Inorg. Chem. 1981, 20, 186-194
186 Table VII. Some Magnetic and Structural Features CU-CU,
$~(cU-w),
comulex
A
dee-
[Cu(5-Cl-dpn)] ICu(3-N09-salun)1, a,c iCu(5,6-&nzc&lpn)] zaJ [Cu(S-NO,-salpn)]
2.92 3.01 3.04 2.96 3.00 3.01
103.7 103.5 104.0 106.0 103.2 104.1
P 3e
7,
dea-
u, cm-'
13.7 2800 9.6 2 8 0 0 10.4 2800 4.0 21000 6.8 2600 1.0 2600
salpn = salicylaldehyde 3-aminopropanol Schiff base. Because of the very low observed paramagnetism (no maximum in the magnetic susceptibility vs. temperature curve at accessible temperatures), the values of 2.J cannot be estimated accurately, Reference 23. though lower limits are clearly implied. Reference 24. e Reference 8 and this work.
in the alkoxy chelate series is probably due to the different strain effects produced by the wide variety of multidentate chelates employed in the comparison. Table VI1 compares the various parameters of the complexes 1 and 2 with some other Cu(I1) complexes of tridentate alkoxy ligands. There is obviously a general correlation between Cu-Cu distances, 4, T , and 2J values, but no direct linear relationship is observed. The effect of changing the chelate ring size from six to seven members on going from 2 to 1 is a barely significant decrease in the magnetic moment (from 0.57 to 0.38 pB at 300 K),
consistent with the small changes in geometry around Cu2+. In the absence of data on any other complex containing a 7-membered chelate ring in this position, it is difficult to suggest why compound 1 is not completely diamagnetic, since it appears to contain the ideal geometry (T = Oo) for complete coupling. The dramatic decrease in magnetic moment as the chelate ring containing the bridging oxygen atom increases from five to six members is consistent with previous observation^'^ and is associated with structural effects discussed above. As the bridging oxygen becomes trigonal, rather than tetrahedral, spin pairing between Cuz+ ions is facilitated because of more favorable orbital overlap.zs Interactions between Cu2+ ions in complexes containing 5-membered chelate rings, where association into tetranuclear units may occur, are small but detectable, and we are currently undertaking a study on a group of such compounds in an attempt to elucidate further the relationship between structure and magnetic properties. Acknowledgment. This work was supported by Grant No. A-259 from the Robert A. Welch Foundation (A.E.M.) and by the National Research Council of Canada (C.J.W.). Supplementary Material Available: Tables of calculated and observed structure factors for complex 1 (Table A) and complex 2 (Table B) (17 pages). Ordering information is given on any current masthead page. ~~~~~
( 2 5 ) Muto, Y.;Kato, M.; Jonassen, H.B.; Ramaswamy, H.M. Bull. Chem. Soc. Jpn. 1961,40, 1535.
(24) Lemay, H.D.; Hodgson, D. J.; Pruettiangkura, P.; Theriot, L. J. J. Chem. SOC.,Dalton Trans. 1979, 78 1.
(26) Johnson, C. K.Report ORNL-3794; Oak Ridge National Laboratory: Oak Ridge, Tenn., 1965.
Contribution from the Departments of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Y6, and Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
Crystal and Molecular Structure of Two Isomeric Iron Carbonyl Derivatives Which Contain an Extensively Rearranged Bis(tertiary phosphine) ROGER E. COBBLEDICK, WILLIAM R. CULLEN,* FREDERICK W. B. EINSTEIN,* and MANGAYARKARASY WILLIAMS
Received June 13, 1980 1
I.
