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Structural study of iron carbonyl derivatives
429
Jourrai of Orgonometallic Chemistry, 131(1977) 429-438 0 Elscvier Sequoia S-A., Lzusanne - Printed in The Netherlands
STRUCTURAL
STUDY
IV *. SYNTHESIS
OF IRON CARBONYL
AXD CRYSTAL
DERIVATIVES
AND MOLECULAR
STRUCTURE
OF
~u~-I~-(SCH~)F~(CO)ZP(CHJ)~I~
l, DANIEL
GUY LE BORGNE
GRANDJEAN
Laboratoire de Crktallochimie, LA. No. 254 au C.N.R.S.. U.E.R., Structure et Proprit?t& de la Mat&e, Universild de Renneq 35031 Rennes-Cedex (France) RENk MATHIEU
and RENk POILBLANC
Laboratoire de Chimie de Coordizzation du C_N.R.S., ELI? 4142, 31030 (France)
Toulouse-Cede-x
(Received November 8th, 1976)
Summary The preparation of the compound [p-(SCH3)Fe(CQ)2L]2, with L = P(CH3)3, is described. Spectroscopic studies show that this compound exists as syn and anti isomers, with respect to the orientation of the SCH3 groups relative to the metal-metal bond. The crystal and molecular structure of the syrz isomer has been determined by a single-crystal X-ray study. The complex crystallizes in the tetragonal space group P4,2I2 (or P43212) with 2 = 5. The intensities were measured on a Nonius CAD-4 automatic diffractometer. The structure has been refined to R and R” values of 0.058 and 0.650 respectively, for 2156 independent reflections. The molecular structure contains two Fe(C0)2P(CH3)3 moieties (with the phosphine ligands in axial positions) bridged through the sulfur atoms of the syn-SCH3 groups. The iron-iron bond Iength is 2.518(l) A. A comparison is made with similar iron carbonyl derivatives without phosphine substituents.
Introduction Several structures of iron carbonyl derivatives containing an Fe& core, i.e. a symmetrical double S-bridge between two Fe(CO)3 groups linked by a me’&metal bond, have been determined by X-ray studies; for exemple: [CIHSSFe(CO)& (II) [Zl, [C6H5CSFe(C0M2 (III) 133, and [CH3SFe2(C0)J2S (IV) [4f_ But, to our knowledge, there have been no structural studies of similar complexes where one of the CO of each Fe(CO), group has been replaced by *
For
part III,see
ref. L
430
a phosphine &and L. We have determined the crystal structure of one such compound, [p-(SCH,)Fe(CO),P(CHs)& in order to compare the two types of derivatives and to assess the influence of the ligand L = P(CH,), on the molecular structure, particularly on the metal-metal bond. Preparative details and structural hypothesis The compound [p-(SCH3)Fe(CO),P(CH,)31 2 (I) was prepared from the reaction of a slight excess of P(CH& (0.6 ml) with [p-(SCHs)Fe(CO),], (1 g) in boiling hexane during ten hours. Crystallization in n-hexane gave air-stable brown crystals of various sizes, but with clean faces. The compound shows three active infrared bands in the v(C0) stretching region (1987-6 (s); 1943.1 (ms) and 1923.1 cm-’ (s) in hexadecane solution) and the proton NMR spectra shows one doublet in the P-CHs region (‘i-8.50 ppm; ‘J(PH) 8.4 Hz) and one triplet in the S-CH3 region (7 8.09 ppm; ‘J(PH) I Hz). Prom these two observations, we conclude that the complex has a C,, symmetry (structure A), in accordance with the observations of Haines et al. on the [y-(SCH,)Fe(CO)IL]2 complexes with L = P(C2H5)3 or P(OCHs)s [5J. However, in cur case, the examination of the infrared spectra of the mother liquor of crystahization shows the existence of a second isomer for which, from the infrared and NMR da&ta, and by comparison with the studies of Haines et al. [ 51, structure B can be proposed. The crystallographic study of this second complex
isin progress.
(A)
(5)
X-ray data collection and structure determktion Caystal data C!,tHZ,O,P&Fe, (en isomer); mol. wt. 470.09. Tetragonal system: a = b = 13.27812); c = 23.942(7) A. V= 4221 A'. d, = 1.48. 2 = 8. Space group: P4,212 (or P4s212 enantiomorph; we have not attempted to determine Yne absolute structure). The unit-ceil parameters, obtained from Weissenberg and precession photographs, were refined using the 6 angles of 15 reflections measured on a Nonius CAD-4 automatic diffractometer.
a31
~.
Collection of X-ray diffraction data The intensities of 6430 reflections (xtitfi equivalent measurements for hkl and khf) were collected at room temperature, for 2 < 0 < 30”, on the automatic diffractometer. The crys+;i used had such dimensions as pR -< 1 for the MO-K, radiation (0.71069 A). Consequently, no absorption corrections were deemed necessary. The characteristics of the diffractometer measurements were as follows: graphite monochromator, w-26 scan technique, scan angle: S = 0.90 + 0.30 tg 0 (in degrees), detector aperture: D = 2.50 + 0.40 tg 0 (in mm). Intensities of equivalent reflections were averaged using the program MAXE [6], after the usual Lorentz and polarization corrections were applied. Reflections having a(l)/1 > 1 were considered to be unobserved. Finally, 2222 independent reflections were retained and used in the subsequent structure analysis. Solution
and refinement
of the structure
heavy atoms (2 Fe, 2 S and 2 P) of the molecule which constitutes the asymmetric unit were located using the multisolution method with MULTAN The six
molecule C2”.
