2134 Inorganic Chemistry, Vol. 17, No. 8, 1978
Robert I>. Wilson and James A- Ibers Contribution from the Department of Chemistry, Northwestern University, Evanston, Jllinois 60201
Structure of Chloronitrosyl($--suRfur RuCl(N0) (r2-S02) (W, ROBERT D. WILSON and JAMES A. TBERS* Received February 14, 1978 Chloronitrosyl(q2-sulfur dioxide) bis(triphenylphosphine)ruthenium, RUC~(NO)(~~-SO~)(PP~~)~, on the basis of an X-ray structure determination of its CH2Clzsolvate, is shown to possess q2 coordination of the SOzgroup to the Ru atom. About the Ru atom are trans axial PPh3 groups and a basal plane consisting of the C1 ligand, the N O ligand (with Ru-N-0 linear), and the S,O bonded SO2 group. As opposed to the T~ coordination of C 0 2 and CS2 to transition metals, wherein the metal-ligand systems are planar, atom 0 ( 2 ) , which is not bonded to the Ru atom, is I .24 A out of the plane of atoms Wu, S, and O(1). Through the use of it was established that a weak band at 895 cm-' in the spectrum of the componnd containing SI6O2arises from the presence of SO2. The geometrical features of the present structure are compared with those in Rh(NO)(q2-S02)(PPh3),,the only other example where T J coordination ~ of SO2 has been established. The compound RuCI(NO)(SO~)(PP~~)~-CW~C~~ crystallizes in space group C,'-PI of the triclinic system with two formula units in a cell of dimensions a = 13.629 (2) A, b = 15.255 (3) A, c = 10.106 (2) A, a = 92.70 (l)', (3 = 104.41 (2)', y = 65.48 (l)', V = 1848 A3, pal& = 1.498 g/cm3, and pobsd= 1.5 1 (1) g/cm3. The structure has been refined to a conventional R index on F,, of 0.063 on the basis of 182 variables and 5379 observations.
concentrations we assumed that the reduction step was quantitative. The discovery of the bent mode of coordination of the SO2 Dark green crystals of R u C ~ ( N O ) ( P P can ~ ~ )be~ grown from such molecule to transition metals' was followed shortly by firm solutions by vapor diffusion, using pentane as the nonsolvent. These characterization of the bent mode of coordination of the NO crystals show an infrared band at 1735 cm-' (vs), which may be ligand to transition metal^.^,^ In the ensuing years a conassigned to vN4. At the expense of this band, a new nitrosyl band siderable body of chemical and structural knowledge has grows at 1768 cm-' if the cell plates are exposed to dioxygen. In evolved on NO coordination4 and somewhat less on SO2 addition, a band at 878 cm-', assignable to the presence of the R u 0 2 coordination.5 We6 recognized that NO and SO2 are both group, appears. These band positions are for the species RuC1amphoteric ligands that are capable of acting as Lewis acids (NO)(02)(PPh3)2.9 Owing to the instability of crystals of RuGl. (M-L bond mainly 0 in character, long M-L bond, bent (NO)(PPh3)*,no elemental analyses were obtained. However, it was possible to obtain unit cell data: triclinic, space group P1 or PI, a geometry) or as Lewis bases (multiple and short M-L bond, = 9.16 A, b = 11.03 A, c = 10.73 A, a = llO.Qo,(3 = 86.5', 7 = linear or planar geometry) and that such amphoteric ligands 122.9', V = 838 A3. Since PI is the much more common space group are a convenient probe of the electronic characteristics of the and since the assumption of one formula unit per cell yields the metal system. A question that we asked was how do the reasonable calculated density of 1.34 g/cm3, it is likely that in the acid-base properties of the NO and SOz ligands differ from solid state a center of symmetry is imposed on the molecule. Hence, one another. An obvious way to answer this question exit is probable that the phosphine groups are trans, the coordination perimentally is to synthesize and characterize complexes about Ru is planar, and the NO and Gl ligands are disordered. containing both NO and SO2 ligands. One that has been at Chloronitrosyl(q2-sdfurdioxide)bis(tripReaaylphosp~ne~r~~he~~~~~~ hand for a number of years now7 is R U C I ( N O ) ( S O ~ ) ( P P ~ ~ )This ~ compound was prepared by the original literature method.' A freshly prepared solution of 0.21 mmol of R U C ~ ( N O ) ( P P ~in, )40 ~ (where Ph = phenyl), prepared by the addition of SO2 to mL of benzene was treated with 1 atm of SO2gas for 5 rnin to yield R u C I ( N Q ) ( P P ~ ~ )One ~ . could envisage the Ru atom in this a bright red solution (vNz0 1758 cm-' (s), vSQ2 1150 cm-' (m)). complex possessing a square-pyramidal coordination geometry, Removal of solvent and excess SO7gas under vacuum yielded a powder either with a basal, linear Ru-N-0 linkage and an axial, of the desired material. pyramidal Ru-S02 geometry or with a basal, planar Ru-SOZ Chloronitrosyl(q2-suldurd i o x i d e ) b i s ( 8 r i p h e r n y ~ ~ ~ o ~ p h ~ r n e ~ ~ ~ ~ h e geometry and an axial, bent R-N-0 linkage, depending