298 V. G. ALBANO, P. L. BELLON,AND M. SANSONI
Inorganic Chemistry CONTRIBUTION FROX ISTITUTO DI CHIMICAGENERALE DELL’UNIVERSITA D I MILANO, hlILAh., ITALY
The Crystal and Molecular Structure of Diiodocarbomethoxycarbonyl(2,2’-bipyridyl)iridium[Ir12CO(C,,H,N,)(C2H302)]1 BY V. G. ALBANO, P.L. BELLON,*AND M. SAXSON1 Receioed Septembev 26, 1968
Diiodocarbomethoxycarbonyl(2,2’-bipyridyl)iridium[ ?12(COOCH3)( CP)(CI&ZH~)] crystallizes in space group C2h5,P21/n, with unit cell dimensions a = 8.92 (1)8, b = 17.87 (2) A, c = 10.93 (1) A, p = 103.55 (lo)’, and Z = 4. The structure has been determined from about 1500 independent reflections (measured by counter methods) and refined by full-matrix least squares to a conventional R factor of 0.043. It consists of a packing of discrete monomeric molecules in which the metal atom displays a distorted octahedral coordination with the two iodine atoms in trans positions. On the basis of the observed Ir-C distance (2.05 ( 2 ) A), the carbomethoxy group seems to be linked to the metal via a pure u bond. The observed coplanarity of the -COO group with the metal atom, the carbonyl, and the two nitrogen atoms of bipyridine seems to be due to an angulated hydrogen bond connecting the “ketonic” oxygen of the carbomethoxy group with an a-carbon atom of the bipyridine. The Ir-C bond connecting the metal with the carbonyl ligand is rather short (1.80 (2) 8) although the C-0 bond (1.11( 2 )A) and the stretching frequency (2050 cm-l) do not indicate a particularly strong metal-carbonyl interaction. Owing to a steric repulsion of two hydrogen atoms, the 2,2’-bipyridine ligand is not planar, and, consequently, the chelate ring is also not planar.
The instabilities of certain metal carbonyl cations in water, which undergo a characteristic reaction to give neutral hydrides and Con, support the view that the electrophilic nature of such complexes is localized on the carbon atom of the carbonyl group. The above reaction, in fact, has been shown3 to occur via a carboxylic intermediate M-COOH. Although no one metal-carboxylic derivative has been found stable enough to be isolated and characterized, Kruck and N ~ a khave ~ , ~obtained a number of neutral carboalkoxycarbonyl derivatives of manganese and rhenium, prepared by the nucleophilic attack of alkoxy ions on the corresponding cationic complexes. A similar series of Ir(I) and Rh(1) complexes has been d e ~ c r i b e d ,and, ~ , ~ more recently, Malatesta* has isolated a series of carboalkoxy derivatives of iridium(III), obtained by the reaction
as that suggested recently by Treichel, et al.,9 for metal-acyl bonds 0 M-C
+
//
\
M=C
O ,-
\
0-R
0-R
In this connection it should be noted that the stretching frequency of the carboxylic C=O group in a number of carboalkoxy derivatives4+ falls in the range 1620-1700 cm-’ (1G20 c i ~ i -in~ this compound) whereas the corresponding range for ordinary esters is 16801820 cm-l, with just a narrow overlap with the previous one. Collection of X-Ray Data and Their Corrections for Systematic Errors
The complex crystallizes from hot 2-propanol into beautiful yellow-orange prismatic tablets. On the basis of Weissenberg and precession photographs, the The present paper deals with the crystal structure space group has been determined as monoclinic PZ1/n10 determination of one of the iridium(II1) compounds, namely, of diiodocarbomethoxycarbonyl(2,2‘-bipyri- with the following cell dimensions: a = 8 . 9 2 (1) A, b = 17.87 (2) A, c = 10.93 (1) A, p = 103.55 ( l 0 ) O . dy1)iridium. The interest for this determination arises Agreement between observed and computed specific from the lack of structural information on the carboxy gravities has been obtained for 2 = 4 ( p c s ~ = c ~ 2.65 and carboalkoxy groups linked to transition metals. g/cm3, Pmeasd = 2.60 (5) g/cm3). The latter value The electronic interactions between the metal and a was determined by flotation in iodomercurate solution. carboxy or a carboalkoxy group could be, in prinThe intensities of about 2100 reflections have been ciple a t least, described in terms of a u bond plus some measured a t room temperature on a Pailred singlecontribution of a d,-p, interacticjn of the same kind crystal diffractometer with M o KO! radiation mono(1) This work was performed under t h e auspices of the Italian Consiglio chromatized with a Si [I11] single crystal cut. Nazionale delle Ricerche. , The crystal was mounted along the u axis to avoid (2) Address inquiries t o this author. Ir14(C0)2- 4- 2L
4-OR- -+-IrI2(COOR)L2(CO) + 21-
(3) E. L. Muetterties,Imug. Chem., 4, 1841 (1965). (4) T.Kruck and RI.Noak, Chem. B e y : ; 97, 1693 (1964). (5) T. Kruck, Z. Naluvfovovsch., 16b, 709 (1961). (6) L. Malatesta, G. Caglio, and M . Angoletta, J . Chem. Soc., 6974 (1965). (7) W. Hieber and F. Frey, Chem. Bey., 99, 2614 (1966). (8) L. Malatesta and M. Angoletta, private communication.
