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Insertion of Tetrafluoroethylene into the Fe-Fe Bond
(14) T. C. Farrar and E. D. Becker, "Pulse and Fourier Transform NMR", Academic Press, New York, 1971, p 20. (15) J. T. Gerig, G. B. Matson, and A. D. Stock, J. Magn. Reson., 15, 382 f1974). > (16) S.J. Opella. D. J. Nelson, and 0. Jardetsky, J. Chem. Phys., 64, 2533 (1976). (17) J. T. Gerig, J. Am. Chem. SOC.,QS, 1721 (1977). (18) D. W. Scott, D. R. Douslin, J. F. Messerly, S. S. Todd, I. A. Hossenlopp,T. C. Kincheloe.and J. P. McCullough, J. Am. Chem. SOC., 81, 1015(1959). A structure of benzotrifluoride in a nematic solvent has been reported: J. Degelan, P. Diehl, and W. Niederberger, Org. Magn. Reson., 4, 721-723 (1972). (19) L. J. Berliner and S.S.Wong, J. Biol. Chem., 249, 1668 (1974). (20) L. J. Berliner and 8. H. Landis in "Nuclear Magnetic Resonance in Molecular Biology," B. Pullman, Ed., D. Reidel Publishing Co., Dordrecht, Holland, 1978, pp 311-322. (21) A. Kalk and H. J. C. Berendsen, J. Magn. Reson., 24, 343 (1976). (22) L. G. Werbelow and A. G. Marshall, J. Magn. Reson., 11, 299 (1973). (23) G. B. Matson, J. Chem. Phys., 65, 4147 (1976). (24) J. H. Noggle and R. E. Schirmer, "The Nuclear Overhauser Effect", Academic Press, New York, 1971, p 45. (25) I. Solomon, Phys. Rev., 99, 559 (1955). (26) D. E. Woessner, J. Chem. Phys.. 36, l(1962). (27) R. Rowan Ill, J. A. McCammon, and B. D. Sykes, J. Am. Chem. SOC.,g6, 4773 (1974). (28) W. E. Hull and B. D. Sykes, J. Mol. Biol., 98, 121 (1975). (29) (a) M. W. Pandit and M. S. Narasinga Rao, Biochemistry, 14,4106-41 10 (1975); (b) M. J. Gilleland and M. L. Bender, J. Biol. Chem., 251,496-502 (1976); (c) R. Tellam and D. J. Winzor, Biochem. J., 161, 687-694 (1977). (30) T. A. Horbett and D. C. Teller, Biochemistry, 12, 1349 (1973). (31) (a) K. E. Neet and S.E. Brydon, Arch. Biochem. Biophys., 136,223 (1970); (b) K. E. Neet, K. M. Sackrison, G. R. Ainslie, and L. C. Barritt, ibid., 160, I
7487
569 (1974). (32) A. N. Kuznetsov, B. E M , and G. V. Gyul KhaMhnyan, Mol. Biol. (Moscow), 9, 871 (1975). (33) W. L. C. Vaz and G. Schoellmann, Biochim. Biophys. Acta, 439, 206 (1976). (34) A. Gierer and K. Wirtz, 2.Naturforsch.A, 8, 532 (1953). (35) R. C. Weast, "Handbook of Chemistry and Physics", Vol. 50, Chemical Rubber Publishing Co., Cleveland, Ohio, p F-4. (36) E S. Gould, "Mechanism and Structure in Organic Chemistry", Holt. Rinehart and Winston, New York, 1959, p. 51. (37) (a) K. Wuthiick and G. Wagner, Trends Biochem. Sci., 3, 227-230 (1978); (b) I. D. Campbell, C. M. Dobson, G. R. Moore, S. J. Perkins, and R. J. P. Williams, FEES Lett., 70, 96-100 (1976). (38) Reference 24, p 28. (39) (a) J. E. Anderson and W. P. Slichter, J. Chem. Phys., 43, 433 1965); (b) A. M. I. Ahmed and R. G. Eades, J. Chem. SOC.,faraday Trans. 2, 1623 ( 1972). (40) T. E. Bull and J. Jonas, J. Chem. Phys., 52, 1978-1983 (1970). (41) J. Angerer and W. Suchanski, J. Magn. Reson., 21, 57-65 (1976). (42) T. E. Burke and S.I. Chan, J. Magn. Reson., 2, 120 (1970). (43) B. R. Appleman and B. P. Dailey, Adv. Magn. Reson., 7, 272 (1974). (44) L. G. Werbelow and D. M. Grant, Adv. Magn. Reson., 9, 190-301 (1977). (45) L. G. Werbelow, J. Magn. Reson., 34, 123-127 (1979). (46) H. Jensen and K. Schaumburg, Mol. Phys., 22, 1041 (1971). (47) J. B. Lambert and L. G. Greifenstein, J. Am. Chem. SOC.,95, 6150 (1973). (48) (a) I. B. Golovanov. V. N. Gazleov, I. A. Soboleva, and V. V. Smolyaninov, J. Gen. Chem. USSR(€ngl. Trans/.),43,905 (1973); (b) B. Kaufman, M.S. Thesis, State University of New York, Stony Brook, 1972. (49) W. E. Hull and B. D. Sykes, Biochemistry, 15, 1535 (1976). (50) J. L. Lippert, D. Tyminski, and P. J. Desmeules, J. Am. Chem. SOC.,98, 7075 (1976).