upon Diethyl Ether Solvate. This compound was obtained by recrystalthe relative basicities of SO2 and NO. As is sometimes the lization of the above powder from diethyl ether4ichloromethane. The case in transition-metal chemistry, the stumbling block in this compound crystallizes with four formula units in space group experiment was our inability to obtain suitable crystals of the Ca5-P2,/n of the monoclinic system in a cell of dimensions a = 16.499 (3) A, b = 23.216 (4) A, c = 10.138 (2) A, and 0 -- 96.46 (1)". A complex. After successive tries over a period of years this has complete X-ray diffraction data set out to a 20 limit of 105' (Cu K a now been accomplished, and the results of the structural study radiation) was collected and analyzed in the usual way.'" The final are presented here. As often occurs, the geometry we find for R index on F, for the 3514 intensities above background was 0.067. the complex is neither of the possibilities we anticipated. Although this structure analysis clearly established the basic geometry Experimental Section of the complex,'' there were several unsatisfactory features of the
Compound Preparation and Characterization. Manipulations of all solutions and solids were done under dry N2 flow. Reactions were carried out under a static N2 atmosphere. Crystals of RuCl(NO)(PPh3)2 required an inert-atmosphere drybox for successful manipulation. All solvents were distilled under N2from the appropriate drying agents. Infrared spectra were measured in Nujol mulls and C6H6solutions using Perkin-Elmer 727-B and I-R 283 spectrophotometers. Elemental analyses were performed by H. Beck of the Northwestern University Analytical Laboratory. Chloronitrosylbis(tripheny1phosphine)ruthenium. This complex was prepared by the literature m e t h d 7 Kn a typical run 0.16 g (0.21 mmol) of RuCl3(NO)(PPh3)? was dissolved in 40 m L of benzene, and an excess of Zn dust was added. After 2 h under reflux, the dark green solution was filtered and stored at room temperature under N2 gas. It was used in this way for further syntheses. For estimation of
0020-1669/78/1317-2134$01,00/0
structure. In particular, the molecule appeared to possess a noncrystallographic twofold axis in that there was disorder of the NO and C1 ligands and the Ru-SO2 arrangement was also disordered. There were also difficultiesin the location of the terminal carbon atoms of the diethyl ether solvate molecule. Hence, attention was directed at obtaining the desired compound as other than the diethyl ether solvate. Chloronitrosyl(q2-sulfur dioxide)bis(tripBaenylphosphine)ruthe~~~m Dichloromethane Solvate. Powder of the solvate-free material was recrystallized from dichloromethane-pentane by vapor diffusion to yield the dichloromethane solvate as red-orange crystals. These crystals appear to undergo facile loss of solvent. Anal. Calcd for RuC1(NO)(S02)(P(C6H5)3)2.CH2C!2: c,52.90; H, 3.84; N, 1.67. Found: C, 52.95; W, 4.05; N, 1.33. Infrared spectra (Nujol mulls) are similar to the spectra from benzene solution and show vN=0 at 1754 cm-'
0 1998 American Chemical Society
Inorganic Chemistry, Vol. 17, No. 8, 1978 2135
RuCl(N0) (v2-SOJ (P( C6H5)3)2*CH2C12
CrystallographicStudy of RuC1(NO)(q2-SOz)(PPh3)2.cHpz. The specimen was sealed in a glass capillary in order to minimize solvent loss and decomposition. Preliminary film data failed to reveal any symmetry, other than the trivial center of symmetry, for this compound, and hence it was assigned to the triclinic system. On the basis of the setting angles of 15 manually centered reflections (50 C 28(Cu K a l ) C 6S0), the reduced cell constants presented in Table I were obtained. The crystal chosen for data collection showed little mosaicity. Data were collected at room temperature on a Picker FACS-1 diffractometer using methods general in this laboratory.1° Important features of the data collection are summarized in Table I. The structure was solved in a facile manner, using procedures and computer programs described before.I0 Space group Pi was assumed. The positions of the atoms in the inner coordination sphere were clear from a three-dimensional, origin-removed Patterson map. All nonhydrogen atoms were located on a subsequent difference Fourier map. Included in the final cycle of least-squares refinement were the contributions from hydrogen atoms placed at their calculated positions. The carbon atoms of the phenyl rings were constrained to the rigid-group appr~ximation'~ with isotropic thermal motion, while all other atoms were allowed to vibrate anisotropically. The occupancy of the solvent molecule was also varied. This final refinement converged to values of R and R, of 0.063 and 0.075, respectively,and to an error in an observation of unit weight of 2.00 electrons for the 182 variables and 