showing
the pseudo-symmetry
P_
-
_-
-_-
~,9lJ1nn~etl otimdnrtl tlavintianu nrc given in pnrentlicscs, The nnisotroplc lllcrn~nl pnwwters nrc of the! form: expl-(h*/l~ 1 + lrql2* +l2pJJ +21lhp1* + 2/lI/l1J 1. t?lql*3)1 P----P-Y -.-.A-----..-_____-_*-"-I x N PI I P33 022 PJ2 PJ3 023 _--~-.-__ --_...---_P_-.--_--Pw-__cl___ 12.1(0,2) b%(l) 32OG.1(0.8) 1894,3(0.8) 2081.G(O.4) B3.7(0.7) 4(1.3(0.7) 2.6(OA) --0.3(O.G) 0.2(0.3) 0.2(0,0) l.O(O.3) Ve(2) 3803,1(0.4) 26H4,2(O.R) 3062.2(0.4) (iO.3(O.H) 4G.7(0.7) 12,7(0.2) 0(0,3) lL3(0.4) 2373.3(0.8) W(2) 12(l) 2038(2) 3401(2) -1.4(O.G) 0*7(O.G) 4Nl) S(1) fi1(2) 2366.0(0.8) @J(l) 1 G.O(O..J) --13(l) 2784(2) 4846(2) 3*4(O.D) -1.7(0.0) S(2) 1163,4(O.J1) f%(l) 13.5(0.4) 32!J0(2) 21Grj(2) 1,7(0.0) --0.1(O.B) 64(l) O(l) P(l) 350G.3(O.D) 71(2) Ol(2) 17.0(0.~1) -N) 3020(2) 3.7(0.7) --o.fl(O.7) 3774(2) l'(2) 34(2) --24((J) 2162(3) SSO(S) 104(G) 1370(4) 61(4) O(1) Q(2) O(3) 46(2) 90(G) W.1) 21(4) - 22(G) 209K.J) 42fJ7(G) --l(3) -2(3) O(2) l!mJ(G) 3670(3) N(G) loe(ci) 30(2) --12(G) 1742(G) 2OW O(3) R(3) m(2) 3644(3) 114(G) 10x63) 11117(G) 20(G) --Q(3) 4708(G) O(U 170) 213G(3) 40(G) 70(G) 3(G) 1260(G) 2111(O) 17(2) 3(4) C(1) G(3) 61(G) 4(;(G) 2(3) 730((1) 2000(S) 20(2) G(3) 3R9l(G) 2(4) C(2) 3418(3) ti7(6) l!i(2) 2l!JZ(tj) 00(G) 24x%(7) -2(3) O(3). G(G) C(3) 3406(3) m(7) lG(2) 1737(7) 14(G) 42GG(7) 82(7) 2(3) C(4) 4(3) 248G(4) R7(8) 3405(7) 33(G) -&I) 1282(7) fw7) 26(2) ---R(3) C(5) 2441(4) 49(G) 1.27(9) 2G(2) 2040(a) -G(G) 3(3) -4(4) R786(0) C(G) 217(13) 22(2) 2G30(10) 071(4) --7(O) lI(3) 4476(e) 7W) 3(G) C(7) 182(11) 173(11) lG(2) 916(3) 24!39(9) 31Gtw3) tcG(9) O(4) 17(4) C(Q 362(20) ll(i(l1) 19(2) 734(4) -lOG(12) --12(4) 2003(13) 1119(10) 4(G) cw 3731(G) 82(!J) G2(4) 401!)(9) 124ClO) -64(G) 2008(8) -l(G) lO(7) WO) 206(13) 4277(4) 121Cll) -24(4) 3(ilJ3(9) -l(9) --7(4) 4286(c)) 17(2) et111 lG8(12) 32(3) 3330(G) 97(n) -Gl(I3) 27(G) -12((J) 4648(10) 4UGS(R) W2)
ATOMIC PARAMJYJYSRS (X104)
TAIIMS 1
433
INTERATOMiCBONDLENGTHSANDBONDANGLES Estimatedstandarddeviationsaregiveninparenthesa
Fe(l)--Fe(2)
2.518(l)
Fe
2276(2j 2.278(2) 3.26-J(2) 2.270(2)
Fe
2.228<2) 2215(2j 2.790(3)
Fe(V-C
l-754(8) l-755(7) 1.745(3) l-726:8)
Fe(l)-S(l)-Fe(Z) Fe
67.31<0.09j 67.22(0.09) 75.66(0.07) 75.91(0.07) 114.2(0.3) 113.4(0.2) 114.9(0.3) 114.2(0.3) 178.4(0.7) 179.5(0.7) 178.6(0.7) 179.7(0.7)
cm-O(l) cm-O(2) C(3)_0(3) C(4)-O(4)
1.139<10) 1.129(10) l.l54(1Oj 1.166(11)
S(l)-C(5) S<2)--c(6)
1.807(S) l-819(9)
Pw-c(7j P(l)_C(8) P(l)--c(9j P<2j-C(lOj P(2j--c(l~j P(2)-cc12j
1.781(10) 1.804(11) 1.786(12) l-772(11) 1.804(S) l-807(12)
Fe(l)-P(ljC(7j Fe(l)_P(l)-C(8) Fe(l)_P(l)-C(9) Fe(2)-P(2)_C(lO) Fe<2j-P(2)--C(llj Fe(2j-P(2j-C<12)
116.7(0.3) 115.7<0.3) 115.9(0.4) 114.8cO.3) 116.6(0.3) 117.5<0.3)
C(7)-P(l)-C(8) CN-PW-C(9) C(9)_-p(1)--c(7) c(1oj-P(2j-c(11) c
100.5(0.5) 103.7(0.6) 102.1<0.6) 101.7(0.5) 101.8(0.5) 102_2<0.5)
program [ 71. Some oxygen and carbon atoms also appear on a Fourier synthesis computed with the normalized structure factors E of the set of phases having $he best “figure of merit”. Their positions, as those of the remaining nonhydrogen atoms, were obtained unambiguously from a series of difference-Fourier maps computed on the basis of the heavy atoms parameters. Refinement of positional and isotropic thermal parameters of the 22 independent non-hydrogen atoms led to a value for the index R = ~(IF,I - KIF,l)/IzlFoI of 0.097. Least-squares refinements were performed using SFLS-5 program [S] _ The quantity minimized was IZ:w(lF,i - KIF,I)‘_ Atomic scattering factors, Af’ and Af” coefficients of anomalous dispersion for Fe, S and P atoms, and the weighting scheme used are described in a previous publication [ 9]_ Although the positions of all 24 hydrogen atoms were not confirmed from a difference-Fourier synthesis, we have included their contribution in the refinement, with positions calculated assuming idealized tetrahedral geometry for the methyl groups. The parameters of hydrogen atoms were held fixed &I further cycles of refinement. The contribution of hydrogen atoms reduces the R index
Fig. 2. Perspec:ive vie= of the C~-CSCH3)Fe(CO),?(CH;)3 bond. and P(CH3)3 groups rrlstive!y to the iron-iron >
12 mohxule
showing
the disposition
of SC&f3
in a significant way and gives rise to a more homogeneous set of bond distances ancl angles for the remaining atoms. Anisotropic thermal parameters were then introduced for the 22 non-hydroger: atoms, and two further cycles of refine_ment of positional and anisotropic thermal parameters for these atoms reduced R to a final value of 0.058 for 2156 independent reflections (66 weak reflections exhibiting large disagreements between IF,{ and i F,i were rejected). The value of the weighted index R” = [C.s;(fFoi - KIF,[)‘/GWIFOi’]“’ is 0.050. In the last refinement cycle, no parameter shifts were greater than 0.20 of the corresponding estimated standard deviations. A table of observed and calculated structure factors is available on rec_uest_ FinaI coordinates and anisotropic thermal pkameters for the 22 non-hydrogen atoms, with estimated standard deviations in parentheses, are given in Table i. The atomic numbering scheme used can be seen on Fig. l.and 2, which give two perspective views of the molecule along two perpendicular directions, plotted with program ORTEP [lo]. interatomic distances and bond angles are given in Table 2. Description
