90
Organometallics 1986, 5 , 90-94
Synthesis and Characterization of Bis( diphenylphosphido) bis( pentamethylcyclopentadieny1)thorium ( I V ) , [(q5-C5(CH&],Th( PPh,), Debra A. Wrobleski, Robert R. Ryan," Harvey J. Wasserman, Kenneth V. Salazar, Robert T. Paine, and David C. Moody Los Alamos National Laboratory, University of California, Los Alamos, New Mexico 87545 Received April 23, 1985
The first diorganophosphido actinide complexes Cp*2Th(PRZ),(Cp* = T ~ - C ~ ( C H R ~=)Ph, ~ , Cy, Et) have been prepared by reaction of Cp*zThC12with LiPR2. These complexes have been characterized spectroscopically, and Cp*zTh(PPh2)zhas been structurally characterized by a complete single-crystalX-ray diffraction study. This compound crystallizes in the space group P2,/c with a = 35.071 (8) A, b = 15.203 (6) A, c = 21.840 (11)A, (3 = 92.97 ( 2 ) O , at T = -95 "C, and V = 11629.3 A3 and 2 = 12 (Mo K a , radiation, X = 0.709 30 A). The structure refined to RF = 0.08 and RwF = 0.07. There are three crystallographically independent molecules in the asymmetric unit. All three molecules exhibit pseudotetrahedral geometry about the thorium atom with the pentamethylcyclopentadienyl ligands and two diphenylphosphido groups occupying the four coordination sites. While the angles about the phosphorus atoms are far from the tetrahedral, there is no evidence for significant Th-P multiple bonding. The average Th-P distance is 2.87 (2) A.
Introduction The recent literature reflects a burst of activity in the area of heterobimetallic complexes.' Incentives to study this area of chemistry include, for example, the desire to understand the difference in selectivity observed for mixed bimetallic heterogeneous catalysts compared to their homometallic analogues.2 A second commonly stated goal is to activate small oxygen-containing molecules, e.g., CO, C02, SOz, etc., toward unusual reactivity patterns. The use of phosphido ligands to form bridges between dissimilar metal centers, e.g., early and late transition metals, has been especially fruitful, and many such complexes have now been r e p ~ r t e d . ~ Two distinct routes to the preparation of heterobimetallic complexes with bridging phosphido ligands have proven successful. Perhaps the most commonly used route involves the deprotonation of a coordinated secondary phosphine3 followed by metathesis with a metal halide to form the heterobimetallic complex. A second route requires metathesis of a coordinated halide using M(PPhJ4 (M = Na, Li) to form the neutral phosphido transitionmetal compound. The resulting complex contains a terminal phosphide that displays many of the properties of a tertiary phosphine including simple displacement reactions with transition-metal complexes containing labile ligands to form the desired bimetallic complex. Especially intriguing to us was the recent appearance of several reports of group 419 metal phosphido complexes with an attendant rich chemistry toward low-valent transitionmetal fragment^.^ In some cases, metal-metal bonding (1)(a) Bruno, J. W.; Huffman, J. C.; Green, M. A.; Caulton, K. G. J . Am. Chem. SOC.1984,106,8310.(b) Casey, C. P.; Jordan, R. F.; Rheingold, A.L. Ibid. 1983,105,665.(c) Wrobleski, D. A.; Day, C. S.; Goodman, B. A.; Rauchfuss, T. B. Ibid. 1984,106,5464.(d) Rosenburg, S.;Whittle, R. R.; Geoffroy, G. L. Ibid. 1984,106,5934. (e) Breen, M. J.; Shulman, P. M.; Geoffroy, G. L.; Rheingold, A. L.; Fultz, W. C. Organometallics 1984,3,782. ( f )Regragui, R.; Dixneuf, P. H.; Taylor, N. J.; Carty, A. J. Ibid. 1984,3,814.(9) Chandler, D.J.; Jones, R. A.; Stuart, A. L.; Wright, T. C. Ibid. 1984,3, 1830. (2) Sinfelt, J. H. "Bimetallic Catalysts"; Wiley: New York, 1983. (3)Roberts, D.A.; Geoffroy, G. L. In "Comprehensive Organometallic Chemistry"; Wilkinson, G., Stone, F. G. A,, Abel, E. W., Eds.; Pergamon Press: Oxford, 1982;Vol. 6,Chapter 40. (4)Wade, S.R.; Wallbridge, M. G. H.; Willey, G. R. J . Chem. SOC., Dalton Trans. 1983.2555 and references therein.
has been strongly implicated for the resulting heterobimetallic complexes. Our interest in the preparation of bimetallic actinide-transition metal complexes has led us to investigate the phosphido coordination chemistry of the actinide metals, a previously unexplored area. We report here the synthesis and molecular structure of the first diorganophosphido actinide complex Cp*,Th(PPh,), [Cp* = q5-C5(CH3),]. The preparation of the first heterobimetallic phosphido complex via coordination of the Ni(CO), fragment to the molecular species reported here has recently been communicated.6 The Th-Ni distance was found to be significantly shorter than that expected for a nonbonded contact, and a bonding interaction is strongly implied.