5379 observations. The occupancy of the solvent molecule was found to be 0.94 ( l ) , and hence the compound is the monosolvate. An analysis of Cw(lFol - lFc1)2as a function of IFoI, setting angles, and Miller indices indicated no unusual trends. Eighteen of the nineteen highest peaks (0.89-0.58 e/A3) in the final difference Fourier map are associated with the carbon atoms of the constrained phenyl rings. This suggests a slight inadequacy of the isotropic treatment of these atoms. But previous experienceI4 has indicated that relaxation of this isotropic model, while reducing the R index and increasing the computational costs, does not significantly improve the definition of the chemically more interesting parts of a structure. Final positional and thermal parameters are tabulated in Tables I1 and 111. Root-mean-square amplitudes of vibration are given in Table IV.Is In Table V the values of 10IFol and 10IFcl for the reflections used in the refinement are given.Is
Table I. Crystal Data and Data Collection Procedures for
RuC1(N0)(qz-S0,)(PPh3),~CHzCl, C 3,H3,C13N03PzRuS 840.1 1 Ci' -Pi (triclinic) a 13.629 (2) A b 15.255 (3) A C 10.106 (2) A a 92.70 (1)" P 104.41 (2)" 7 65.48 (1)' V 1848 A s Z 2 Pcalcd 1.498 g/cm3 Pobsd 1.51 (1) g/cm3 temp 22 " C complex plate of approx dimensions crystal shape 0.31 mm X 0.21 mm X 0.10 mm crystal vol 0.0071 mm3 Cu K a (h(Cu Ka,) 1.540 562 A) radiation prefiltered through 1 mil thick Ni foil 71.6 cm-I linear absorp coeff (p) transmission factors 0.224-0.5 5 2 3.9 mm wide by 3.7 mm high, 30 cm detector aperture from the crystal takeoff angle 3.5" scan speed 2.0" in 28/min 20 limits 5 .O- 160.0" bgd counts 10 s at each end of scan with rescan option scan range 0.9" below Ka, to 0.8" above Ka, data collected &, k k , I < 0 P 0.04 unique data, Fo2> 3u(FOa) 5379
formula formula wt space group
and only one rather broad band at 1140-1 155 cm-I clearly assignable to SOzabsorption. The high value of the N O absorption is consistent with a linear Ru-N-0 linkage.I2 Chloronitrosyl(q2-sulfur dioxide-l8O)bis(triphenylphosphine)ruthenium. Approximately 0.3 mmol of S1802was condensed into an evacuated Schlenk tube containing a frozen solution of 0.05 mmol of freshly prepared R u C ~ ( N O ) ( P P dissolved ~ ~ ) ~ in benzene. On warming, the green glass changed to a red-orange solution. Removal of solvent under vacuum afforded a yellow-orange powder whose I R spectrum showed a weak band at 864 i 1 cm-I which appears at 895 i 5 cm-' in the corresponding S1602spectrum. A possible shift in the band that occurs at 1140-1 155 cm-I in the Sl6O2spectrum could not be detected, perhaps because this band overlaps with bands from phenyl modes. Sulfur Dioxide-I80. The S1802was produced simply by burning an excess of sulfur on an electrically heated nichrome wire in a sample tube containing 1802 and NZ. The S1*02sample was separated from excess sulfur and from any residual 1802 by trap-to-trap condensation. The isotopic purity of the resultant sample was established from gas-phase I R spectra.
Results and Discussion The crystal structure of RuC1(NO)(q2-SO2)(PPh3),.CH2C12 consists of well-separated molecules of metal complex and solvent. A packing diagram is shown in Figure 1. All intermolecular contacts appear to be normal. Intramolecular distances and angles are given in Table VI. The overall molecular structure of the metal complex is shown in Figure 2, while Figure 3 displays the inner coordination sphere and some important distances and angles. Rather than the anticipated square-pyramidal coordination about the Ru atom with either an axial, bent Ru-N-0 linkage or an axial, bent Ru-S02 geometry, the coordination geometry actually found is that of a trigonal bipyramid with trans, axial
Table 11. Positional and Thermal Parameters for the Nongroup Atoms of RuC1(NO)(q2-SOz)(PPh,),~CHzCl, A ~!~C.o*.*~***~*.*..**.*ooo*~:~oo..
......... 2
RU
c.~a49001431
n.ia84881351
s
0.04989116)
0.05302112) 0.296581111
p i t i PIZI
CLll) 011) 012)
N 0131
Clll CLl2l
CL13)
-0.090671is) 3.26397(14) 0.17944117) 3.11148145) 0.11836147) 0.03226148) 0.00625151) 0.28941181 6.21952142) J.40896164)
8ilB
822
.~....0.*...0~~00..0.*00..***000000~.0.00000*...0.*00000
o.ion4811ii
0.25207114l 3.68073135) -0.036451351 3.236991411 0.265131441 0.44707(60 5.55062144) 0.42805(531
0.i6578215ii 0.187561191 o.zi4271i81 o.iit931i61 0.35567120) 0.315751461 0.13567151l -0.002641581 -0.11256161l 0.3641114l 0.35409159l 0.473671@81
5.50141
4.01121
8~01116l
4.69191
6.691151
5.41113) 8.841171 11.621541
11.80156l 6.86150) 9.99158) 53.81321 19.79158l 35.91111
3.92181 4.30181 6.781121 5.961291 5.081271 5.36134) 7.971411 7.231431 19.351591 26.32175l
833 8.08191 12.131221 10.461201 8.341181 12.57123) 9.771541 13.651661 10.101681 12.88177) 31.61221 47.1112) 71.31191
E12
....