Insertion of Tetrafluoroethylene into the Fe-Fe Bond of ( p ( SCH3)Fe( C0)3)2, Its Thermal Rearrangement to a Bridging Carbene Ligand, and the Transformation of the Carbene to a Perfluoromethylcarbyne Ligand. Structures of p( SCH3)2p( C2F4)Fe2(CO)6 and p( SCH3)2p( FCCF3)Fe2( CO), at - 162 O C J. J. Bonnet,la R. Mathieu,Ia R. Poilblanc,*la and James A. Ibers*Ib Contributionf r o m the Laboratoire de Chiviie de Coordination, B.P. 4 / 4 2 , 31 030 Toirlouse-Cedex, France, and the Department of C'heniistry, Northwestern Unirersit.r. Eranston, Illinois 60201, ReceiL'ed March 23, 1979
Abstract: The insertion of tetrafluoroethylene into the Fe-Fe bond of the dinuclear complex (p(SCH3) Fe(C0)3)2 is photochemically induced. When the temperature of the reaction is stabilized at 20 'C, the major product is the yellow dinuclear species p(SCH3)2p(C*F4)Fe2(C0)6 ( I ) , where C2F4 bridges the Fe atoms with two u(C-Fe) bonds, the C-C bond being parallel to the Fe-Fe axis. When the temperature is higher, i.e., 35 'C, the product is the red dinuclear species p(SCH3)2p(FCCF3)Fe2(co)6 (2), which contains a >CF-CF3 carbene bridge. It is possible by heating 1 to obtain 2 and a mechanism for this reaction is proposed, based in part on a study of the action of BF3 on 1. The action of BF3 on 2, followed [BF4] (7),which may be a perfluoby the addition of trimethylphosphine, affords [p(SCH3)2Fe2(C0)3(PCH3)3)2(CCF3)] romethylcarbyne complex. A proof for the two different kinds of insertion of C2F4 is presented in the form of crystal structure determinations of 1 and 2. In 1 each iron atom is octahedrally coordinated to three carbonyl groups, two bridging S atoms, and one C atom of C2F4. The Fe-Fe separation is 3.31 1 ( I ) A, the dihedral angle around the S atoms is 1 35.0', and the average FeS-Fe angle is 91.6'. Compound 1 crystallizes in the orthorhombic space group D$Pbcu in a cell of u = 15.029 (8), b = 13.561 (5), c = 15.437 (8) A. Compound 2 crystallizes with eight formula units in space group C3h-P21/~of the monoclinic system in a cell of dimensions u = 11.545 (3). b = 16.681 (5), c = 16.830 (6) A w i t h p = 97.86 (2)'. Based on 2471 and 4416 unique reflections for 1 and 2, respectively, the structures were refined by full-matrix least-squares techniques to conventional agreement indices (on F) of R = 0.044 and R, = 0.049 for 1 and R = 0.039 and R, = 0.048 for 2.In 2, each iron atom is also octahedrally coordinated, being bound as in l to three carbonyl groups, two bridging S atoms, but here to the same bridging C atom of the >CF-CF3 carbene group. The Fe-Fe separation averages 2.963 A, the dihedral angle around the sulfur atoms is 107.2', and the average Fe-S-Fe angle is 79.39'. The Fe2S2 unit is more compact in 2 than in 1 but less compact than in the starting material (p(SCH3)Fe(CO)3)2. The flexibility of such molecules around the S-S axis, together with the reactivity of the Fe-Fe bond, is discussed.
T h e s t u d y of t h t reactivity of t h e metal-metal bond in dinuclear complexes toward alkynes, alkenes, or more generally small u n s a t u r a t e d molecules i s an increasing field of interest. 0002-7863/79/ 1501-7487$01 .OO/O
T h i s i s particularly t r u e for dinuclear complexes with metal to metal multiple bonds.'J However, insertion reactions of alkynes a n d alkenes into metal-metal single bonds in dinuclear
0 1979 American Chemical Society
7488
Journal of the American Chemical Society
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/ December 5 , 1979
l'ahle 1. Suiiimnry ol' Crystal Data and Intensity Collection compd I'oriii u 1); I'or in u la wcig h t t l (:it - 162 "C) h ('
/j 1'. /
dcnsitq (calcd, -162 "C density (mc;isurcd (20 "C) in aqucous ZnCI?) qxice group crystal dimensions boundary fuccs of thc prism crystal volume tcmp r:idiation linear absorption coefficient transmission factors receiving apcrture t:ikc-ol'fanglc s u n spccd sc;in range biickground counts 2 0 limits l'in;il no. of variables
\taiidard &or in an observation of u n i t weight
I I ( S C H ~ ) ~ I I ( C Z F ~ ) F(1) ~Z(C~)~ C I oH 6 FJ Fe?O&? 473.97 aniu 15.029 (8) 13.561 (5) 15.437 ( 8 ) 3146 8
A A A
I I ( S C H ~ ) ? I I ~ ( F C C F I ) F C ? ( 2C)O ) ~ C I OH). I .68. J p l i = I I Hz (P(CH3)3), 1.57 ppm, J p t l = I I .5 H7. 26". These cell constants and other pertinent data are listed in Table ( I'i C H .I 13 1. Preparation o f [ ~ ( S C H ~ ) ~ F ~ Z ( C O ) ~ ( P ( C H ~ ) ~ )(7). Z ( To C C F ~ I.) ~Intensity ~ B F ~ ]data were collected at - 162 "C. A total of 621 8 intensities ;I \oIuiion o f 5 in CHlC12 was added at room temperature a stoichioreflections were recorded out to 20( Mo) < 50'. The data were processed in the normal manner using a value of p of 0.04.14Only those inctric iiinount of BF3.O(CHj)?. The reddish solution turned bright rcd and diethyl cthcr was added. Evolution of C O was detected. with were used in subsequent 4416 unique reflections having Fo2 > 3a(FO2) I nio1 of CO bcing cvolvcd pcr mol of 5. From thc solution a t -20 OC calculations. ci;irk rcd ,tals precipitated. [p(SCHl)rFe?