Experimental Section Materials and Methods. All compounds described herein are highly air- and moisture-sensitive in the solid state. Syntheses were routinely conducted under a nitrogen atmosphere using Schlenk techniques. Toluene was freshly distilled from sodium benzophenone ketyl under nitrogen and transferred to reaction vessels via high vacuum techniques. Thc~*,Cl,~ and LiPRz (R = Et, Cy)s were prepared according to published procedures. LiPPh, was purchased from Alfa Products and used without further purification. Infrared spectra were recorded on a Perkin-Elmer 683 spectrophotometer as Nujol m& using KBr plates. UV-visible spectra were obtained on a Perkin-Elmer 330 spectrophotometer in toluene. Proton and 31P{1H) NMR spectra were obtained on a Bruker WM 300 wide-bore spectrometer at 300 and 121.5 MHz, respectively. Benzene-d6 was used as a lock solvent for most spectra. Phosphorus chemical shifts (6) are reported relative to external 85% H3P04. Positive chemical shifts are assigned to resonances (at higher frequency) downfield from the reference.
Elemental analyses were obtained from Schwarzkopf Microanalytical Laboratory. ~
(5) Baker, R. T.; Tulip, T. H.; Wreford, S. S. Inorg. Chem. 1985,24,
1379. (6)Ritchey, J. M.;Zozulin, A. J.; Wrobleski, D. A.; Ryan, R. R.; Wasserman, H. J.; Moody, D. C.; Paine, R. T. J . Am. Chem. SOC.1985, 107,501. (7) Fagan, P. J.; Manriquez, J. M.; Maatta, E. A,; Serjam, A. M.; Marks, T. J. J . Am. Chem. SOC.1981,103,6650. (8) LiPRz (R = Et, Cy) were prepared in hexane from PRzH and n-BuLi: Issleib, K.; Tzachach, A. Chem. Ber. 1959,92,1118.
0276-733318612305-0090$01.50/0 0 1986 American Chemical Society
Organometallics, Vol. 5, No.
Table I. Crystal Data and Data Collection" formula
C44H50PZTh 35.071 (8) 15.203 (6) b, A 21.840 (11) c, A 92.97 (2) 6, deg MO KCXI,0.709 30 radiation, A monochromator graphite 8-28 scan method 0-50 28 limit, deg -95 temp, "C a, A
monoclinic m1/c Z 12 11629.1 v, A3 p (calcd), g/cm3 1.50 mol w t 872.9 40.0 abs coeff, cm-' variable scan speed 14518 no. of reflctns 7764 reflctns obsd I2 2 4 crystal system space group
"&= xllFol - l F c l l / x l ~ o l= 0.07. R w F = C W l l F O I - l ~ c l l / x l ~ = ol 0.08. a ( p ) = a,(F) + 0.02 p. u , ( P ) = error due to counting statistics. Two standards every 2 h. Preparation of Bis(pentamethylcyclopentadieny1)bis(diphenylphosphido)thorium(IV), C P * , T ~ ( P P ~(1). ~)~ Treatment of Cp*,ThCl, (1.7 g, 3 mmol) in 35 mL of toluene with an excess of LiPPh, (1.73 g, 9 mmol) in 65 mL of toluene results in a rapid color change to dark purple. Following filtration to remove excess LiPPh2 and LiCl and concentration to 5 mL, addition of hexane (100 mL) and cooling the solution to -30 "C affords a deep purple crystalline product (67% yield) which is extremely moisture- and air-sensitive. 'H NMR: 6 7.9-7.0 (m, 20 H, Ph), 1.925 (s, 30 H, C5(CH3),). 31P(1H) NMR (121.5 MHz, C,Hs): 6 +144 (s). IR (Nujol mull): 1575 (m) cm-'. UV-vis (toluene): 570 (4440), 498 nm (sh, 2740 cm-' M-'). Anal. Calcd for C,HmP2Th: C, 60.53; H, 5.77; P, 7.10; Th, 26.60. Found C, 60.34; H, 5.85; P, 7.12; Th, 26.88.
Preparation of Bis(pentamethylcyclopentadieny1)bis(diethylphosphido)thorium(IV),C P * , T ~ ( P E ~(2). , ) ~Treatment of Cp*,ThC12 (3.44 g, 6 mmol) with LiPEh (1.15 g, 12 "01) in toluene (125 mL) resulted in a rapid color change to deep cherry red. Following filtration, the solvent was removed in vacuo. Hexane (20 mL) was added and cooled to -78 "C to give dark red crystals which were isolated (ca. 60% yield) by filtration and drying the product in vacuo. 'H NMR: 6 2.419 (dq, 8 H, CH2CH3, JH-H = 7.5 Hz, J p - H = 2.35 Hz), 2.133 (s, 30 H , C,(CH,),), 1.384 (dt, 12 H, CHZCH,, J p - H = 12.8 Hz).31P(1H)N M R 6 136 (s).
