A (C6H5)2C2--PF3-(
CsH5)3P-Rhz
Inorganic Chemistry, Vol. 15, No. 1, 1976 97
Derivative
(29) M. F. Farona, P. A. Lofgren, and P. S. Woon, J . Chem. SOC.,Chem. Commun., 246 ( 1 974). (30) M. A. Bennett, R. N. Johnson, G. B. Robertson, T. W. Turney, and P. 0.Whimp. Inorg. Chem., 15, 97 (1976). (31) (a) R. W. Kiser, M. A. Krassoi, and R. J . Clark, J . Am. Chem. Soc., 89,3654 (1967); (b) R. E. Sullivan and R. W. Kiser, Chem. Commun., 1425 (1968); (c) R. W. Kiser, M. A. Krassoi, and R. J. Clark, quoted by R. W. Kiser in “Characterization of Organometallic Compounds”, M. Tsutsui, Ed., Interscience, New York, N.Y., 1969, Part I , p 197. (32) J. Lewis and B. F. G. Johnson, Acc. Chem. Res., 1, 245 (1968). (33) R. K. Harris, Can. J . Chem., 42, 2275 (1964). (34) G. Cetini, 0.Gambino, P. L. Stanghellini, and G. A Vaglio, Inorg. Chem., 6, 1225 (1967). (35) F. A. Cotton, L. Kruczynski, B. L. Shapiro, and L. F. Johnson, J . Am. Chem. SOC.,94, 6191 (1972). (36) J. G.Bullitt, F. A. Cotton, and T. J. Marks, Inorg. Chem., 11,671 (1972); 0 . A. Gansow, A. R. Burke, and W. D. Vernon. J . Am. Chem. Soc., 94, 2550 (1972). (37) . , R. D. Adams and F. A. Cotton. J . Am. Chem. Soc., 94. 6193 (1972); 95, 6589 (1973); Inorg. Chem., 13, 249 (1974). (38) Noise decoupling approximates a rate process: R. R. Ernst, J . Chem. Phys., 45, 3845 (1966). However it remains constant over the set of measurements, as is evident from the similar widths at half peak heights for the low- and high-temperature extremes, and it is nearly complete, as shown by the observed lorentzian line shapes. The broadness arising from incomplete decoupling can therefore be included in a constant T2
which we use here to account for contributions to line width apart from the rate process under investigation. (39) We discuss the barrier to exchange in terms of AC* rather than the enthalpy of activation, H , or the activation energy, Ea,calculated from the Arrhenius equation. Although there is not a strict 1:l correspondence, any errors should be common to all of the data and it is the differences which are significant. (40) R. D. Adam and F. A. Cotton, Inorg. Chim. Acta, 7 , 153 (1973); R. D. Adams, D. E. Collins, and F. A. Cotton, J . Am. Chem. Soc., 96, 749 ( 1 974).
(41) j : P. jesson and P. Meakin, J . Am. Chem. Soc., 96, 5760 (1974). (42) R. S. Berry, J . Chem. Phys., 32, 933 (1960). (43) I. Ugi, D. Marguarding, H. Klusacek, P. Gillespie, and F. Ramirez, Ace. Chem. Res., 4, 288 (1971). (44) L. Kruczynski, L. K. K. Li Shing Man, and J. Takats, J . Am. Chem. SOC.,96, 4006 (1974); S. T. Wilson, N. J. Coville, J. R. Shapley, and J. A. Osborn, ibid., 96, 4038 (1974). (45) L. Kruczynski and,!. Takats, J . Am. Chem. Soc., 96, 932 (1974). (46) C. G. Kreiter, S. Stuber, and L. Wackerle, J . Orgunomet. Chem., 66, C49 (1974). (47) G. Rigatti, G. Boccalon, A. Ceccon, and G. Giacometti, J . Chem. SOC. Chem. Commun., 1165 (1972). (48) J. D. Warren and R. J . Clark, Inorg. Chem., 9, 373 (1970). (49) J. D. Warren, M. A. Busch, and R. J . Clark, Inorg. Chem., 11,452 (1972). (50) M. A. Bennett, R. N. Johnson, and T. W. Turney, Inorg Chem., 15, 1 1 1 (1976).
Contribution from the Research School of Chemistry, The Australian National University, Canberra, A.C.T. 2600, Australia
Correlated Intermolecular and Intramolecular Ligand Exchange in p-Acetylene-bis(1igand)tetrakis(trifluorophosphine)dirhodium Complexes and the Crystal and Molecular Structure of the Diphenylacetylene-Triphenylphosphine Derivative Rh2(PF3) 4 [P(C6Hs) 31 2(C6H5C2C6%)-(C2%) 2 0 M. A. BENNETT,* R. N . J O H N S O N , G . B. ROBERTSON, T. W. T U R N E Y , and P. 0. W H I M P
Received June 3, I975
AIC50379S
The acetylene complexes Rhz(PF3)6(ac) (ac = CsHsC2C6H5, CsH5C2CH3, or ~ - N O ~ C ~ H ~ C ~ C Oreact ~ C with ~HS) monodentate tertiary phosphines and arsines (L) to give disubstitution products Rh2(PF3)4Lz(ac) and with ophenylenebis(dimethylarsine), G - C ~ H ~ [ A S ( C H (diars), ~ ) ~ ] ~ to give Rh2(PF3)z(diars)2(ac) (ac = CsHsCzCsHs or CsHsCzCH3). The reaction with monodentate ligands is reversed by the action of PF3. The crystal and molecular structure of the diphenylacetylene-bis(tripheny1phosphine) derivative [L = P(C6H5)); ac = CsHsCzC6Hs] has been determined by three-dimensional X-ray structural analysis using 6834 independent reflections, with I / u ( I ) 2 3.0, collected by counter methods. The complex crystallizes in the triclinic space group Pi (GI, No. 2) with a = 21.186 (9) A, b = 12.994 (5) A, c = 12.942 ( 5 ) A, CY = 114.10 ( 2 ) O , p = 64.36 (2)”, y = 115.33 (2)O, and 2 = 2. The structure was solved by conventional heavy-atom methods and was refined by block-diagonal least-squares methods to final weighted and unweighted R factors of 0.046 and 0.042, respectively. The molecule is structurally similar to cobalt-carbonyl-acetylene complexes such as C02(C0)6(y-C6H5C2C6HS) and consists of two [Rh(PF3)2[P(C6H5)3]] moieties bridged by diphenylacetylene, the C=C bond of which is above and approximately normal to the Rh-Rh axis. The triphenylphosphine groups are on the same side of the molecule as the bridging acetylene, and the Rh-Rh distance [2.740 (1) A] is in the range expected for a rhodium-rhodium single bond. The 19F N M R spectra of the disubstitution products containing unsymmetrical acetylenes, Rh2(PF3)4L2(RC2R1), show signals due to PF3 groups in two different environments a t or just below room temperature, but on raising the temperature intramolecular PF3 exchange takes place. This process appears to be initiated by dissociation of the tertiary phosphine or arsine (L). The free energies of activation, A G , for the intramolecular process have been estimated by approximate line shape analysis of the 19F N M R spectra and are higher for the tertiary phosphine than for the tertiary arsine derivatives. In the one case studied, the electron-withdrawing acetylene ethyl p-nitrophenylpropiolate gives rise to a higher AG* than either diphenylacetylene or 1-phenylpropyne. Possible mechanisms involving the fluxional behavior of a coordinately unsaturated intermediate are discussed. A 1: 1 mixture of R ~ ~ ( P F ~ ) ~ [ A s ( C H ~ ) ( C ~ H~)~]Z(C~I-I~C and ~ CRh2(PF3)6(C6H5C2CH3) H~) undergoes intermolecular PF3 exchange in the temperature range 50-82’, The diars derivatives Rhz(PF3)z(diars)z(ac) perhaps via a pentakis intermediate R~~(PF~)S[A~(CH~)(C~H~)~](C~H~C~CH~). show temperature-independent IH and 19F N M R spectra in the range -9OO to room temperature, but their structure could not be determined unambiguously.
Introduction In the previous paper,’ we showed that octakis(trifluorophosphine)dirhodium, Rhz(PF3)s, reacts with a variety of acetylenes (ac) to give bridging acetylene complexes Rh2(PF3)6(ac), the PF3 groups of which undergo rapid intramolecular exchange at room temperature. The preparation of tertiary phosphine and arsine substitution products was
undertaken in order to obtain crystalline derivatives suitable for X-ray structural analysis. It was also hoped that a study of their variable-temperature 19F NMR spectra would assist in determining the mechanism of intramolecular exchange in the parent compounds. This paper reports the preparation and ligand-exchangebehavior of the substitution products, together with a single-crystal X-ray analysis of the diphenylacetyl-
98 Inorganic Chemistry, Val. 15, No. I, 1976
Bennett et al.
Table I. Elemental Analvses and Melting Points % calcd Compda
Mp,”C
C
ene-bis(tripheny1phosphine) derivative, Rh2(PF3)4[P(C6H~)~]~(C~H~CZC~H~).(CZHS)~O. A preliminary account of the structure analysis has appeared elsewhere.2 Experimental Section Experimental, spectroscopic, and line-shape fitting procedures are as previously described.’ Analytical data and melting points are in Table I. The following preparations are representative of the procedures used. ~-Diphenylacetylene-bis(triphenylphosphine)tetrakis( trifluorophosphine)dirhodium(O)(Rh-Rh) Monoetherate, Rh2(PF3)4[P(C~HS)~]Z(C~HSC~C~H~).(C~H~)~O. A solution of Rhz(PF3)6(C6HsCzCsHs) (0.09 8)’ in diethyl ether (5 ml) was treated with triphenylphosphine (0.20 g, excess). After 1-2 min the solution was filtered to remove undissolved ligand. After 30 min the filtrate had turned dark red and, on keeping a t -5O, slowly deposited burgundy-colored crystals. These were collected and dried in vacuo to give 0.06 g (46%) of the required product. The unsolvated complex was obtained by carrying out the reaction in n-pentane. p 1-Phenylpropyne-bis(diphenylmethylarsine)tetrakis( trifluoro-
H
P
% found Other
c
€I
P
Other
Table 11. Crystal Data for Rh,(PF,), [ P(c6 HS), l,(C6HsC, C6Hs).(C, H,),OQ a = 21.186 (9) Abic a = 114.10 (2)” b = 12.994 (5) A p = 64.36 (2)” c = 12.942 (5) A y = 115.33 (2)” Crystal color deep red Formula C,,H,,F, ,P6 Rh, -(C,H5),0 Mol wt 1334.6 Cell vol 2792.2 A 3 Pcalcd = 1.59 g cm-3 Pobsd = 1 5 7 (j) g miSpace group P 1 (Ci’ , No. 2) Z = 2 Crystal dimensions 0.030 X p(Cu Ka) = 71.45 cin-l 0.007 X 0,010 cmd I
’
Cell dimensions were measured at 20 t 1°C. Estimated standard deviations (in parentheses) in this and the following tables, and also in the text, refer to the least significant digit(s) in each case. The “reduced” cell, obtained from a Delaunay reduction [ B. Delaunay, Z . Kristallogr., Kristallgeom., Kristallphys., Kristallchem., 84, 109 (1933)] isa‘ = 12.994 A, b‘=19.470A,~’=12.942~,a’=101.18”,~’=114.10~,y’= 101.19*, cell volume 2792.2 A,. Crystal dimensions are parallel to a * , b*, and c*, respectively.