of the structure and discussion .
.Tne molecular structure of qr’n-[,u-(SCH3)Fe(CO)2PCCH,),I:! is wholly consis’:ent with the IR and NMR spectrographic data given above. The two ligands L = P(CH,), are trans to the metal-metal bond, axially coordinated to each iron atom, and the CHj groups of the bridgkg sulfur atoms are in a syn-endo position, as can be seen from Fig_ 2_ The molecular geometry can be described, as in t.he case 03 simikr
435
[Fe(COh-p-(SR)] z d erivatives [ 2-41, as arising from the junction of the basal planes of two distorted tetragonal pyramids along the S---S edge. The iron atoms are displaced from their basal planes, respectively, by 0.33 and 0.27 A in the direction of the apical atoms P(1) and P(2). The dihedral angle between the planes Fe(l)-S(l)-S(2) and Fe(2)-S(l)-S(2) is 90.9”. Furthermore, the two iron atoms are linked by a metal-metal bond of length 2.518(l) A. It is interesting to compare this geometry with that found in similar complexes containing Fe& -bridged systems, without direct S-S bond, and without phosphine ligands. This comparison of the main structural characteristics is given in Table 3. It appears that the replacement of one CO group cn each iron atom by the ligand P(CH3)3 does not ah&r in a significant way the geometrical parameters of the Fe&-bridged core. The main differences compared with the nearest derivative, [C2HSSFe(C0)3]2 (II) [2], involve the mean S-Fe-S angle and the dihedral angle between the two Fe-S-S planes. However, it is interesting to note that the values of these two angles for compound II are also greater than corresponding values in the three other non-substituted derivatives of Table 3. No doubt, these differences may be due, in part, to the non-bonding S.-S dis’~ce, which is greater in the first derivative than in the other four, possibly in connection with the unti-syn problem. Let us consider now the influence of the substitution of one CO by a P(CHj), ligand on Fe-C(O) and C-O distances of the two remaining car-bony1 groups. The mean value of Fe--C(O) bond lengths is 1.745(l) A in [I.I-(SCH,)Fe(CO),P(CH,),], Dwhile it is l-81(2) A in the nearest non-substituted derivative II. For the other compounds of Table 3, the mean Fe--C(O) value is also greater than in the present structure, except for [CH3SFe2(C0)6]2S (IV) [ 4 1, but the low value found in this derivative seems surprising, and is probably due to the poor precision of the structural results. In another compound for which we have determined the structure with a precision analogous to that of the present work, viz. (C,H,SNHjFe,(CO), 191, the mean Fe-C(O) distance is l-788(3) A. The observed significant shortening of the remaining Fe-C(O) bond lengths, caused by the replacement of one CO by a phosphine ligand, agrees well with the z-acceptor character weaker for a phosphine than for CO. Such a shortening of M--C(O) bond lengths has also been noted in chromium carbonyl derivatives. specially for the CO groups trays to phosphine ligands [12,13]_ On the other hand, in some mononuclear iron carbonyl derivatives having phosphine ligands, whose structural characteristics have been tabulated by Haymore and Ibers 1141, there is not such a significant shortening of Fe- -C(O) bond lengths as tlnat observed in the present study. Concerning C-O distances, the mean value in the present complex (1.147(5) A) is not significantly different from values found in the non-substituted derivatives of Table 3. The mean value for Fe-C-O angles is 179.0(3)“, nearer 180” than in most other iron carbonyl derivatives where the current values are in the range 177-178”. The mean S-C bond length is 1.813(6) A, and the mean Fe-S-C angle is 114.2(Z)“, in good agreement with corresponding values in compounds II and IV of Table 3. The mean -Fe-P distance is 2.221(l) A, a value which agrees well with reported ones in some mononuclear iron carbonyl derivatives possessing
436
437
TARLE
4
PlaneI: Plane through Fe(l). Fe(Z) and the midpointofS(l)_S(2). Euuotion: 0.9595X-0.2948 Y-00.0137 Z-3.3326= 0 = -0.033(2) -9.19?<2) -1.991<6) 2.047(6) -1.999(7) 2.140(S)
P(l) P(2) O(l) 0<2) O(3) C(4)
C(1) C(2) C(3) C(4) C(5) C(6)
_ -1.21i(8)
C(7) CW C(9) C
l-250(8) -1.212(9) l-275(9) -3.108(9) 3.130(9)
l-323(11) -1.432(12) +x036(17) -1.865<11) 0.485<12) 0.549<13)
Plane If: Plane through S(l).S(2) and the midpoint of Fe
3.159(2)
C(l)
P(2)
-3.120(2) l-914(7) 1.98-t(7) -2.014(7) -2.091(7)
C(2) C(3) C(4) C(5) C(6)
O(1) O(2) O(3) O(4) OX,
I’,
%are
coordin&esinA
bthe
1.642(S)
C(7)
l-701(8) -1.696(8) -l-753(8) -0.025(9) -O.O22(9)
orthonormalsystem:a,
c*Ac.