Preparation of Bis(pentamethylcyclopentadieny1)bis(dicyclohexylphosphido)thorium(IV), Cp*2Th(PCy,), (3). Treatment of CpC2ThC12(287 mg, 0.5 mmol) with LiPCy, (204 mg, 1.0 "01) results in a slow color change to burgundy red over the period of 2 days. Following filtration, the solvent was removed in vacuo to give a red oil. Due to its high solubility in organic solvents, 3 was characterized in solution. 'H NMR: 6 2.246 (s, br, Cy), 2.233 (s, Cy), 2.139 (s, C,(CH,),), 2.110 (s, Cy), 2.058 (s, Cy), 2.013 (s, Cy). 31P{1H)NMR: 6 205 (s). Crystal Structure Analysis. Cell and intensity data are given in Table I. X-ray quality crystals of Cp*pTh(PPhz)pwere obtained by slow cooling of a hot hexane solution of 1. A crystal (0.2 X 0.2 X 0.3 mm) was selected and mounted in a glass capillary in an inert-atmosphere drybox. The capillary was sealed with epoxy, removed from the box, and flame sealed. Data were collected a t -95 "C on an Enraf-Nonius CAD4 diffractometer equipped with an Isotherm boil-off flowing N2 low-temperature system, using variable speed 8-28 scans. Two standard reflections were monitored after every 2 h and were used to correct for long-range intensity variations. A correction for the effects of absorption was derived from the intensity variation of a reflection near x = 90" which was measured as a function of $. A spherical correction was superimposed on the resulting curve. The structure was solved by using standard Patterson and Fourier methods. There are three crystallographically independent Cp*,Th(PPh,), molecules in the asymmetric unit. The refinements were carried out using neutral atom scattering factors and appropriate anomalous scattering terms.g Because of the size of the problem, i.e., three molecules in the asymmetric unit, rigid-body constraints were applied to all phenyl and Cp* groups. The phenyl rings were assumed to have Dshsymmetry with d ( C C ) (9) Cromer, D. T.; Waber, J. T. "International Tables for X-ray Crystallography"; Kynoch Press: Birmingham, England, 1974; Table 2.2A. Cromer, D. T. Ibid., Table 2.3.1.
I, 1986 91
= 1.39 8,. For the Cp* groups d(C-Qint = 1.42 8, and d(C-C),, = 1.53 8, were used and held fixed in the refinements, and D5h symmetry was assumed in the starting model. However, in the refinements the symmetry constraint was relaxed to C5"and a distance parameter between the two planes, one defined by the five internal carbon atoms-and the other by the five external carbons, refined to 0.25 A. All carbon atom thermal parameters were allowed to refine independently. Anisotropic thermal parameters were included for the three independent thorium atoms and the six independent phosphorus atoms. A secondary extinction parameterlo was refined, but no hydrogen atoms were included. The final model with 141 atoms, 324 parameters refined to RF = 0.08 and RwF = 0.07.
Results and Discussion The metathesis reaction of Cp*,ThCl, with LiPR, (R = Ph, Et, Cy) in toluene yields the highly air-sensitive thorium complexes Cp*,Th(PR&. The rate of substitution of the phosphido group with the chloride is dependent on the steric bulk of the R groups. When R = Ph and Et, the substitution proceeds within minutes while the cyclohexyl reaction requires days. Because of its high solubility in nonpolar organic solvents, the cyclohexyl derivative was not isolated as a solid but was characterized spectroscopically. A unique feature of this class of thorium complexes is their intense purple/red color. This is highly unusual for Th(1V) organometallic complexes since most are colorless" although there is some evidence for highly colored Th(1II) compounds such as ThCp3.12 We attribute the transitions (Amu = 570,498 nm for 1) in the visible region to phosphido ligand-to-metal charge-transfer bands. An ORTEP projection of molecule 1 is shown in Figure 1. Fractional coordinates and selected distances and angles are given in Table I1 and Table 111, respectively. Clearly, all three molecules are conformationally equivalent. While some related distances and angles differ significantly, from a statistical point of view, it would be difficult to claim that any chemical difference can be inferred from these. Structures which contain three identical molecules in the asymmetric unit are extremely uncommon. The reason for this unusual behavior is unclear in the present case. Inspection of intramolecular distances and of the packing diagram show no unusual interactions which would indicate incipient trimerization. All three molecules exhibit the pseudotetrahedral geometry which is ubiquitous among structures of the type C P * ~ M X ~ , where M is an early transition metal and X is a halide or pseudohalide. Although many structures containing bridging phosphido ligands have now been reported, reports of structures with a terminal PR2 ligand are rare.13J4 An early-transition-metal complex analogous to ours, viz., Cp2Hf(PEt2),, has been structurally ~haracterized.'~Its structure differs from the present one in one important respect: the conformation about the phosphorus atoms. The hafnium structure exhibits one phosphorus atom with pyramidal geometry while the other is planar, indicative of p r - d r ligand to metal bonding. In the present structure (10) (a) Zachariasen, W. H. Acta Crystallogr. 1967,23, 558-564. (b) Larson, A. C. Ibid. 1967,23, 664-665. (11) See, for example: (a) Marks, T. J.; Wachter, W. A. J . Am. Chem. SOC.1976,98, 703. (b) Sonnenberger, D. C.; Mintz, E. A.; Marks, T. J. J. Am. Chem. SOC.1984, 106, 3484. (12) (a) Kanellakopulos, B.; Dornberger, E.; Baumgartner, F. Inorg. Nucl. Chem. Lett. 1974,10, 155. (b) Bruno, J. W.; Kalina, D. G.; Mintz, E. A.; Marks, T. J. J. Am. Chem. SOC.1982, 104, 1860. (13) (a) Domaille, P. J.; Foxman, B. M.; McNeese, T. J.; Wreford, S. S. J. Am. Chem. SOC.1980,102, 4114. (b) Rocklage, S. M.; Schrock, R. R.; Churchill, M. R.; Wasserman, H. J. Organometallics 1982,1,1332. (c) Baker, R. T.; Krusic, P. J.; Tulip, T. H.; Calabrese, J. C.; Wreford, S. S. J. Am. Chem. SOC.1983, 105, 6763. (14) Baker, R. T.; Whitney, J. F.; Wreford, S. S. Organometallics 1983, 2, 1049.