(C0)3Solution and Refinement of the Structures. Complex 1. The two iron atoms together with the two sulfur atoms were located in a normal (PiCH?)j)z(CCF3)][BF4]. mp 182 OC dcc. Anal. Calcd for C II H ? ~ B F ~ F C : O ~C. P ~25.57; S ~ : H. 3.93; F. 21 3 0 . Found: C , 25.55; Patterson synthesis. The positions of the remaining nonhydrogen atoms were obtained through the USULII combination of full-matrix H, 3.72; F, 21.74. IR u(C0): 2042 VS,2015 S, 1984 w (CH2CI2 S O ~ U least-squares refinements and diffcrcncc Fourier syntheses. Around tion). IH NMR: 6 2.62 (SCH3, q) J P H = 2.6 Hz, 2.13 (SCH3, s), 1.96 the fluorine atoms of the C ~ F group J eight electron density ninxima (P(CH3)3) J P H = I O Hz, 1.65 ppm (P(CH3)3) JPH= 1 I Hz. I9F NMR: 6 78.4 ppm (CF3, broad signal). of height 4-5 e/A' were located on a difference Fourier map. These maxima correspond to two alternative positions for four lluorine Collection and Reduction of the X-ray Data. A. Compound 1. Preliminary photographic data revealed that crystals of 1 belong to the atoms. Owing in large mensure to the acquisition 01' low-temperature orthorhombic system and show systematic extinctions (Ok1, k = 2n data. the disorder problcin has been rcsolved. even though the shortest + 1 ; h01, I = 2n + I ; hkO, h = 2n 1 ) consistent with the space group distance between the miixima ib about 0.7 A. During the course of D&Pbcu. All cell constants were obtained as previously describedI4 full-matrix. Icast-squarcs refinement the positional and thermal pu-
+
+
+
1490
Journal of the American Chemical Society
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101:25
/
Table IV. Positional and Thermal Parameters for the Atoms of p(SCH3)2p( FCCFj)Fe2(CO)6 (2) 0
A
FElI14 0.0200351521
75.80149)
FE(PI4 -0.038332I53r
2.36 I 2 5 1
?I+.B~(~OI
I . T S 126)
0.426633f54)
74.9~fmi
I. I O I271
0.569485 f52)
70.79 147)
0.bIf261
0.11n5451911
22.37 1791
I .61(44
23.39 182 I
3.116145b
FElII# TE17IB 5lIIA
I
5 121A
-0. I365091931
stiin
z~zin
0.4059841931
Z7.671R31
-0.59146)
0.6214321941
26.09fe31
-n.93(46)
Ftl14
Iz71
-4.11121
0.19957122)
36.0 172)
-3.*112)
0.11554 I251
64.7 176)
5.3(I41
0.0h99l (251
68.5 (271
-1o.afI4l
-0.09425 122)
35.9
F12)h Ff31A F 1416
Ff1)R
0.54126 122)
4 0 . 1 1721
1.31I21
0.30024 (231
47.0 (731
4.2(141
0.3 I763 1241
55 .T (25)
22.1 c 1 4 )
7 1 .5 f 781
18.4116)
-0.10310 (291
51.300)
2.TI151
0.259891281
33.61271
3.41151
0.0770Of301
5 4 . 7 1 31 I
4.21171
F121a F1311 TI411 0.41981
f2hl
01llA 012IA Of3)A
61414 -0.27900(31)
55.7 I331
7.5f111
47.4130)
-2.7tlbl
36.b I 7 8 1
5.9IISJ
64.2 1 341
6.btIb)
52.8 f 321
-3.4f181
~O.Z(?TI
- I - 1 1 1b1
57.0 131 I
3.7IlII
36.4 177)
5.6llbl
31 . O 1 361
9.2
48.1f421
1.3121 I
tzn I
24.7 134)
6.11191
411.5 (441
-0.3 1221
36.2(381
4 . 1 122)
24.9 f 34 1
3.1(lIl
35.4 I371 24.b 135)
Z.Zf2II
-I.IfZOI
34.7 I37 )
-3.4 12@)
42.Tf41)
-0.5 (231
30.7(371
4.11221
41.71421
3.1 121 1
25.0 (361
0.3(20l
34.7 136)
8 . 3 (20)
73.3 1351 24 .T l 341
z.oim> -2.21201
37.3(381
1.2fLI)
26.1 I34 I
-5.2 f 19 I
31.4136)
1.21 19)
45 .Z (421
1.4124)
2.9 0.021
2.9
0.155
2.9
H3C17l 3.0 3.0 3.0
0.477
3.1
0.512
3. I
0.306
3.1
0.675
2.9
n7c(71
njccii
1.11171
.a (291
3I
YICl8I W7CIRI
2.9
2.*
December 5 , 1979
Poilblanc, Ibers, et al.
/ Insertion of Tetrafluoroethylene into the Fe-Fe Bond
149 1
I
I
F'I
I'F F
F
F
/
L
-
~
I
I
S
+
I
3
A 2 Proposcd mechnnisni o f rcarriingcnicnt of thc (IF, bridging ( , the > C F CF? bridge i n group in ~ ( S C H ? ) ? ~ ( C ? F J ) F ~ ? ( CtoO )give p ( SC H ?)?p(FCC F 3 ) Fe?(C 0 ) h . Figure 2.
\ketch ofthc structurc ofp(SCH~)?p(C.F~)Fe2(Co)h without the wrbonyl groups to hho\r the two different environments for fluorine
I,'igure 1. A ;itoni\
F(2). F ( 4 ) a n d F'( I ) . I ( 3 ) .
rametcrs of thc eight fluorine atoms uere allowed to vary independently. A variable occupancy factor. N. \vas assigned to those four fluorine atoms giving almost a staggered geometry. and the occupancy ofthc other four fluorine :itonis \vi15 conbtrained to I - CY. Atomic scattering factors for the nonhydrogen atonis were t a k e n froin the usual t a b ~ l a t i o n .whereas '~ the hydrogen scattering factors uscd were those of Stewart et ;i1.IX Anomalou.; dispersion terms for the Fc and S atonis were included i n F,.'' Refinement of an isotropic model converged to value\ of K and K,, of 0.067 and 0.076. A difference Fourier map clearly revealed the positions of the six H atoms of the two methyl groups. Their positions wcrc idealized (C- tI = 0.95 A ) . Their contributions to F , were then fixed during the final cjcles of refinement which included an isotropic secondary extinction correction and anisotropic thermal paranicters ('or all but the hydrogen atoms. For each hydrogen atom. a n isotopic thcrmal parameter \viis ;issigned w i t h ii ~ a l u eI .0 A 2greater than that of the C atom to which it is attached. The f i n a l positional a n d thermal pariiincters of all atoms appcar i n Tablc 1 1 . The occupancq of atoms F( I ) - F ( 4 ) is 0.54 a n d that of :itoms F( I )'- F(4)' is 0.36. 'Titblc I l l contitiris the root-incan-square amplitudes of vibration.:" A listing of the observed and calculated structure ;iinplitudcs i 9 acailablc."! Complex 2. The direct methods approach."' based on 499 normnlizcd structure factors, biclded the correct positions of the four Fe and four S atonis bclonging to two independent dinuclcar niolccuIe~ in the as) mnietric u n i t . .A11 other titonis. including the hjdrogcn Litonis of the methyl groups, were round i n rubrequcnt difference Fourier syntliehes. The cxislcncc of the > C F C F j bridge came a s a complete ment o f a completcl) isotropic model for the t w o independent ~iiolecule~ w i t h no contribution froin t i atoms converged to viilues of K of 0.060 and K,, of0.073. A subbcquent difference Fourier map revealed the positions of hqdrogen atoms of the methjl groups. These were treated 2s in 1. The final full-matrix least-squares rcl'inc~iients, involving 1 3 3 \ariablca and 341 6 obhcrvations, were carried out by remote hookup to the CDC 7600 computer at Lawrence Berkclcq Laboratorq. Final v:iIues of the p;rrnnicters of all atoms arc given in Table IV. The root-mciin-squarc amplitudes of vibration a r c listed i n Table V.'" A listing o f the observed a n d calculated structure a n i plitudes is available."'
