 1.516 (0.011) 1.526 (0.012) 1.534(0.011) 1.31'7 (0,011) 1.345(0,011)
Av .
Free NBTY
1.553
1.522
I .554(0 006)
1.552 (0.006)
1.530
1.547(0.006)
1,547
1.558
1.331
1 366(0 010) 1.366 (0.010)
1 ,366
1 333"
107.0
109,l
100.0
96.4
100.3
102.2
Angle, deg. c1-c?;c3
c2-c3-c4
106.9 (0 .I-)
108.6(0.8) 105.3(0.4) 106.9 105.9 ( 0 , 3 ) 107.8 ( 0 . 6 ) 98.7 ( 0 . 6 ) 97.6 ( 0 . 4 )
107.0 (0.4) 99.5 ( 0 . 4 ) 99.4
cs-cI-c7 CaC4-C7 cp-c1-cs cs-c4-cs
a
100.2 ( 0 . 6 ) 100,9( 0 , 5 ) 102.7 ( 0 . 7 ) 104.1(0.4)
100.4 ( 0 , 4 ) 103.4
100.3 ( 0 . 3 )
X o t coordinated.
ments in this laboratory gave bands a t 1460 and 1560 cm.-' for the NBD-CuC1 complex. The description of the structure of the complex of copper(1) chloride with 2-butyne5 appears to be very similar to that of NBD-CuC1. An eight-membered ring with 4 symmetry was found with alternating copper and chlorine atoms. The carbon atoms of the acetylenic group lie in the same plane as the copper atom and the two adjacent chlorine atoms. Sufficient details of this structure are not available to make further comparisons. The structure of KBD-CuC1 may be compared with two other copper(I) complexes which show similarities in configuration as well as a trend toward tetrahedral geometry about the copper atom. I n the structure of potassium dicyanocuprate(I), KCU(CN)Z,~'the copper atom is surrounded by three ligands: two carbon atoms from cyanide ions a t distances of 1.915 and 1.922 A. and one nitrogen from a third cyanide ion a t 2.052 A. The angles between these groups are 134.2, 112.3, and 107.3'. The sum, 353.8', indicates that the ligand groups are not completely coplanar, but deviate in the direction that atoms would be if they occupied three of the four corners of a tetrahedron about the copper. There appear to be no groups in apical positions for a bipyramidal arrangement or a tetrahedral arrangement. I n the structure of azoinethanecopper(1) chloride1* the copper and chlorine atoms form a double alternating chain. The copper atom in one chain has as ligands two chlorine atoms in the chain a t 2.319 and 2.368 A., and the third ligand is a nitrogen atom in the azomethane molecule a t 1.993 A. The angles between these ligands are 109.2 (the chain angle), 107, and (11) D. T. Cromer, J. Phys. Chem., 61, 1388 (1957). (12) J. D. Brown a n d J. D. Dunitz, Acta Cryst., 13, 28 (1960).
132.1'. Again the sum (348.3') indicates further deviation from planarity. I n this structure the fourth ligand is a chlorine atom from the second chain of the double strand a t a distance of 2.547 A. In this case, the configuration about the copper could equally as well be called a distorted tetrahedral configuration as a distorted trigonal planar arrangement. I n the structure of 1,5-cyclooctadienecopper(I) chloride a slightly distorted tetrahedral configuration was reported for the arrangement about the copper.13 I n the structure of K2C~C1314 a more nearly symmetrical tetrahedral coordination about copper(1) exists, and in copper(1) chloride, which has the zinc sulfide (zinc blende) structure type, the coordination is perfectly tetrahedral. Thus, i t appears that coordination from the extremes of perfectly tetrahedral to trigonal planar (though not symmetrical trigonal planar) arrangements occur with examples in the intermediate configurations. A black and white categorization of the hybridization of the orbitals of copper as either sp3 or sp2, etc., is thus not possible. I n all the examples with the exception of copper(1) chloride the ligands about copper are not equivalent, so that symmetry requirements do not make the idealized hybrid orbitals mandatory. I n the olefin, acetylene, and azomethane complexes, filled d orbitals of copper(1) may interact with the vacant antibonding a-orbitals of the carbon or nitrogen atoms. This type of interaction would drain away some electron density from the region where the orbitals from the copper are directed toward the chlorine atoms. These orbitals could then adopt more p-character. The orbitals directed toward the olefin could then have (13) J . H. van den Hende and W. C. Baird, J . Am. Chem. Soc., 66, 1000 (1963). (14) C. Brink and C. H. MacGillavary, Acta Cryst., 2, 158 (1949).
