Organometallics 1982, 1, 881-883
or related reactions can be observed in different transition-metal systems. Registry No. 1,81360-30-7; 2,81360-32-9;6,81360-33-0; [Ir(P(CH3)3)1][Cl],
60314-48-9.
Crystal and Molecular Structure of Trlbenzylalumlnum, a Novel r]'-Arene Coordlnated Structure
mol formula mol wt cryst syst space group cell dimens a b C
z
Received February 22, 1982 Summary: The molecular and crystal structure of tribenzylaluminium has been determined by single-crystal X-ray diffraction techniques. The compound was found to crystallize in the orthorhombic system, space group Pbca , with unit-cell dimensions of a = 9.480 (3) A, b = 34.248 (1 1) A, c = 10.546 (5) A, dcalcd= 1.165 g ~ m - ~ , V = 3424 (2) A3, and Z = 8. Full-matrix least-squares refinement on 1100 data gave R F = 5.3% and R,, = 5.6%.
The structures for a wide variety of organoaluminum compounds have been reported and show that these species form bridged dimers in the solid state. The structures of trimethylaluminum,' of triphenyl-,2 dimethyl-p-phenyl-,3 and tri-o-tolylaluminum,4 of diisobutyl-p-(trans-tert-butylvinyl)-aluminum,5and of tricyclopropylaluminum6have all been determined and shown to have symmetrically bridge bonds. Diphenyl-p-(phenylethy1)-aluminum,'and dimethyl-p-cyclopentadienyl-aluminum, on the other hand, are unsymmetrically bridged. The only monomeric species for which structures have been reported are trimethylaluminumgand dimethylcyclopentadienylaluminum~o both determined by electron diffraction under conditions which lead to dissociation. We now wish to report the crystal and molecular structure of tribenylaluminium, a molecule which has a unique structure in the solid state with the A1(CH2Ph), units bound together through strong intermolecular interactions between C(22)', one of the ortho carbon atoms of the phenyl group on the adjacent molecular unit, and the vacant p orbital of the aluminum atom. Experimental Data. Tribenzylaluminum was prepared from dibenzylmercury" (6.0 g, 0.015 mol) and aluminum (1) Lewis, P. H.; Rundle, R. E. J. Chem. Phys. 1953 21,987. Vranka, R. G.; Amma, E. L. J. Am. Chem. Soc. 1967,89, 3121. Huffman, J. C. C.; Streib, W. E. J. Chem. SOC. D 1971, 911. (2) Malone, J. F.; McDonald, W. S. J. Chem. SOC., Dalton Trans. 1972, 2646. (3) Malone, J. F.; McDonald, W. S. J. Chem. Soc., Dalton Trans. 1972, 2649. (4) Barber, M.; Liptak, D.; Oliver, J. P., submitted for publication in Organometallics. (5) Albright, M. J., Butler, W. M.; Anderson, T. J.; Glick, M. D.; Oliver, J. P. J. Am. Chem. SOC. 1976,98,3995. (6) Ilsley, W. H.; Glick, M. D.; Oliver, J. P.; Moore, J. W. I n o g . Chem. 1980. 19. 3572. _._. -- -(7) Stucky, G. D.; McPherson, A. M.; Rhine, W. E.; Eisch, J. J.; Considine, J. L. J. Am. Chem. SOC.1974, 96,1941. (8) TeclC, B.; Corfield, P. W. R.; Oliver, J. P. Inorg. Chem. 1982,21, 458. (9) Almenningen, A.; Halvorsen, S.; Haaland, A. Acta Chem. Scand. 1971,25, 1937. (10) Drew, D. A.; Haaland, A. Acta Chem. Scand. 1973, 27, 3735. I
Table I. Experimental Data from the X-ray Diffraction Study on Tribenzylaluminum