Results Syntheses and Reactions. When C2Fj is added to a benzene solution of (p(SCH3)Fe(C0)3)2 and irradiation is carried out so that the temperature of the solution is ca. 20 "C, a dia111a p net ic d i n uc l ea r com pou n d, p (SC H 1 ) 2p ( C 2 F j ) Fe 2 ( C 0)(, ( I ) , may be obtained froin this solution as yellow crystals. The
spectral properties of 1 are completely consistent with its solid-state structure as found by diffraction methods (vide infra). Complex 1 shows an infrared spcctrum in the v ( C 0 ) stretching region which is very similar to that observed for p(SCH3)2p(F3CC=CCF3)Fel(CO)6 in which the alkyne is CT bonded to the two iron atoms.': The IH N M R spectrum shows clearly that the two SCH3 groups are in the anti position. The I9F N M R spectrum shows an approximate AB system in a region of resonance for ClF4 bridging two metallic centers;*' this A B spin system is consistent with the fact that since the S C H l groups are i n the anti position two of the four fluorine atoms are indeed nearer to the SCHl group which is in the endo position (Figure 1). When ClF? is added to a benzene solution of (p(SCH3)Fc(CO)3)? and irradiation is carried out so that the temperature of the solution is ca. 35 OC, a different product is obtained. From this red solution a diamagnetic dinuclear complex, p(SCH?)+(FCCF,)Fe?(CO){, (2), is obtained as red crystals. The nature of this product was first established from the solid-state crystal structure (vide infra). The spectral properties of this material are consistent with that formulation. The ' H N M R spectrum shows that the complex is a mixture of syn and anti isomers in the ratio 2/ 1. The IyF N M R spectrum shows two sets of signals, a doublet and a quartet, in the ratio 3:1 consistent with a rearrangement of the C ~ F group J into a carbene bridge >CF-CF,, as in Co?(C0)7(FCCF?)." It is also possible to effect this rearrangement and obtain 2 by heating 1 in refluxing pentane. This transformation even occurs in the infrared beam of the Perkin-Elmer 225 spectrometer. Compound 2 is stable in the solid state but in solution i t gives, under vacuum, a green precipitate (3). Compound 3 is soluble in acetone or dichloromethane, but the solution is unstable and quickly turns red. The infrared spectrum shows this red solution to be a mixture of (p(SCH))Fe(C0)3)2 and 2. I f CD gas is added to a solution of 3. the same mixture is rcodily obtained. Furthermore, if P(CH?)? is added, I - ( ( S C H ~ ) 2 p ( F C C F 3 ) F e 2 ( C 0 ) 4 ( P ( C H ~ ) ~ )( 25 ) and (p(SCH,)Fe(CO)lP(CH.3)3)2 are obtained. The instability of 3 prevents further characterization. although a chemical analysis of the fresh precipitate agrees satisfactorily with the formulation ((p(SCH,)Fe(CO),)?(C,FJ)),,. The fluorine migration which leads from 1 to 2 is a wellestablished reaction, as it occurs, for instance, in the reaction of nucleophilic carbonyl metal anions with perfluoroallyl chloride'! and in the reactions of hexafluorobuta- I ,3-diene
Journal of the American Chemical Society
7492
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December 5, 1979
:F,
L
‘
J
Figure 4. Stereoscopic view of a unit cell of p(SCHJ)~p(C2Fd)Fe2(C0)6. T h e x axis is horizontal from left to right, t h e y axis is perpendicular from bottom to top, and the z axis comes out of the paper. The vibrational ellipsoids are drawn at the 30% level. Hydrogen atoms are omitted. Disorder of the fluorine atoms is not shown.
Y
L
of the proposed mechanism and identified J group to the >CF-CF, products in the rearrangement of the C ~ Fbridging bridge and to the C-CF? terminal carbyne group. Figure 3. Ovcrnll summary
with hydridopentacarbonylmanganese.23 The same type of rearrangement has also been observed in the reaction of hexafluoropropene with Pt( 1 ,5-C8H 12)2, for which a mechanism has been suggested.” A similar mechanism is proposed here (Figure 2). In the proposed intermediate compound A of Figure 2 there is a a - r bonded vinyl group. We can consider the P-carbon atom of this group to be electrophilic, as it is, for instance, in O S ~ H ( H C = C H ~ ) ( C O ) , ,Thus . ~ ~ it seems reasonable that an attack of F- on this carbon atom of the CF2 group generates the carbene compound 2. Attempts to isolate the proposed intermediate compound A of Figure 2 using Figure 5 . A perspective reprcscntation of ;I molcculc 01‘ BFj*O(CH3)2, a fluoride ion abstractor for metal perfluop(SCHJ)Ip(C?F4)Fe?(CO)h.The Librational ellipsoids arc drawn ;it 50% roalkyl compounds,’s failed when starting with compound 1. probability level. The labeling scheme is ;IIK \hewn. But if P(CH3)3 is added, two CO groups being substituted, the expected parent compound [p(SCH3)2Fe2(C0)4range to give 7 ? The most probable route seems to be the ab(P(CH3)3)2(FCCF2)] [BF4] (6) is obtained. When starting straction of F- from BF4- giving compound 5 which is then with c~(SCH~)~~(CZF~)F~~(CO)~P(CH~)~)~ (4), compound attacked by the liberated BF3 to give compound 7 after CO 6 is obtained in better yield. As for compound 4, compound 6 evolution. These proposed reactions are sketched in Figure shows three infrared-active bands in the u ( C 0 ) stretching 3. region but these are shifted to higher frequencies and a new, Description of the Structures of 1 and 2. The crystal strucstrong band at 1600 cm-’ appears which is in the region of the ture of 1 consists of the packing of eight dinuclear molecules. o(C=C) stretching frequency of a coordinated fluoro olefin.26 A stereoscopic packing diagram of the unit cell is shown in Another strong band at 1030 cm-’ is characteristic of BFd-. Figure 4. Bond distances and bond angles are given i n Tables This result strongly suggests that 6 has structure A of Figure VI and V11, respectively. Figure 5 shows a perspective view of 2. Furthermore, this structure is consistent with the IH N M R molecule 1 which includes the labeling scheme, while the stespectrum, which shows the two phosphine ligands to be reoscopic view in Figure 6 depicts the disorder of the fluorine chemically different. Unfortunately the low solubility of 6 atoms. Table VII120 presents information on least-squares together with its low stability at room temperature did not planes. The dinuclear molecule has roughly a mirror plane allow us to obtain its IyF N M R spectrum. containing the two sulfur bridging atoms and the midpoint When a solution of 6 in dichloromethane is left a t room between the two iron atoms. Each iron atom is octahedrally temperature, the color rapidly changes from violet to deep red coordinated to two bridging sulfur atoms of the methylthiolato and I mol of C O gas is evolved per mol of 6. Infrared spectra groups, three carbon atoms of the carbon groups, and one in the u ( C 0 ) stretching region show that a new compound 7 carbon atom of the C2F4 group. The “flap” angle, the dihedral has been formed which exhibits three infrared-active v ( C 0 ) angle between the two planes containing S( I ) , S(2), and the bands a t slightly lower frequencies and with different relative intensities than 6. The 19F N M R spectrum shows a single equatorial carbon atoms of the carbonyl groups, is 135.0’ (Table V I I I ) , the separation of the two iron atoms is 3.3 1 1 ( I ) resonance a t 78.4 ppm. Furthermore compound 7 is obtained when 5 is reacted with 1 equiv of BF3*O(CH3)2. Compound A, and the mean Fe( I j-S-Fe(2) angle is 91.6 (I)’. These values show clearly that the dinuclear unit is opened around 7 analyzes as [ Fe,( S C H 3)2( CO)3( P( C H 3)3)2(CCF3)] [ BF41. the S-S axis compared with the (p(SC2Hj)Fe(CO)3)2 comAs the I H N MR spectrum of 7 shows that the phosphine liplex.” The C’FJ group bridges the two iron atoms through two gands are chemically different, we propose a structure for 7 a(C-Fe) bonds (C(9)-Fe( 1 ) and C( IO)-Fe(2)), so that the in which the C-CF3 group is a terminal carbyne ligand and in which there is an Fe-Fe bond. Such a compound would appear C(9)-C( IO) bond is parallel to the Fe( 1)-Fe(2) direction. The to be the first example of a perfluoroalkylcarbyne complex. At C(9)-C( 10) bond distance of 1.534 (7) 8, is typical for a single this point, a question remains unanswered: how does 6 rearbond. The methyl groups have their expected staggered con-
Poilblanc, Ibers, et al.