(9) P H Treichel, R. L. Subkin, K. W Barnett, and D. Reichard, I n o v g .
Chem., 5 , 1177 (1966). (10) This space group refers t o a reduced cell. The cell of the slandavd setting having space group P21/c is related to t h e present one in the followc. ing way: a1 = - a , bi = b, CI = a
+
Vol. 8, No. 2, February 1969
~IIODOCARBOMETHOXYCARBONYL(~,~’-BIPYRIDYL)IRIDIUM 299
systematic double-reflection effects. A set of seven reciprocal lattice layers, from Okl to 6kl up to an equiinclination angle of 16” and to a maximum I ’ of 54”, were recorded by the w-scan technique. After the collection of data had been completed, a number of reflections of the equatorial layer were reevaluated to check whether any crystal decay had occurred. Since no decay was apparent, all of the measured intensities were given the same scale factor throughout the subsequent analysis. It was then decided that, in order to carry out the structural determination, a 15-fold excess of observations, with respect to the number of parameters (see later) to be determined and refined, would be sufficient. Therefore, 1498 independent reflections, with a relative counting esd lower than 0.25, were sorted out of about 2100 measurements and used in the present analysis. After the Lorentz and polarization factors had been applied, by taking into account the polarization of the incident beam,” the resulting Fo2 set was corrected for absorption. This effect turned out to be a very important one, owing to the p value (117 cm-l) and the specimen used. This was a roughly hexagonal platelet with ten well-developed faces, having dimensions 0.028 cm along the rotation axis and 0.015 X 0.018 cm in directions normal to it, the volume being 388 X ~ m . ~ Very accurate nieasurements of the faces were taken on an optical-reflection goniometer and the transmission factors-in the range from 0.19 to 0.40-were computed with a program based on the Busing and Levy12method. Structure Solution and Refinement The coordinates of the iridium and iodine atoms were determined by inspection of a three-dimensional Patterson function and refined isotropically by least squares. The conventional R factor for this part of the structure was 0.16. All of the remaining atoms were subsequently located on a difference Fourier. The structure was refined by full-matrix least squares. The variables were three positional and six anisotropical thermal parameters for each of the three heavy atoms, three positional and one isotropic thermal parameters for each of the 0, N, and C atoms, and finally an overall scale factor giving a total of 100 parameters. The atomic scattering factors were chosen as follows : for f andfI the Thomas-Fermi-Dirac statistical model curves13 corrected for the real part of the anomalous dispersion;I4for fo,fN, and fc the curves from the selfconsistent variational field method. l 6 The minimized function was 2 w ( F o - [ F c ] ) 2w, being the reciprocal variance of Fo. This variance has been (11) W. L. Bond, Acta Cvyst., 12, 375 (1959). (12) W. R. Busing and H. A. Levy, ibid., 10, 180 (1957). (13) L. H. Thomas and K. Umeda, J . Chem. Phys., 26, 239 (1957). (14) “International Critical Tables for X-Ray Crystallography,” Vol. 111, The Kynoch Press, Birmingham, England, 1962, p 213. (15) R. McWeeny, Acta Cvyst., 4, 513 (1951).