The bis(tertiary phosphines) (C~HI~)~PC=CP(C~HI~)~(CF~)~ [A ( n = 2), B (n = 3)] and (C6H5),PC 25", measured on a Picker FACS-I computer-controlled, four-circle diffractometer using Mo K a radiation. The compound has a formula weight of 898.2 and crystallizes in the space group PZ,/c with cell dimensions a = 15.348 (6) A, b = 9.231 (5) A, c = 26.839 (12) A, ,3 = 104.90 (3)', and V = 3674.6 A3. dw = 1.60 (flotation) and d,,, = 1.62 g cm-,, Z = 4, X(Mo K a l ) = 0.70926 A, p(Mo K a ) = 9.89 cm-I, and T = 22 (1) "C. Intensity data for one quadrant were collected with the use of a scintillation counter with pulse-height analysis and graphite-monochromatized Mo K a radiation. The 8-28 scan technique was used, and data were collected in two sets. For reflections with 28 I 30" a scan of 1.4' base width was used with background counts for 10 s at both scan limits. Reflections having 30' < 28 I 40" were measured with a base width of 1.1" with 20-s background counts at the scan limits. For both sets the scan was extended to allow for spectral dispersion, and the scan rate was 2" m i d in 28. Two standard reflections were measured every 60 reflections, and the maximum variation was 1 3 % during the data collection. A total of 3435 reflection intensities with 4" I 28 I 40" were measured, of which those 2612 with a net count >2.3u(I) were considered observed, where ul = [S+ (t8/tb)2(131 B2) (kr)2]1/2, where S is the total scan count, BI and B2 are the background counts, t, is the scan time, tb is the total background time, k is a constant set a t 0.03, and the net count I = S - (t,/rb)(B1+ B2).The intensities were corrected for Lorentz and
+
polarization effects. No correction was made for absorption. The positions of the iron atoms in V were obtained from a three-dimensional Patterson function. A cycle of least-squares refinement followed by a difference Fourier revealed the remaining nonhydrogen atoms. Refinement continued with isotropic thermal parameters and later anisotropic parameters for the iron, phosphorus, fluorine, and carbonyl atoms. A difference Fourier synthesis based on reflections having (sin 8)/X < 0.34 revealed the positions of most of the hydrogen atoms. Positions of the hydrogen atoms were calculated by using a C-H bond length of 1.00 A and assigned isotropic temperature factors of the carbon atom to which they were attached. Further refinement in which the hydrogen atom parameters were not varied converged with final R factors R I = xllFol - IFcll/CIFol = 0.055 and R2 = [xw(lFo- FcI)z/~wIFo12]1/2 = 0.059 for the observed reflections. The largest peaks on the final difference map (0.46 1 0.12 e k') occurred near the iron atoms. In the early stages of refinement unit weights were used while in the later stages weights w = l/uF,' where uF0 = uI/(2(Lp)F0). An analysis of xw(lFd - lFC1)' as a function of IFol, (sin @/A, and Miller indices showed no unusual trends. Atomic scattering factors, including anomalous dispersion corrections for the iron atoms, were taken from the literature.*' A list of observed structure amplitudes and calculated structure factors and calculated fractional atomic coordinates for the hydrogen atoms are available as supplementary material. Computer programs used in the structure determination and refinement have been described elsewhere.25 Complex VI. Very small, rep crystals were obtained from diethyl ether. There was insufficient material to attempt a recrystallization, and the largest crystal available (0.15 X 0.18 X 0.20 mm) was used for data collection. Unit cell dimensions were obtained from a least-squares fit of the setting angles of 11 reflections (28 > 20") measured on the automatic diffractometer. The compound has a formula weight of 972.3 and crystallizes in the space roup P2Jc with cell dimensions a = 12.45 (2) A, b = 17.21 ( 5 ) c = 18.86 (3) A, ,3 = 97.67 (9)", and V = 4005 A'. de,, = 1.56 (flotation) and d& = 1.61 g cnr3,2 = 4, X(Mo K a J = 0.70926 A, p(Mo Ka) = 9.17 cm-I, and T = 22 (1) OC. Intensity data out to 28 = 30" were collected with a scan base width of 1.3" with background counts of 40 s at the scan limits and a reduced scan rate of 1" min-I in 28. Measurements of 1623 unique reflection ~ ~ intensities were made, of which only the 934 with I > 2 . 3 were considered observed and used in structural refinement. Lorentz and polarization corrections were applied but no correction was made for absorption. A Patterson synthesis located the two iron atoms, and subsequent Fourier syntheses gave the positions of the remaining nonhydrogen atoms of the molecule. Full-matrix least-squares refinement followed by a difference synthesis indicated the presence of solvent of crystallization. Although the crystals were crystallized from diethyl ether only, three solvent peaks were located on the difference map. These peaks were assigned as carbon atoms with site occupancies of 1.O and included in the refinement. The site occupancies were not refined. Anisotropic thermal parameters for the iron and fluorine atoms were