1 Insertion o j Tetrafluoroethylette into the Fe-Fe Bond
'fable VI. Selected Distances
(A)
in p ( S C H I ) 2 p ( C ? F A ) F e ? ( C O ) h
(1)
Fc( I )-Fc(2)
F c Fe ~ ~ 3.31 1 ( I )
7493
Table V I I . Selected Angles (deg) in ~ ( S C H 1 ) ? p ( C ? F J ) F e ? ( C O ) h (1)
S-Fe-S 80.49(5)
S ( I)-Fc( I)-S(2)
Fc-S Fc( I )-S( I ) I C ( I) - S ( 2 )
Fc(l)-S(I) F'c(2 ) -s ( 2 )
l.'e( I ) - - C ( I ) Fc( I ) ~ C ( 3 ) Fc( 2 ) - C ( 4 ) 1 C(-)-C(h)
2.3 I 2 ( 2 ) 2.3 l O ( 2 ) 2.306(2) 2.3 10(2)
S-Fe-C(trans-equatorial) 2.310(3)"
Fc-C(cquutoria1) I .802(6)
I .802(5) I .799(5)
Fc( 1 ) - C ( 9 ) Fc( 2 ) - C ( I 0 ) C(Y)-C( IO)
S(2)-Fc( I ) - C ( 3 ) S ( I ) - Fe( 2 ) - C ( 4) S ( 2 ) - Fe(2)-C(6)
1.801 ( 5 )
S( I )-Fc( I ) - C ( 3 ) S( I)-Fc(2)-C(h)
1.801(6)
I .858(5j 2.033( 5)
S(2)-Fe-C(cis-equatorial) I .859(6)
S(Z)-Fe( I ) - C ( I ) S ( 2) - F c (2) - C (4)
C ( 9 ) - F(2)' C( IO)-F(3) C( 10)-F(4) C( l O ) - F ( 3 ) ' C( 10)- F(4)'
93.5( 2)
2.024( I I )
2.01 6( 5 )
5 ( 2) - Fe- C ( ii x 1 a 1 ) 88.8(2) 88.4(2)
C - C(C2Fd) 1.534(7)
}
I .827(5) I .357(9) I .444(9) I .430( I I ) I .362(9)
1.5539) I .300(8)
1.241 ( 9 ) 1.61 7( 10)
-
C(2)-0(2) C(3) -O(3) C(4)-0(4) C(5)-0(5) c ( 6 )-O( 6 )
S( I)-Fe( I ) - C ( 9 ) S ( 2)-Fe( I ) - C ( 9 ) S( I)-Fe(2)-C(IO) S ( 2 ) - F c ( Z ) - C ( 10)
83.2(2) 87.3(2) 82.0(2) 88.8(2) Fc-S-Fc
Fc( I)-S( I ) - F e ( 2 ) Fc( I )-S(Z)-Fe( 2)
91.58(5)
l,'c(I ) - S ( I ) - C ( 7 ) f..c(?)-S(l ) - C ( 7 )
107.6(2) Fc-S(2)-C(U)
I"( I )~ S ( 2 ) - C ( X ) Fc ( z) -S ( 2) - c ( 8 ) 1 . I 32(7)
I 13.2(2) Fe-C-F
F,'c(I) C ( 9 ) - F ( 1 )
I l6.5(5)
I .I 26(6)
F"c( I ) - C ( 9 ) - F ( 2 )
1.139(6)
I'c( l ) - C ( 9 ) - F ( l ) ' I:c( I ) - C ( 9 ) - F ( 2 ) ' I-c( 2) - C ( I 0) - F( 3)
109.4(4) 107.1 ( 5 )
1.127(6)
9 I .6 l ( 5 )
F e d ( I)-C(7)
1.41( 13)
1.132(h) I .I77(6)
1.142(6)
88.6(2)
S- F c - C ( C l FJ)
1.821(8)
CEO
C( I ) -0(I )
93.4(2)
93. I ( 2 )
S( I )-Fc-C(;ixial)
C-F
C(Y) F ( I ) C ( 9 ) - F(2) C ( 9 ) - F ( I)'
Y I.5(2)
9 1I .h( .4(2) 2)
s-c S( I ) - C ( 7 ) S(Z)-C(X)
1
171.5(7)
S( I )-Fe-C(cia-cquntorial)
Fc-C ( a x iilI )
Fc( I ) C(2) Fc(2) C ( 5 )
I 7 1 .6(2) I 7 I .7(2) 170.4(2) 172. I ( 2 )
S ( I )-Fc( I ) - C ( I )
~~
t l c r c :ind i n subsequent distance and angle tables the number in p;irenthcscs following a mean value is the larger standnrd deviation o/' :I singic observation as estimated from the inverse niatrix or from the individual values on the assumption that thcy arc from the sanie
popu I;II ion.
figuration with respect to the S-Fe bonds, as shown by the values for the H-C-S-Fe torsion angles (Table IX).20 Model building of the dinuclear molecule of 1 shows that the two alternative positions for the fluorine atoms of the bridging C2F4 group can be reached with only a slight deformation of the S( I)-Fe( 1)-C(9)-C( 10)-Fe(2)-S(2) ring, i.e., with slight shifts of the C(9) and C ( IO) capbon atoms. This observation explains why the disorder of the fluorine atoms has satisfactorily been resolved without taking account of alternative positions for the two carbon atoms C(9) and C( IO) to which they are attached; the anisotropic thermal motion of the carbon atoms is sufficient to handle this. However, the eight C-F bond distances vary from 1.357 (9) to I .444 (9) A around atom C(9) and from 1.240 (9) to I .6 17 ( 1 0) A around atom C ( IO). These variations are likely a manifestation of the disorder. The crystal structure of 2 consists of the packing of eight dinuclear molecules. There are two independent dinuclear niolecules, which we denote A and B, in the asymmetric unit.