C(8) C(9) C(l0) C(l1) C(l2)
3.429(10)
3.361(9) 4.66700) -3.611<13) -4.617(g) -3.152<11)
cf.
ph.osphine lig.ands [14]_ The mean P-C bond length of 1.792(G) A is appreciably loSer than values found in the same mononuciear compounds, and than those which are observed in a few binuclear compounds having one or more phosphine ligahds whose structures have been determined_ Concerning the mean Fe-P-C and C-F-C angles, respectively 116.2(l)” and 102.0(2)“, the values are in very good agreement with the ones found in the literature. These angles around P atoms deviate from ideal tetrahedral geometry in the usual way. Examination of Fig. 1 shows that the molecular symmetry of [p-(SCH3)Fe(CO),P(CH&], is close to C?,“, at least in its central part: Deviation from this
433 TAI3LE
5
SHORTEST
INTERMOLECULAR
s(l:I--.c(9=) s(2:r---c(l2IV)
o(l)---c(ll~=~I) o(2).--c(5*‘1j Ot2)---C(8v1’)
3.91 x 3.82 3.67 3.71 3.73 3.63 3.60
DISTANCES.
REFERRED
TO MOLECULE
O(3)---C(7V) 0(3)---C(ll~X) C(l)---WV) C(3)---C(7V) C(1).--C(?V)
3.47 -9 3.57 3.81 3.59 3.88
c(sP-c
3.91
C
3.63
I (r. y. L) =
a N=lmbering of molecules. XI: r.: i-,l~lII;’ 2iIV:_ I + 1, --x. 2 + li? + 1.7 +,i; V: 7 +_i.,x -1, VI: r + i. Y + 4.7 + 4: X-II: r t y$ 2. y - 7_, -7 l 3; VIII: y - f2. x + 4. z - 1,; 1x: x -‘I. ?+z, 2 -i 3.
*+a;
symmetry is essentially produced by the P(CH,), groups which clearly are not in an eclipsed conformation as would be the case with a true Cz, symmetry for the whole molecule. This is also evident from Table 4 which gives deviations of atoms from the mean least-squares planes I and II of the two pseudo-mirror planes, one through Fe(l), Fe(2) and the midpoint of S(l)-S(2), and the other through S(l), S(2) and the midpoint of Fe(l)-Fe(2). The angle between these two planes is exactly 90.0” _ The crystal packing in [r_L-(SCH,)Fe(CO)2P(CIIJ)J3 is shown in Fig. 3, and the shortest intermoiecular distances are given in Table 5. The packing arises from normal Van der Waals interactions; none of the intermolec*ulardistances ere beiow the sum of Van der Waals radii of corresponding atoms. References 1 2 3 4 5 6 7 8 9 10 11 12 13 11
G. Le Borgne and 0. Gracdjean, Xcta Cryst. B.in orep55. L.F. Dab? and C-H. Wei. Inorg. Chem.. 2 (1963) 328. H-P- Q.eber sod R-F. Bryan. J. Chem. Sot. A, (1967) 182. J.bK. Colemor., A. Wojcicki. P.J. PolIick and L.F. Dahl. Ioor=. Chem.. 6 (196i) 1236. 3.X. De Beer. R-J. HJnes. R. Greatrex and N.N. Greenwood. J. Chem. Sot. A, (1971) 3271. J.Y. Le X+rouille, Th&x de 3eme cycle. Rennes. 1972. G. Germain. P. Main and XX. Woolfson, Acta Cryst. A. 27 (1971) 368. C-T. Prewitt, Fortran IV fclI-matrix crystallographic least-squares program. SFLS-5. 1966. C- Le Borgne and D. Grand&m. Acta Cryst. B. 29 (1973) 10-10. C-K. Johnson. ORTEP. Report ORAL-3794. Oak Ridge National Laboratory, Tennessee. G. Le Borgne and D. Grandjean, J. Organometal. Chem., 92 (1975) 381. G. Huttner and S. Schelle. J. Cryst. Mol. Strut., 1 (1971) 69. L-J. Gugzenbe-zer. U. Rlabunde and R.X. Schunn, Inorg. Chem.. 12 (1973) 1143. B.L. Hrvmore and J-A. Ibers. Inorg. Chem.. 14 (1975) 1369.