vol
A. F. M. Maqsudur Rahman, Kanlz F. Slddlqul, and John P. Oliver' Department of Chemistry, Wayne State University Detroit, Michigan 48202
881
Dcalc 9 radiation M o monochromator reflctns measd 28 range scan type scan speed bkgd measuremt std reflctns
unique data unique data with F2 > 2.50(Fo') abs coeff, p
~C21H21 300.38
orthorhombic Pbca 9.480 (3) A 34.248 (11) A 10.546 (5) A 3424 ( 2 j AB
8
1.165 g ~ m ' ~
KZ (a = 0 . 7 1 0 6 9 a ) graphite crystal h,+k,+l 4 5" w
2 . 0 " min-I the ratio of the background to scan time was 0 . 5 . 3 std reflctns measd every 97 reflctns; no significant deviation from the mean was observed 2604 1100 1 . 0 8 2 cm-I
F(000)
1280
max shift/error for last least squares cycle RF
0.00749
RWF
5.6% where R w = {&( IFCl)*/ZWIFo121V'
5.3% where RF =
E 1 IFo/ - IFc( l / ~ l F o l IFoI -
powder (4.0 g, 0.15 mol, 8-20 mesh) following the literature procedure.12 The reactants were placed in a tall cylindrical vessel, equipped with a standard taper joint and stopcock. The vessel was evacuated and 50-60 mL of toluene distilled into it. It was attached to a pressure equalizing system filled with Ar gas to maintain approximate atmospheric pressure. It as then heated in an oil bath (-100 "C) continuously for 3 days. The reaction mixture was worked up by using standard Schlenk techniques, yield -60% of purified Al(CH,Ph),. A suitable single crystal for X-ray diffraction studies was grown from a benzene solution and was mounted in a thin-walled glass capillary tube under an Ar atmosphere in a drybox. The tube was plugged and, on removal from the drybox, flame sealed and mounted on a goniometer head. The data were collected on a Syntex P2' automated diffractometer with Mo Ka radiation diffracted from a highly oriented graphite crystal in the bisecting condition with a w scan. The specific conditions, unit cell, unit dimensions, and other experimental parameters are given in Table I. Solution and Refinement of t h e Structure. The crystal was found to be orthorhombic and was assigned to the space group Pbca on the basis of systematic absences. The crystallographic data on the unit cell and other pertinent data are collected in Table I. The structure was initially solved by light atom techniques through the use of MULTAN" which gave positions for all 22 nonhydrogen atoms. The hydrogen atom positions were calculated by
- - I
(11) Nesmeyonov, A. V.; Borisov, A. E.; Novikova, N. V. Izu. Akad. Nauk SSSR,Otd. Khim. Nauk 1959, 1216. (12) Eisch, J. J.; Biedermann, J.-M. J. Organomet. Chem. 1971, 30, 167. (13) Germain, G.; Main, P.; Wolfson, M. M. Acta Crystallogr., Sect. B 1970, B26, 274.
0276-733318212301-0881$01.25/0 , 0 1982 American Chemical Society I
,
I
~
882 Organometallics, Vol. 1, No. 6, 1982
Communications
Table 11. Atomic Coordinates for Tribenzylaluminum atom X Y Z 0.1251 ( 2 ) 0.3819 (1) Al 0.8565 ( 2 ) ~~
c1 c2 c3 c11 c12 C13 C14 C15 C16 c21 c22 C23 C24 C2 5 C26 C3 1 C3 2 c 33 c34 c 35 C36