92 Organometallics, Vol. 5, No. 1, 1986
Wrobleski et al.
Table 11. Positional Parameters for Cp*2Th(PPh2)2 atom
X
Y
z
0.23884 (3) 0.90987 (3) 0.2086 (2) 0.5504 (2) 0.9548 (2) 0.1959 (3) 0.1602 (3) 0.1720 (4) 0.1513 (4) 0.2218 (4) 0.2815 (3) 0.3056 (3) 0.2625 (4) 0.3446 (4) 0.2290 (4) 0.6246 (3) 0.6484 (3) 0.6103 (4) 0.6838 (4) 0.5771 (4) 0.5288 (3) 0.4995 (3) 0.5176 (4) 0.4826 (4) 0.5584 (4) 0.8561 (3) 0.8296 (3) 0.8417 (4) 0.8165 (4) 0.8787 (4) 0.9603 (3) 0.9756 (3) 0.9313 (4) 1.0194 (4) 0.9099 (4) 0.3915 (4) 0.3269 (5) 0.3454 (6) 0.2668 (5) 0.2702 (5) 0.2275 (4) 0.1274 (5) 0.1651 (3) 0.0987 (4) 0.3033 (4) 0.2413 (4) 0.2589 (5) 0.5827 (5) 0.6585 (5) 0.5462 (4) 0.6776 (6) 0.5958 ( 5 ) 0.7214 (4) 0.4745 (5) 0.5086 (4) 0.4421 (4) 0.5991 (5) 0.5830 (4) 0.6428 (4) 0.9425 ( 5 ) 0.8486 (3) 0.9883 (3) 0.8103 (5) 0.9261 (4) 0.7876 (4) 0.8832 (4) 0.9878 (4) 0.9170 (5) 0.9992 (5) 0.9301 (4) 1.0520 (3)
0.22505 (7) 0.18799 (6) 0.3690 ( 5 ) 0.1423 (5) 0.3186 ( 5 ) 0.2256 (7) 0.1954 (7) 0.0260 (7) 0.3526 (7) 0.0677 (9) 0.1865 (6) 0.1214 (7) -0.0192 (8) 0.2549 (9) 0.0712 (10) 0.3220 (7) 0.3726 (7) 0.5201 (8) 0.2371 (9) 0.4499 (10) 0.2787 (7) 0.3246 (7) 0.4916 (7) 0.1652 (7) 0.4280 (9) 0.2205 (6) 0.1621 (6) -0.0054 (6) 0.3297 (6) 0.0757 (9) 0.1175 (7) 0.0787 (7) -0.0585 (9) 0.1980 (9) -0.0047 (10) 0.2930 (14) 0.2887 (12) 0.1969 (11) 0.5192 (12) 0.4248 (9) 0.5489 (11) 0.2781 (10) 0.3557 (11) 0.3921 (10) 0.4968 (12) 0.4299 (11) 0.5025 (12) -0.0137 (12) 0.1959 (12) -0.0378 (11) 0.2842 (11) 0.0719 (10) 0.1791 (13) 0.2547 (9) 0.1640 (11) 0.1362 (11) -0.0029 (12) 0.0765 (10) -0.0013 (11) 0.4585 (11) 0.3018 (10) 0.4388 (11) 0.2208 (9) 0.3719 (10) 0.3587 (10) 0.5306 (11) 0.2881 (10) 0.5254 (11) 0.2222 (11) 0.4177 (9) 0.2770 (13)
0.37695 (4) 0.41272 (4) 0.4457 (3) 0.5204 (3) 0.3561 (3) 0.2654 (4) 0.3480 (4) 0.3584 (7) 0.2999 (7) 0.2434 (7) 0.4855 (4) 0.4008 (4) 0.3925 (7) 0.4471 (7) 0.5103 (7) 0.5060 (5) 0.5994 (4) 0.6061 (7) 0.5544 (7) 0.4761 (6) 0.6992 (4) 0.6083 (4) 0.6116 (7) 0.6438 (7) 0.7381 (6) 0.3176 (4) 0.4024 (4) 0.3836 (7) 0.3821 (6) 0.2654 (6) 0.5008 (4) 0.4035 (4) 0.3861 (6) 0.4580 (6) 0.5216 (6) 0.2317 (10) 0.2639 (7) 0.1807 (7) 0.1784 (6) 0.2671 (8) 0.2633 (8) 0.5593 (6) 0.4877 (7) 0.4957 (8) 0.5126 (8) 0.4977 (8) 0.5930 (6) 0.8030 (6) 0.7339 (7) 0.7081 (8) 0.8217 (8) 0.7137 (8) 0.7822 (10) 0.3923 (7) 0.4671 (7) 0.4412 (8) 0.3870 (6) 0.4775 (8) 0.4758 (8) 0.6426 (6) 0.5501 (6) 0.5653 (7) 0.6190 (7) 0.5528 (7) 0.5768 (8) 0.3395 (8) 0.2958 (6) 0.2464 (6) 0.1981 (6) 0.3255 (8) 0.2621 (8)
the angles about the phosphorus atoms have values which are far from tetrahedral; the largest variations are exhibited for Th-P-C angles. Included in Table IIID are the angles between the Th-P vectors and the normal to the C-P-C'