Table 111. Details of X-Ray Data Collection phosphine)dirhodium(O)(Rh-Rh), R~~(PF~)~[As(CH~)(C~HS)~]~-
( C H ~ C ~ C ~ HDiphenylmethylarsine S). (0.30 g, excess) in n-pentane Radiation Cu Ka (10 ml) was added to a solution of Rh2(PF3)6(CH3C2C6&) (0.21 Wavelength 1.5418 A Monochromator Graphite crystal g) in n-pentane (15 ml) under nitrogen. The solution rapidly turned 3.0” Tube takeoff angle dark red and, after a small amount of flocculent buff precipitate had 28.5 cm Crystal to counter distance been filtered off, was kept at -10’ for 2 days. The burgundy-colored Scan technique 6-26 scans crystals were washed with three IO-ml portions of n-pentane and dried 2”/min Scan speed in vacuo to give 0.18 g (63%) of the required product. Scan width From 0.95” below the Cu K a , Collection and Reduction of X-Ray Intensity Data. Approximate maximum to 0.95” above the unit cell dimensions for crystals of R ~ ~ ( P F ~ ) ~ [ P ( C ~ H S ) ~ I ~ ( C ~ H ~ Cu K a , maxiyum of each peak C2C6Hs).(C2Hs)20 were obtained from preliminary Weissenberg (Okl, Scan range limits 3” G 26 G 125 l k l d a t a ) and precession (h01,hll, hkO, hkl data) photographs which Total background counting 20 sec showed no evidence of diffraction symmetry higher than Ci (1). The timeQ choice of the centrosymmetric triclinic space group Pf (Ci’, No. 2) “Standard” reflection (0541, (803), (065) has been confirmed by the successful solution and refinement of the indicesb structure. Crystal stability 7% isotIopjc decay The crystal chosen for data collection was transferred to a Picker Form of data collected hkl, hkl, hkl, hkl FACS-I fully automatic four-circle diffractometer, and was aligned Total data collected 9929 with the crystal a axis and the instrumental 9 axis approximately No. with Z/o(Z) > 3.0 6834 coincidental. Accurate cell dimensions and crystal orientation matrix, No. wlth I / o ( l ) > 6.0 5765 together with their estimated standard errors, were obtained from a Backgrounds were counted on either “side” of each the least-squares refinement3 of the 28, w , x, and @ values obtained reflection (10 sec each side) at the scan width limits and were for 12 carefully centered high-angle reflections (28 > 83’). Full details assumed to be linear between these two points. The three of the crystal data are listed in Table 11. “standard” reflections were monitored after each 40 Details of the experimental conditions and data collection methods measurements throughout data collection. used are outlined in Table 111. During data collection, the intensities 6834 reflections of the terminal data set was 0.026. of the three “standard” reflections showed a regular, time-dependent To conserve computing time, the structure was initially solved and decrease of 7%. Crystal decomposition was assumed to be isotropic refined using data for which I / u ( I ) 2 6.0 (5765 reflections). and independent of 28; before further calculation the intensity data Solution and Refinement of the Structure. A three-dimensional were corrected accordingly. Patterson map showed the positions of the two rhodium atoms and Reflection intensities were reduced to values of IFol.4 and each the six phosphorus atoms. The remaining atoms of the molecule were reflection was assigned an individual estimated standard deviation located from successive difference Fourier syntheses. The structure [o(F0)].4 For this data set, the instrumental “uncertainty” factor ( p ) 5 was refined by block-diagonal least-squares methods to final unwas assigned a value of 0.001112. Reflection data were sorted, weighted and weighted R factors of 0.042 ( R ) and 0.046 ( R w ) , equivalent reflections were averaged, reflections with I / u ( I ) < 3.0 respectively. Atomic scattering factors for the nonhydrogen atoms were discarded as being unobserved,4 and those reflections for which were taken from ref 6; those for Rh, P, and F were corrected for the the individual background measurements differed significantly (Le., real and imaginary parts of anomalous scattering.’.g t4.00)4 were also discarded. The statistical R factor (Rs)4 for the
Inorganic Chemistry, Vol. 15, No. I, 1976 99
A (CsHs)2C2-PF3-(C6H5)3P-Rh2Derivative Table IV. Details of Least-Squares Refinement Set no.
Conditions
1 2
All atoms isotropic; hydrogen atoms not included; q u a l (unit) weights At this stage, reflection data were corrected for absorption effectsb All atoms isotropic; hydrogen atoms not included; individual weightsC were used in these and all subsequent cycles All atoms anisotropic;d hydrogen atoms not included All nonhydrogen atoms anisotropic; fixed isotropic hydrogen atom contributions included
3 4
No. of reflections I/aQ 5765 6.0 6834 3.0 6834 6834
3.0 3.0
No. of cycles 3 6
0.091 0.091
Rw 0.099 0.112
6 6
0.051 0.042
0.060 0.046
Ra
a R = CllFoI- IFcll/cIFoIand R , = {XW[IFoI- IFc1]2/~w/Fo12}1’2, where IFolis the observed and iFclis the calculated structure factor and w is the weight. The function minimized throughout the least-squares process was Zw(lFoi - lFc1)2. A grid of 20 X 6 X 8 Points Individual (parallel to a*, b*, and c*, respectively was used. The transmission factor (applied to lFoiz) ranged from 0.406 to 0.723. weights were of the form lo(F,)1-2. )The anisotropic temperature factor takes the form exp[-@,,h2 + PZ2k2+ Pno12 + 2pI2hk + 2p13hl +
When fixed phenyl hydrogen atom contributions were included in the scattering model, it was assumed that the C-H distances were 1.087 A. The phenyl hydrogen atoms were assigned fixed isotropic temperature factors 10% greater than the equivalent isotropic temperature factor of the carbon atoms to which they were bonded (Le., BH = 1.1Bc&). The hydrogen atom coordinates and temperature factors were recalculated prior to each refinement cycle. Scattering factors for hydrogen atoms were taken from the tabulation of Stewart et a1.9 No attempt was made to include the hydrogen atoms of the solvent ether molecule in the scattering model. A full account of the course of refinement is given in Table IV. On the final refinement cycle, no individual parameter shift was greater than 0.1 of the corresponding parameter esd (estimated standard deviations derive from inversion of the block-diagonal matrices). A final electron density difference map showed no unusual features, and there were no positive maxima greater than 0.4 e/A3. The standard deviation of an observation of unit weight, defined as [Cw(lFol- IFc1)2/(rn- n)]l/2 [where m is the number of observations and n (=676) is the number of parameters varied], is 1.72; cf. a value of 1.O expected for ideal weighting. An examination of FO and FC shows no evidence of serious extinction effects, and there is no serious dependence of the minimized function on either IF01 or A-1 sin 6. Final atomic positional and thermal parameters, together with their estimated standard deviations (where appropriate), are listed in Tables Va and Vb. A listing of observed and calculated structure factor amplitudes [XlO (electrons)] is available (see the paragraph a t the end of paper regarding supplementary material). Computer Programs. The data reduction (SETUP), sorting (SORTIE), Fourier (ANUFOR), block-diagonal least-squares (BLKLSO), and absorption correction (ACACA) programs have been described elsewhere.10 The figures were produced using O R T E P . ~ All ~ calculations were carried out on the CDC3600 computer of the CSIRO Division of Computing Research, Canberra, and the Univac-1108 computer of The Australian National University Computer Centre.
Results and Discussion Chemistry. The acetylene complexes Rh2(PF3)6(ac) (ac = C6H5C2C6H5, C ~ H S C ~ C H or ~p-NO2C6H4CzCO2C2Hs) , react with tertiary phosphines or arsines (L) at room temperature to give red, crystalline disubstitution products Rhz(PF3)4Lz(ac), while with the bidentate ligand ophenylenebis(dimethylarsine), o-C6H4[As(CH3)2]2 (diars), red disubstitution products Rh2(PF3)2(diars)z(ac) (ac = C6HsC2C6H5 or C6H5C2CH3) are obtained. The reaction seems to be general, but only those complexes containing arylacetylenesand diaryl-substitutedligands could be isolated. Although the complex with ac = CH3C2CH3 and L = P(C6H5)3 was identified by NMR spectroscopy, derivatives containing dialkylacetylenes or dimethylphenylphosphine were not obtained in a pure state and have not been studied further. The substitution reactions are similar to those of the analogous Coz(CO)6(ac) complexes but occur even more readily; e.g., the formation of mono- and bis(tripheny1phosphine) derivatives from Co2(C0)6(C6H5C2C6Hs) is reported to require heating to 70O.12 We have been unable to isolate monosubstitution products such as Rh2(PF3)5[P(C6H5)3](C6H5C2C6H5),although analogous Co2(C0)5 complexes are known.123’3
Figure 1. Overall stereochemistry of one molecule of Rh2(PF3), [P(C,H,),], (C,HSC2C,HS), together with the atomnumbering scheme.
Reaction of Rh2(PF3)6(C6HsC2C6H5) with 1 equiv of triphenylphosphine gives the bis(1igand) derivative as the only isolable product, and there is no evidence for the presence of the monosubstitution product in a 1:l mixture of Rh2(PF3)6(C6&C2C6Hs) and Rh2(PF3)4[P(C6Hs)3]2(c6H5c2CsHs). However, the derivative Rhz(PF3)s [As(CH3)((26H5)2](C6H5C2CH3) may be present in a 1:l mixture of R~~(PF~)~[AS(CH~)(C~H~)~]~(C~H~C~CH~) and Rh2(PF3)6(C6H5C2CH3) above 50’ (see below). Description of the Structure of Rh2(PF3)4[P(C6H5)3]2(C6HsC2C6Hs).(C2H5)20. The crystal structure, as defined by the unit cell dimensions, symmetry operations, and atom coordinates of Tables Va and Vb, consists of discrete monomeric molecular units which have approximate C2 symmetry about an axis through the midpoints of both the acetylene and rhodium-rhodium bonds. The molecule consists of two Rh(PF3)2[P(C6H5)3] moieties bridged by a diphenylacetylene molecule, the C=C bond of which is above and approximately normal to the Rh-Rh axis. The atom numbering scheme is shown in Figure 1, and a perspective view of the molecule is shown by the stereopairs of Figure 2. The contents of one unit cell are shown by the stereopairs of Figure 3. In each of these figures, the thermal ellipsoids (where shown) have been drawn to include 50% of the probability distribution, and, for clarity, the hydrogen atoms have been omitted. Principal bond distances and interbond angles, together with their estimated standard deviations, are listed in Table VI, while bond distances and angles within the six triphenyl-
Bennett et al.
100 Inorganic Chemistry, Vol. 15, No. 1, 1976
Figiue 2. Stereoscopic view of the molecule.