0.8065 ( 6 ) 0.6964 ( 6 ) 0.9683 ( 6 ) 0.9207 ( 6 ) 0.9968 ( 7 ) 1.1047 ( 7 ) 1.1400 ( 8 ) 1.0665 ( 9 ) 0.9583 (8) 0.5654 ( 6 ) 0.5107 ( 6 ) 0.4064 ( 7 ) 0.3519 ( 7 ) 0.3973 ( 7 ) 0.5009 ( 7 ) 0.8603 ( 6 ) 0.7919 ( 8 ) 0.6839 (8) 0.6408 (8) 0.7083 ( 9 ) 0.8156 ( 7 )
0.3330 ( 2 ) 0.4050 ( 1 ) 0.4198 ( 2 ) 0.3113 ( 2 ) 0.2819 ( 2 ) 0.2627 ( 2 ) 0.2723 ( 2 ) 0.3012 ( 2 ) 0.3206 ( 2 ) 0.3876 ( 2 ) 0.3521 ( 2 ) 0.3313 ( 2 ) 0.3464 ( 2 ) 0.3828 ( 3 ) 0.4034 ( 2 ) 0.4439 ( 2 ) 0.4 299 ( 2 ) 0.4510 ( 2 ) 0.4860 ( 3 ) 0.5002 ( 2 ) 0.4799 ( 2 )
0.0351 ( 6 ) 0.2225 ( 5 ) 0.0232 ( 6 ) -0.0326 ( 6 ) 0.0243 ( 6 ) -0.0375 ( 7 ) -0.1606 (8) -0.2209 ( 6 ) -0.1582 ( 6 ) 0.1697 ( 5 ) 0.2153 ( 5 ) 0.1486 ( 7 ) 0.0396 (7) -0.0034 ( 5 ) 0.0603 ( 6 ) -0.0467 ( 5 ) -0.1553 ( 6 ) -0.2101 ( 6 ) -0.1624 (8) -0.0573 (8) -0.0011 ( 6 )
Table 111. Selected Interatomic Distances (A ) and Angles (Deg) in Tribenzylaluminum Bond Distances Al-C( 1) Al-C( 2) A-c( 3 1 C(l)-C(ll) C( 2)-C( 21)
1.982 ( 6 ) 1.997 ( 6 ) 1.989 ( 6 ) 1.494 (8) 1.486 ( 7 )
C(l)-Al-C(2) C(2)-Al-C(3) C(l)-Al-C(3) Al-C(1)-C(l1) Al-c(2)-C(21) Al-c(3)-C(31)
Bond 113.5 ( 2 ) 115.1 ( 2 ) 114.8 ( 3 ) 118.4 ( 4 ) 106.4 ( 3 ) 105.0 ( 4 )
C(3)-c(31) Al-C(22)’ Al-C(21)’ Al-C(23)’
1.507 (8) 2.453 ( 6 ) 2.940 ( 6 ) 2.987 ( 6 )
Angles Al-C(22)’-c(21) Al-C(22)’-C(23)‘ C(l)-Al-C(22)’ C(2)-Al-C(22)‘ C(3)-Al-C(22)‘
95.3 ( 3 ) 97.7 ( 4 ) 96.8 ( 2 ) 105.4 ( 2 ) 109.0 (3)
using HFINDR.14 Then, two additional cycles of refinement were carried out on all nonhydrogen atoms with the hydrogen atoms in fured positions to give the f d parameters listed. Atomic coordinates for the non-hydrogen atoms are presented in Table I1 with selected interatomic distances and angles given in Table 111. Anisotropic thermal parameters, hydrogen positional parameters, interatomic distances and angles in the benzene rings, and observed and calculated structure amplitudes are a~ai1able.l~ Results and Discussion. A perspective drawing of the structure is given in Figure 1 with the atoms in the tribenzylaluminum unit labeled. Selected bond distances and angles are given in Table 111. The benzyl groups are directly bound to the aluminum atoms through the methylene carbon atoms with an average A1-C distance of 1.989 A which is at the upper end of the range normally observed for terminal A1-C distances, both in the solid state16and gas phase” but nearly (14) Local versions of the following programs used: (1) SYNCOR, W. Schmonseea’ program for data reduction; (2) FORDAP,A. Zaltkin’s Fourier program; (3) HFINDR, A. Zalkin’s idealized hydrogen program; (4) o m and o m , W. Busing, K. Martin,and H. Levey’s full-matrix least-squares program and function error program; (5) ORTEP, C. K. Johnson’s program for drawing crystal models. Scattering factors were taken from: Ibers, J. A.; Hamilton, W. C. ”International Tables of X-ray Crystallography”, I11 Kynoch Press: Birmingham, England, 1974; Vol. IV. (15) See the paragraph at the end of the paper regarding supplementary material. (16) Oliver, J. P. Adu. Organomet. Chem. 1977, 15, 235. (17) Haaland, A. Top. Curr. Chem. 1976, No. 53, 1.