1,
+
X-Ray Crystallography"; Kynoch Press: Birmingham, England, 1962; Vol. 3, p 273. ( 2 5 ) Einstein, F. W. B.; Jones, R. D. G. Inorg. Chern. 1972, 1 1 , 395. (24) "International Tables for
Inorganic Chemistry, Vol. 20, No. 1, 1981 189
Two Isomeric Iron Carbonyl Derivatives allowed to refine, and hydrogen atoms in calculated positions (C-H = 1.OO A) were included as fixed contributions. The discrepancy factors after the last cycle were R1 = 0.072 and R2 = 0.066. The largest peak ( - 3 a ) on the final difference map was near the iron atoms. In the least-squares refinement xwllFol - lFcl12was minimized Anomalous dispersion corrections were made for where x = l/a,:. the iron atoms. Final positional and thermal parameters for both isomers V and VI are listed in Table 111. Interatomic distances and angles with estimated standard deviations are given in Table IV. Relevant least-squares plane data for selected atomic groups are listed in Table V.
Results and Discussion The reaction of the fluorocarbon-bridged bis(tertiary , I phosphines) (C6H5)2PC=CP(C6H5)2(cFz)~ (n = 2-4) with iron carbonyls gives the chelate complexes (L-L)Fe(CO), in addition to compounds of structure D.2 We now find that chelate derivatives I and I1 are also obtained from A and B. The I9FN M R spectra.of I and I1 are very similar to those of the free ligand. However, this must be due to stereochemical nonrigidity since the crystal structure of I shows that the phosphorus atoms are situated in the axial and equatorial positions of a distorted trigonal bipyramid.26q27 In spite of the presence of the bulky (C6H11)2Pgroups, the Fe-P bond lengths are not significantly elongated. In contrast the bis(dicyclohexy1)phosphino analogue of C forms the chelate complex (L-L)Mo(CO),, among others, in which the M w P bonds are longer than usual.6 Similar M(CO), chelate derivatives are formed by C;5 thus the failure of C to give a (L-L)Fe(CO), complex is at first sight surprising. It seems that the bite of the ligand is too large to chelate to iron. An identical situation prevails in the reactions of ( C H , ) , A S C = C A S ( C H ~ ) ~ ( C Fwith ~ ) ~ iron carbonyls. The bis monoligate derivative (L-L)Fel(CO)g is isolated and a complex of this formula, IV, appears to be formed by C although not enough was obtained for complete characterization. The mass spectrum of IV shows the molecular peak at m / e 954 and other peaks associated with the loss of up to eight carbonyl groups. The v(C0) bands (Table 11) are similar in energy and pattern to well-characterized related compounds obtained by the coupling reaction shown in eq 3.28 I
(C6H,,)2PC=CC1 c(cF2)'?
i
Fe(C0)5
-
(C6H5)2PC=C-c=C
I
(COhFe
c(C F2) 4> p( c6H5k
I
other
t podu&
(3)
Fe(CO)4
Only one of the new ligands gave a (L-L)Fe2(C0)6 complex of structure D. This compound, 11, is obtained in very low yield (2%) in spite of the use of reaction conditions reported to be the best for the preparation of such complexes.29 The yield is increased slightly when Fe3(C0)lzis used. The pattern of the infrared spectrum of I1 is very similar to that of other molecules of this known structure.* The band frequencies are lower than those of the bis(dipheny1phosphino) a n a l ~ g u e .The ~ failure of B to give a derivative, (L-L)Fe(C(26) Einstein, F. W. B.; Huang, C.-H. Acta Crystallogr., Sect. 8 1978, 834, 1486. (27) Similar nonrigid (L-L)Fe(CO), derivatives of known crystal structure have been described:" (a) Brown. D. S.: Bushnell. G. W. Acta Crvstallogr. 1967, 22, 292. (b) Cotton, F. A,; Hardcastle, K. I.; Rusholme, G. A. J . Coord. Chem. 1973, 2, 217. (28) The coupled ligand shown in eq 3 has not been prepared by more conventional means.s,6 (29) Chia, L. S.; Cullen, W. R.; Sams, J. R.; Scott, J. C. Can. J . Chem. 1 9 5 , 53, 2232.