Vol. 3, No. 11, November, 1964
MULTIDENTATE LIGANDEQUILIBRIA1541 Duax, who assisted in the intensity measurements. Part of this work was supported by grant DA-ARO(D)-31.. 124-G26 from the Army Research Office (Durham). A further grant from the Petroleum Research Fund enabled H . L. H . to obtain the intensity data which led to the solution of the structure.
more s-character, which should be more suitable for better overlap with the bonding a-orbital of the Olefin. Acknowledgment.-The authors wish to express their thanks t o Prof. J. Hayes of the Geology Department, University of Iowa, for the use of the single crystal orienter, and to Miss Carol Valley and Mr. William
CONTRIBUTION FROM
THE
DEPARTMENTS OF CHEMISTRY AND ORGANIC CHEMISTRY, UNIVERSITY OF SYDNEY, SYDNEY, AUSTRALIA
Multidentate Ligand Equilibria. 11. Complex Formation between Iron(I1) and Some Hydrazones of Pyridine-2-aldehyde BY ROWLAND W. GREEN, PETER S. HALLMAN,’
AND
FRANCIS LIONS
Received June 5, 1964 Formation and deprotonation equilibria have been studied for iron( 11) complexes of the three tridentate chelates, 6-methylpyridine-2-aldehyde-2’-pyridylhydrazone,pyridine-2-aldehyde-2’-pyrimidylhydrazone, and pyridine-2-aldehyde-3’-methyl2’-pyrazinylhydrazone. The respective measured stability constants were log PI: 6.3, 6.0, 7.9; log pz: 12.6, 14.0, 15.6; and the acid dissociation constants of the respective cationic bis complexes were pK,: 6.28, 4.56, 4.12; pK2: 7.95, 6.09, 5.61. A method is described for calculating stability constants and deprotonation constants from p H titration data when the buffer regions of the two equilibria overlap.
Introduction
Results
A class of multidentate ligands has been reported2 in which each ligand is capable of forming cationic and neutral complexes with bivalent transition metal ions. Addition of alkali to the cationic complexes deprotonates imino groups not involved in coordination to the metal, forming stable uncharged species. The previous paper of this series3 discussed the equilibria of metal complex formation and deprotonation for the tridentate ligand pyridine-2-aldehyde-2‘-pyridylhydrazone(PAPHY) . Three related ligands, 6-methylpyridine-2aldehyde-2 ‘-pyridylhydrazone (I),pyridine-2-aldehyde2‘-pyrimidylhydrazone (11) , and pyridine-2-aldehyde3’-methyl-2’-pyrazinylhydrazone(111) have now been studied in coordination with iron(I1).
Acid Dissociation Equilibria of the Free Ligands.Solutions of each ligand in perchloric acid (4 moles), alone and in the presence of iron(I1) (0.5 mole), were titrated with sodium hydroxide solution (10-2 M ) . Detailed experimental results are given in the Append i ~ .I n~ discussing the titrations, in view of the potentially acidic character of the N H group, we shall refer to species 1-111 as HL. The equilibrium constants are defined in Table I, and for purposes of computation we further define three quantities, LT, the total ligand concentration in all its forms, b, the number of moles alkali added in the titration, and
I1
a “$J CH,
,NH
111
Experimental The three ligands were taken from the same specimens prepared by Geldard and Lions.z Experimental methods of studying the equilibria have also been described previously . a (1) Petroleum Research Fund Fellow, Sydney University. (2) J. F. Geldard and F. Lions, Inorg. Chem., 2, 270 (1963). (3) R. W. Green, P. S. Hallman, and F. Lions, ibid., 8, 376 (1964).
g = (ZiWiLl
+ Z~[MH&~I)/LT
(1)
easily calculable from the titration data. This last quantity, the average number of protons attached to L-, falls below 1 only when deprotonation of the imino group occurs. In spite of the presence of four nitrogen atoms in ligand I, its g values were found not to exceed 2.9 even a t the beginning of the titration, and there was no spectrophotometric evidence for heavier protonation a t lower pH. I t could therefore be treated as a diacid base and the first two dissociation constants of the conjugate acid, H3L2+, could be calculated from the titration in the usual way, with small activity corrections estimated from the Ciintelberg f o r m ~ l a . They ~ appear in Table I as pK1 and pK2. (4) For Appendix, order Document No. 8059 from the Chief, Photoduplication Service, Library of Congress, Washington 25, D. C., Auxiliary Publications Project, remitting 81.25 for microfilm (35-mm.) or $1.25 for photocopies. (5) E. Gdntelberg, 2. physik. Chem., 188, 199 (1928).