C
B
B
Figure 3. Stereoscopic view of the contents of one unit cell. Only the thermal ellipsoids for the solvent molecule have been drawn to include 50% of the probability distribution. The sequence of atoms in the solvent molecule is C(lS)-C(2S)-O(lS)-C(3S)-C(4S).
phosphine phenyl rings are listed in Table VII. The results of weighted least-squares planes calculations14 are collected in Table VIII, and some important torsion angles are listed in Table IX. Many features of the geometry of the Rhl(PF3)4[P(C6Hs)3] 2(C6H5C2C6H5) molecule are similar to those observed for the cobalt carbonyl derivatives Co2(C0)6(C6H5C2C6H5),15 C02(C0)6(C6F6)i6 (C6F6 = hexafluoro-l-en-3-yne), and related molecules.~7-20 Thus, the angles Rh-Rh-P(triphenylphosphine) average 148.7', compared with an average value of 148.1" found for the two corresponding Co-Co-C angles in Co2(C0)6(C6F6)16 (i.e., the Co-C0-C angles on the same "side" of the molecule as the bridging diphenylacetylene group). In contrast, the Rh-Rh-P(PF3) angles average 104.5'; cf. 100.3' (average) for the corresponding Co-Co-C angles in C02(C0)6(C6F6)~~ and an average value of 101" for those of Coz(C0)6(C6H5C2C6H5).i5 The acetylenic carbon-carbon distance in the bridging diphenylacetylene group [C(l)-C(2) = 1.369 (7) A] is significantly longer than that expected for free acetylenes [ 1.206 (5) A],21 and it is also longer than the distance found for acetylenes which are coordinated to only one metal atom (ca. 1.29 A).22 The present distance is, however, in excellent
agreement with that observed for C O ~ ( C ~ ) ~ ( C ~ H S C ~ C ~ H ~ which was originally reported as 1.46 A15 but was subsequently refined to 1.369 A.23 A similar distance [1.36 (3) A] has also been found for the bridging carbon-carbon bond length in C02(C0)6(C6F6).16 The angles C(2)-C(l)-C(ll) and C(l)-C(2)-C(21) [141.1 (5) and 141.5 (5)', respectively] are equal within experimental error ( 3 . 0 ~ )but are significantly different from the value of 180" normally expected for the C s C - C angle in "free" acetylenes. Surprisingly the present bond angles do not differ appreciably from those in P ~ [ P ( C ~ H ~ ) ~ ] ~ ( C ~ H ~ C Z C [average 14l0]24 despite the fact that the CGC distance in the present complex is ca. 0.05 A greater than that in the Pt(0) derivative [1.32 (9) The distances C(l)-C(ll) and C(2)-C(21) [1.459 (7) and 1.460 (7) A, respectively] are equal within experimental error and are similar to the value of 1.46 A expected for carboncarbon single bonds between sp2 and sp (approaching sp2) hybridized atoms.25 Within the two phenyl rings of the diphenylacetylene moiety, the bond lengths and bond angles appear normal and average 1.388 8, and 120.0°, respectively. The dihedral angle between these two phenyl rings is 42.1O . The distances Rh(1)-C(l) and Rh(2)-C(2) [2.097 (5) and
a]?
A (C~HS)ZC~-PF~--(C~HS)~P-R~~ Derivative
Inorganic Chemistry, Vol. 15, No. 1, 1976 101
Table Va. Refined Atomic Positional and Thermal Parameters for Rh,(PF,),[P(C,H,),],(C,H,C,C,H,).(C,H,),O ATOH
2
I
I
BElLI1
BE1122
11L1133
Ut1123
8f.lAI1
BE1112
0.001VVIIl O.OO189III
0~00b12111
0.00bULll3I
0.001iOI2I
-0.u0114121
0.U00850I
0~0377801
0.00522131
0~U0bV013l
0.00109lIl
'0.0014lIZl
0.000781ll
-0.2Yb33112I
0.187591I2l
0.002bbI51
OtUObb4lIII
O.U07*9II2I
0~U014bIbl
-U.00154lbI
U.001561Vl
-0.O338SIlYI
0~3085hI1YI
O.OO2b5ISl
o.oioqqiisi
O.OO8rolIII
C.OOZ13I7I
-0.00U5017I
0.00281112I
O.OY377I111
0.2Vb93lI31
0~001Ob151
0.008551I3I
0.0079OI13l
0.00143I7I
-0.0023117l
U.00102IIII
0.1217b11Il
.0*153081121 0.13521l141
0.00212I4I
O.OO5941I1I
u.007571121
0.00122151
-0.00133Ib)
0.0013519l
0.00298151
C*OO7bbI131
0.00970111I
O.UO249I7I
-0.DOUb9I7I
0.001b011II
0.08I38IIYI
n.0027*151
0.00730I131
O.UIO5I115l
0~000*01bI
-0.00280l7I
U.00217111I
0,31bb11I
O.0024I II
0.0151151
0.02191bI
0.001hl2l
-0.00U2121
0.0094111
0.044UI4l
0*3080l4 I
0.0042 I2 I
0.0184l5l
OtU22Zlbl
0.00b0 I2 I
0.008715 I
0*441813l
0.0057 121
0.014518 I
0.0073 111
O.OO8bIYI
0.259201
0.0018l4l
01404313l
0~007312l
0*017115l
0.0131l*l
0.2723121
0.171401
0.310101
0.005h121
0.0089IJI
010135141
0.0025 121
Fl1231
0.358bI21
0.0h9b13I
0.2552131
0.0028l1l
0.0151141
0.0155151
0.001 b l 2 l
-0.001bIZl
0.00131*l
FIIIII ritizi
0.1705l21
0*2b1913I
0*2b93l3l
0.0050l2 I
0.0150l51
0.0107l41
0.004712l
-0.0019l2I
-0.00J9Ol
0.0999 I2 I
0.1483131
01 1 4 4 5 1 3 1
0.00281 I I
O.OI7~151
O.O151l*l
0.004 1 I 2 I
.0.0013121
F12131
0.1949Ol
0.3121141
0*102bl41
n.0074121
0.0155151
0 . 0 2 5 V I 11
0 . 0 0 8 U I 11
r12zi1
0.3b28Ol
0.36501 31
0.12871bl
0.00bb12I
O.OOb2I3I
0.04l2llOl
0.00121 2 1
FIZZZI
0.3921131
0.2311014I
O.Ib5315l
0.008213I
0.0228 I 7 I
0.031218I
-0.00b9I31
-O.oI3*IYl
0.01111bI
r1?231
0.434l121
-0*01b414I
O~OOZbI1l
0.021llbl
O.Ol85lbl
-0.0012121
-0.0021121
0.00591 51
C I I I
0.201 7 1 1 1
0.258OI 4 I -O.O98YIYI
0.0u51 141
0.0021121
0.0056 1 4 I
0*00b219 I
0. O O O S l 2 I
-0.0013121
O.OOO8I 3 1
CI2I
0.2729131
-0.Oh9914I
-0*00bOI41
0.002212l
0.0058 I 4 I
O*OObl I 4 I
0 . 0 0 0 9 I 21
-0*001212l
0.001bl3l
-0.002JI2I
0.001b1~1
0.17477131
9YIII
0.20705121
-0.0557813l
RHIZI
0.2b029121
0.095h20l
*lIOl
O.18bh4L8I
* I l l 1
0.1002218I
PI121
0.27408181
Pl2Ol
0.292b501
Pl2II
0.1823118l
0~2OtOOlI3I
PI2Zl
0.35892181
0.23b4h1131
riiiii
0.029*12I
-0.1418I4l
riiiii
0.Ob28121
riii3i
0.0905
FIIZII f I1221
Ill
0.001 b l 3 I
-0~000b131
0.Oi01151
D l 001 I I'I I
-0.U0u112l
0.0Ob51+ I
-0.00hb131 -0*0046I2I
-0.003bI3I
0.00351* I
0.0041 Ill
0.0119t51 -0.002915I
-0.011011l
C I I I I
0.14u2131
-0*15b3I4l
-0.059114l
O.OO2bI2I
0.0055lYI
0.UO79l51
O.OOObI
Cl121
0.0743131
-0.Ib5OI5l
-0.0019l51
0.0023121
0.007715 I
0.009415l
0.00101 21
-O~OOPOOl
0.00191 4 1
CI13l
0.023h13l
-0.22b7I5l
-0*Ob501hI
0.0029 I 2 I
0.01021bl
0,0133171
0.0008131
-0.0032l3l
0.0033151
CIIYI
0.04b9l1l
-0.2787151
-0*18511bl
0*0039l3I
0.U1051bl
0.01Yll8l
0*0002131
-0~0051lYl
O.OO29IbI
C115l
0.120bl4 I
-0.270OlII
-0.244515l
0.004b I 3 I
0.00831bI
O.OOl3lbl
o.uoIu13l
-0.0018IJI
0*0002151
CIIbl
0.1709I3l
-0.2098l41
-0.181215l
0.0032121
0.0070151
0.0073 I 5 I
0.001313 I
'0.0020131
0.0010111
Cl21l
0.3322131
-0*1232l41
-0~0735141
0.0028121
0.OOb71YI
0.00b814 I
0*0025l
PI
-0.000b12:
o.ooi
c1221
0.1041111
-0.0598151
-0*Ob7bl5l
0.002512 I
0.01011bI
0~01071bI
0.0020l31
-0.0014I3I
o.oozvl51
-0.0007131
O.OO33lbI
0.00001
0.00*1l7I
21
aiqi
Cl231
0.4594l3l
-0.11111bI
-0rnl292Ibl
0.0027121
0.0l44181
0.0IIIl7I
0.0037 1 3 1
CI24I
0.4**819l
-0a227hIbl
-0aI987lbI
0.0045131
O a U 1 b 0 I8 I
0.01 29 I8 I
0.00b1l41
C125l
0.3747141
-0-2922151
-0*2050Ihl
0.00531 31
0.00951 b I
0~0109l71
0.004bI~l
.0.00151*l
0.0000151
ClZbl
0.318501
-0.2401151
-0.1433l51
0.0034121
0.0080151
0.0077l51
0.002713I
-0.0009I3I
0.0010l41
C I I I I I
0.2blb131
-0.2703151
0.2005151
010034121
0.0078151
0.0025131
-0.OO2OIII
0.001 21'41
Cl1121
0+133701
-0.2108I5l
0~14b7151
0.0035 I2 I
0.0107Ibl
0.0082 I5 I 0~01091h I
0.0031 13 I
-0~0021131
0.001 1I 5I
Cl1131
0.39
-0.2159161
0.1959lh I
0.0031131
0.011418l
0.0140181
0 . 0 0 ~ 0 1 4I
-0.0023l41
0.00291 b l
C I I I Y I
0.378511l
-0.32OIIbl
0*l944lbl
0.0052 I3 1
0*01b119l
O.OI11l8I
0.L1059l 4 I
-0.003b1'41
0 . 0 0 0 8 Ib l
C11151
0.309 I I 4 I
-0.3809Ibl
0.24571bl
0100b71*l
0.0124171
0.013b181
0.00531~l
-0.0043l41
O*UO23IbI
C111b1
0.2181141
-0
0.2507 I 6 I
0.005213I
0.01071bI
0~012417l
-0.0037IYI
0.0031151
CI121l
0.1b57l1l
-0.3712141
O*Oh1114I
0.0027 I2 I
0.001b141
0.007315l
0.0029l 4 1 0.001lIZl
-?.001313l
0.001714l
Cl1221
0.l102131
-0.3807151
0.0230l51
O.OO32t2l
0.OOb915l
0.0091 I b I
0.00061 3 1
-0~0022131
0.0028I4I
C1123l
0.093YI 4 I
-0.4724151
-0.0745161
0.0041 1 3 1
U.00941 b I
0.0111l7I
o.ooooia)
'0,00*2l~l
CI12Yl
0. I 2 9 b I Y I
-0.5557Ibl
-0*1309lhl
O~OObbl4l
0.00911bI
O l U I 09 I 7 I