-2.OllEl -2.81110) -2.2719) -1.9718) -3.501121 -3.76134) -3.13132) -2.31133) -2.91139) -8.63198) -2.631151 -8.181691
..C.O*O.**
813
...,..*.
2.5713 I 4.531151 3.571141
Z.ZOIIZI 1.881161 4.561441
6.211501 3.581471 2.401551
17.51221 7.71166l -1t3.5Illl
E23
-0.78 ( 3 1 -0.811111 -1.451ini -n.ie(qi -2.971131 -0.321321 -1.741341 -1.181381 2.28145l -3.60177) 6.081651
18.03195l
.o..*.o*.*+r.*.**.*o*.o.o.o.o.4ooo.oo*o.o.oo..oooo.o.,oo.o*.*.*o.o.o.o.ooo.o.o.o*.o~....*.o...*.. A
E S T I M A T E 0 STANDARD C E U I A T T C N S I N T H E L E A S T S I G N I F I C A N T F I G L R E I S )
FOR?'
.
OF T H E A N I S O T R O P I C THERHAL E L L I P S C I C I ARE T H E THERMAL C O E F F I C I E N T S Y 1 0
IS: E X P I - l B l 1 H
2
2
ARE G I V E h I h F A R E N T H E S E S I N T H I S PNO ILL S U B S E Q U E N T TABLES.
2
4 E Z P K 4633L t Z 8 l Z H K t 5 8 1 3 H L t 2 B 2 3 K L ) 1 .
E
THE O U A N T I T I E S G I V E N I N THE TABLE
THE
2136 Inorganic Chemistry, Vol. 17, No. 8, 1978
Robert D. Wilson and James A. Ibers
Table 111. Derived Parameters for the Rigid Group Atoms of RuCl(NO)(q*-SO,)(PPh,),.CH,CI,
........!.*.....*..*......**....*...~~:.** .....~*.........*.E..**.**..*.*...!l...**..*
*.:
*ATOM ..*.*.**
2
2
....
ATCM
e
f..**.*..*...+t.....
P'
Clll)
-0e12915143)
0.25888137)
0.353841451
3.641131
C1411
0~340331361
0.175211321
0.124331481
C l l i l
-3.238031381
5.2695714CI
0.339931471
5.211181
GI421
0.456351361
0.136101261
0.16832148)
3.961121
CIl31
-G.26547137)
0.23758146)
0.446781€31
6.501201
GI431
0.512951361
0.1933713.51
0.162951561
5.311181
C (141
-u
0 .I9490 1 4 4 I
0.56755 ( 5 2 )
6.32 I 2 2 1
C (441
0.45353 (46)
5.28975 I 3 6 1
0 - 1 1 3 5 9 (601
6.06 1181
C1151
-0.075131451
0.184221411
0.581461441
6.321201
C145)
C.3!750146)
0.32886(261
0.069601601
6.821211
C1161
-5.347731331
0.2162114CI
0.474611551
5.181161
Cl461
0.28G9Gt3Cl
0.271591341
0.074971551
5.541203
CI211
-0.2098C1341
0.319791331
0.067321401
3.521111
GI511
-0.249251381
-0.068211311
0.065491331
3.231111
Cl22)
-;.21289136)
J.24272lZCl
-0.010881481
4.25 (14)
Cl521
-0.280921391
-0.109551311
0.158321461
4.511141
C1231
-0.303951451
0.25694133)
-0.121521471
5~111161
GI531
-0.2E3971441
-0.08666135)
0.29500142)
4.881161
Cl24)
-G.39191137)
0.3482514CI
-0.153971471
6.031201
C154)
-0.215361441
~0~022461361
0.338851331
4.511141
~(251
-0.388821381
0.425321301
-0.075781561
6.281i91
c1551
-0.ic3701~o1
0.246021451
CIZEI
-0.297761441
0.411101281
0.034871491
4.961161
C156)
-0.22064140)
4.781141 3.97113)
C(31)
-u.09310149)
0.41485135)
0.251661611
4.121141
GI611
0.3E191136)
-0.009031281
0.217341431
3.561111
Cl321
-G.054151511
0.45588145)
0.16758154)
5.561181
Cl621
0.3€879141)
-0.010621311
0.35732147)
4.781161 5.991181
,18402 ( 5 2 1
o.oi8e.r(321 -0.004051311
3.521111
0.109351411
C133)
-u.05619157)
0.547431451
0.19074171)
6.551251
C163)
0.447051471
-0~091411391
0.44227135#
CI341
-0.097181651
0.59794137)
0.29798182)
8.051271
Cl641
0.5184314CI
-0.170611321
0.38723150)
5.651181
C135)
-5.13613170)
0.556901531
0.?82061721
12.171431
C1651
0~511551411
-0~169021301
0.247251531
5.13(181
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*
-3.134091611
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+
8
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9.591361 ~
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R I G I D GROLP P A R A U E T E R S
A
GROUP
Y
C
**..*
...*.....~~...........*.*~..***.*..*...*..r.**t...t
2
C
G R P 11
-3.15658133)
0.226891251
G R P 12
-Li . 3 L J 8 € I 2 9 1
0.334021251
G R P 13
-6.59514 135)
0,50639 (321
G R P 21
U.396931301
0.252481241
GRP 2 2
- 0 . 2 3 2 3 1 (25)
-0.04535 I 2 1 1
a.