1965.
Jourrai of Orgonometallic Chemistry, 131(1977) 429-438 0 Elscvier Sequoia S-A., Lzusanne - Printed in The Netherlands
STRUCTURAL
STUDY
IV *. SYNTHESIS
OF IRON CARBONYL
AXD CRYSTAL
DERIVATIVES
AND MOLECULAR
STRUCTURE
OF
~u~-I~-(SCH~)F~(CO)ZP(CHJ)~I~
l, DANIEL
GUY LE BORGNE
GRANDJEAN
Laboratoire de Crktallochimie, LA. No. 254 au C.N.R.S.. U.E.R., Structure et Proprit?t& de la Mat&e, Universild de Renneq 35031 Rennes-Cedex (France) RENk MATHIEU
and RENk POILBLANC
Laboratoire de Chimie de Coordizzation du C_N.R.S., ELI? 4142, 31030 (France)
Toulouse-Cede-x
(Received November 8th, 1976)
Summary The preparation of the compound [p-(SCH3)Fe(CQ)2L]2, with L = P(CH3)3, is described. Spectroscopic studies show that this compound exists as syn and anti isomers, with respect to the orientation of the SCH3 groups relative to the metal-metal bond. The crystal and molecular structure of the syrz isomer has been determined by a single-crystal X-ray study. The complex crystallizes in the tetragonal space group P4,2I2 (or P43212) with 2 = 5. The intensities were measured on a Nonius CAD-4 automatic diffractometer. The structure has been refined to R and R” values of 0.058 and 0.650 respectively, for 2156 independent reflections. The molecular structure contains two Fe(C0)2P(CH3)3 moieties (with the phosphine ligands in axial positions) bridged through the sulfur atoms of the syn-SCH3 groups. The iron-iron bond Iength is 2.518(l) A. A comparison is made with similar iron carbonyl derivatives without phosphine substituents.
Introduction Several structures of iron carbonyl derivatives containing an Fe& core, i.e. a symmetrical double S-bridge between two Fe(CO)3 groups linked by a me’&metal bond, have been determined by X-ray studies; for exemple: [CIHSSFe(CO)& (II) [Zl, [C6H5CSFe(C0M2 (III) 133, and [CH3SFe2(C0)J2S (IV) [4f_ But, to our knowledge, there have been no structural studies of similar complexes where one of the CO of each Fe(CO), group has been replaced by *
For
part III,see
ref. L
430
a phosphine &and L. We have determined the crystal structure of one such compound, [p-(SCH,)Fe(CO),P(CHs)& in order to compare the two types of derivatives and to assess the influence of the ligand L = P(CH,), on the molecular structure, particularly on the metal-metal bond. Preparative details and structural hypothesis The compound [p-(SCH3)Fe(CO),P(CH,)31 2 (I) was prepared from the reaction of a slight excess of P(CH& (0.6 ml) with [p-(SCHs)Fe(CO),], (1 g) in boiling hexane during ten hours. Crystallization in n-hexane gave air-stable brown crystals of various sizes, but with clean faces. The compound shows three active infrared bands in the v(C0) stretching region (1987-6 (s); 1943.1 (ms) and 1923.1 cm-’ (s) in hexadecane solution) and the proton NMR spectra shows one doublet in the P-CHs region (‘i-8.50 ppm; ‘J(PH) 8.4 Hz) and one triplet in the S-CH3 region (7 8.09 ppm; ‘J(PH) I Hz). Prom these two observations, we conclude that the complex has a C,, symmetry (structure A), in accordance with the observations of Haines et al. on the [y-(SCH,)Fe(CO)IL]2 complexes with L = P(C2H5)3 or P(OCHs)s [5J. However, in cur case, the examination of the infrared spectra of the mother liquor of crystahization shows the existence of a second isomer for which, from the infrared and NMR da&ta, and by comparison with the studies of Haines et al. [ 51, structure B can be proposed. The crystallographic study of this second complex
isin progress.
(A)
(5)
X-ray data collection and structure determktion Caystal data C!,tHZ,O,P&Fe, (en isomer); mol. wt. 470.09. Tetragonal system: a = b = 13.27812); c = 23.942(7) A. V= 4221 A'. d, = 1.48. 2 = 8. Space group: P4,212 (or P4s212 enantiomorph; we have not attempted to determine Yne absolute structure). The unit-ceil parameters, obtained from Weissenberg and precession photographs, were refined using the 6 angles of 15 reflections measured on a Nonius CAD-4 automatic diffractometer.
a31
~.
Collection of X-ray diffraction data The intensities of 6430 reflections (xtitfi equivalent measurements for hkl and khf) were collected at room temperature, for 2 < 0 < 30”, on the automatic diffractometer. The crys+;i used had such dimensions as pR -< 1 for the MO-K, radiation (0.71069 A). Consequently, no absorption corrections were deemed necessary. The characteristics of the diffractometer measurements were as follows: graphite monochromator, w-26 scan technique, scan angle: S = 0.90 + 0.30 tg 0 (in degrees), detector aperture: D = 2.50 + 0.40 tg 0 (in mm). Intensities of equivalent reflections were averaged using the program MAXE [6], after the usual Lorentz and polarization corrections were applied. Reflections having a(l)/1 > 1 were considered to be unobserved. Finally, 2222 independent reflections were retained and used in the subsequent structure analysis. Solution
and refinement
of the structure
heavy atoms (2 Fe, 2 S and 2 P) of the molecule which constitutes the asymmetric unit were located using the multisolution method with MULTAN The six
molecule C2”.