C(10)
Figure 1. View of the structure of V showing the atomic numbering scheme.
O),, may be due to steric hindrance caused by bulky groups and a decrease in the bite of the ligand.,O Apparently C does not form a (L-L)Fe2(C0), derivative of structure D because the double bond in the necessarily puckered seven-membered chelate ring would be too far away from the second iron atom to bind to i t s However, as can be seen in Table I, two molecules of formula (L-L)Fe2(C0)6, V and VI, can be isolated from the reaction of C with iron carbonyls. The mass spectra of both isomers show a molecular ion followed by loss of six C O groups. However, no peak corresponding to the free ligand ( m / e 618) is present, so some ligand fragmentation has taken place. Crystal Structure of V. A perspective view of the molecule is shown in Figure 1. The most striking features in the formation of this complex are the cleavage of one diphenylphosphino group and the fragmentation of the other. The cleaved group bridges the two iron atoms with distances Fe(1)-P(l) = 2.239 (3) and Fe(2)-P(1) = 2.219 (3) A. Fragmentation of the remaining diphenylphosphino group occurs by cleavage of a phenyl ring from P(2) and attachment of the phenyl ring to the cyclobutene ring by a carbon-carbon bond at the point of cleavage of P(1). As a result of this fragmentation, a modified phosphido group is formed which also bridges both the iron atoms. This bridge is not symmetrical since Fe(1)-P(2) is 2.197 (2) A and Fe(2)-P(2) is 2.241 (2)
A.
In structures of the general type Fe2(CO),(p-X),, each of the iron atoms can be considered to be in a distorted octahedral environment consisting of three carbonyl groups, two bridging atoms, and an F e F e bond. The bond lengths and angles and dihedral angles for the central four-membered ring differ markedly with the type of bridging atom. For phosphorus bridging atoms, apart from the structure of FeZ(CO),[p-P(CF3)2]z,distances and angles lie within the ranges Fe-Fe = 2.619-2.665 A, Fe-P = 2.203-2.233 A, Fe-P-Fe = 72.&74.3', and flap angles (angle between the FeP, planes) = 10&107.3°.31 In the structure of Fe,(CO),[p-P(CF,),], (30) Cullen, W. R.; Mihichuk, L. Can. J . Chem. 1973, 51, 936.
Cobbledick et al.