Fc(Z)-C( IO)-F(4) Fc(Z)-C( IO)-F(3)' f'c( 2 ) - C ( I 0)- F( 4)'
Fe( I ) - C ( 1)-O( I ) Fc( 1 ) - C ( 2 ) - 0 ( 2 ) l'c( I ) C ( 3 ) - 0 ( 3 ) Fc(Z)-C(4)-0(4) FC( 2) - C ( 5) -0( 5)
F C (2 ) - C ( 6 ) - 0 ( 6 )
I14.0(5) 105.3(4) I17.5(5)
I 11.9
l20.8(5) 104.2(4) Fe-C-0 178. I(5) 178.8(5) I78.3(5)
178.5(5)
178.4(5)
178.4(5) I78.l(5j C C-F
C(IO)-C(Y)-F( I) C( I 0 ) - C ( 9 ) - F ( 2 ) C( l O ) - C ( 9 ) - F ( l ) ' C( IO)-C(9)-F(2)' C ( 9 ) - C ( 10)- F(3) C (9)- C ( 1 0)- F (4 j C ( 9 ) - C ( IO)-F(3)' C ( 9 ) - C ( IO)-F(4)'
F( I ) - C ( 9 ) - F ( 2 ) F ( 1 )'-C(9)-F(2)' F(3) C(IO)-F(4) F ( 3 ) ' - C ( IO)-F(4)'
114.1(5) 97. I ( 5 ) 97.8(6)
I I8.6(6)
106
97.4(5) I I7.0(5) I Ih.l(6) 93.3(7)
99
7494
Journal o j t h e American Chemical Society
/ / 0 / : 2 5 / December 5, I979
\
c (IO)
\-
Figure 7. Stcrcoxopic Yicw ol';i unit cell oI'p(SCHj)?p(FCCFj)Fc?(CO)(,. The .s axis is pcrpcndicular. the _I' axis goes from right I O left. and lhc z i i x i h coiiic\ out or [lie piipcr. 'The vibration;il cllip\oid\ ;ire draicn a t the 30% probnbilit! Ic\cI. Hydrogen atonis ilrc oiiiittcd.
A stereoscopic packing diagram of the unit cell is shown in
Figure 7. Bond distances, bond angles, and least-squares planes are listed in Tables X, X I , and XII,'(' respectively. Figure 8 shows a perspective view of one molecule of compound 2. The dinuclear molecule has roughly a mirror plane which contains atoms S( I ) , S(2), and C(9) (see Table XI]). Each iron atom is octahedrally coordinated to two bridging sulfur atoms of the methylthiolato groups, three carbon atoms of the carbonyl groups, and the bridging carbon atom of the CF-CF3 group. The "flap" angle between the two planes containing S( I ) , S(2), :ind the equatorial carbon atoms of carbonyl groups averages 107.6 (5)' (Table X I I ) . The mean value for the separation of Ihc two iron atoms is 2.963 (6) 8, and the mean Fe( I)-S-Fe(2) ;ingle is 79.4 ( 2 ) O . The Fe& core is thus more compact than in 1 but less than in (p(SC?Hi)Fe(C0)3)2.The CF-CF1 group behaves as a bridging carbene, the fluorine atoms of the trifluoromethyl portion being in a staggered position with respect to the C(9)- F( I ) bond i n both molecules A and B, as can be seen in Figure 8 or from F(i)-C( 10)-C(9)-F( 1 ) ( i = 2, 3, or 4 ) torsion angles given in Table X111.20 The average Fe-C bond of 2.037 8, in 2 is in the expected range",2x for a carbene group bridging twao metal atoms. The two methyl groups occupy positions which give an anti configuration for both molcculcs A and B. For the methyl group i n the endo position, in both molecules A and B the hydrogen atoms are eclipsed with rcspect to the S-Fe bonds (see Table X l l l for H-C-S-Fe torsion angles). For the methyl group i n the exo position, the hydrogen atoms are in the staggered configuration in molecule A and in the eclipsed configuration in molecule B with respect to the S--Febonds. This difference in the configuration of the t-I atoms on the exo methyl group is the major one between molecules A and B. The average Fe-C(carbony1) distance trans to any bridging sulfur atom (1.801 8, for 1, 1.790 8, for 2) lies within the expccted rangc.'" 3 3 The Fe-C axial carbonyl distance, however, is significantly longer (1.859 (6) 8, for 1, 1.848 ( 5 ) A for 2) suggesting facile CO abstraction which is consistent with the formation of the green product 3. The Fe2S2 core varies considerably from compound 1 to compound 2 and is compared with those observed in various
( p ( S R ) F e ( C 0 ) 3 ) 2complexes'" 3 ' in Table XIV. As pointed out earlier,34different substituents on the sulfur bridging atom
Poilblanc, Ibers, et al.
/
Table XI. Selected Bond Angles (deg) i n P(SC H 3 )2p( FCC F3) Fe?(CO)o niolecule A
nioleculc B
S( I)-Fe( 1)-S(2) S(1)- Fe(2)-S(2)
S-Fe-S 81.62(5) 81.49(4) 81.36(5) 81.53(4)
S(I)-Fe( l)-C(l) S(2)-Fe( 1 )-C( 2) S( 1)-Fe(2)-C(4) S(2)-Fe(2)-C(5)
S-Fe-C(trans equatorial carbonyl) 168.3(1) 168.5(2) 170.6( 1) 171.7(2) 169.6(2) 169.6(1) l70.2( 1 ) 173.1 (1)
S( I)-Fe( I)-C(2) S(2)-Fe( 1)-C( 1) S(l) -Fe(2)-C(5) S(2)-Fe( 2)-C(4)
S-Fe-C(cis equatorial carbonyl) 90.4(2) 89.1( I ) 94.0( 1) 9 4 . q 1) 89.6( 1) 92.3(1) 93.9(2) 91.6(1)
1
I
S(2)-Fe( 1 )-C( 3) S( 1)-Fe(2)-C(6) S(2)-Fe( 2)-C(6)
S( I)-Fe( l)-.C(9) S(2)- Fe( 1 )-C(9) S( 1 )-Fe(2)-C(9) S(2)- Fe( 2)-C( 9)
S-Fe -C(carbene) 79.2(1) 78.5( 1) 79.9( 1) 79.8(1) 79.0(1) 78.9(1) 79.5(1) 80.0(1)
Fe( I)-S( l)-Fe(2) Fe( I )-S( 2)- Fe( 2)
Fe-S- Fe 79.31(4) 79.61(4) 79.25(4) 79.37 (4))
1 1
Fe( l)-S(l)-C(7) Fe(2)-S( I)-C(7)
Fe-S-CHj(exo) 108.5(2) 108.8(2) 109.4(2) 109.3(2)
Fe( I)-S(2)-C(8) Fe(2)-S(2)-C( 8)
Fe-S-CHl(endo) I 13.4(2) 1 1 1.0(2) 1 I1.7(2) 112.2(2)
Fe( 1)-C(9)-Fe(2)
Fe-C-Fe 93.4(1) 93.3(1)
Fe( 1 )-C(9)-F( 1) Fe(2)-C(9)-F( 1 )
Fe-C--F 113.1(3) 111.9(3) 1 l1.6(3) 112.9(3)
Fe( l)-C(9)-C( 10) Fe(2)-C(9)-C( IO)
Fe- C-C 118.4(3) I20.7(3) 120.0(3) 18.3(3)l
Fe( I)-C( I)-O( I ) Fe( I)-C(2)-0(2) Fe( I)-C(3)-0(3) Fe(2)-C( 4)-O( 4) Fe(2)-C(5)-0(5) Fe( 2) -C( 6) -0(6)
Fe-C=O 178.3(4) 178.6(5) 178.2(4) 177.8(5) 176.5(4) 178.7(4) 178.6(4) 178.2(4) 179.7(4) 177.5(4) 177.0(4) 177.2(4)
F( I)-C(9)-C(IO)
F-C-C 100.3(4) 101.1(3)
C ( 9)-C( 1 0)-F( 2) C(9)-C( IO)-F(3) C(9)-C( lO)-F(4)
F-C-CF3 I 12.8(4) 1 12.8(4) I12.1(4) 1 l1.9(4) I I2.2(4) 1 13.3(4)
F(2)-C( IO)-F(3) F(2)-C( IO)-F(4) F(3)-C( IO)-F(4)
F-C-F of CF3 106.5(4) 106.0(4) 107.0(4) 106.8(4) 105.7(4) 105.4(4) .