0.002YI 4 I
-0.00*0141
-0.0002l51
Cl125l
0.1835l 4 I
-0.5482Ibl
-O*O9lblbl
0~00bh141
01011b171
0.0119llI
0.0047l41
.0.0019l4l
-0~00251hI
C112bI
0.2014l4 I
-0*955b151
090021 Ib I
0.004b131
O.UOPb1 b I
0*01031bI
0~002110l
-0.0010141
-0*0002l51
CII31I
0. I105lJl
-0.2891151
0.3155l5l
0.003912I
0.0083151
0 * D O 8 0 I5 1
0.0021 1 3 1
-0.0011131
0.0025l41
C1132l
o.o*aiiYi
-0.385bIbl
0*3043Ibl
O.OOYbOI
0~010bl71
0*00991bI
0.000 II'I I
-0.0013141
0.0028 I 5 I
Cl1331
-0.00931Yl
-0.YlO917l
0.4058 I 6 I
0.00501 3 I
0.0198191
0.011201
-0.00lII4l
-0.0004141
0.00V7 I 7 I
C113YI
-0~OObOIYI
-0.3432171
0.5171lbl
0.00hOlYI
O.Ul5119l
0.0115181
D.OO2V15I
c11151
0.055415l
-0.2492IbI
0.5297 I b l
0.007514l
0.012217l
0.00751 b I
0.002b I5 I
-0.001SI*l
0.0023
Clllbl
O*I127l11
-0.22341bI
0.4301l51
0.0052131
O~OIO7Ibl
0.00831bI
0.0017 II f I
-0.0018131
0.0028 I 5 I
C1211l
0~2200l31
0.1212141
-0.l932l4l
0.002bI21
O~OOb4IYl
0.00b7141
0.001512 I
-0.001b121
0.0003l41
c12121
O~I474I3l
0*0582151
-0*147915l
0.00251 21
0.007YI5 I
0.011bIbl
0.0015I3I
-0.001b13l
0.0023141
CI213I
0.093II3I
0.0476158
-0.1884Ibl
O.OO29I2 I
0.01 I2lbl
0.01351 7 1
0.0020131
-0.0028131
0.00231 b I
CI2I4l
0.11 17141
0.09971 b I
-0.27451bI
0~001313l
0.014518l
0.012Pl7 I
0.0037141
-0.00*21*1
0.00031bI
c12151
0.18251'41
0.1h47Ibl
-0.3191151
0.0049l3l
0.0139171
0.00891bl
8.00391 4 1
-0tO03lI3I
0.0015t5I
C121hl
0.2312131
0.17b2 I 5 I
-0.280b15I
0.0038121
0.01131b1
0.0078151
0.002101
-0.00I90l
0.0027151
CI22ll
0.3h29Ill
0.2h2314l
-0.1781l51
o . 0 0 2 4 121
0.00h5l4I
0 . ~ 0 8 9I 5 I
0.001UI
-0.002213l
Cl222l
0.345bI*I
0.3b7715l
-0*10b3l51
0.001711l
0.0Ob715l
0.01031bI
O.OO1011 3 1
0.002114I 0 .OD 121 5 I
C12231
0.3970I1I
C.4759151
-0.II941bl
n.OOb511I
0. no* I I5 I
0.013J18l
CI224I
0,1b57IYI
0.1801 I b I
-0.202V171
0.001501
0.0090lbl
O.OI9SlIOl
Cl225l
0~481bIYI
0.379YIbI
-0.2713I8I
0.0029121
o.01~51ni
0.U254llZI
Cl22bI
0.4301131
0.2bPb151
-0.Zb121bI
0.0030121
C.OOV7lb I
0.017419I
C1231l
0.33141JI
0.0128I*l
-0.20121151
0.0030121
0.0018 I 5 1
Cl2321
0.3038 1 4 I
-0.0478151
-0.37a8151
0.0038 1 3 1
C1231l
0.3154111
-0.12b4lbI
-0*1/b3Ibl
c12341
0.39h514 I
-0~I4251bI
-0.479YIbI
C1235l
0.4253141
-0.0849IhI
C123bl
0*3920I3l
-0~00b1151
14 I 4
I
I
357h l b I
I
21
1I
O.OOO9I+ I
'0.001bOl
0 . 0 0 J 1 151
0+005717I
I5 1
-0.0011111l
0.0023151
-0.0053151
0.00731bl
0.OOOhl4 I
-0.0018l51
U.0113l8l
0.00191 11
-O.OOObl*l
0~0070Ibl
0.0082151
0.00 I 7 I1 I
'0.0OO8131
0.00201
0.U1031bI
0.00911hI
0.002LI3I
-0.0011l31
O.OOl2l5l
0.OOhblYI
0.0123l8I
Oa0098l7I
0.004hI51
-0.0018141
0.00bhIYI
O.UIZIIBI
O.UI27181
o.uo54 I 5 1
-0.0002151
-0.3877l7l
0.0049l3l
0.0147l01
0.0148181
0.0055141
0.00051
-0.28b915l
0~003b121
O.UO9bIbl
O.OOP9l h I
0.00201I11
0.0000l31
0*00*bl5l
0.0008l3 I
'O.OPI*l3I
4 I
4 I
-0.00191bI 0.00U5 16 I
0.005917
I
01151
0~68711151
0.5b3bIhl
0. 1 1 h 9 I 7 I
0 . 0 1 20 I 5 I
0.0222110l
0.02e31l2l
-0.008*01
0.0051 I 9 I
CII5I
0.5993101
0*b3091121
0*4747112l
O.OO9Ol7I
0.0190122l
0.03Ybl2lI
.O.OO32110I
-0.01051101
0.0205l181
CIZSI
0.b17b17l
0.55b7112l
0.50881101
n.01oi171
G.0447I2bI
0.01V2114I
-O.OIOYlIlI
-0.005818l
0.0133lIbI
(1351
0.71171lll
0.19221161
0.4835IIeI
0.0207IIY1
0.01311281
O.Ub2Ol39l
0.0055I11l
~0~01581201
0~02991271
c1451
0.78121111
0.52bb117I
0.YbO41141
0.0113l9l
G.Ub0513*l
0.0130121l
0.0132l151
2.089 (5) A, respectively] are in excellent agreement but are significantly shorter than Rh(l)-C(2) and Rh(2)-C(l) [2.121 (5) and 2.128 (5) A, respectively], which, in turn, are also equal within experimental error. These differences indicate that the CGC bond of the bridging acetylene group is not
0* 00051b I
O.OOI21IZI
0.0I93l23l
precisely normal to the Rh-Rh axis. The Rh-Rh distance [2.740 ( I ) A] is only slightly longer than the corresponding distances found in the metal (2.69 A)26 and in (CsHs)zRh2(CO)3 [2.681 (2) A]*' and is taken to indicate the presence of a metal-metal bond. A similar Rh-Rh
102 Inorganic Chemistry, Vol. 15, No. 1, 1976
Bennett et al.
Table Vb. Calculated Hydrogen Atom Coordinates and Fixed Isotropic Thermal Parameters for Rh, (PF ,),[P(C, H, ),I2 (C, H,C,C, H , ) C , H 5)20a ,111"
I
MI121
*IIlI
2
'I
nik..21
Ain*
1
2
I
MI1..2I
-o.*>v
0.ll5
1.0
-0.03*
-0.213
-0.019
5.7
-0.U58
-C.'tO6
O*IVh
9.U
.U.051
8.7
1.0ib
.O.I2Y
0.091
'1.1
fl.O*b
Y I I * I
0.007
-0.126
'0.234
b.2
-O.lb*
0.59b
w1151
0.11s
-0.311
-0.3'40
5.1
o.o5n
-0.lV5
O*blV
7.v
HIIbI
0.229
-0.201
-0.227
Y.3
0.1b1
-C.I*Y
0.*'41
b*J
"I221
O.*l6
HI211
0.515
HIZYI
0.032
-0.01'1
5.1
U.Il*
0.01b
-0.080
-0.011
-0.124
b.1
0.03b
-0.001
-0.152
5.9
0.YBV
-0.2e.a
.O.2*7
7.1
0.Ob9
0.091
-0.100
b.6
*.I
HI251
O.lb3
-c.im~
-0.259
6.9
0. IVb
0.207
-0.3mi
b.2
MI2bl
0.1.3
-0.29 1
-0. I *t
'1.6
0.29*
0.227
-0,317
5.1 5.9
HI1121
0.111
-0.IY1
osion
5.*
0.291
0.3bl
-0*0*1
M I l l l l
o.Y*a
-0.
0.IU5
b.7
o.in4
0.5511
-0.OLl
7.0
" I I I Y I
0.92'
-0.340
O.IV2
7.2
0.50b
0.5b5
-0.212
7.2 a.2
180
MI1151
0.299
-o.L(Y~
0.285
7.0
0.53b
0.38Y
-0,131
Y f I I b )
O.lV2
-0.1106
0.292
6.2
U.Y*J
c.ina
-0.117
b.1
"I1221
0.0s1
-0.115
0.069
Y - b
0.256
-0,033
-0.175
5.9
HI1231
0.051
.0.*79
-0.105
6.0
0.111
-0.l7li
'0.551
8.0
nI12'4l
0.115
-O*bZB
-0.2Ob
7.1
OIY22
-0.201
-0.557
8.4
HI1251
0.212
-0.b14
-o.i*n
7.7
0.Y71
-0.099
-0.lPI
7.6
*I126l
0.21'1
-0.4*9
5.v
U.*I*
0.0YI
-0.213
5.3
0.012
Hydrogen atoms are numbered according t o the carbon atoms t o which they are bonded. Table VI. Principal Bond Distances and Interbond Angles for Rh,(PF,), [P(C,H,),],(C,H,C,C,H,).(C~H,),O Atoms
m=l
Rh(1)-Rh(2) Rh(m)-P(m0) Rh(m)-P(mZ) Rh(m)-C(2) P(mO)-C(mll) P(mO)-C(m31) P(m 1)-F(m12) P(m2)-F(m21) P(m2)-F(m23) C(ml)-C(m2) C(m3)-C(m4) C(m5)-C(m6) O(lS)-C(2S) C(lS)-C(2S)
2.740 (1) 2.388 (1) 2.211 (1) 2.121 (5) 1.829 (6) 1.827 (6) 1.533 (4) 1.555 (4) 1.552 (4) 1.394 (7) 1.371 (9) 1.391 (8) 1.33 (2) 1.44 (2)
Rh(2)-Rh(1)-P( 10) Rh(2)-Rh(l)-P(11) Rh(2)-Rh(l)-P(12) Rh(2)-Rh(1)-C( 1) Rh(2)-Rh( 1)-C(2) C( 1)-Rh(l)-C(2) P(m0)-Rh(m)-P(m 1) P(m l)-Rh(m)-P(mZ) Rh(m)-P(mO)-C(m2 1) C(m1 l)-P(mO)-C(m21) C(m21)-P(mO)-C(m31) Rh(m)-P(ml)-F(m12) F(m1 1)-P(m1 )-F(ml2) F(ml2)-P(ml)-F(ml3) Rh(m)-P(m2)-F(m22) F(m21)-P(m2)-F(m22) F(m 22)-P(m 2)-F(m 2 3) C(2)-C(l)-C(11) C(m)-C(ml)-C(m2) C(m2)-C(m 1)-C(m6) C(m2)-C(m3)-C(m4) C(m4)-C(m5)-C(m6) C(2S)-0(1S)-C(3S) 0(1S)-C(3S)-C(4S)
149.01 (4) 108.13 (4) 100.73 (4) 50.1 (1) 48.9 (1) 37.9 (2) 95.81 (5) 97.14 (6) 115.7 (2) 101.8 (2) 103.2 (2) 122.7 (2) 93.2 (3) 97.7 (3) 117.7 (2) 95.8 (2) 97.4 (2) 141.1 (5) 121.0 (4) 118.4 (5) 120.1 (5) 119.6 (5) 109 (1) 111 (1)
m=2
Atoms
(a) Bond Distances, A C(l)-C(2) 2.389 (1) Rh(m)-P(ml) 2.222 (2) Rh(m)-C(m) Rh(m)-C( I) 1.821 (5) P(mO)-C(m2 1) 1.828 (5) P(ml)-F(mll) 1.547 (4) P(m 1)-F(m 13) 1.505 (4) P(m2)-F(m22) 1.543 (4) C(m)-C(ml) 1.407 (8) C(m2)-C(m3) 1.387 (10) C(m4)-C(m5) 1.392 (9) C(m6)-C(ml) O(1S)-C(3S) C(3S)-C(4S)
m=l 1.369 (7) 2.227 (2) 2.079 (5) 1.831 (5) 1.553 (4) 1.527 (4) 1.545 (4) 1.459 (7) 1.390 (8) 1.388 (9) 1.394 (7) 1.52 (2) 1.27 (3)
m=2
2.217 (2) 2.089 (5) 2.128 (5) 1.842 (5) 1.539 (4) 1.550 (5) 1.518 (6) 1.460 (7) 1.370 (8) 1.379 (10) 1.391 (7)
(b) Interbond Angles, Deg
96.49 (5) 98.00 (6) 115.4 (2) 101.4 (2) 101.9 (2) 123.3 (2) 96.1 (2) 94.9 (2) 124.0 (2) 96.7 (3) 92.4 (2) 121.2 (4) 118.1 (5) 119.9 (6) 120.1 (6)
distance (average 2.73 A) has been observed for Rh4(CO)i2.28 The configuration about the rhodium-rhodium axis is not precisely eclipsed (see Table IX). The torsion angles between the PF3 phosphorus atoms average 9.0', but the torsion angle between P(10) and P(20) is 24.3'. The increased staggering of the triphenylphosphine groups in the solid state is most probably a consequence of the fact that the triphenylphosphine groups and the bridging diphenylacetylene group are on the same "side" of the molecule.