computed from the variance of the corresponding FO2, assumed to bel6
where Vc,is the counting statistical variance and A is a parameter. The assignment of the A value was made before refinement, in such a way as to render w A 2 / n [with A2 = (Fo - F J 2 and n being the number of reflections] approximately constant and unitary over the entire range of the FO’s.l7 A preliminary analysis showed that 0.04 was a fairly good value. Before the last two cycles, the evaluation of A was repeated and 0.06 was found to be more satisfactory. I n both of the weighting schemes, the five strongest reflections (002, 103, 061, 160, and 203) appeared to be overweighted. The difficulty of assigning them reasonable weights on the basis of the statistical model assumed and, more than that, the possibility of extinction effects led us to disregard these reflections in the refinement. Their values (see Table I), computed on the basis of the final molecular model, appeared to be stronger than the experimental ones, indicating a moderate extinction effect. (The maximum observed discrepancy arises for the lowest angle reflection 002, having Fo = 450 and F, = 528 electrons.) The agreement indices after convergence were R = 21Fo - IFc / / 2 F o = 0.043 and Rw = { 2 w ( F o [ Fcj)2/2wFo2*” = 0.055, with a final value of the error-fit function of 1.30. The above indices, for a preliminary refinement done with the heavy atoms constrained to isotropic vibration, were R = 0.062 and R, = 0.086.lS None of the 11 hydrogen atoms bonded to the methyl and to the bipyridyl groups has been taken into account in this refinement, nor did any show in a difference Fourier, which was computed on the basis of the final atomic coordinates. I n this map the maximum observed electron density was 0.5 e-/b3, partly due to vibrational anisotropy in the lighter part of the molecule, which has not been taken into account. I n Table I the final list of computed and observed structure factor moduli is given in electrons. The positional and thermal coordinates for the heavy, anisotropically refined part of the molecule are listed in Table 11, and the positional and isotropic thermal parameters for the light part of the molecule are collected in Table 111.
I
The Crystal and Molecular Structure
A layer of the crystal structure composed of molecules related by a set of coplanar inversion centers and (16) P. A. Agron, R. D. Ellison, and H. A. Levy, ibid., 23, 1079 (1967). (17) D. W. J. Cruickshank and D. E. Pilling, “Computing Methods in X-Ray Crystal Analysis,” Pergamon Press Ltd., London, 1966. (18) All of the computations of the present determination have been done on a n I B M 7040 computer. The programs used were local versions of the following entries of the 1966 “International World List of Crystallographic Programs”; 7528, 7531, 7532, 7535 for Fourier a n d Patterson analysis and for structure factors and least-squares computation. Counter data reduction, absorption correction, interatomic distances and angles, and best-plane determinations were based upon Fortran 4 programs prepared in the author’s laboratory and were not quoted in the “International World List.”
V. G . ALBANO,P.L. BELLON,AND M. SANSONI
300
Inorganic Chemistry
TABLEI LIST O F COMPUTED (FC)AND OBSERVED(FO) STRUCTURE FACTOR MODULIIN ELECTROXS OBTAIXEDAFTER CONVERGENCE OF THE LEAST-SQUARES REFIKEMENT K FO / F C /
H
L
4 149 h 166 3 110 12 9 2 14 i a i 10 36 20 L h 2 2 73 4 62 5 749 6 446 7 95 U 168 52
9
I2 I3
144 I74 325
96
-j 3
IO
3 -3 3
12 1 2 1 1 2 4
100
14s
4s
-3
-5
3 -3 3 -3 3 3 -3 3
-4 4 -4 4
70 43 57 95 214 ? I 8 71 71 I35 1 4 0 709 718
92
I1
64 I7 29 11 n 5 14 b 3 15 k4
97
63 33 95 h4 41
s
4R
49
57
13 16
31
15 17
59
34
hi) O h 5R 50 55 5 5 5 5 55 20 36 3 I64 I64
I* 19 22
24 71 30
4 h7 R
$;
31 71 7 6 9 b2 70 10 12" l ? h I I 13)9 1 4 4 16 6 6 5 9
I 47 4 4 2 39 7 9 3 116 I23 4 150 160 5 105 I l l 9 I O 3 110 IO 5 4 5 7 1 2 5 7 61
-0 -0
-0
-0 -0 _n
-4 4 -4 - 44 4 -4 -4
- 44 4 -4
2 -5
9
143 59 54
i*n
57
53 70 14 177 1 7 4
12
-5
5 -5
5 -5 5
-5
-5 6 6 h
-6 h
-6 - 6h
-2
5 201 ? I 3 5 106 1 0 9
67 7 2 h 134 1 4 1 7 42 4b R 279 2 8 3 n 290 303 4 4 h 43 9 27 25 I I 58 66 II 37 4n 6
I5 16 19
6 -6
41 ?4
49
-" -0
-3 -0 -1 -0
-0 -0
-0 -0 - 00
o I
hl
-1 -1
IO
in
71
53 3) 156
146
749 245
1
1 -1 1
-I 1 -1
1 -1 I
i4n
-I
I30 141 163
1 -1 ?2
1'12
75
77 51
2 - 22
I4 119 1 1 9
2
IO 11
53 70
74
;; ;1;
17; 78 60 511 70
*a
50
H
K
F0 /FCl
U
K
FO I F r ,
-; 2 -22
-$ -2 2 -2
-2 -?