Figure 1. A prespective view of the tribenzylaluminum molecule with labeling and its intermolecular interactions. identical with the value obtained for monomeric A1Me3.9 The phenyl groups are arranged in a propellar like fashion forming dihedral angles of 62.9’, 101.5’, and 82.5’ between the ring planes and the plane described by the methylene carbon atoms. None of the methylene carbons are closer than 3.687 A to an aluminum atom in an adjacent molecular unit ruling out the typical form of electron-deficient bridge bonding observed in organoaluminum derivatives. However, examination of the atoms in the AlC, moiety reveals that the C-Al-C angles average 114.5’ with the Al atom displaced 0.475 A above the plane described by the three methylene carbon atoms. This dramatic distortion from planarity toward a tetrahedral arrangement suggests some other strong interaction must be taking place. Examination of the intermolecular Al-C distances shows that C(22)’ is only 2.453 (6) A away from the A1 atom in the adjacent Al(CH,Ph), moiety. Further, the Al-C(22)’-C(21)’ and Al-C(22)’-C(23)’ angles are 95.3’ and 97.7O with the Al-C(21)’ and Al-C(23)’ distances equal to 2.940 (6) and 2.987 (6) A, respectively, showing that the Al atom lies just outside of the ring, nearly directly above C(22)’, and not over the a-electron system. These results demonstrate that the aluminum atom is bound specifically to C(22)’ in the adjacent tribenzylaluminum moiety through its vacant p orbital. This interaction is quite strong with the observed A1-C distance only 0.25 A greater than the AI-C observed for electron-deficient bridge b o n d P and 0.2 A greater than that observed in the dimethyl-p-cyclopentadienyl chain.8 A further indication of the strength of this interaction may be obtained by comparing the geometry around the Al atom in this species with that obeserved in addition compounds. The two most convenient mesures of this are the average C-Al-C angle and the Al-E distance. In tri-o-tolyaluminum diethyl etherate, the respective values are 114.4’ and 1.928 A,4 in bis(trimethy1aluminum) p-dioxinate, they are 116.8’ and 2.02 A,18in trimethylaluminum dimethyl etherate (gas phase), they are 117.8’ and 2.014 A,19and in the trimethylaluminumtrimethylamino adduct (gas phase), they are 114.8 and 2.099 A.21 In each of these cases where strong bond formation is known to occur the C-A14 angles are equal to or greater than those observed in the tribenzylaluminum moiety, thus, indicating the interaction between the phenyl carbon atom and the vacant p orbital on the aluminum is quite strong. This previously unobserved interaction leads to formation of chain type structure with the bridging between units occurring through the phenyl ring and to (18) Atwood, J. L.; Stucky, G . D. J. Am. Chem. SOC.1967,89, 5362. (19) Haaland, A.; Samdal, S.;Stokkeland, 0. Acta Chem. Scand. 1973, 27, 1821. (20) Anderson, G. A.; Forgaard, F. R.; Haaland, A. Acta Chem. Scand. 1972,26, 1947.
883
Organometallics 1982,1, 883-884
the marked distortion of the tribenzylaluminum molecule.
Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research. Registry No. tribenzylaluminum, 14994-03-7.
Supplementary Material Available: Tables containing hydrogen atom positional parameters anisotropic thermal parameters for nonhydrogen atoms and isotropic thermal parameters for hydrogen, C-C bond lengths and C - C C angles in the aromatic ring, and observed and calculated structure amplitudes (12pages). Ordering information is given on any current masthead page. Figure 1. An ORTEP diagram showing 50% electron density probability ellipsoids of one of the two independent cations of MO(CO)~[PP~~(CH~)~SM~~]+ in the crystal of Mo(C0)4[PPh2(CH2)2SMe21+BF4-.
Positively Charged Ligands. The Structure and Bonding of Coordinated Sulfonium Cations: Synthesis and Crystal and Molecular Structure of Mo( CO),[PPh,( CH2)2SMe,]+BF,Richard D. Adams' and Mahmoud Shiralian Department of Chemistry Yale University New Haven, Connecticut 065 7 7 Received March 9, 1982
S~"aty: The complex Mo(CO),[ PPh#2H2)2SMe2]+BFi, I, has been synthesized by alkylation of the lone pair of electrons on the sulfur atom in Mo(CO),[Ph,P(CH),SMe], 11. Singlecrystal X-ray structural analysis of both I and I1 have been performed. For I: space group P2,lc; a = 16.928 (5) A, b = 21.786 (12) A, c = 13.900 (9) A, p = 106.38 (4)'; Z = 8, p(calcd) = 1.540 g/cm3. For 11: space group P2,2,2,; a = 8.150 (6) A, b = 14.229 (6) A, c = 17.209 (9) A; Z = 4, p(calcd) = 1.559 g/cm3.