GRP 2 3
.*.*.
4401 7 I2 7 I
-0.08982124)
C
CELTA
8
EPSILCN
ETA
-z.e.1991321
-2.0659l36l
0.4607013a1
-1.4840137)
-0 - 0 4 3 3 3 1341 o . 2 7 4 a 2 1471 0.118961331 0.20217131) 0.30229 135)
0.4576132 I
-2.8358l30 I
1.98451951
-2.0151146)
0.6756132) -2.7295196) 2.9727130 I
1.08221291 -G.43241321
2.9782 I 3 3 1 t.0~791241
-i.588913ii
-2.32461791
2.02561271
-1.54401761
...~....,,*....*....~,.*...*..~".~~.~..*..*.~****...**.*~***~.l*..t*t*l
A
X
9
Y
9
E ARE ThE F R A C T I O N A L C C C R C I L A T E S O F THE O R I G I N OF T H E R I G I D G R O L P . THE R I G 1 0 GROUP O R I E N T A T I O N ANGLES OELTA. C ETAIPIDIANS) H A V E BEEN CEFINEO PREVICUSLY~ S.J. L a PLICA A N D J.&. IEERS, A C T A C R Y S T A L L C G R . , 18, 5 i i 1 1 9 6 5 1 .
AND 2
c c AND SILCN,
EP-
Figure 1. Stereoview of a unit cell of RUC~(NO)(~~-SO~)(PP~~)~.CH~C~~. The axes are as indicated with c coming up out of the plane of the paper. The vibrational ellipsoids are drawn at the 40% probability level. Hydrogen atoms have been omitted.
ing 3 Rin
I
c (45) ing 4 Ri Ring 5
Figure 2. Perspective view showing all nonhydrogen atoms of the RuCI(NO)(v2-SO2)(PPh,), molecule and indicating the numbering scheme used. The vibrational ellipsoids are drawn at the 40% level.
Figure 3. Inner coordination sphere for RUC~(NO)(~~-SO~)(PP~,)~, with relevant bond lengths and angles shown. The vibration ellipsoids are drawn at the 50% probability level.
Phosphine groups and with the equatorial ligands being c1, bound through atoms S and O(1). a linear NO, and ??*-SO2 The basal plane contains atoms Ru, S, C1( l), O( l ) , N, and
~
Inorganic Chemistry, Vol. 17, No. 8, 1978 2137 Table VI. Selected Distances (A) and Angles (deg) in
RuC1(NO)(~2-S02)(PPh,)2~CH,C12 Ru-P(l) Ru-P(2) Ru-Cl(1) Ru-S R U-N Ru-O(l) S-0(1) S-0(2)
Bond Distances P(l)-C(ll) 2.433 (2) P(l)-C(21) 2.430 (2) P(l)-C(31) 2.432 (2) P(2)-C(41) 2.337 (2) P(2)-C(51) 1.740 (6) P(2)-C(61) 2.144 (6) N-0(3) 1.504 ( 5 ) C(l)C1(2) 1.459 ( 5 ) C(l)-C1(3)
Table VII. Comparison of Distances and Angles for the Two Examples of M ( q 2 S 0 2 )Coordination Rh(NO)(u2- RuC1(NO)(q2S O Z ) ( ~ ~ ~ S~O) Z )"( P P ~ ~ ) , ~
1.814 (6) 1.827 (4) 1.814 (6) 1.819 (6) 1.831 (4) 1.817 (4) 1.122 (8) 1.52 (1) 1.65 (2)
Bond Angles P(l)-Ru-P(2) 172.09 (6) Ru-S-O(l) 63.6 (2) P(l)-Ru-Cl(l) 88.16 (7) Ru-S-0(2) 117.6 (2) P(2)-Ru-C1(1) 87.74 (7) O(l)-S-0(2) 113.7 (3) 117.2 (2) P( l)-Ru-N 89.1 (2) Ru-P(l)-C(ll) Ru-P(1)-C(21) 112.5 (2) P(2)-Ru-N 87.8 (2) 111.0 (2) 92.15 (6) Ru-P(l)-C(31) P( l)-Ru-S 111.6 (2) P( 2)-Ru-S 95.76 (6) Ru-P(2)4(41) Ru-P(2)-C(51) 112.3 (2) P(l)-Ru-O(l) 91.9 (1) Ru-P(2)-C(61) 117.9 (2) P(2)-Ru-O(1) 94.4 (1) Cl(l)-Ru-S 123.79 (7) C(ll)-P(l)-C(21) 104.4 (3) 84.9 (1) C(l1)-P(1)-C(31) 106.2 (3) Cl(l)-Ru-O(l) G(21)-P(l)-C(31) 104.5 (2) Cl(l)-Ru-N 125.6 (2) C(41)-P(2)-C(51) 102.3 (3) N-Ru-S 110.6 (2) N-RU-O(l) 149.5 (2) C(41)-P(2)-C(61) 104.8 (2) C(51)-P(2)-C(61) 106.6 (2) S-RU-0 (1) 38.9 (1) C1(2)C(l)-C1(3) 115.1 (12) Ru-N-0(3) 177.8 ( 5 ) Torsion Angles R~-P(l)-C(ll)-C(12) -136.6 (4) R~-P(l)-C(21)-C(26) -140.7 (4) -1 36.8 ( 5 ) R~-P(l)-C(31)-C(36) C(l l)-P(l)-P(2)-C(61) - 2.2 (3) 1.3 (3) C(21)-P(l)-P(2)-C(5 1) Ru-P(2)-C(41)4(42) 146.4 (4) Ru-P(2)-C(5 1)-C(5 2) 112.4 (3) R~-P(2)-C(61)-C(66) 145.3 (4) C(3 1)-P( l)-P(2)-c(41) -1.1 (3) Interplanar Angle 110.3 (3) Plane 1 (Ru,S,O(l))-Plane 2 (S,0(1),0(2))