atom
X
V
2
0.57800 (3) 0.2909 (2) 0.6234 (2) 0.8913 (2) 0.2016 (3) 0.1702 (3) 0.1795 (3) 0.1285 (4) 0.2090 (4) 0.2590 (3) 0.3104 (3) 0.2739 (3) 0.3340 (4) 0.2797 (4) 0.6044 (3) 0.6518 (3) 0.6192 (3) 0.6762 (7) 0.6225 (4) 0.5384 (3) 0.5047 (3) 0.5203 (3) 0.4707 (4) 0.5368 (4) 0.8630 (3) 0.8354 (3) 0.8466 (3) 0.8033 (4) 0.8631 (4) 0.9361 (3) 0.9848 (3) 0.9456 (3) 0.9989 (4) 0.9644 (4) 0.3823 ( 5 ) 0.3637 (6) 0.3177 (4) 0.2395 (5) 0.2822 (4) 0.2429 (5) 0.0957 (4) 0.1621 (4) 0.1334 ( 5 ) 0.2944 ( 5 ) 0.2768 ( 5 ) 0.2324 (4) 0.5540 ( 5 ) 0.6036 (4) 0.5671 (5) 0.7131 (5) 0.6503 (4) 0.6941 (6) 0.4415 (4) 0.5080 (4) 0.4756 (5) 0.6336 (5) 0.5739 (4) 0.6175 ( 5 ) 0.9785 (4) 0.9163 (3) 0.9621 (5) 0.7824 (4) 0.8434 (4) 0.8207 (5) 0.8901 ( 5 ) 0.9032 ( 5 ) 0.9370 (4) 1.0382 (5) 0.9741 (3) 1.0268 (5)
0.28022 (7) 0.3336 ( 5 ) 0.1573 (5) 0.3094 (5) 0.1358 (7) 0.2625 (6) 0.1173 (6) 0.2021 (9) 0.2695 (9) 0.1112 (7) 0.1928 (6) 0.0710 (7) 0.0943 (10) 0.2406 (9) 0.3997 (7) 0.3052 (7) 0.4309 (7) 0.3886 (11) 0.2750 (10) 0.3684 (7) 0.2516 (6) 0.3966 (6) 0.3292 (10) 0.2263 (9) 0.1285 (7) 0.2414 (6) 0.0925 (6) 0.1516 (9) 0.2828 (8) 0.0470 (7) 0.1371 (6) 0.0231 (7) 0.0668 (10) 0.1538 (10) 0.2304 (13) 0.3222 (11) 0.2261 (12) 0.5704 (9) 0.4463 (11) 0.4761 (11) 0.3283 (12) 0.2919 (10) 0.4058 (9) 0.5229 (11) 0.4503 (11) 0.4560 (12) -0.0583 (10) 0.0513 (11) 0.0273 (12) 0.2436 (14) 0.2604 (12) 0.1552 (10) 0.2059 (12) 0.2337 (10) 0.1152 (9) -0.0283 (10) 0.0495 (12) 0.0511 (11) 0.4742 (10) 0.4073 (11) 0.3877 (10) 0.2858 (12) 0.2288 (9) 0.3667 (8) 0.5648 (9) 0.4570 (11) 0.4519 (11) 0.2368 (12) 0.2479 (11) 0.3027 (11)
0.60160 (4) 0.3142 (3) 0.6738 (3) 0.5051 (3) 0.2814 ( 5 ) 0.3065 ( 5 ) 0.3325 ( 5 ) 0.3933 (6) 0.2072 (6) 0.4705 (5) 0.4424 ( 5 ) 0.4181 ( 5 ) 0.3535 (6) 0.5441 (6) 0.5202 (5) 0.5550 ( 5 ) 0.5780 ( 5 ) 0.6545 (5) 0.4442 ( 5 ) 0.6903 ( 5 ) 0.6484 (5) 0.6341 (5) 0.5533 ( 5 ) 0.7580 (5) 0.3180 (4) 0.3699 (4) 0.3705 (4) 0.4557 ( 5 ) 0.2645 (5) 0.4811 (5) 0.4528 (5) 0.4209 ( 5 ) 0.3468 (5) 0.5660 (5) 0.1870 (8) 0.2702 (8) 0.2192 (9) 0.2054 (8) 0.2093 (8) 0.2941 (6) 0.5408 (7) 0.5328 (7) 0.4692 (6) 0.5712 (8) 0.4759 (6) 0.5563 (8) 0.7695 (8) 0.7751 (8) 0.6802 (6) 0.8246 (8) 0.7764 (9) 0.7368 (8) 0.4000 (7) 0.4259 (7) 0.4748 (7) 0.4160 (8) 0.4177 (8) 0.5065 (6) 0.6210 (7) 0.6085 (7) 0.5312 (6) 0.6139 (7) 0.5871 (7) 0.5449 (7) 0.2821 (8) 0.3612 (6) 0.2681 (7) 0.2083 (7) 0.2419 (8) 0.3059 (6)
plane (144.7' for tetrahedral geometry). The most notable of these is that associated with P(5) (110.4') which is also associated with the shortest Th-P distance (2.834 A). However, since no significant correlation can be found
Organometallics, Vol. 5, No. 1, 1986 93
Synthesis of [($- C5(CH,)J2Th(PPhJ,