showing
the pseudo-symmetry
P_
-
_-
-_-
~,9lJ1nn~etl otimdnrtl tlavintianu nrc given in pnrentlicscs, The nnisotroplc lllcrn~nl pnwwters nrc of the! form: expl-(h*/l~ 1 + lrql2* +l2pJJ +21lhp1* + 2/lI/l1J 1. t?lql*3)1 P----P-Y -.-.A-----..-_____-_*-"-I x N PI I P33 022 PJ2 PJ3 023 _--~-.-__ --_...---_P_-.--_--Pw-__cl___ 12.1(0,2) b%(l) 32OG.1(0.8) 1894,3(0.8) 2081.G(O.4) B3.7(0.7) 4(1.3(0.7) 2.6(OA) --0.3(O.G) 0.2(0.3) 0.2(0,0) l.O(O.3) Ve(2) 3803,1(0.4) 26H4,2(O.R) 3062.2(0.4) (iO.3(O.H) 4G.7(0.7) 12,7(0.2) 0(0,3) lL3(0.4) 2373.3(0.8) W(2) 12(l) 2038(2) 3401(2) -1.4(O.G) 0*7(O.G) 4Nl) S(1) fi1(2) 2366.0(0.8) @J(l) 1 G.O(O..J) --13(l) 2784(2) 4846(2) 3*4(O.D) -1.7(0.0) S(2) 1163,4(O.J1) f%(l) 13.5(0.4) 32!J0(2) 21Grj(2) 1,7(0.0) --0.1(O.B) 64(l) O(l) P(l) 350G.3(O.D) 71(2) Ol(2) 17.0(0.~1) -N) 3020(2) 3.7(0.7) --o.fl(O.7) 3774(2) l'(2) 34(2) --24((J) 2162(3) SSO(S) 104(G) 1370(4) 61(4) O(1) Q(2) O(3) 46(2) 90(G) W.1) 21(4) - 22(G) 209K.J) 42fJ7(G) --l(3) -2(3) O(2) l!mJ(G) 3670(3) N(G) loe(ci) 30(2) --12(G) 1742(G) 2OW O(3) R(3) m(2) 3644(3) 114(G) 10x63) 11117(G) 20(G) --Q(3) 4708(G) O(U 170) 213G(3) 40(G) 70(G) 3(G) 1260(G) 2111(O) 17(2) 3(4) C(1) G(3) 61(G) 4(;(G) 2(3) 730((1) 2000(S) 20(2) G(3) 3R9l(G) 2(4) C(2) 3418(3) ti7(6) l!i(2) 2l!JZ(tj) 00(G) 24x%(7) -2(3) O(3). G(G) C(3) 3406(3) m(7) lG(2) 1737(7) 14(G) 42GG(7) 82(7) 2(3) C(4) 4(3) 248G(4) R7(8) 3405(7) 33(G) -&I) 1282(7) fw7) 26(2) ---R(3) C(5) 2441(4) 49(G) 1.27(9) 2G(2) 2040(a) -G(G) 3(3) -4(4) R786(0) C(G) 217(13) 22(2) 2G30(10) 071(4) --7(O) lI(3) 4476(e) 7W) 3(G) C(7) 182(11) 173(11) lG(2) 916(3) 24!39(9) 31Gtw3) tcG(9) O(4) 17(4) C(Q 362(20) ll(i(l1) 19(2) 734(4) -lOG(12) --12(4) 2003(13) 1119(10) 4(G) cw 3731(G) 82(!J) G2(4) 401!)(9) 124ClO) -64(G) 2008(8) -l(G) lO(7) WO) 206(13) 4277(4) 121Cll) -24(4) 3(ilJ3(9) -l(9) --7(4) 4286(c)) 17(2) et111 lG8(12) 32(3) 3330(G) 97(n) -Gl(I3) 27(G) -12((J) 4648(10) 4UGS(R) W2)
ATOMIC PARAMJYJYSRS (X104)
TAIIMS 1
433
INTERATOMiCBONDLENGTHSANDBONDANGLES Estimatedstandarddeviationsaregiveninparenthesa
Fe(l)--Fe(2)
2.518(l)
Fe
2276(2j 2.278(2) 3.26-J(2) 2.270(2)
Fe
2.228<2) 2215(2j 2.790(3)
Fe(V-C
l-754(8) l-755(7) 1.745(3) l-726:8)
Fe(l)-S(l)-Fe(Z) Fe
67.31<0.09j 67.22(0.09) 75.66(0.07) 75.91(0.07) 114.2(0.3) 113.4(0.2) 114.9(0.3) 114.2(0.3) 178.4(0.7) 179.5(0.7) 178.6(0.7) 179.7(0.7)
cm-O(l) cm-O(2) C(3)_0(3) C(4)-O(4)
1.139<10) 1.129(10) l.l54(1Oj 1.166(11)
S(l)-C(5) S<2)--c(6)
1.807(S) l-819(9)
Pw-c(7j P(l)_C(8) P(l)--c(9j P<2j-C(lOj P(2j--c(l~j P(2)-cc12j
1.781(10) 1.804(11) 1.786(12) l-772(11) 1.804(S) l-807(12)
Fe(l)-P(ljC(7j Fe(l)_P(l)-C(8) Fe(l)_P(l)-C(9) Fe(2)-P(2)_C(lO) Fe<2j-P(2)--C(llj Fe(2j-P(2j-C<12)
116.7(0.3) 115.7<0.3) 115.9(0.4) 114.8cO.3) 116.6(0.3) 117.5<0.3)
C(7)-P(l)-C(8) CN-PW-C(9) C(9)_-p(1)--c(7) c(1oj-P(2j-c(11) c
100.5(0.5) 103.7(0.6) 102.1<0.6) 101.7(0.5) 101.8(0.5) 102_2<0.5)
program [ 71. Some oxygen and carbon atoms also appear on a Fourier synthesis computed with the normalized structure factors E of the set of phases having $he best “figure of merit”. Their positions, as those of the remaining nonhydrogen atoms, were obtained unambiguously from a series of difference-Fourier maps computed on the basis of the heavy atoms parameters. Refinement of positional and isotropic thermal parameters of the 22 independent non-hydrogen atoms led to a value for the index R = ~(IF,I - KIF,l)/IzlFoI of 0.097. Least-squares refinements were performed using SFLS-5 program [S] _ The quantity minimized was IZ:w(lF,i - KIF,I)‘_ Atomic scattering factors, Af’ and Af” coefficients of anomalous dispersion for Fe, S and P atoms, and the weighting scheme used are described in a previous publication [ 9]_ Although the positions of all 24 hydrogen atoms were not confirmed from a difference-Fourier synthesis, we have included their contribution in the refinement, with positions calculated assuming idealized tetrahedral geometry for the methyl groups. The parameters of hydrogen atoms were held fixed &I further cycles of refinement. The contribution of hydrogen atoms reduces the R index
Fig. 2. Perspec:ive vie= of the C~-CSCH3)Fe(CO),?(CH;)3 bond. and P(CH3)3 groups rrlstive!y to the iron-iron >
12 mohxule
showing
the disposition
of SC&f3
in a significant way and gives rise to a more homogeneous set of bond distances ancl angles for the remaining atoms. Anisotropic thermal parameters were then introduced for the 22 non-hydroger: atoms, and two further cycles of refine_ment of positional and anisotropic thermal parameters for these atoms reduced R to a final value of 0.058 for 2156 independent reflections (66 weak reflections exhibiting large disagreements between IF,{ and i F,i were rejected). The value of the weighted index R” = [C.s;(fFoi - KIF,[)‘/GWIFOi’]“’ is 0.050. In the last refinement cycle, no parameter shifts were greater than 0.20 of the corresponding estimated standard deviations. A table of observed and calculated structure factors is available on rec_uest_ FinaI coordinates and anisotropic thermal pkameters for the 22 non-hydrogen atoms, with estimated standard deviations in parentheses, are given in Table i. The atomic numbering scheme used can be seen on Fig. l.and 2, which give two perspective views of the molecule along two perpendicular directions, plotted with program ORTEP [lo]. interatomic distances and bond angles are given in Table 2. Description