O(3) and none of these atoms deviates from the best weighted least-squares plane by more than 0.021 (5) A. Atom O(2) is 1.24 from this plane. The q2 mode of bonding of SO2 to a transition metal has been observedI6only once before in Rh(NO)(q2-S02)(PPh3),. Comparisons will be made primarily between these two structures, although if one considers the SO2ligand as occupying a single coordination site, then the Rh complex is four-coordinate and tetrahedral and the Ru complex is five-coordinate and trigonal bipyramidal. Nevertheless, since the Rh-N-0 geometry is distinctly bent, one could consider it to be formally a Rh+-NO- system isoelectronic with the present Ru°C1-NO+ system. Table VI1 compares the various distances and angles relevant to SO2coordination in these two compounds. Despite a different metal and different coordination number, the M-S distances are essentially the same. But the Mo-O( 1) distances are markedly different. In the Rh complex the Rh-0 distance of 2.342 (5) A is far longer than a Rh-0 single-bond distance exemplified by those of 2.079 (7) and 2.091 (8) A in Rh(NO)(S04)(PPh3)2.17One could consider the SO2 bonding in Rh(NO)(SO,)(PPh,), as tending toward the more usual S-bonded pyramidal SO2 arrangement. In the present Ru complex there is no such tendency. The Ru-0 bonded distance of 2.144 (6) A is near to the presumed Ru-0 single-bond distances of 2.079 (7) A in R u C I ( N O ) ( S O , ) ( P P ~ ~ )and ~ ' ~of 2.1 11 (5) A in R U ( S O ~ ) ( C O ) ~ ( P P ~ ~ ) ~ . ' ~ Previously'6 this S,O-bonded geometry for SO2 has been compared with related q2 arrangements observed for Ni-C02 in Ni(COz)(PCy3)20(Cy = cyclohexyl) and for Pt-CS2 in Pt(CS2)(PPh3)2.21Yet it is important to note that in these
Bond Distances, A 2.326 (2) 2.342 ( 5 ) 1.493 ( 5 ) 1.430 ( 5 ) Bond Angles, Deg O(1)-M-S 37.3 (1) M-S-O(l) 71.9 (2) M-S-0 (2) 106.4 (2) 0(1)-S-o(2) 115.1 (4) Interplanar Angles, Deg M-S-O(l)/S-O(1)-0(2) 100.3 (3)
M-S M-O(l)C S-O(l) S-0(2)
2.337 (2) 2.144 (6) 1.504 ( 5 ) 1.459 ( 5 ) 38.9 (1) 63.6 (2) 117.6 (2) 113.7 (3) 110.3 (3)
Reference 16. Present work. In both compounds 0(1) refers to the oxygen atom which is bound to the metal. This differs from the notation of Ryan and Moody.16 a
former structures the q2-C02and q2-CS2ligands are coplanar with the metal, whereas in the two instances of q 2 - S 0 2 coordination this is not the case. The dihedral angle between M, S, and 0 ( 1 ) and S, 0 ( 1 ) , and O(2) is 110.3 (3)' in the present structure and 100.3 (3)O in Rh(N0)(qz-S02)(PPh3)2,16 In view of the multiple modes of coordination of SOz in transition-metal complexes, can one differentiate among these using spectroscopic techniques? Such differentiation would aid markedly in the selection of compounds for structural study, as it has in the nitrosyl and aryldiazo22fields. K ~ b a s ~ ~ indicates that in general if the M-SO2 geometry is bent, the S=O stretching frequencies occur near 1200 and 1050 cm-', while if the M-SOZ geometry is planar, these frequencies occur near 1300 and 1100 cm-'. (The antisymmetric and symmetric stretching frequencies in SO2 are at 1340 and 1150 while those in Pt'(CH3)(PPh3)21-S02,in which there is a very weak I-S interaction, occur at 1322 and 1138 ~ m - l . ~In ~) Rh(NO)(q2-S02)(PPh3)2bands attributed to SO2are