Table 111. Interatomic Distances (A) and Angles (deg) for Cp*,Th(PPh,),apb Th( 1)-P( 1) -P( 2) -C(1) -C( 2) -C( 3 ) -C(4) -C(5) -C( 11) -C( 1 2 ) -C( 1 3 ) -C( 1 4 ) -C( 1 5 ) -CP( 1) -CP( 2)
2.861 ( 7 ) 2.887 (8) 2.76 (1) 2.80 (1) 2.84 (1) 2.84 (1) 2.78 (1) 2.74 (1) 2.80 (1) 2.86 (1) 2.85 (1) 2.77 (1) 2.54 2.54
A. Distances from the Thorium Atoms Th( 2)-P( 3) 2.873 ( 7 ) 2.883 ( 7 ) -P( 4 1 -C( 21) 2.74 (1) -C( 22) 2.79 (1) 2.86 (1) -C( 23) 2.84 (1) -C( 24) 2.77 (1) -C(25) -C( 31) 2.78 (1) -C( 32) 2.81 (1) -C( 33) 2.85 (1) -C( 3 4 ) 2.84 (1) -C( 3 5 ) 2.81 (1) -CP( 3 1 2.52 -CP(4) 2.55
Th( 3)-P( 5 ) -P(6 ) -C(41) -C( 4 2) -C(43) -C( 4 4 ) -C(45) -C(51) -C( 52) -C( 53) -C( 5 4 ) -C( 5 5 ) -CP(5) -CP( 6 )
2.834 ( 7 ) 2.857 ( 7 ) 2.73 (1) 2.78 (1) 2.85 (1) 2.84 (1) 2.77 (1) 2.74 (1) 2.76 (1) 2.83 (1) 2.86 (1) 2.80 (1) 2.53 2.53
P( 1)-C( 6 4 ) -C( 70) P( 2)-C( 76) -C(82)
1.85 (1) 1.85 (1) 1.83 (1) 1.83 (1)
B. Phosphorus-Carbon Distances P(3)-C(88) 1.85 (1) -C( 94) 1.86 (1) P( 4)-C( 1 0 0 ) 1.85 (1) -C( 1 0 6 ) 1.82 (1)
P( 5)-C( 1 1 2 ) -C( 118) P( 6)-C( 1 2 4 ) -C( 1 3 0 )
1.84 (1) 1.83 (1) 1.86 (1) 1.85 (1)
94.2 ( 2 ) 134.9 110.3 100.1 99.9 110.5
C. Angles about the Thorium Atoms P( 3)-Th-P(4) 91.4 ( 2 ) Cp( 3)-Th-Cp( 4 ) 133.7 Cp( 3)-Th-P( 3) 100.5 Cp( 3)-Th-P( 4 ) 109.8 Cp( 4)-Th-P( 3) 111.5 Cp(4)-Th-P(4) 102.3
P( 5)-Th-P( 6 ) Cp( 5)-Th-Cp( 6 ) Cp(5)-Th-P( 5 ) Cp( 5)-Th-P( 6 ) Cp( 6)-Th-P( 5 ) Cp( 6)-Th-P( 6 )
90.4 ( 2 ) 132.9 101.9 111.5 111.1 101.2
P( 1)-Th-P( 2 ) Cp( 1)-Th-Cp( 2 ) Cp( 1)-Th-P( 1) Cp( 1)-Th-P( 2 ) Cp( 2)-Th-P(1) Cp( 2)-Th-P( 2) Th( l)-P( 1)-C( 6 4 ) Th( 1)-P( 1)-C( 70) C( 64)-P( 1)-C( 70) Th( l ) - P ( 2)-C( 7 6 ) Th( 1)-P( 2)-C(82) C( 76)-P( 2)-C(82) Th( 2)-P( 3)-C( 8 8 ) Th( 2)-P( 3)-C( 9 4 ) C( 88)-P(3)-C( 9 4 )
D. Angles about the Phosphorus AtomsC 123.0 ( 7 ) Th( 2)-P(4)-C( 1 0 0 ) 117.2 ( 6 ) Th( 2)-P( 4)-C( 1 0 6 ) 101.9 ( 8 ) [127.1] C( 100)-P( 4)-C( 1 0 6 ) 121.0 ( 6 ) Th( 3)-P( 5)-C( 1 1 2 ) 118.2 ( 7 ) Th(3)-P(5)-C(118) 104.9 ( 8 ) [125.9] C(112)-P(5)-C(118) 120.9 ( 7 ) Th( 3)-P( 6)-C( 1 2 4 ) 115.1 (6) Th( 3)-P( 6)-C( 1 3 0 ) 103.4 ( 8 ) [130.7] C( 124)-P( 6)-C( 1 3 0 )
119.1 ( 6 ) 121.1 ( 6 ) 105.9 (8) [123.6] 124.3 ( 6 ) 124.9 ( 6 ) 105.5 (8) [11Q.4] 120.8 ( 6 ) 117.7 ( 6 ) 104.2 ( 8 ) [127.3]
a Cp denotes the centroid for the Cp* ring calculated from the inner carbon atom positions. Atoms listed in this table are numbered in molecules 2 and 3 in the same sequence as in molecule 1. Carbon atom numbers are incremented by 24 between molecules 1and 2 and between molecules 2 and 3 ; a n = 2 for phosphorus atoms; and Cp( 1)corresponds t o Cp(4) and Cp( 6 ) while Cp( 2 ) corresponds t o Cp( 3 ) and Cp( 5). Brackets [ ] denote angle between the Th-P bond and the C-P-C' plane normal.