Rh( l)-Rh(2)-P(20) Rh( l)-Rh(2)-P(2 1) Rh(l)-Rh(2)-P(22) Rh(1 )-Rh(2)-C(l) Rh( l)-Rh(2)-C(2) C( 1)-Rh(2)-C(2) P(mO)-Rh(m)-P(m2) Rh(m)-P(mO)-C(mll) Rh(m)-P(mO)-C(m31) C(m1 l)-P(mO)-C(m31) Rh(m)-P(m l)-F(m 11) Rh(m)-P(ml)-F(m13) F(m1 l)-P(ml)-F(ml3) Rh(m)-P(mZ)-F(m2 1) Rh(m)-P(m2)-F(m23) F(m2l)-P(m2)-F(m23)
148.48 (4) 101.25 (4) 107.78 (4) 49.1 (1) 49.9 (1) 37.9 (2) 95.36 (5) 117.4 (2) 115.0 (2) 101.6 (2) 120.5 (2) 120.7 (2) 95.3 (3) 121.6 (2) 123.4 (2) 94.7 (2)
C(l)-C(2)-C(21) C(m)-C(ml)-C(m6) C(ml)-C(m2)-C(m3) C(m3)-C(m4)-C(m5) C(m5)-C(m6)-C(m 1) C(1 S)-C(2S)-O(lS)
141.5 (5) 120.5 (5) 120.8 (5) 120.4 (6) 120.7 (5) 107 (1)
95.16 (5) 117.5 (2) 116.3 (2) 102.0 (2) 118.7 (2) 121.7 (2) 95.6 (2) 121.5 (3) 120.8 (2) 93.8 (3) 120.6 (4) 121.2 (5) 120.1 (6) 120.5 (5)
The Rh-P(PF3) distances (average 2.219 A) are significantly shorter than the Rh-P[P(C6H5)3] distances (average 2.388 A), probably reflecting the increased r-bonding ability of PF3 as a ligand relative to P(C6H5)3. The P-F distances [range 1S O 5 (4)-1.555 (4) A; average 1.539 A] are considerably shorter than those found for free PF3 [1.569 (1) 8, by electron diffraction] .*9 Similar P-F bond length contractions have been observed for PF3.BHP and Pt(PF3)431 and have been attributed to u-electron donation
A
Inorganic Chemistry, Vol. 15, No. 1, 1976 103
(C~HS)~CZ-PF~-(C~H~)~P-R~Z Derivative
Table VII. Bond Distances and Interbond Angles within the Triphenylphosphine Phenyl Rings of Rhz (PF31 4 [P(C6 Hs )312 (C6 H5 Cz C, H5 )*(Cz H s)zO Atoms m=l,n=l m=I,n=2 m=l,n=3 m=2,n=1
m=2,n=2
m=2,n=3
C(mnlbC(mn2) C(mn2)- C(mn3) C(mn3)-C(rnn4) C(rnn4)-C(rnn5) C(mnS)-C(rnn6) C(mn6)-C(mnl)
1.829 (6) 1.387 (8) 1.389 (9) 1.349 (IO) 1.348 (IO) 1.412 (10) 1.400 (8)
(a) Bond Distances, A 1.831 (5) 1.826 (6) 1.403 (8) 1.387 (9) 1.392 (8) 1.396 (IO) 1.368 (9) 1.364 (10) 1.375 (11) 1.368 (11) 1.389 (9) 1.373 (9) 1.372 (8) 1.393 (8)
1.821 (5) 1.385 (7) 1.395 (8) 1.364 (9) 1.366 (10) 1.387 (9) 1.415 (7)
1.842 (5) 1.403 (8) 1.384 (9) 1.382 (IO) 1.334 (IO) 1.393 (9) 1.355 (8)
1.828 (5) 1.401 (8) 1.373 (9) 1.378 (11) 1.361 (IO) 1.406 (9) 1.378 (8)
P(m0)-C(mn1 )-C(mn2) P(m0)-C(rnn1 )-C(mn6) C(mn2)-C(mn l)-C(mn6) C(mnl)-C(mnZ)-C(mnf) C(rnn2)-C(mn3)-C(mn4) C(mn3)-C(mn4)-C(mn5) C(mn4)-C(mn5)-C(mn6) C(mn1 )-C(mn6)-C(mn5)
119.2 (4) 121.4 (4) 118.9 (5) 120.1 (6) 120.9 (6) 120.5 (7) 120.9 (6) 118.6 (6)
(b) Interbond 118.0 (4) 123.3 (4) 118.7 ( 5 ) 120.3 (5) 119.7 (6) 120.6 (6) 119.9 (6) 120.9 (6)
121.3 (4) 120.6 (4) 117.8 ( 5 ) 121.1 (5) 119.7 (6) 121.0 (6) 120.1 (6) 120.2 (5)
117.8 (4) 123.9 (5) 118.3 (5) 120.3 (6) 119.8 (6) 119.5 (6) 121.5 (7) 120.5 (7)
122.3 (4) 118.8 (4) 11 8.9 (5) 121.0 (6) 11 8.9 (6) 122.0 (7) 119.0 (6) 120.2 (6)
P(rnO)-C(rnn 1)
Angles, Deg 122.9 (4) 119.9 (4) 117.2 (5) 120.0 (6) 121.4 (7) 119.2 (7) 120.2 (7) 122.1 (7)
Table VIII. Least-Squares Planes within Rh,(PF3)4[P(C6H~),],(C,",).(C,H,),0 (a) Best Weighted Least-Squares Planes Plane
Atoms defining plane
Equationa
1 2 3
C(ll)-C(16) phenyl ring C(21)-C(26) phenyl ring C(11 l)-C(116) phenyl ring C(121)-C(126) phenyl ring C(131)-C(136) phenyl ring C(211)-C(216) phenyl ring C(221)-C(226) phenyl ring C(231)-C(236) phenyl ring
-0.3229X t 0.9288Y - 0.18202 + 2.5947 = 0 -0.2881X t 0.5446Y 0.78772 + 2.1 174 = 0 -0.1184X- 0.4685Y 0.87552 + 1.1441 = O 0.2144X + 0.7536Y - 0.62142 2.5941 = 0 -0.7841X + 0.6206Y - 0.01 1 8 2 7.2699 = 0 0.2436X- 0.6557Y- 0.71462- 0 . 9 1 2 0 = 0 -0.7209X t 0.1562Y 0.67522 1.8450 = 0 0.1174X + 0.8974Y - 0.42532 - 2.9223 = O
4
5 6
7 8
-
-
+ + +
(b) Deviations of Atoms from Best Planes, A Atom
Plane 1
Atom
all) C(12) C(13) C(14) C(15)
-0.002 (5) 0.005 (6) -0.004 (7) -0.004 (7) 0.007 (6)
C(16) C(1) C(2) C(21)
Atom
Plane 1 -0.003 0.053 -0.114 -0.741
(6) (5) (5) (5)
Plane 3
Plane 4
Plane 5
m = 1, n = 1
m= 1,n =2
m =l,n =3
Atom
Plane 2
Atom
Plane 2
C(21) (322) C(23) (324) C(25)
0.002 (5) -0.003 (6) 0.000 (7) 0.005 (7) -0.006 (7)
C(26) C(1) C(2) C(11)
0.002 (6) 0.1 10 (5) -0.031 (5) 0.683 (5)
Plane 7 m=2,n=2
Plane 8 m=2,n=3
Plane 6 m=2,n=l
C(mn1)
-0.005 (5) 0.004 (5) -0.008 (6) -0.001 (6) 0.006 (7) 0.007 (5) 0.009 (6) -0.009 (6) -0.004 (8) -0.005 (6) 0.002 (8) 0.008 (7) -0.007 (7) 0.010 (7) -0.002 (10) -0.004 (7) 0.008 (9) -0.011 (7) -0.002 (7) -0.002 (7) 0.012 (7) -0.006 (9) 0.004 (8) 0.005 (10) 0.006 (7) -0.005 (7) 0.001 (10) -0.008 (9) 0.004 (8) -0.006 (7) 0.000 (7) 0.001 (6) -0.006 (8) -0.005 (6) 0.015 (8) -0.003 (6) 0.021 (1) 0.080 (2) 0.193 (1) -0.059 (2) 0.079 (1) P(m0) 0.183 (1) a The equations of the planes LX + MY + NZ + D = 0 refer to orthogonal coordinates. The equations to transform from triclinic (fractional) to orthogonal (angstrom) coordinates are X = 2 1 . 1 8 6 1 ~- 5 . 5 5 9 0 ~+ 5.60002, Y = 0 . 0 ~+ 1 1 . 7 4 5 2 ~- 3.19932, and Z = 0 . 0 ~+ 0 . 0 ~+ 11.22052. C(mn2) C(rnn3) C(mn4) C(mn5) C(rnn6)
Axis atoms
Atom 1
Atom 2
Torsion angle? deg
P(20) 24.27 Wl),W2) P(10) P(21) 8.52 RhU), W 2 ) P(11) P(22) 9.52 W l ) , Rh(2) P(12) C(21) 20.58 CUI, C(2) C(11) a The torsion angle is defined as the dihedral angle between the two three-atom planes [axis atoms, atom 11 and [axis atoms, atom 21.