found at 1138 and 948 crn-'.I6 Thus, there may be reasonable spectroscopic criteria for distinguishing the various modes of attachment of SO2 to metal systems. But there are also difficulties. Whereas the band at 948 cm-' is very strong in Rh(NO)(q2-S0,)(PPh3),, there is only a very weak band in this region (895 cm-') in RuCI(NO)(~~-SO~)(PP~~)~. In order to establish that this band indeed arises from the presence of q2-S02,the spectrum of the corresponding SI8O2compound was obtained. This spectrum shows only one shifted band, a weak band at 864 f 1 cm-', which corresponds to the 895 f 5 cm-' band in the S602 spectrum shifted by about the amount predicted on the basis of a simple-harmonic-oscillator approximation. No other bands are shifted on isotopic substitution, although the band at 1140-1 155 cm-', which from the spectral analysis of Rh(NO)(q2-S02)(PPh3),was assigned to the presence of SO2,partly overlaps with bands arising from phenyl modes. It thus appears that a low-frequency band (890-950 cm-') may be useful as an indication of the presence of S,O-bonded S02. However, in view of the great differences in intensity of this band in the two compounds known to exhibit this mode of coordination, considerable care must be exercised in searching the indicated region of the spectrum. Failure to find this band is presumably the cause of the incorrect structural assignment16 for RuC1(NO)(S02)(PPh3), made previously from infrared spectral results. Although there have been attempts to understand in molecular orbital terms the modes of attachment of SO2 to transition metals, these have not been markedly useful for the prediction of geometries. Thus, the predictionS that a d8 complex should exhibit a bent M-S02 geometry (in conso-
2138 Inorganic Chemistry, Vol. 17, No. 8, 1978
Fuller, Molzahn, and Jacobson
nance with the structural results on the two known examples1i6) was followed almost immediately by the discovery26 of a d8 complex with a planar M-S02 geometry and concomitant rationalization of the result in molecular orbital terms. But there is no anticipation on theoretical grounds for the q2 mode of coordination of SO2 to be found in the literature nor has there yet appeared an ex post facto rationalization. It may be that as the number of structurally characterized SO2 complexes increases, our ability to predict geometries will also improve. It clearly is an interesting question whether the q2 mode of bonding of SOz will remain rare or whether the two known structures are the forerunners of a large class of compounds. The bent mode of bonding of NO to transition metals was novel in 19682and is now probably as common as the linear mode. Acknowledgment. This work was kindly supported by the National Science Foundation (Grant CHE 76-10335). We are indebted to Matthey-Bishop, Inc., for the loan of precious metal used in this study. We thank Dr. R. R. Ryan and Dr. D. C. Moody for informative preprints of their recent results. Registry No. RUC~(NO)(~~-SO~)(P(C~H~)~)~.CH~CI, 66701-48-2. Supplementary Material Available: Root-mean-square amplitudes of vibration (Table IV) and a listing of structure amplitudes (Table V) (38 pages). Ordering information is given on any current masthead page.
References and Notes (1) S. J. La Placa and J. A. Ibers, Inorg. Chem., 5, 405 (1966).