with the 31P(1H)NMR spectrum of Cp2Hf(PCy2),which reveals two resonances at low temperature supporting the structural evidence for single and double M-P bonds.14 It is interesting that the zirconium and hafnium systems achieve an 18-electron count with one single and one double M-P bond while the thorium system exhibits no multiple Th-P bonding in spite of its formal 16-electron count. We note, however, that the electron count for other thorium complexes ranges from 16e in C P * ~ T ~ ( C H toJ ~ ~ ~ 24e in Cp4Th.16 The Th-P distance, averaged over all six linkages, is 2.87 (2) A, a value which compares well with the Hf-P(pyramidal) distance (Hf-P = 2.682 A) in Cp2Hf(PEtJz when proper allowance is made for the difference in ionic radii.17 In addition, this distance is only slightly shorter than the Figure 1. ORTEP view of molecule 1of [(q5-C5(CH3),]ZTh(PPh2)2. Th-P distance of 2.884 (2) A in the Th-Ni complex6 mentioned above. The structure of a thorium-phosphine among the remaining distances and the corresponding complex, Th(CH2Ph),(Me2PCH2CH2PMe2), has recently angles, n o conclusions regarding possible multiple bonding appeared18 in which the average thorium-phosphorus effects can be drawn. The 31P(1H)NMR spectrum for the thorium complexes consists of a singlet between 6 +136 and 6 +205 a t 25 OC, (15) Manriquez, J. M.; Fagen, P. J.; Marks,T. J. J. Am. Chem. SOC. similar to that observed for early transition complexes with 1978,100, 3939. terminal phosphido ligands.14 The low-temperature (16) Fischer, E. 0.;Triebner, A. Z.Naturforsch., E : Anorg. Chem., Org. Chem., Biochem., Biophys., Biol. 1962, 17B, 276. spectrum (-120 "C, toluene-d,/methylcyclohexane) of 1 (17) Shannon, R. D. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., shows no evidence of line broadening, indicating that the Theor. Gen. Crystallogr. 1976, A32, 751. phosphido ligands are equivalent on the NMR time scale, (18) Edwards, P. G.; Anderson, R. A.; Zalkin, A. Organometallics 1984, in agreement with the solid-state structure. This contrasts 3, 293. A
94
Organometallics 1986, 5, 94-98
distance is considerably longer, at 3.155 (10) A as would be expected for a Lewis acid-base interaction. The chemistry of the Cp*,Th(PR& complexes and other actinide analogues, in combination with a number of late-transition-metal fragments, is currently under investigation in our laboratory. Preliminary results, including the preparation of the above-mentioned nickel complex, (19)In this paper the periodic group notation is in accord with recent actions bv W A C and ACS nomenclature committees. A and B notation is eliminated because of wide confusion. Groups IA and IIA become groups 1 and 2. The d-transition elements comprise groups 3 through 12, and the p-block elements comprise groups 13 through 18. (Note that the former Roman number designation is preserved in the last digit of the new numbering: e.g., 111-3 and 13.)
indicate that a large number of bimetallic complexes can be successfullv" DreDared. _ -
Acknowledgment. This work was performed under the auspices of the u.s. Department of Energy and, in part, under the auspices of the Division of Chemical Energy Sciences, Office of Basic Energy Sciences, u.s. Department of Energy. Registry No. 1, 93943-04-5; 2, 98720-31-1; 3, 98720-32-2; Cp*ThClz,67506-88-1; LiPPh2,4541-02-0; LiPEt2, 19093-80-2; Lipcyzy 19966-81-5*
Supplementary Material Available: Tables of anisotropic parameters as
as
and
Of Observed
stn~cturefactors and isotropic tk"-nl Parameters (45 Pages). Ordering information is given on any current masthead page.