190 Inorganic Chemistry, Vol. 20, No. I, 1981 Table 111
(a) Fractional Atomic Coordinates (X l o 5 for Fe and P; X lo4 for F, 0, and C) and Isotropic Temperature Parameters (X l o 3 A’) for V X Y 2 U X Y Z U 2353 (3) 4513 (9) 5514 (5) 4980 (4) 65190 (7) 2111 (3) 3669 (9) 6048 (5) 12337 (4) 70029 (7) 1691 (3) 4124 (8) 7961 (5) 13437 (7) 31601 (22) 69527 (13) 1505 (3) 5403 (8) 8230 (5) 7109 (7) 15722 (22) 78286 (13) 1788 (3) 6168 (9) 8974 (6) 736 (2) -2128 (5) 8394 (4) 2264 (3) 5654 (9) 9441 (5) 811 (2) -859 (5) 9590 (3) 2454 (3) 4392 (9) 9177 (5) -237 (2) -2671 (5) 8343 (4) 2171 (3) 3631 (8) 8451 (5) -181 (2) -1385 (5) 9529 (3) 316 (3) 221 (8) 8195 (5) -631 (2) 2902 (5) 8768 (4) 504 (3) -1090 (9) 8768 (6) -654 (2) 3201 (5) 7375 (4) -64 (3) -1406 (10) 8737 (6) -1620 (2) 2108 (6) 8303 (4) -182 (3) -56 (8) 8178 (5) -1644 (2) 2420 (6) 6897 (4) -664 (3) 716 (8) 1896 (5) 552 (3) 2898 (9) 4644 (4) -790 (3) 2299 (9) 7949 (6) 5441 (7) 56 (3) 6886 (5) -1364 (3) 1827 (10) 7682 (6) -430 (3) 923 (8) 5913 (4) -1172 (3) 319 (8) 7623 ( 5 ) 1628 (3) 392 (7) 5410 (5) 910 (3) 2536 (8) 8890 ( 5 ) 600 (3) -1800 (8) 6395 (5) 605 (3) 3685 (8) 9057 (5) 2101 (3) -343 (7) 8385 (5) 743 (3) 9872 (6) 4424 (9) 528 (3) 2850 (11) 5358 (6) 1174 (3) 4041 (10) 10504 (6) 227 (3) 4359 (11) 6732 (6) 1479 (3) 2909 (10) 10364 (6) -69 (3) 1621 (10) 6156 (6) 1348 (3) 2143 (9) 9555 (5) 1478 (3) 567 (10) 6028 (6) -1461 (3) -1010 (8) 7350 (5) -814 (11) 851 (3) 6672 (6) -1254 (3) -2145 (10) 6987 (6) 1766 (4) 108 (9) 7843 (6) -1530 (4) -3424 (12) 6754 (7) 1634 (3) 4112 (8) 6153 (5) -2020 (4) -3470 (11) 6897 (7) 1404 (3) 5336 (9) 5738 (5) -2229 (3) -2378 (10) 7233 (6) 1656 (3) 6161 (10) 5208 (6) -1965 (3) -1118 (9) 7466 (5) 5717 (10) 2120 (3) 5121 (6) ~
(b) Final Anisotropic Parameters (A’ X lo4 for Fe; A’ X l o 3 for P, F, 0, and C) for V
Fe(1) Fe(2) P(1) P(2) F(l) F(2) F(3) F(4) F(5) F(6) F(7) F(8)
u,,
u 2 2
366 (8) 428 (8) 39 (1) 37 (1) 121 (4) 69 (4) 108 (4) 74 (4) 100 (4) 123 (4) 135 (5) 117 (5)
495 (9) 404 (8) 38 (1) 38 (1) 61 (4) 87 (4) 50 (3) 85 (4) 63 (4) 58 (3) 86 (4) 88 (4)
u,
u 1 2
355 (8) 45 (6) 379 (8) -42 (6) 2(1) 33 (1) 3 (1) 32(1) 29 (3) 78 (4) 36 (3) 73 (4) 72(4) -2 (3) 23 (3) 83 (4) 69 (4) -28 (3) 60 (3) 25 (3) 69 (4) -17 (4) 60 (3) 34 (4)
u,3
u,
80 (5) -13 (6) 162 (6) -1 (6) -2 (1) 11 (1) 2 (1) 12 (1) 29 (3) 54 (3) -7 (3) 4 (3) 23 (3) -12 (3) l(3) 43 (4) 3 (3) 20 (3) 41 (3) 5 (3) 64 (4) 5 (3) l(3) 9 (3)
O(1) O(2) O(3) O(4) O(5) O(6) C(1) C(2) C(3) C(4) C(5) C(6)
Ull
un
u 3 3
u 1 2
33 (4) 109 (6) 69 (5) 82 (5) 113 (6) 76 (5) 34 (6) 55 (6) 47 (6) 72 (7) 76 (7) 66 (7)