of the structure and discussion .
.Tne molecular structure of qr’n-[,u-(SCH3)Fe(CO)2PCCH,),I:! is wholly consis’:ent with the IR and NMR spectrographic data given above. The two ligands L = P(CH,), are trans to the metal-metal bond, axially coordinated to each iron atom, and the CHj groups of the bridgkg sulfur atoms are in a syn-endo position, as can be seen from Fig_ 2_ The molecular geometry can be described, as in t.he case 03 simikr
435
[Fe(COh-p-(SR)] z d erivatives [ 2-41, as arising from the junction of the basal planes of two distorted tetragonal pyramids along the S---S edge. The iron atoms are displaced from their basal planes, respectively, by 0.33 and 0.27 A in the direction of the apical atoms P(1) and P(2). The dihedral angle between the planes Fe(l)-S(l)-S(2) and Fe(2)-S(l)-S(2) is 90.9”. Furthermore, the two iron atoms are linked by a metal-metal bond of length 2.518(l) A. It is interesting to compare this geometry with that found in similar complexes containing Fe& -bridged systems, without direct S-S bond, and without phosphine ligands. This comparison of the main structural characteristics is given in Table 3. It appears that the replacement of one CO group cn each iron atom by the ligand P(CH3)3 does not ah&r in a significant way the geometrical parameters of the Fe&-bridged core. The main differences compared with the nearest derivative, [C2HSSFe(C0)3]2 (II) [2], involve the mean S-Fe-S angle and the dihedral angle between the two Fe-S-S planes. However, it is interesting to note that the values of these two angles for compound II are also greater than corresponding values in the three other non-substituted derivatives of Table 3. No doubt, these differences may be due, in part, to the non-bonding S.-S dis’~ce, which is greater in the first derivative than in the other four, possibly in connection with the unti-syn problem. Let us consider now the influence of the substitution of one CO by a P(CHj), ligand on Fe-C(O) and C-O distances of the two remaining car-bony1 groups. The mean value of Fe--C(O) bond lengths is 1.745(l) A in [I.I-(SCH,)Fe(CO),P(CH,),], Dwhile it is l-81(2) A in the nearest non-substituted derivative II. For the other compounds of Table 3, the mean Fe--C(O) value is also greater than in the present structure, except for [CH3SFe2(C0)6]2S (IV) [ 4 1, but the low value found in this derivative seems surprising, and is probably due to the poor precision of the structural results. In another compound for which we have determined the structure with a precision analogous to that of the present work, viz. (C,H,SNHjFe,(CO), 191, the mean Fe-C(O) distance is l-788(3) A. The observed significant shortening of the remaining Fe-C(O) bond lengths, caused by the replacement of one CO by a phosphine ligand, agrees well with the z-acceptor character weaker for a phosphine than for CO. Such a shortening of M--C(O) bond lengths has also been noted in chromium carbonyl derivatives. specially for the CO groups trays to phosphine ligands [12,13]_ On the other hand, in some mononuclear iron carbonyl derivatives having phosphine ligands, whose structural characteristics have been tabulated by Haymore and Ibers 1141, there is not such a significant shortening of Fe- -C(O) bond lengths as tlnat observed in the present study. Concerning C-O distances, the mean value in the present complex (1.147(5) A) is not significantly different from values found in the non-substituted derivatives of Table 3. The mean value for Fe-C-O angles is 179.0(3)“, nearer 180” than in most other iron carbonyl derivatives where the current values are in the range 177-178”. The mean S-C bond length is 1.813(6) A, and the mean Fe-S-C angle is 114.2(Z)“, in good agreement with corresponding values in compounds II and IV of Table 3. The mean -Fe-P distance is 2.221(l) A, a value which agrees well with reported ones in some mononuclear iron carbonyl derivatives possessing
436
437
TARLE
4
PlaneI: Plane through Fe(l). Fe(Z) and the midpointofS(l)_S(2). Euuotion: 0.9595X-0.2948 Y-00.0137 Z-3.3326= 0 = -0.033(2) -9.19?<2) -1.991<6) 2.047(6) -1.999(7) 2.140(S)
P(l) P(2) O(l) 0<2) O(3) C(4)
C(1) C(2) C(3) C(4) C(5) C(6)
_ -1.21i(8)
C(7) CW C(9) C
l-250(8) -1.212(9) l-275(9) -3.108(9) 3.130(9)
l-323(11) -1.432(12) +x036(17) -1.865<11) 0.485<12) 0.549<13)
Plane If: Plane through S(l).S(2) and the midpoint of Fe
3.159(2)
C(l)
P(2)
-3.120(2) l-914(7) 1.98-t(7) -2.014(7) -2.091(7)
C(2) C(3) C(4) C(5) C(6)
O(1) O(2) O(3) O(4) OX,
I’,
%are
coordin&esinA
bthe
1.642(S)
C(7)
l-701(8) -1.696(8) -l-753(8) -0.025(9) -O.O22(9)
orthonormalsystem:a,
c*Ac.