170.2( 1.5)
92.0(2.1)
9 I . 5( 2.6)
79.4(6)
79.4(2)
I
109.0(5)
1
112.4(1.1)
93.4(1)
1
I
av
values
,
Table XIV. Comparison of Selected Average Values of Distances (A) and Angles (deg) in ~ ( S C H ~ ) ~ ( C ~ F ~ ) F(1) ~ Zand (CO)~ ~ ( S C H ~ ) ~ L ( F C C F ~ ) F( 2~) with ~ ( CThose O ) ~ in p(SR)Fe(C0)3)2 ComDounds
81.50( 1 1 )
S-Fe-C(axial carbonyl) 95.1 ( I ) 94.1 ( I ) 88.0(1) 89.4( 1) 93.0( 1 ) 91.9(1) 88.8(1) 91.9(1)
S( I)-Fe( l)-C(3)
7495
Insertion of Tetrafluoroethylene into the Fe-Fe Bond
l12.4(7)
1 19.4( 1.2)
178.0(9)
100.7(6)
I12.5(5)
106.2(6)
Distances 3.31 1 (1) 2.3 lO(3) 1.801(5) 1.859(6) 2.986(2)
Fe( 1 )-Fe( 2) Fe-S Fe-C(equatoria1) Fe-C(axia1)
s-s
Fe-S-Fe S-Fe-C(trans) S-Fe-C(cis) S- Fe-C( axial) flap angle
2.963(6) 2.320(4) 1.790(7) 1.848(5) 3.029(7)
Angles 91.61(5) 79.4(6) 171.5(7) 170.2(1.5) 91.5-93.4 92.0(2.1) 88.6-93.5 91.5(2.6) 135.0 107.6
2.507-2.540 2.248-2.28 1 1.772-1.810 2.81 7-2.932 67.0-68.8
87.9-95.2
of thiolate groups produce only small differences in the geometry of the central Fe& core; the ranges are reported in Table XIV. This relatively constant geometry can be considered typical when the bridging atoms are sulfur and when the bent Fe-Fe bond is present. This geometry is only slightly affected when these complexes are protonated to yield hydrido-bridged species.j3 But, as expected, there is a considerable change in Fez& geometry when a carbene (compound 2) or C2 (compound 1) bridge is formed. Major changes occur in the "flap" angle, the Fe-S-Fe angle, and the Fe-Fe distance, while the Fe-S distances are only slightly affected (Table XIV). The changes naturally are larger for compound 1 than for compound 2. Acknowledgments. J.J.B. wishes to acknowledge the receipt of a NSF-CNRS Exchange Fellowship, which has made his leave from the University of Toulouse possible. This work was supported in part a t Northwestern University by the National Science Foundation (Grant CHE76-10335). Supplementary Material Available: Tables of observed and calculated structure amplitudes for compounds 1 and 2, root-mean-square itniplitudes of vibration (Tables I l l and V ) . least-squares planes (T;ibles V l l l and XII), and torbion angles (Tables IX and X I I I ) (36 Ixtges). Ordering information is given on any current iliasthead pagc.
References and Notes (a) Laboratoire de Chimie de Coordination. (b) Northwestern University. (a) Bailey, Jr., W. I.; Chisholm, M. H.; Cotton, F. A,; Murillo, C. A,; Rankel, L. A. J. Am. Chem. SOC.1978, 100, 802-806. (b) Chisholm, M. H.;Cotton, F. A.; Extine, M. W.; Rankel, L. A. bid. 1978, 100, 807-81 1. Chisholm, M. H.; Cotton, F. A.; Extine, M. W.; Kelly, R. L. J. Am. Chem. SOC. 1978, 100,3354-3358. Davidson, J. L.; Sharp, D. W. A. J. Chem. SOC.,Dalton Trans. 1975, 2283-2287. Hoehn, H. H.; Pratt, L.: Watterson. K. F.; Wilkinson, G. J. Chem. SOC. 1961, 2738-2745. Booth, B. L.; Haszeldine. R. N.; Mitchell, P. R.; Cox, J. J. Chem. Commun. 1967, 529-530. Fischer, E. 0.; Maasbol. A. Angew. Chem. 1964, 76,645. Huttner, G.; Regler. D. Chem. Ber. 1972, 105, 2726. Yamamoto, T.; Garber, A.R.; Wilkinson, J. R.; Boss, C. B.; Streib, W. E.; Todd, L. J. J. Chem. SOC.,Chem. Commun. 1974,354-356. Aumann, R.; Wormann, H.;Krugger, C. Angew. Chem., Int. Ed. Engl. 1976, 15, 609-610. Cook, P. M.; Dahl, L. F.; Dickerhoof, D. W. J. Am. Chem. SOC.1972, 94, 55 11-5513. Herrmann. W. A. Angew. Chem.. lnt. Ed. Engl. 1978, 17, 800-812, and references cited therein. Mathieu, R.; Poilblanc, R. J. Organomet. Chem. 1977, 142, 351-355. Corfield, P. W. R.; Doedens, R. J.; Ibers, J. A. Inorg. Chem. 1967, 6 , 197-204. Doedens, R. J.; Ibers. J. A. Ibid. 1967, 6, 204-210. See, for example, Waters, J. M.;Ibers, J. A. Inorg. Chem. 1977, 16, 3273-3277. (16) The Northwestern absorption program, AGNOST, includes both the Coppens-Leiserowitz-Rabinovich logic for Gaussian integration and the
1496
Journal of the American Chemical Society
Tompa-De Meulenaur analytical method. In addition to various local programs for the CDC 6600 computer, modified versions of the following were employed: MULTAN, direct method program of Main, Germain,and Woolfson, Zalkin's FORDAP Fourier summation program, Johnson's ORTEP thermal ellipsoid plotting program, and Busing's and Levy's ORFFE error function program. Our full-matrix least-squares program, NUCLS, in its nongroup form, closely resembles the Busing-Levy ORFLS program. (17) Cromer, D. T.; Waber, J. T. "International Tables for X-ray Crystallography", Vol. IV; Kynoch Press: Birmingham. Enaland. 1974: Table 2.2A. Cromer, D. T. bid.; Table 2.3.1. (18) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J. Chem. Pbys. 1965, 42, 3- 1 7-5 3-1.7. 9- . (19) Ibers. J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781-782. (20) See paragraph at end of paper regarding supplementary material. (21) Green, M.; Laguna, A.; Spencer, J. L.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1977, 1010-1016. (22) (23)
McClellan, W. R. J. Am. Chem. SOC.1961, 83, 1598-1601. Tattershall, B. W.; Rest, A. J.; Green, M.; Stone, F. G. A. J. Cbem. SOC.