193 (8) 62 (5) 111 (6) 102 (6) 75 (5) 87 (6) 113 (9) 70 (7) 59 (7) 64 (7) 56 (7) 35 (6)
93 ( 5 ) 83 (5) 72 (5) 111 (6) 91 (6) 84 (5) 58 (6) 38 (5) 51 (6) 60 (6) 47 (6) 68 (7)
17 (5) 11 (4) -13 (4) -24 (4) -25 (5) 4 (4) 24 (6) 6 (6) -1 (5) -12 (6) 2 (6) 4 (5)
‘13
10 (4) 31 (4) 2 (4) 67 (5) 34 (5) -4 (4) 3 (5) 17 (5) 8 (5) 33 (6) 29 (5) 28 (6)
‘23
-24 (6) 19 (4) -39 (5) -8 (5) -35 (5) 39 (4) -15 (6) -3 (5) -2 (5) 5 (5) -6 (5) 15 (5)
(c) Fractional Atomic Coordinates (X l o 4 for Fe, P, F, and 0; X lo’ for C) and Isotropic Temperature Parameters (A2 X 10’) for VI X Y z U X Y Z U 465 (1) 42 (9) 232 (2) C(13) 336 (2) 2933 (2) 2814 (2) 1820 (3) 113 (13) 510 i2j 171 i 2 j 359 i3j 3865 i2j 1936 i2j 744 (3) 124 (15) 583 (2) 189 (2) 408 (3) 2519 (8) 2232 (12) -3528 (12) 129 (15) 593 (2) 260 (3) 433 (3) 2369 (9) 1195 (11) -2620 (14) 158 (17) 543 (3) 318 (3) 427 (3) 1314 (9) 2812 (12) -2878 (13) 125 (14) 468 (2) 302 (2) 373 (3) 1157 (8) 1776 (10) -1994 (12) 49 (10) 273 (2) 233 (2) -152 (2) 644 (9) -494 (11) 3190 (10) 84 (13) 231 (2) 196 (3) -259 (3) 1205 (9) 4185 (10) -1024 (12) 110 (16) 171 (3) 229 (3) -221 (3) 1173 (8) 3512 (11) 1616 (12) 61 (10) 218 (2) 260 (2) -127 (2) 1742 (8) 4473 (1 1) 1035 (13) 188 (1) 306 (2) 40 (9) -39 (2) 3775 (4) 47 (3) 2000 (5) 2490 (6) 65 (12) 129 (2) 358 (2) -32 (3) 3671 (4) 40 (3) 2316 (4) -993 (6) 43 (11) 153 (2) 375 (2) 3775 (11) 89 (3) 4154 (12) 1319 (14) 81 (8) 57 (10) 217 (1) 322 (2) 119 (9) 2572 (12) 66 (2) 3566 (13) 3764 (18) 390 (1) 25 (8) 337 (1) - 128 (2) 1799 (11) 83 (8) 1663 (12) 1985 (14) 62 (10) 459 (2) 358 (2) -113 (2) 5094 (10) 70 (7) 3014 (11) 1154 (13) 99 (13) 482 (2) 436 (2) -129 (2) 4851 (10) 75 (7) 591 (13) 754 (14) 97 (13) 431 (2) 489 (2) -146 (2) 2636 (10) 58 (6) 918 (10) 284 (12) 117 (14) 365 (2) 472 (2) -164 (3) 348 (10) 149 (2) 360 (2) 28 (9) 83 (11) 339 (2) -151 (2) 395 (2) 70 (11) 271 (2) 329 (2) 297 (3) 405 (1) 22 (8) 182 (2) -203 (2) 226 (2) 43 (9) 207 (2) 189 (2) 403 (1) 26 (8) 105 (2) -193 (2) 463 (2) 256 (2) 100 (2) 41 (9) 58 (10) 430 (1) -269 (2) 56 (2) 51 (10) 451 (2) 108 (2) 68 (2) 67 (10) 461 (1) -350 (2) 94 (2) 316 (2) 135 (2) 34 (9) 48 (2) 82 (11) 173 (2) 459 (2) -362 (2) 350 (1) 117 (1) 34 (9) 321 (2) 426 (1) 50 (9) 216 (1) -285 (2) 72 (11) 315 (2) 127 (2) 414 (2) 440 (90) 361 (8) 434 (9) 593 (11) 91 (12) 291 (2) 473 (2) 68 (2)
Inorganic Chemistry, Vol. 20, No. 1, 1981 191
Two Isomeric Iron Carbonyl Derivatives Table III (Continued)
Y
z
U
-25 -6 (2) 39 (2)
299 (2) 335 (2) 360 (2)
91 (11) 103 (12) 78 (11)
X
C(10)
439 (3) 349 (3) 290 (2)
C(12) '(11)
X
C(40) C(41)