C(8) C(9) C(l0) C(l1) C(l2)
3.429(10)
3.361(9) 4.66700) -3.611<13) -4.617(g) -3.152<11)
cf.
ph.osphine lig.ands [14]_ The mean P-C bond length of 1.792(G) A is appreciably loSer than values found in the same mononuciear compounds, and than those which are observed in a few binuclear compounds having one or more phosphine ligahds whose structures have been determined_ Concerning the mean Fe-P-C and C-F-C angles, respectively 116.2(l)” and 102.0(2)“, the values are in very good agreement with the ones found in the literature. These angles around P atoms deviate from ideal tetrahedral geometry in the usual way. Examination of Fig. 1 shows that the molecular symmetry of [p-(SCH3)Fe(CO),P(CH&], is close to C?,“, at least in its central part: Deviation from this
433 TAI3LE
5
SHORTEST
INTERMOLECULAR
s(l:I--.c(9=) s(2:r---c(l2IV)
o(l)---c(ll~=~I) o(2).--c(5*‘1j Ot2)---C(8v1’)
3.91 x 3.82 3.67 3.71 3.73 3.63 3.60
DISTANCES.
REFERRED
TO MOLECULE
O(3)---C(7V) 0(3)---C(ll~X) C(l)---WV) C(3)---C(7V) C(1).--C(?V)
3.47 -9 3.57 3.81 3.59 3.88
c(sP-c
3.91
C
3.63
I (r. y. L) =
a N=lmbering of molecules. XI: r.: i-,l~lII;’ 2iIV:_ I + 1, --x. 2 + li? + 1.7 +,i; V: 7 +_i.,x -1, VI: r + i. Y + 4.7 + 4: X-II: r t y$ 2. y - 7_, -7 l 3; VIII: y - f2. x + 4. z - 1,; 1x: x -‘I. ?+z, 2 -i 3.
*+a;
symmetry is essentially produced by the P(CH,), groups which clearly are not in an eclipsed conformation as would be the case with a true Cz, symmetry for the whole molecule. This is also evident from Table 4 which gives deviations of atoms from the mean least-squares planes I and II of the two pseudo-mirror planes, one through Fe(l), Fe(2) and the midpoint of S(l)-S(2), and the other through S(l), S(2) and the midpoint of Fe(l)-Fe(2). The angle between these two planes is exactly 90.0” _ The crystal packing in [r_L-(SCH,)Fe(CO)2P(CIIJ)J3 is shown in Fig. 3, and the shortest intermoiecular distances are given in Table 5. The packing arises from normal Van der Waals interactions; none of the intermolec*ulardistances ere beiow the sum of Van der Waals radii of corresponding atoms. References 1 2 3 4 5 6 7 8 9 10 11 12 13 11
G. Le Borgne and 0. Gracdjean, Xcta Cryst. B.in orep55. L.F. Dab? and C-H. Wei. Inorg. Chem.. 2 (1963) 328. H-P- Q.eber sod R-F. Bryan. J. Chem. Sot. A, (1967) 182. J.bK. Colemor., A. Wojcicki. P.J. PolIick and L.F. Dahl. Ioor=. Chem.. 6 (196i) 1236. 3.X. De Beer. R-J. HJnes. R. Greatrex and N.N. Greenwood. J. Chem. Sot. A, (1971) 3271. J.Y. Le X+rouille, Th&x de 3eme cycle. Rennes. 1972. G. Germain. P. Main and XX. Woolfson, Acta Cryst. A. 27 (1971) 368. C-T. Prewitt, Fortran IV fclI-matrix crystallographic least-squares program. SFLS-5. 1966. C- Le Borgne and D. Grand&m. Acta Cryst. B. 29 (1973) 10-10. C-K. Johnson. ORTEP. Report ORAL-3794. Oak Ridge National Laboratory, Tennessee. G. Le Borgne and D. Grandjean, J. Organometal. Chem., 92 (1975) 381. G. Huttner and S. Schelle. J. Cryst. Mol. Strut., 1 (1971) 69. L-J. Gugzenbe-zer. U. Rlabunde and R.X. Schunn, Inorg. Chem.. 12 (1973) 1143. B.L. Hrvmore and J-A. Ibers. Inorg. Chem.. 14 (1975) 1369.
1965.