Table I. Selected Internuclear Separations (A ) with Esds in Mo(CO),[PPh,(CH,),SMe,]+BF,-,I and Mo(CO),[PPh,(CH,),S&], I1 1
atoms Mo-S
molecule 1 molecule 2
2.420(1) Mo-P 2.485 (1) Mo-Cftrans S) 1.943 (5) Mo-C( trans P) 1.992 (6) Mo-C( av 2.005 (5) trans COS) S-C( av Me) 1.816 (6)
2.405 (1) 2.520 (1) 1.945 (6) 1.958 (5) 1.988(5)
av
2.412 2.502 1.944 1.975 1.997
I1 2.547 (1) 2.521 (1) 1.957 (4) 1.977 (4) 2.018 (4)
1.822 (6) 1.819 1.778(5)
0.100 g (0.213 mmol) of I1 and 0.100 g (0.675 mmol) of Me30+BF4-were vigorously stirred at room temperature, under nitrogen in CH2C12solvent (40 mL) for 2 days. The solution was filtered, and I was crystallized by addition of hexane to give white crystals, yield 65%.' This pseudooctahedral complex contains the chelating ligand Ph2P(CH2)2SMe2+ in which the sulfur atom is formally positively charged. It is hoped that a structural analysis of I would provide further evidence about the nature of the metal-sulfur bond and its effect on the bonding of the In 1976 we reported the first example of a coordinated other ligands to the metal atom. Thus, single-crystalx-ray sulfonium cation.' An X-ray structural analysis of one structural analyses of both Is and II? have been performed of these complexes, [MeC5H4Mn(C0)2SMe2Et]+BF4-, for comparative purposes. Both will be described briefly showed an unusually short metal-sulfur bond distance.2 here.1° High-frequency stretching of the carbonyl ligands indicated An ORTEP drawing of I is shown in Figure 1. The comthat the sulfonium ligand was strongly electron withpound crystallizes with two formula equivalents in the drawing, and a bonding model which included a significant asymmetric crystal unit. Structurally, both molecules are amount of d,-d, back-bonding was proposed.2 Since then very similar. Table I presents selected bond distances for other examples of complexes containing positively charged both independent cations of I, their averaged values, and ligands have been Interestingly the complex, I the corresponding bond distances in 11. In comparisons C5H5Mo(C0)2[PNMe(CH2)2NMe], in which the with 11, we will use the averaged values of I. phosphorus atom of the cyclic, positively charged phosphenium ligand, (PNMe(CH2)2NMe)+,is coordinated to (6) Ross, E. P.; Dobson, G . R. J. Znorg. Nucl. Chem. 1968, 30, 2363. the metal atom, showed an unusually short metal-phos(7) 'H NMR of I (CDZClp): 6 7.51 (m, Ph), 4.03 (dt, CH2, JP-H= 21.6 phorus bond distance. This was also interpreted in terms Hz, JH-H = 6.2 Hz), 3.52 ( 8 , Me), 2.74 (dt, CH2,J p - H = 6.8 Hz, J H - H = 7.3 of a a back-bonding effect and was supported by MO Hz). (8)For I space group ?'2Jc, No. 14; a = 16.928 (5) A b = 21.786 (12) calculation^.^^ A, c = 13.900 (9) A, j3 = 106.38 (4)'; Z = 8, p(cald) = 1.540g/cm3. We have now synthesized the chelate complex MoLeast-squaresrefinement on 4912 reflections,F 2 2 3.0u(F') produced the (C0)4[PPh2(CH2)2SMe2]+BF,-, I via alkylation of the lone fmal residuals R1= 0.700and Rz = O.O84.'O Hydrogen contributions were not included in this analysis. Only atoms heavier than fluorine were pair of electrons on the sulfur atom in the chelate complex refined anisotropically. M o ( C O ) ~ [ P P ~ ~ ( C H ~ ) ~IL6q7 S M ~In ] , a typical preparation (9) For 11: space group P212121,No. 19;a = 8.150 (6) A, b = 14.229 (6) A, c = 17.209 (9) A; 2 = 4, p ( d d ) = 1.559g/cm3. Least-squares rei
(1) Adams, R. D.; Chodosh, D. F. J. Organomet. Chem. 1976,120, C39. (2) Adams, R. D.; Chodosh, D. F. J. Am. Chem. SOC.1978, 100,812. (3) Stein, C. A.; Taube, H. J. Am. Chem. SOC.1978,100, 336. (4) (a) Montemayor,R. G.; Sauer, D. T.;Fleming, S.; Bennett, D. W.; Thomas, M. G.; Parry, R. W. J. Am. Chem. SOC. 1978, 100, 2231. (b) Bennett, D. W.; Parry, R. W. Ibid. 1979,101, 755. (5) (a) Light, R. W.; Paine, R. T. J. Am. Chem. SOC. 1978,100,2230. (b) Hutchins, L. D.; Paine, R. T.; Campana, C. F. Ibid. 1980,102,4521.
finement on 1699 reflections, p Z 2.0o(F) produced the final residuals R1= 0.025 and Rz = 0.022. Hydrogen atom contributionswere included
in the structure factor calculations, but they were not refined. All nonhydrogen atoms were refined anisotropically. (10) Intensity data were collected on an Enraf-Nonius CAD-4 automatic diffractometer. Both structures were solved by the heavy-atom method. All calculations were done on a Digital PDP-11/45 computer using the programs of the Enraf-Nonius SDP program library (version 16).
0276-7333f 8212301-0883$01.25/0 0 1982 American Chemical Society