from the ligand to the metal.31 The F-P-F angles are significantly less than the tetrahedral angle (average 95.3') and are in good agreement with values of 97.7 (2) and 98.9 (7)O found for the corresponding angles in PF329 and Pt(PF3)4,31 respectively. Although the geometry of the solvent ether molecule is far
from ideal, there is no evidence of disorder. There are no unusually short contacts between the solvent ether molecule and molecules of Rhz(PF3)4[P(C6Hs)3] Z ( C ~ H S C ? ~ C ~ H S ) . Spectroscopic Properties and Fluxional Behavior. The bis(monodentate ligand) complexes of symmetrically disubstituted acetylenes, R ~ z ( P F ~ ) ~ L ~ ( Rshow C ~ Rone ) , doublet of ca. 1400-Hzseparation due to P-F coupling ( ~ J P F ~JPF) in their room-temperature 19F N M R spectra, whereas the complexes of unsymmetrical acetylenes show two such doublets in their low-temperature limiting spectra (Table X). These observations suggest that the complexes are all structurally similar to R~z(PF~)~[P(C~HS)~]~(C~HSC~C~HS) and that in solution they possess the time-averaged eclipsed structure shown in the form of a Newman projection along the Rh-Rh bond in Figure 4. In this structure, the PF3 groups are all equivalent when R = R' and fall into two inequivalent pairs when R # R'. We emphasize that this structure is time averaged since, as noted previously, the triphenylphosphine
+
104 Inorganic Chemistry, Vol. 15, No. 1 , 1976
Bennett et al.
Table X. I9F NMR Dataa Compd
@F (multiplicity, " J ~ F " )
Rh,E'F,), [ P ( C ~ H S ) ~ ] Z ( C , H ~ C Z C , H S ) Rhz (PF31.q[P(CH3 H 5 ), I 2 (C6 H jcz C, H 5 ) Rh,(PF,), [As(C,H,), I,(C,H,C,C,H,) Rh,(PF,), [P(C,H,), l,(C6HsC2CH3) Rh2 (PF3)4 [P(CH3 H s )z I 2 (C6 H sCzCH3 ) ~ h 2 ( ~ ~ 3 ) 4 ~ ~] Z(( C~~ H ~ , ~C , )C H ( ~~) ~6 ~ s ~ z Rhz (PF3)4 [As(C, H 5 ) 3 1 2 (C, Hs Cz CH3) Rh,(PF,), [ ~ ~ ( ~ 6 ~ s ) 3 ] , ( ~ 6 ~ j ~ , ~ ~ 3 ~ c Rh2(PF3) 4 [As(CH, H I2 1, ( c 6H CZ )d Rh, (PF 1, [As(CH3 H ,1, ( c 6€3 c, CH3Ie Rh2(PF 3 ) 4 [As(C, H 1 3 1 2 @-NO, c, H4C,C0 ,C, H ,)d Rh,(PF3),[A~(C6H,)312(p-N0,C,H,C,C0,C,H~~f
5.58 (d, 1390) 5.75 (d, 1385) 5.68 (d, 1385) 4.35 (d, 1360), 5.69 4.62 (d, 1360), 5.78 3.22 (d, 1410) 5.51 (d, 1385) 4.00 (d, 1360), 5.24 4.83 (d, 1365), 5.79 5.41 (d, 1385) 4.41 (d, 1385), 6.11 5.79 (d, 1415) -0.19 (dd, 1375ji 0.20 (dd, 1360)'
Rh,(PF,),(diars),(C,H,C,C,H,)g Rh,(PF3),(diars),(C,HsC,CH3)h
(d, 1380) (d, 1385) (d, 1390) (d, 1385) (d, 1405)
+
a Chemical shifts (@F)in ppm upfield of internal CFC1, measured in toluene at +24" except where indicated. "JPF" (in Hz) = l ' J p ~ 3 J p ~and I is believed accurate to 210 Hz. Abbreviations: d, doublet; dd, doublet of doublets. In toluene at 110". In THF at -30". In C,HjF at 24:. e In C,H,F at 55". In C,H,F at 85". g J ~ =h23 ~f 2 Hz; spectrum similar at -77". J R ~ F= 21 + 2 Hz; spectrum ''.Jp,'' = ' J p p similar at -91".
'
Table XI. Free Energy of Activation for Intramolecular Exchange of Trifluorophosphine in Complexes Rh2(PF,),L,(RC,R')a Compd Rh,(PF,), [As(C,Hj), I , ( C ~ H S C , C H ~ ) Rh, (PF,), [ As(CH3)(C6H, ) 2 I,(C,H, C,CH,) Rh, (PF ), [ P(CH I (C, H 1 1 (C, H C, CH,) Rhz (PF3 1 4 [P(C,Hs), I,(C6H,CzCH;) RhZ(PF3),[AS(C6Hj)3I ~ ( ~ - O ~ N C 6 H , C , C 0 , C , H j )
Solvent
Temp, "C
Rates, sec-'
AG*, kcal/mol
Toluene Fluorobenzene p-Xylene Toluene Fluorobenzene
-16-+ 12 28-44 69-100 30b 62-80
20400 20-80 40-300 (20 60-500
13.5 ? 0.3 15.8 f 0.5 17.9 i 0.5 >16 16.9 f 0.5
a Rates were estimated by comparison of I9F NMR spectra with calculated line shapes over temperature range given. A G * in the table was The instability in solution at a mean of values obtained over the range and none fell outside the range indicated by the estimated error. higher temperatures together with poor solubility prevented observation of intramolecular exchange of PF,.
Table XII. 'H NMR Dataa S
Compd
Acetylenic methyl groups
R~~(PF,),IP(CH~)(C~H~)ZIZ(C,",) Rhz (PF3)4 IP(C6 H j 1 3 Iz(C6H jCzCH3) Rh2(PF3), [As(C,Hj)31,(C6HjC2CH;)b Rh,(PF,), [P(CH3)(C,Hs),Iz(C,HsCzCH,) Rh,(PF,), [AS(CH,)(C,Hs),Iz(C6HsCzCH3)C Rh,(PF,), [ A S ( C H ~ ) ( C , H ~ ) , I , ( C , H ~ C , C H ~ ~ ~ Rh,(PF3), [P(C6Hj);Iz(CH;CzCH;)e Rh2(PF3), [ ~ S ( ~ 6 ~ ~ ~ ) ~ I ~ @ - ~ ~ Rh,(PF,),(diars), (C6H,C2C6Hs) Rh, (PF,), (diars),(C,H,C2CH3)
(multiplicity, J p , c ~ ~ ) Ligand methyl groups 1.42 (d, 7)
2 ~
2.18 (t, br, 14) 2.20 (qn, br, 7) 1.57 (t, br, 17) 2.20 (qn, br, 7) 1.89 (t, br, 16) 1.89 (t, br, 14) 61.10 ~ 4(t),~ 3.94 z ~ (q)g ~ z 2.81 (t, br, 8)
1.50 (d, 7) 1.57 (s) 1.34 (s, br) ~ 2 ~ s ~ ~
1.14 (s), 1.58 (s) 1.18 (s), 1.32 (s), 1.50 (s), 1.56 (s)
a Chemical shifts ( 6 ) in ppm downfield of internal TMS, measured in C,D, at 32" except where indicated. Coupling constants (J)are in Hz. Abbreviations: s, singlet; t, triplet; q, quartet; qn, quintet; br, broad. All aromatic signals are in the normal range S 6.5-8.0. In CHCl,. In C,H,F at +59". In C,H,F at -4". e Not isolated in a pure state. In C6HjF. g Ethyl resonances;JcH,-CH, = 7 Hz.