7
3 144 36 5 111 6 87 h 123 7 ?q R 107 4
R
q
9
io
IO 11 II 12 I3
143 31 !36 qn
136 L3 100 97 '6 113 116 137 I L 5 1ri 112 121 12s 1.5 161 67 6 7 31 3 1 40
13
I?
::
60 60
2;3 1 2,;3 0 519 58
3 119 ! 6 5 3 111 i n 7
4 1 9 1 !SI 4 2 4 ) 251 5 1 6 9 166
5 137 142 6 ?4 26 n 32 3 2 9 135 I 3 6 9 59 h l I O 5 9 61
I0 1 0 8 1 0 9
1 2 7 1 73 I 2 I04 I 0 6 I 5 3 8 41 43 1 49 2 55 60 3 225 7 1 4 3 1 3 3 140 4 z a 27 4 36 3 7 5 57 62 5 3? 3 7 6 26 30
P 36 ? O 38 3 4 I C 7R 7 7 I O I24 1 3 3 9
11 ILL 1 4 8
I1 113 l l q 15 4 4 4 1 16 4 9 5 5
2
0 450 5 2 5 1 69 b9 2 32 3 1 73
61
6
103 I 0 5 75 71
12
24: 2 % 78 9 1
5
Fn
/FCt
U
K En
IFTI
W
K FO I F 0
1
I .I .I 2 .? .?
.2 2 .7
.2 .2
.2 2
-2 .2 .7
1 3 104 193 1 4 I64 1 0 7 2C 41 17
21 57 4 8 h2 22 65 I 249 758
12
I2 I,, I5 0
05 hq
43
43 56
61 70
"I 45 47
0I I00 I 2 2 I;? 91) li I P39 7 7 110 It 60 59 5 4R 46 'I1 52 7 5c 55 53 8 54 a 8) 1 93 47 n6 n4 6
7,;
3 - 33
.,+3
3
-3 - ?3
-3 3 -3 - 33
3 -3 3 -3 -3 3
.3 .3
1 IO5 0 l I 7 G
.L
4
-4 .4
-5
-5 -5 -5 .5
- 44
-:
5 7 4
I4 3 I 3 5
71 O n
39 I 3 1 511 89 44
h7 L(I
37
94
:;
7 21 37 2 0 '5 87 43 71
Ln 34
9P Oh
96 Lh 711 7 3 'I6 55 5 6 56 7 1 1 9 116 a \ a 56
- 66
2i 160 73
7' 84
-6 -6
5? 9
~n 73
40 7 9
'7
75
L =
I1
?
99
6
47 49
3
-3 4 4
89
.4 4
.L
-3
33 31 84
4
K
2 6R a5 Rh 6 38 6 hl 62 1 1 5 1 159
36 36
i
H
.33 3
19
03
/FCf
I
76 I-? 4 76
211 2
Fn
-3
74 71 61
62
X
-2 2 -2 2 -2 3
15 16 lh I0
LP
H
-4 -4 4
I 113 139 2 152 1 5 1
-7
0 -0 -0 -0
-1
5
6
LO
12
63 50
99 ' 3
47 63 h4
56
63
IO? 6'1
- 1I -1 - 1I
n0 I
1 5h 04 h l
-44
-I
11
14
h9
4 --i *
- 1I - 1I
hh
54 01 5P LI
04 1 59
18
7 I
CI
44
1-4
4 -4 4 -4 -4 -4 4
-- 4