q2-Vinyl and q2-Ketenyl Ligands as Analogues of Four-Electron Alkyne Ligands Douglas C. Brower, Kurt R. Birdwhistell, and Joseph L. Templeton" W. R. Kenan, Jr. Laboratory, Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27514 Received April 29, 1985
The donor and acceptor properties of [a2-HC=CH2]- and [$-HC=CO]- ligands resemble those of $-RC=CR ligands. In monomeric complexes requiring four-electron donation from an alkyne unit, the role of the rl electron pair of the alkyne can be fulfilled by related filled orbitals in [HC=CH2]- and [HC=CO]- (the charge provides a closed shell for the atoms in the free ligand). The two anionic Cz-based fragments also have empty n-acceptor orbitals which behave analogously to the T,,* and r* functions of alkynes and alkenes, respectively. Extended Huckel molecular orbital calculations suggest that in coordination spheres containing r-acids the orientation of a2-ketenylligands is determined by frontier orbital interactions, whereas the orientation of $-vinyl ligands is dictated largely by steric effects.
Introduction Comparing the electronic structures of new or unsymmetrical ligands with simpler or more thoroughly studied cases often aids in rationalizing molecular structures and predicting chemical reactivity;' this is the essence of Hoffmann's isolobal anal~gy.~ Metallacyclopropene complexes, 1 (also called $-vinyl derivatives or cyclic alkylidenes, see Scheme I), and metallacyclopropenone complexes, 2 (also called v2-ketenyl derivatives), are two examples of metal-stabilized organic fragments which have been prepared by metal-mediated ligand reactions. Conversion of metal-bound alkynes to q2-vinylligands has been accomplished by nucleophilic attack a t an alkyne carbon with hydride reagent^,^ thiols or thiolates? nitrogen5 and phosphorus6 reagents, and isonitriles.' $-Ketenyl ligands
Scheme I
a
therein. (3)(a) Green, M.;Norman, N. C.; Orpen, A. G. J. Am. Chem. SOC. 1981,103,1267. (b) Allen, S.R.; Green, M.; Orpen, A. G.; Williams, I. D. J. Chem. SOC.,Chem. Commun. 1982,826. (c) Allen, S.R.; Beevor, R. G.; Green, M.; Norman, N. C.; Orpen, A. G.; Williams, I. D. J . Chem.
SOC.,Dalton Trans. 1985,435. (4)(a) Davidson, J. L.; Shiralian, M.; ManojloviE-Muir, L.; Muir, K. W. J. Chem. SOC.,Dalton Trans. 1984,2167. (b) Carlton, L.;Davidson, J. L.; Miller, J. C.; Muir, K. W.J. Chem. SOC.,Chem. Commun. 1984,Il. (c) Davidson, J. L. J. Chem. SOC.,Chem. Commun. 1979,597. (5)(a) Davidson, J. L.; Murray, I. E. P.; Preston, P. N.; Russo, M. V. J. Chem. SOC.,Dalton Trans. 1983,1783. (b) Davidson, J. L.; Murray, I. E. P.; Preston, P. N.; Russo, M. V.; ManojloviE-Muir,L.; Muir, K. W. J . Chem. SOC.,Chem. Commun. 1981,1059.
b
0
2
Table I. Extended Hiickel Parameters exponents orbital
H
c2s
c2, 02,
(1)(a) Pettit, R.;Sugahara, H.; Wristers, J.; Merk, W. Discuss. Faraday SOC.1969,47,71.(b) Mango, F.D.; Schachtachneider,J. H. J. Am. Chem. SOC.1971,93, 1123. (c) KostiE, N. M.; Fenske, R. F. Organometallics 1982,I , 974. (d) Albright, T. A. Tetrahedron 1982,38,1339. (2)(a) Hoffmann, R.Angew. Chem., Znt. Ed. Engl. 1982,21,711.(b) Stone, F.G. A. Angew. Chem., Int. Ed. Engl. 1984,23,89and references
b
1
OZP
W5d w 6 ~ W 6 ~
s;
H(i,i),eV -13.6 -21.4 -11.4 -32.3 -14.8 -10.37 -8.26 -5.17
.i-2
1.3 1.625 1.625 2.275
2.275 4.982 (0.6685) 2.341 2.309
2.068 (0.5424)
have been prepared by coupling reactions between carbyne and carbonyl ligandsa and by rearrangement of 11'-ketenyl ligands after loss of another ligand.g We now show, (6)Davidson, J. L.;Wilson, W. F.;ManojloviE-Muir, L.; Muir, K. W. J. Organomet. Chem. 1983,254,C6. (7) (a) Davidson, J. L.; Vasapollo, G.; ManojloviE-Muir, L.; Muir, K. W. J. Chem. SOC.,Chem. Commun. 1982, 1025. (b) Morrow, J. R.; Tonker, T. L.; Templeton, J. L., manuscript in preparation. (8) (a) Kreissl, F. R.; Sieber, W. J.; Alt, H. G. Chem. Ber. 1984,117, 2527. (b) Fischer, E. 0.;Filippou, A. C.; Alt, H. G.; Ackermann, K. J. Organomet. Chem. 1983,254,C21. (c) Birdwhistell, K. R.; Tonker, T. L.; Templeton, J. L. J. A m . Chem. SOC.1985,107,4474.
0276-7333/86/2305-0094$01.50/0 0 1986 American Chemical Society