'\ I /
L groups of R ~ ~ ( P F ~ ) ~ [ P ( C2(C&C2C6H5) ~HS)~] are appreR ciably staggered in the solid state. It may of course be that the resulting inequivalence of PF3 groups is too small to be c: I C/R' observed by 19F N M R in solution, but it seems more likely / that there is a low-energy process which averages the position of the triphenylphosphine groups in the eclipsed conformation. On raising the temperature, the signals of the inequivalent PF3 groups in the unsymmetrical acetylene complexes broaden, PFj PF, coalesce, and finally sharpen again to give one doublet. This change occurs between 70 and 100' in the case of Rh2(PFigure 4. Proposed time-averaged structure of Rh,(PF3),L2(RC,R') viewed along the Rh-Rh axis. A second F~)~[P(CH~)(C~H~)~]~(C~HSC~CH~), but in the analogous Rh(PF3)2L group is behind and the one sllown. tertiary arsine derivatives it takes place a t appreciably lower temperatures (Table XI). The triphenylphosphine derivative the rates and free energies of activation (AG*) shown in Table is rigid a t 40' but unfortunately undergoes irreversible deXI. It is qualitatively evident from the temperature ranges composition above this temperature; 19F N M R spectroscopy confirmed by the AG* values that the barrier showed that even at 24' about 15% of R ~ Z ( P F ~ ) ~ ( C ~ H and ~ C quantitatively ~to PF3 rearrangement is higher for the tertiary phosphine CH3) had been formed after 12 hr. The process responsible derivatives than for the tertiary arsine derivatives. This for the coalescence behavior is reversible and arises from suggests that the intramolecular rearrangement of PF3 groups intramolecular rather than intermolecular exchange of PF3, may be intimately associated with intermolecular exchange since the high-temperature spectra contain fine structure of the phosphine or arsine; tertiary arsines are generally more attributable to the complex spin system of Rh(PF3)2. Apweakly bound and are more labile than tertiary phosphines, proximate line-shape analysis' of several of these spectra gave '\
A
A (C6H.5)2C2-PF3-( CsH5) 3P-Rh2 Derivative
Inorganic Chemistry, Vol. 15, No. 1, 1976 105
Scheme I as is evident from their exchange behavior with a-allylic palladium(I1) complexes and dienerhodium(1) complexes.32 Evidence for ligand exchange also comes from 1H N M R spectra (Table XII). In the triphenylarsine complex of 1phenylpropyne ( C ~ H S C ~ C Hthe ~ )acetylenic , methyl resonance appears as a quintet at 34O as a result of coupling with four apparently equivalent 31P nuclei of coordinated PF3 ( J = 7 Hz); there is also some broadening due to coupling with 19F. This suggests rapid exchange at 34O which renders all the PF3 groups equivalent. The same behavior is observed for the analogous diphenylmethylarsine complex at 59'. In the analogous tertiary phosphine complexes the acetylenic methyl resonance appears as a broad triplet ( J = 14 Hz), as a consequence of coupling to two equivalent 31P nuclei of one pair of trifluorophosphine ligands (cf. the arsine complex below), so that these complexes cannot be undergoing rapid ligand dissociation can occur at either end of the initial exchange on the N M R time scale at 34O. The broadening molecule, any such process will average all the PF3 enviprobably arises from smaller couplings to the 31P nuclei of the ronments. One possibility consists of a bending mode which other pair of PF3 groups and of the pair of P(C6H5)3 groups, brings the two PF3 groups into the plane of the metal-metal and possibly also to 19F nuclei. At lower temperatures (-4') bond, followed by a 180' rotation about the Rh-Rh axis, and the acetylenic methyl resonance of Rh2(PF3)4[As(Canother bend to bring the PF3 groups to their interchanged H ~ ) ( C ~ H ~ ) ~ ] ~ ( C ~ Halso S Cbecomes ~ C H ~a )triplet ( J = 16 positions (Scheme I). This process is assumed to be fast Hz), showing that exchange is now slow on the N M R time relative to ligand dissociation. Rotation of PF3 groups about scale; this corresponds to the situation found for the phosphine the metal-metal bond has also been proposed to account for complexes at 34O. The triplet of the diphenylmethylarsine the behavior of the di-tert-butylacetylene complex Rh2complex is sharper than that of the tertiary phosphine (PF3)5(t-B~2C2),33which is a stable analogue of the coorcomplexes, presumably because one source of coupling is dinately unsaturated intermediate proposed herein; to this absent. Addition of free diphenylmethylarsine to the solution complex the rhodium-rhodium double-bonded structure I has at -4O gives a separate methyl resonance for this species, showing clearly that intermolecular exchange of the arsine is /R slow at this temperature, but, on warming, the resonances of free and coordinated diphenylmethylarsine coalesce and become a sharp singlet owing to rapid intermolecular exchange of the tertiary arsine. The temperature at which the sharp singlet is observed for the methyl resonance of diphenylmethylarsine is about the same (ca. +59O) as that at which a clear quintet is observed for the acetylenic methyl resonance as a result of intramolecular PF3 exchange (see above). Unfortunately it proved impossible to measure the barrier to I(R = t-Bu) intermolecular exchange owing to the large temperature dependence of the chemical shifts of both the free and cobeen assigned. In this complex, the signals of the inequivalent ordinated arsenic methyl resonance; e.g., for solutions in PF3 groups of the Rh(PF3)2 moiety coalesce on warming from fluorobenzene with TMS as internal reference free di24 to 1 lo", as do those of the Rh(PF3)3 moiety. The free phenylmethylarsine has ~ C 1.29 H ~at 30° and 1.42 at -4O, and energies of activation for the two processes are identical, and coordinated diphenylmethylarsine in Rh2(PF3)4[As(Cit seems reasonable to assume that the PF3 groups rotate about H ~ ) ( C ~ H S ) ~ ] ~ ( C ~ Hhas ~C H ~ at ) 59O and 1.34 ~ C~ HC,1.57 the metal-metal bond. A somewhat different explanation for at -4'. Qualitatively, however, the intermolecular exchange the PF3 exchange in Rh2(PF3)4L(RC2Rt) is to assume that of diphenylmethylarsine in R ~ ~ ( P F ~ ) ~ [ A s ( C H ~ ) (this C ~ -intermediate has the same stereochemistry as Rh2H5)2]2(C6H5C2CH3) occurs over the same temperature range ( P F ~ ) ~ ( ? - B U(structure ~ C ~ ) I). Ligand L can then recombine as intramolecular PF3 exchange, and a rough estimate of the with the intermediate from either side of the molecule, leading intramolecular exchange, based on the change from a triplet to exchange of the PF3 groups. This explanation raises the to a quintet in the acetylenic methyl resonance, gives a barrier possibility that intramolecular PF3 exchange might be inhibited in reasonable agreement with that derived from 19F NMR. if R and R' were sterically very different, since L might prefer We assume therefore, that the intermolecular exchange process to recombine on the same side from which it left. Attempts triggers the intramolecular process. Addition of free tertiary to obtain a pure sample of R~~(PF~)~[As(C~H~)~]Z(~-B~CZH phosphine or arsine to the respective complexes had no effect to test this hypothesis were not successful. A third possible on the rate of intramolecular exchange, showing that the explanation involves dissociation of both ligand molecules from rate-determining step is the loss of phosphine or arsine. The Rh2(PF3)4L2(RC2R1) to give an intermediate Rh2(PF3)4effect of solvent appears to be negligible, since the (RC2R') in which the acetylene can rotate rapidly about an variable-temperature 19F N M R spectra of Rh2(Paxis bisecting the Rh-Rh bond, so that the PF3 environments F~)~[As(C~H~)~]~(C~HSC~C") in toluene and in tetraare averaged. The available data are insufficient to distinguish hydrofuran were indistinguishable. Changes in concentration between these possibilities, though we favor either of the first by a factor of 2 also had no effect on the rates. two given above in view of the isolation and fluxional behavior Dissociation of one ligand molecule from Rh2(PF3)4L2of R ~ ~ ( P F ~ ) s ( z - B uComparison ~ C ~ ) . ~ ~of the AG* values for (RC2R') should give a coordinately unsaturated species R~~(PF~)~[As(C~HS)~]~(C~HSC~CH~) and for Rh2(PF3)4Rh2(PF3)4L(RC2R1),and we require a mechanism which will [As(C6H5)3]~ @ - N ~ ~ C ~ H ~ C ~ C shows O ~ Cthat Z Hthe S )more interchange the PF3 groups of the Rh(PF3)2 moiety in this electron-withdrawing acetylene gives rise to the higher barrier intermediate either before or during reentry of ligand. Since to intramolecular PF3 exchange, as was also found for the
11
106 Inorganic Chemistry, Vol. 15, No. I , 1976
Bennett et al.
Rhz(PF3)6(ac) complexes.1 In the bis(1igand) complexes, however, this electronic effect may well be exerted directly on the rate of ligand dissociation rather than on the rate of intramolecular PF3 exchange. The fact that pairwise PF3 exchange is probably initiated by dissociation of tertiary phosphine or arsine suggests (though it does not prove) that such pairwise PF3 exchange does not occur in the Rh2(PF3)6(ac) complexes. Intermolecular PF3 Exchange. The 1 9 F N M R spectrum of a 1:1 mixture of Rh2(PF3)4[P(C6H5)3]2(C6H5C2C6H5)and Rh2(PF3)6(CsHsczCaHs) at room temperature consists of the two doublets, intensity ratio 2:3, characteristic of each compound. On cooling, the upfield doublet due to the latter complex broadens and separates into two peaks, as observed IIa IIb for the pure compound,l while the low-field doublet remains unchanged. This behavior suggests that the two complexes do not react to form Rh2(PF3)5[P(C6H5)3](CsHsCzCsHs) at or below room temperature. A 1:l mixture of R ~ ~ ( P F ~ ) ~ [ A S ( C H ~ ) ( C ~ H ~ ) ~ I ~ ( C ~ H ~ C2CH3) and R ~ ~ ( P F ~ ) ~ ( C ~ H in S fluorobenzene C ~ C H ~ ) also exhibits a room-temperature 19F N M R spectrum characteristic of each complex, Le., a pair of doublets for the former and one doublet about 3 ppm to higher field for the latter. At higher temperatures (-45') the pair of doublets coalesce owing to the intramolecular PF3 exchange already discussed. PF3 As In the range 50-82O the two separate doublets broaden, coalesce, and finally sharpen again to give a still broad doublet CH, CH3 (the broadening may be due partly to the fact that the boiling point of the solvent had been reached). The process is reIIC versible and must involve intermolecular exchange of PF3 tamers are not observed for either of the complexes at low between the two complexes. Approximate line-shape analyses temperature, the free energy of activation for the process must of the spectra in the range 50-82O yielded rates of 20-250 sec-l be less than ca. 7 kcal/mol, which seems remarkably low in and a free energy of activation of 17.0 f 0.5 kcal/mol. The comparison with the values observed for the complexes intermolecular exchange may involve Rhz(PF3)s[As(Ccontaining monodentate ligands. The N M R results do not H ~ ) ( C ~ H ~ ) ~ ] ( C ~ H ~asC an Z Cintermediate, H~) but the exclude structures containing two bridging di(tertiary arsine) equilibrium, if it exists, is strongly in favor of the 1:l mixture ligands, but since the only example of a complex containing of hexakis and tetrakis complexes at ambient temperature. bridging diars is [RCsH4Mn(C0)2]2(diars) (R = H or o-Phenylenebis(dimethy1arsine) (diars) Derivatives. The CH3),34,35 these structures seem unlikely. At present, bis(di(tertiary arsine)) derivatives Rhz(PF3)2(diars)2(ac) (ac therefore, the structures of the Rhz(PF3)z(diars)z(ac) com= C6H5C2C6H5 or C6H5C2CH3) show one widely spaced plexes are not known with certainty. doublet due to VPFin their 19F NMR spectra further doubled Acknowledgment. We thank the staff of The Australian by coupling to 103Rh (Table X); the spectra do not change on National University Computer Centre for generous allocations cooling to -77' (C6HsCzC6Hs derivative) or -91' of time on the Univac-1108 computer. (C6H5C2CH3 derivative). The methyl resonances of the Registry No. Rhz(PF3)4[P(C6Hs)3]r(C6HsCzCsHs), 4791 3-68-8; di(tertiary arsine) appear as two sharp singlets of equal inR ~ ~ ( P F ~ ) ~ [ P ( C ~ H ~ ) ~ I ~ ( C ~ H ~ C38893-55-9; ~C~H~)*(CZH~)~ tensity in the IH N M R spectrum of the diphenylacetylene R ~ ~ ( P F ~ ) ~ [ A S ( C ~ H ~ ) ~ ] ~ ( 56792-73-5; C~HSCZC~ Rh2(PH~), derivative and as four equal singlets in the spectrum of the 56792-74-6; RhZ(P1-phenylpropyne derivative (Table XII). If the molecules F3)4[P(CsH5)3]2(C6HsC2CH3),56792-75-7; R ~ z ( P F ~ ) ~ [ A s ( C ~ adopt an eclipsed conformation [as assumed also for Rh2H ~ ) ~ ] ~ ( C ~ H S C ~56792-76-8; CH~), R~z(PF~)~[P(CH~)(C~(PF3)4[P(C6H5)3] ~ ( C ~ H S C ~ C there ~ H ~are ) ] ,three possible H ~ ) ~ ] ~ ( C ~ H ~ C Z56792-77-9; CH~), R~~(PF~)~[As(CH~)(C~geometrical isomers, I1 a-c, for the phenylpropyne complex H5)2]2(C6H5CCH3), 56792-78-0; R ~ ~ ( P F ~ ) ~ [ A s ( C ~ H ~ ) ~ I ~ - P (R = C6Hs; R' = CH3): IIb and IIc become enantiomeric in OzNCsH4CzC02CzHs), 56792-79-1; Rhz(PF3)z(diars)zthe case of the diphenylacetylene complex (R = R' = C6Hs). Rh2(PF3)2(diars)z(CsH5CCH3), ( C ~ H S C Z C ~ H56792-80-4; ~), 56792-81-5; Rh2(PF3)4[P(C6H5)3]2(CH3C2CH3),56792-82-6; Clearly the methyl groups on each arsenic atom are inRhz(PF3)6(C6H5CzC6Hs), 38893-58-2; Rh2(PF3)6(CH3C2C6Hs), equivalent in IIa-c. When R = R', we therefore expect two 3901 5-25-3; triphenylphosphine, 603-35-0. methyl singlets in the case of IIa and four singlets for IIb or Supplementary Material Available: A listing of structure factor IIc, and when R # R', we expect four methyl singlets for amplitudes (26 pages). Ordering information is given on any current IIa-c. The possibilities of isomeric mixtures or of different masthead page. orientations on the two rhodium atoms seem to be eliminated Although the by the observation of only one P-F doublet. References and Notes N M R data fit structure IIa for the di(tertiary arsine) de(1) M. A. Bennett, R. N. Johnson, and T. W. Turney, Inorg. Chem., 15. 90 (1976). rivatives, one might have expected an As(CH3)2 group to have (2) M. A. Bennett, R. N. Johnson, G.B. Robertson, T. W. Turney, and P. occupied the position held by triphenylphosphine in the 0 . Whimp, J . Am. Chem. Sor., 94, 6540 (1972). R ~ z ( P F ~ ) ~ [ P ( C ~ H ~ ) ~ I ~structure. (C~H~C An~ alterC ~ H ~ ) ( 3 ) T h e Busing and Levy programs [Acla Crystallogr.,22,457 (1967)] were used for all phases of diffractometer control and data collection. native possibility which meets this objection is a mixture of (4) Formulas used in the data reduction programs: Lp (Lorentz-polarization IIb and IIc in rapid equilibrium. The exchange process could factor) = (cos* 20 + cos2 20m)/[sin 20(l + cos2 2Hm)], where R and R m be a one-ended dissociation of the di(tertiary arsine) or partial ( = I 3.25') are the reflection and monochromator Bragg angles, reSince individual rospectively; I (net peak intensity) = [CT -. (tp/tb)(BI + &)]. where CT rotation about the metal-metal bond.