(d) Anisotropic Temperature Parameters (A'
547 (10) 449 (8) X
Y 4 5 2 (7) 505 (6)
Z
U
435 (7) 446 (5)
275 (58) 210 (43)
10') for VIa
~~
UII U,' U3' Ull '13 '23 U lt Ull '31 u 1 2 '13 22(12) 51 (4) - l O ( 3 ) 3 (3) F(4) 114 (15) 1 1 2 ( 1 7 ) 3 0 ( 1 3 ) - 2 8 ( 1 3 ) 7 (3) 53 (4) Fe(1) SO(4) 8 (10) -5 (3) 6 (3) -4 (3) F(5) 70 (12) 1 1 2 ( 1 7 ) 4 6 (13) -9 (11) 36 (4) 54 (4) Fe(2) 38 (3) 8 (11) 7 (13) F(6) 51 (12) 9 1 (16) 1 1 8 ( 1 7 ) 20 (12) 14 (12) F(l) 46 (13) 207 (24) 56 (13) -1 (14) F(2) 146 (19) 75 (17) 116 (18) -61 (15) -33 (13) 12 (13) F(7) 55 (13) 174 (21) 41 (14) 18 (12) 31 (11) 78 (14) 158 (21) 116 (17) -54 (15) -52 (13) 66 (17) F(8) 129 (16) 63 (15) 8 2 (15) -21 (14) -17 (13) F(3) a
The parameters are in the form exp[-2n2(h'a*'U,,
'23
-6(12) 3 (12) 4 0 (13) 10 (11) 12 (12)
+ . . . + 2hka*b*Ul, + . . .I].
c'i; 0)
Figure 2. View of the structure of VI showing the atomic numbering
scheme.
w
the values are uite different with Fe-Fe = 2.819 (1) A, Fe-P = 2.193 (1) , Fe-P-Fe = 80.0 (l)', and flap angle = 118.9°.31 The differences are attributed to the effects of the electron-withdrawing CF3grou on the phosphorus atom. In V the Fe-Fe bond of 2.604 (2) lies slightly outside the range observed above. The P-Fe-P angles lie within the range, but the Fe-P-Fe angles are on the low side, giving a slightly lower flap angle between the FeP2 planes (98.7') than for the other reported phosphorus bridging compounds.31 As a consequence the Fe-Fe bond is slightly shorter. The dihedral angle between the two Fe2P planes is 103.4' and the P---P contact is 2.831 A, which may indicate an attractive interaction between the phosphorus atoms. Molecular orbital calculations on the [Fe2(CO),(p-PF2)2]series indicate positive overlap populat i o n ~ . In ~ ~the modified ligands, the cyclobutene rings are joined by a short C-C bond of 1.44 (1) A. Similar short connecting bonds are observed in related compounds in the series. The cyclobutene C = C bond distances are 1.35 (1) and 1.371 (1) A. The I9F N M R spectrum of V shows the expected four sets of multiplets (CF2 groups), and the 31Pspectrum consists of two doublets (J(P,P) = 135.1 Hz). Crystal Structure of VI. A perspective view is given in Figure 2. Again a diphenylphosphino group has been cleaved from the starting ligand C and bridges the two iron atoms. However, in this case the remaining fragment bridges the iron atoms in such a way that the phosphorus atom is coordinated
r
(31) Clegg, W. Inorg. Chem. 1976, 15, 1609 and references quoted therein. (32) Burdett, J. K. J . Chem. SOC.,Dalton Trans. 1977, 423.