D. J. Hodgson, N. C. Payne, J. A. McGinnety, R. G. Pearson, and J. A. Ibers, J. A m . Chem. Soc., 90, 4486 (1968). D. J. Hodgson and J. A. Ibers, Inorg. Chem., 7, 2345 (1968); 8, 1282
(1969). B. A. Frenz and J. A. Ibers, M T P Int. Rev. Sci.: Phys. Chem., Ser. One, 11, 33 (1972); R. Eisenberg and C. D. Meyer, Acc. Chem. Res., 8, 26 (1975). R. R. Ryan and P. G. Eller, Inorg. Chem., 15, 494 (1976). K. W. Muir and J. A. Ibers, Inorg. Chem., 8, 1921 (1969). M. H. B. Stiddard and R. E. Townsend, Chem. Commun., 1372 (1969). M. B. Fairy and R. J. Irving, J . Chem. SOC.A , 475 (1966). K. R. Laing and W. R. Roper, Chem. Commun., 1556 (1968). See, for example, J. M. Waters and J. A Ibers, Inorg. Chem., 16, 3273 (1977). R. D. Wilson and J. A. Ibers, Abstract J-9, American Crystallographic Association Meeting, East Lansing, Mich., Aug 7-12, 1977. B. L. Haymore and J. A. Ibers, Inorg. Chem., 14, 3060 (1975). S. J. La Placa and J. A. Ibers, Acta Crystallogr., 18, 511 (1965). L. D. Brown and J. A. Ibers, Inorg. Chem., 15, 2788 (1976). Supplementary material. D. C. Moody and R. R Ryan, J. Chem. Soc., Chem. Commun., 503 (1976); Inorg. Chem., 16, 2473 (1977). B. C. Lucas, D. C. Moody, and R. R. Ryan, Cryst. Struct. Commun., 6 , 57 (1977). J. Reed, S. L. Soled, and R. Eisenberg, Inorg. Chem., 13, 3001 (1974). D. C. Moody and R. R Ryan, Cryst. Struct. Commun., 5, 145 (1976). M. Aresta, C. F. Nobile, V. G. Albano, E. Forni, and M. Manassera, J . Chem. Soc., Chem. Commun., 636 (1975). R. Mason and A. I. M. Rae, J . Chem. SOC.A , 1767 (1970). M. Cowie, B. L. Haymore, and J. A. Ibers, J . Am. Chem. Soc., 98,7608 (1976). G. J. Kubas, Abstracts, 172nd National Meeting of the American Chemical Society, San Francisco, Calif., Sept 3, 1976, No. 240. E. R. Lippincott and F. E. Welsh, Spectrochim. Acta, 17, 123 (1961). M. R. Snow and J. A. Ibers, Inorg. Chem., 12, 224 (1973). R. R. Ryan, P. G. Eller, andG. J. Kubas, Inorg. Chem., 15,797 (1976).
Contribution from Ames Laboratory-DOE and the Department of Chemistry, Iowa State University, Ames, Iowa 5001 1
Crystal and Molecular Structure of the Decacoordinate Compound ( (Hydroxyethyl)ethylenediaminetriacetato)diaquolanthanum( 111) Trihydrate CHARLES C. FULLER, DAVID K. MOLZAHN, and ROBERT A. JACOBSON*
Received M a r c h 31, 1978 The crystal and molecular structure of the trihydrate of ((hydroxyethyl)ethylenediaminetriacetato)diaquolanthanum(III), La[(02CCH2)2NCH2CH2N(CH2CH2OH)(CH2C02)(H2O)2].3H2O (triclinic, Pi,a = 9.476 ( 2 ) A, b = 10.947 (3) A, c = 9.391 (2) A, a = 108.18 ( 2 ) O , /3 = 104.66 (3)O, y = 79.31 (3)O, Z = 2, Mo K a radiation), has been determined by three-dimensional X-ray analysis. The structure was solved by conventional Patterson and Fourier techniques and refined by a full-matrix least-squares procedure to a final conventional discrepancy factor, R = CIIF,,I - IFJI/CIF,,l, of 6.4% for 1637 observed reflections (F, > 2uF0),This molecule crystallizes as a dimer, utilizing the crystallographic center of symmetry. The eight coordination sites satisfied by (hydroxyethy1)ethylenediaminetriacetate include five solely from one group-including one from the oxygen of the hydroxyethyl group-two by a sharing of a carboxymethyl oxygen between the two lanthanum atoms, and one from the carboxymethyl oxygen from the ligand primarily coordinated to the other lanthanum atom. The lanthanum cations are decacoordinate, with a geometry approximating the bicapped square antiprism.
Introduction Powell and Burkholder have demonstrated that the Gd-Eu and Eu-Sm separation factors in cation-exchange elution with ammonium ethylenediaminetetraacetate (EDTA) can be augmented by increasing the temperature from 25 to 92 O C and have shown that similar enhancements should occur in the cases of Ho-Dy and Dy-Tb pairs when (hydroxyethy1)ethylenediaminetriacetate (HEDTA) is the eluent.' The stabilities of the four heaviest HEDTA chelate species (Tm-Lu) are not affected by this increase in temperature, whereas the stabilities of the remaining lanthanide HEDTA species vary significantly with temperature. This difference may be explained by the assumption that the HEDTA ligand always forms pentadentate bonds to the four smaller lanthanides (Lu3+through Eu3+)and hexadentate bonds to those lanthanides larger than Eu3+at temperatures approaching 0 0020-1669/78/1317-2138$01 .OO/O
O C, with the remaining coordination sites being occupied by water molecules. There have been numerous articles recently on compounds exhibiting large coordination numbers, and considerable controversy has arisen over the preferred geometry in cases of high coordination numbers. Thus, the crystal structure determination of LaHEDTA was undertaken in order to provide further information on the coordination of the HEDTA ligand to the lighter lanthanides and the geometry of the resulting complex. Experimental Section Crystal Data. Well-formed white rhombohedral crystals of
LaHEDTA were supplied by J. E. Powell of this laboratory and were used without further purification. A crystal of approximate dimensions 0.4 X 0.4 X 0.2 mm was mounted on a glass fiber. Preliminary precession photographs indicated that the compound crystallized in 0 1978 American Chemical Society