/\/ {b
Inorganic Chemistry, Vol. 15, No. 1, 1976 107
Rhodiacyclopentadiene Complexes is the total peak count in tp sec, and B I and 5 2 are the individual background counts in (tb/2) sec; a ( [ ) (reflection significance) = [CT + ( t p l t b ) 2 ( 5 ~+ &)]I/*; ~ ( F o(the ) reflection esd) = ([a(I)/Lpl2 + (plFol )2}’/2/21F~#~ ( F o(the ) reflection esd from counting statistics alone) = [u(I)/2(Lp)((Fol)]; Rs(the statistical R factor) = x u s ( F o ) / x l F ~ l ; background rejection ratio = [lei - &1/(81+ W. R. Busing and H. A. Levy, J . Chem. Phys., 26,563 (1957); P. W. R. Corfield, R. J. Doedens, and J. A. Ibers, Inorg. Chem., 6, 197 (1967). “International Tables for X-Ray Crystallography”,Vol. 111, Kynoch Press, Birmingham, England, 1962, p 202. C. T. Prewitt, Ph.D. Thesis, Massachusetts Institute of Technology, 1962, p 163.
D. T. Cromer, Acta Crystallogr., 18, 17 (1965). R. F. Stewart, E. R. Davidson, and W. T. Simpson, J . Chem. Phys., 42, 3175 (1965). G. B. Robertson and P. 0. Whimp, Inorg. Chem., 13, 1047 (1974). C. K. Johnson, Report ORNL-3794, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1965. U. Kruerke and W. Hubel, Chem. Ber., 94, 2829 (1961). Y. Iwashita, F. Tamura, and A. Nakamura, Inorg. Chem., 8, 1179 (1969). The method used to calculate weighted least-squares planes is described by D. M. Blow, Acta Crysfallogr., 13, 168 (1960). W. G. Sly, J . Am. Chem. Sot., 81, 18 (1959). N. A. Bailey and R. Mason, J . Chem. Soc. A, 1293 (1968). N. K. Hota, H. A. Patel, A. J. Carty, M. Mathew, and G. J. Palenik, J . Organornet. Chem., 32, C55 (1971). D. Seyferth, R. J. Spohn, M. R. Churchill, K. Gold, and F. R. Scholer,
J . Organomef. Chem., 23, 237 (1970). R. J. Dellaca, B. R. Penfold, B. H. Robinson, W. T. Robinson, and J . L. Spencer, Inorg. Chem., 9,2197 (1970). R. J. Dellaca and B. R. Penfold, Inorg. Chem., 10, 1269 (1971). Chem. Soc., Spec. Publ., No. 18, S17s (1965). G. B. Robertson and P. 0.Whimp, J . Am. Chem. Soc., 97, 1051 (1975). D. A. Brown, J . Chem. Phys., 33, 1037 (1960). J. 0. Glanville, J. M. Stewart, and S. 0. Grim, J . Organomef. Chem.,
7, P9 (1967). J. Dale in “Chemistry of Acetylenes”, H. G. Viehe, Ed., Marcel Dekker, New York, N.Y., 1969, p 1. H. J. Goldschmidt and T. Land, J . Iron Steel Insf., London, 155, 221 (1947). 0. S. Mills and J. P. Nice, J . Organomef. Chem., 10, 337 (1967). C. H. Wei, G. R. Wilkes, and L. F. Dahl, J . Am. Chem. Soc., 89,4792 (1967). Y. Morino, K. Kuchitsu, and T. Moritani, Inorg. Chem., 8, 867 (1969). R. L. Kuczowski and D. R. Lide, J . Chem. Phys., 46, 357 (1967). J. C. Marriott, J. A. Salthouse, M. J. Ware, and J. M. Freeman, Chem. Commun., 595 (1970). K. Vrieze, H. C. Volger, and P. W. N. M. van Leeuwen, Inorg. Chim. Acta, Rev., 3, 109 ((969). M. A. Bennett, R. N. Johnson, and T. W. Turney, Inorg. Chem., 15, 1 1 1 (1976). R. S . Nyholm, S.S. Sandhu, and M. H. B. Stiddard, J . Chem. Soc., 5916 (1963). M. J. Bennett and R. Mason, Proc. Chem. Soc., London, 395 (1964).
Contribution from the Research School of Chemistry, The Australian National University, Canberra, A.C.T. 2600, Australia
Preparation and Fluxional Behavior of New Rhodiacyclopentadiene Complexes Containing Trifluorophosphine M. A. BENNETT,* R. N . J O H N S O N , and T. W. TURNEY Received June 3, 1975
AIC50380R
Dimethyl acetylenedicarboxylate, CH302CCzCOzCH3, and methyl propiolate, HC2COzCH3 (ac), react with dirhodium octakis(trifluorophosphine), Rhz(PF3)8, below room temperature to give red complexes of empirical formula Rhz(PF3)s(ac)z (1, a c = CH302CCzCOzCH3; 2, ac = HCzC02CH3). Above room temperature explosive polymerization of the acetylenes =~ Y(=PCOzCH3; F~)~ ensues. The complexes are assigned a metallocyclopentadiene structure ( F ~ P ) ~ R ~ ( P - C ~ X ~ Y ~(X) R X = COzCH3, Y = H) on the basis of IH and 19F N M R spectra and a preliminary single-crystal X-ray study of the bis(tripheny1phosphine) complex of 2, the acetylene units in 2 being arranged in a “head-to-tail” manner. The Rh(PF3)3 unit in 1 and 2 shows fluxional behavior in the 19F N M R spectra while the Rh(PF3)2 unit remains essentially unchanged, and an intramolecular tritopal rearrangement is suggested. Line shape analysis gives the free energy of activation (AG*) of the process in 1 and 2 as ca. 10.5 kcal/mol.
R~z(PF~)s(CH~O~CC~CO~CH~)Z, 1. Dimethyl acetylenedicarboxylate Introduction (0.6 g, excess) was condensed onto solid Rh2(PF3)8 (0.26 g) at liquid In previous papersl-3 we showed that a wide range of nitrogen temperature under a high vacuum. The mixture was allowed acetylenes (ac) react with dirhodium octakis(trifluor0to warm to +2OoC; gas (PF3, ir identification) was evolved. The phosphine), Rh2(PF3)8, to give binuclear complexes Rh2exothermic reaction was kept at or below 20’ until no more gas came (PF3)6(ac). Single-crystal X-ray analysis of the bis(trioff. Unreacted acetylene was removed at 20’ (0.005 mm) over a 12-hr phenylphosphine) derivative R~~(PF~)~[P(C~H~)~IZ(C~H~period to leave a red solid which was extracted with four 5-ml portions C2C6Hs)I93 showed that the complexes are structurally of isopentane. The solution was filtered and cooled to -5’ to give large red crystals of the complex, mp 162’ (0.15 g, 58%). analogous to the well-known cobalt carbonyl complexes, Anal. Calcd for CizHizFisOsPsRh2: C, 15.5; H, 1.3; P, 16.7; F, Cos(CO)6(ac), obtained from c 0 2 ( c o ) 8 and acetylenes. The 30.6; mol wt 929. Found: C, 15.2; H, 1.4; P, 16.3; F, 29.8; mol wt Cos(CO)6(ac) complexes can react with an excess of acetylene (by mass spectrometry) 929. IH N M R (C6D6):6 3.35 (s, CH3); to give complexes of empirical formula Co2(CO)6(ac)4 or cf. CH302CCrC02CH3 6 3.80. 19F N M R data are in Table I. Co2(CO)4(ac)3 in addition to cyclopentadienones, aromatic (Tris( trifluorophosphine)rhodia)( 1-4-7-2,4- bis( carboxymethyl)trimers, and polymers,4 whereas, with only a few exceptions, cyclopentadiene)bis(trifluorophosphine)rhodium(R~-R~),Rh2the Rhz(PF3)6(ac) complexes are the only organometallic ( P F ~ ) s ( H C ~ C O ~ C HThe ~ ) ~reaction ,~. was carried out as described products which can be isolated from the reaction of Rh2(PF3)8 above, unreacted acetylene being removed from the complex by with acetylenes. Two of these exceptions are dimethyl acettrap-to-trap sublimation. The red solid when recrystallized from ylenedicarboxylate, C H 3 0 2 C C 2 C 0 2 C H 3 , and methyl proisopentane at -78’ gave a 40% yield of the complex, which was further purified by vacuum sublimation. piolate, HC2C02CH3, which form the subject of this paper. Anal. Calcd for CsH8F1504PsRh2: C, 11.8; H, 1 .O; P, 19.0; mol Experimental Section wt 813. Found: C , 12.3; H, 1.3; P, 18.7; mol wt (by mass specExperimental and spectroscopic procedures are as previously described.*J Preparations. Warning! The following reactions become violently explosive if carried out at or above room temperature. It is important to keep to the specified temperatures. (Tris( trifluorophosphine)rhodia)( 1-4-)1-2,3,4,5- tetrakis(carboxymethy1)cyclopentadiene)bis( trifluorophosphine)rhodium(Rh-Rh),
trometry) 813. IH N M R (C6D6):6 3.31 (S, 3 , CH3), 7.80 (m, 1, = C H ) , 8.24 (m, 1, =CH); cf. HC2C02CH3 6 3.41 (s, 3, CH3), 2.56 (s, I , ECH). 19F N M R data are in Table I. (Bis( trifluorophosphine) triphenylphosphinerhodia)( 1-4-7- 2,4bis(carboxymethyl)cyclopentadiene)( trifluorophosphine) (triphenyl-
phosphine)rhodium(Rh-Rh), R~~(PF~)~[P(C~HS)~]~(HC~CO~CH~)~ 3. A solution of triphenylphosphine (0.38 g, excess) in n-pentane ( 1 5