(24) (25) (26) (27) (28) (29) (30) (31) (32) (33) (34)
/
101:25
/ December 5 , 1979
1968,899-902. Churchill, M. R.; DeBoer, B. G.; Shapley, J. R.; Keister, J. B. J, Am. Cbem. SOC. 1976, 98,2357-2358. Reger, D. L.; Dukes, M. D. J. Organomef. Cbem. 1978, 153, 67-72. Fields, R.; Godwin, G. L.; Haszeldine, R. N. J. Cbem. SOC., Dalton Trans. 1975, 1867-1872. Huttner. G.; Gartzke, W. Cbem. Eer. 1972, 105. 2714. Yamamoto, Y.; Aoki, K.; Yamazaki, H. J. Am. Cbem. SOC. 1974, 96, 2647-2648. Dahl. L. F.; Wei, C. H. Inorg. Cbem. 1963, 2, 328-333. Henslee, W.; Davis, R. E. Cryst. Sfruct. Commun. 1972, 403, 185. Coleman. J. M.; Wojcicki. A , ; Pollick, P. J.; Dahl, L. F. Inorg. Cbem. 1967, 6, 1236-1242. Le Borgne, G.; Grandjean. D.; Mathieu, R.; Poilblanc, R. J. Organomet. Cbem. 1977, 131,429-438. Savariault,J. M.; Bonnet, J. J.; Mathieu, R.; Galy, J. C. R. Acad. Sci., Ser. C 1977, 284, 663-665. Clegg, W. Inorg. Chem. 1976, 15, 1609-1613.
Structure of q3-Cyclooctenyltris(trimethyl phosphite)iron(I). Bonding of the q3-Alkenyl Group to 16-, 17-, and 18-Electron ML3 Systems R. L. Harlow, R. J. McKinney, and S. D. Ittel* Contribution NO. 2673 f r o m the Central Research and Decelopment Department, E . I. du Pont de Nemours and Company, Experimental Station, Wilmington, Delaware 19898. Received June 13, 1979
Abstract: The crystal and molecular structure of Fe(q3-C8H~3)(P(OMe)3)3 has been determined at -80 "C by X-ray diffraction. The monoclinic crystals ( C 2 / c ) have unit cell dimensions a = 14.940 (3) A, b = 11.626 (3) A, c = 29.952 (5) A, 0 = 103.88 ( 2 ) " . and V = 5050.5 A3. Full-matrix least-squares refinement led to R(F,) = 0.035 and R, (F,) = 0.036. The coordination sphere about the iron atom is a distorted square pyramid if the q3-cyclooctenylgroup is considered to be a bidentate l i gand. The $-allylic group is symmetrical but skewed with respect to the basalllane. This, twisting allows a hydrogen atom on a carbon atom attached to the a3-allylic group to have a very weak (2.77 (2) ) interaction w i t h the metal center. Extended Huckel theory, with the inclusion of two-body repulsion, has been used to reproduce molecular geometries, including bond lengths, of 16-, 17-, and 18-electron complexes of the type [ M(q3-alkenyl)(P(OMe)3]+'. Barriers to several intramolecular rearrangements have been calculated for these species and agree well with N M R and ESR measurements. The bonding in t h e 16-, 17-, and 18-electron species is discussed.
Introduction The dimeric species, [ Fe(q3-allyl)(C0)3]2, prepared by a
0 C -Fe
-Fe -CO 0 0
one-electron reduction of F e X ( q 3 - a l l y l ) ( C 0 ) 3 complexes (where X = halide), has been shown to exist in equilibrium with its p a r a m a g n e t i c This monomer-dimer cquilibrium is very sensitive to steric effects. T h u s , if substituents a r e a d d e d to t h e allyl group,' or o n e or more of t h e carbonyl ligands a r e replaced with phosphorus ligands,'.' t h e equilibrium is shifted dramatically toward the monomeric species. The p h o s p h i t e complex [Fe(~3-cyclooctenyl)(P(OM e ) ) ) j ] [BF4]4*5(1) undergoes a similar one-electron reduction to give t h e m o n o m e r i c species Fe(q3-cyclooctenyl)(P(OMe)3)xh (2). Complex 2 shows no tendency to form a
0002-7863/79/15Ol-7496$0l .OO/O
P
I
L
d i a m a g n e t i c dimer. Additionally, it is fluxional on the ESR time scale, showing hyperfine coupling to three n o n e q ~ i v a l e n t ~ phosphorus nuclei in slow exchange a t -140 O C . As the system is warmed a dynamic process begins to equilibrate the two similar phosphorus nuclei until a t -60 O C the spectrum appears as a doublet of triplets. As the system is warmed further, a second, independent fluxional process begins to equilibrate all three phosphorus nuclei, giving a quartet a t 140 OC.While we were able to simulate the permutational behavior of the phosphorus nuclei, without some knowledge of the ground-state geometry, we were unable to d r a w any conclusions about the physical d y n a m i c process related to that permutational behavior. The crystal structure of the dimeric species [Fe($C 3 H 5 ) ( C 0 ) 3 ] 2 has been r e p ~ r t e d ,but ~ from spectroscopic measurements the solution structure of 2 is clearly of lower s y m m e t r y t h a n would be expected for half of the dimer. T w o
0 I979 American Chemical Society