to one iron atom and the residual cyclobutene group is u bonded to the other. The iron-iron bond of 2.791 (6) A is longer than that found in the isomer V. The bridging diphenylphosphino group is symmetrically bound with Fe( 1)P ( l ) = 2.197 (9) and Fe(2)-P(1) = 2.206 (8) A, which is slightly shorter than that found in V. The Fe(2)-P(2) distance is longer at 2.274 (8) A. Carbonyl groups on both iron atoms are in a mer arrangement in contrast to the fac distribution in V. This accounts for the marked difference in the infrared spectra of V and VI. The C-C bond joining the cyclobutene rings in VI is 1S O (3) A compared with 1.44 (1) in V, and the C=C bond distances are 1.38 (3) and 1.22 (3) A, respectively. The last distance is unusually short, but the precision in the lengths is not great because of the poor quality of the data. This probably accounts for the unreasonably short C(20)-C(21) single-bond length of 1.37 (4) A. The spectroscopic data reported in Table I1 are in accord with the structure of VI. As mentioned in the Introduction there are a number of instances of cleavage of a (C6H&P moiety from (C6H&PR, where R = C6H5,upon complex formations. Less well-known are compounds in which (C6H5)2Pgroups are cleaved from phosphines, (C6H5)$'R, in which R is an alkyl or aryl group. Carty and co-workersZ3have reported a compound similar to VI from the reaction of (C6H5)2PC*C6H5 with Fe2(C0)9 under mild conditions. The product has the structure
.
I
(CO),FeP(C6H5)2Fe(CO)3C=tCF3 so that the displaced fluorocarbon group is u bonded to one iron atom and qz bonded to the other. A related phosphinoacetylene (C&,)2P=CF3 reacts with iron carbonyls to give products in which the (C6H&P group from one ligand is cleaved and acts in a bridging capacity. The cleaved fluorocarbon group then combines with an intact ( C 6 H 5 ) 2 P G C C F 3ligand to afford complexes E and F. This type of reaction is also seen in G,
\ E
G
\
-7CF3
Cobbledick et al.
192 Inorganic Chemistry, Vol. 20, No. 1, 1981 Table IV (a) Bond Distances (A) for V 1.135 (9) C(17)-C(18) 1.837 (7) C(27)-C(28) 1.821 (7) C(27)-C(32) 1.817 (7) C(28)-C(29) 1.812 (7) C(29)-C(30) 1.36 (1) C( 30)-C(3 1) 1.39 (1) C(3 1)-C(32) 1.41 (1) C( 19)-C(20) 1.35 (1) C( 19)-C(22) 1.34 (1) C(2O)-C(21) 1.40 (1) C(21 tC(22) 1.39 (1) C(22)-C(23) 1.39 (1) C(23)-C(24) 1.39 (1) C(23)-C(26) 1.38 (1) C(24)-C(25) 1.37 (1) C(25)-C(16)
2.604 (2) 2.239 (3) 2.197 (2) 2.219 (3) 2.241 (2) 1.811 (9) 1.78 (1) 1.78 (1) 1.79 (1) 1.79 (1) 1.77 (1) 1.115 (9) 1.148 (9) 1.143 (9) 1.133 (9) 1.148 (9) Fe(2)-Fe(l)-P(l) Fe(2)-Fe(l)-P(2) Fe(2)-Fe(l)-C(l) Fe(2)-Fe( 1)-C(2) Fe(2)-Fe(l)-C(3) P(l)-Fe(l )-P(2) P(l)-Fe(l)-C(l) P(l)-Fe(l)-C(2) P(lbFe(l)-C(3) P(2)-Fe(l)-C(1) P(2)-Fe(l )-C(2) P(2)-Fe( 11-433) C(l)-Fe( 1)-C(2) C(l)-Fe(l)-C(3) C(2)-Fe(l )-C(3) Fe(1 )-Fe(2)-P(l) Fe( l)-Fe(2)-P(2) Fe(1 )-Fe(2)-C(4) Fe(l)-Fe(Z)-C(S) Fe( 1)-Fe(2)-C(6) P(l )-Fe(2)-P(2) P( 1)-Fe(2)-C(4) P(l )-Fe(2)4(5) P(l)-Fe(2)
