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Crystal and molecular structure of a novel coordinatively unsaturated rhodium(II) dimer
dram ELSEVIER
|norganica Chimica Acta 255 (1997) 395-398
Note
Crystal and molecular structure of a novel coordinatively unsaturated rhodium(II) dimer Kun Wang, Thomas J. Emge, Alan S. Goldman * Department of Chemistry. Rutgers-The State University of New Jersey. New Brunswick. NJ 08855-0939, USA Received g February 1996; revised 22 May 1996
Abstract
A novel, coordinatively unsaturated, phosphido-bfidged Rh (i I) dimer [ ( PMe'Bu2)CIRh(/.t-PMetBu) 12 (1) has been characterized. Complex 1 crystallizes in the monoclinic system, space group P2,/c, a = l l . 1 2 1 ( i ) , b=14.887(1), c=22.865(2) A, /3=94.87(1)0, V-- 3771.8( 5 ) A3, Z--4, R(F) = 0.039 and R,~(F -~)= 0.096 for I> 2o'(I). Keyword¢: Crystalstructures; Rhodiumcomplexes;Phosphido-bridgedcomplexes;Unsaturatedcomplexes
1. Introduction A rich and fascinating chemistry of phosphido-bridged Rh(II) and Co(II) dimers has been developed in recent years [ 1-7]. It includes, inter alia, the insertion ofchalcogen atoms [5], CH~ groups (from dihalomethanes) [4], SO~, [3] or acetylenes [5] into the M-M and M-P bonds (Scheme I) [7]. The hope that such complexes might display catalytic reactivity based on cooperative behavior between the metal centers, however, has yet to be realized. In the most general sense, catalysis by transition metal complexes typically requires the presence of vacant coordination sites. The known phosphido-bridged M(II) dimers contain 18-electron metal centers [ I-6,8-10]; although substrate coordination is permitted by the loss of a metal-metal bond, even while maintaining binuclearity [ !-6], it is still reasonable to expect that a vacant coordination site could facilitate catalytic activity. * Corresponding author,
PMe~/
PM~
~zR2
PMe~" R
~e~
R
Scheme I. 0020-1693/97/$17.00 © 1997EIsevie,ScienceS.A. All rightsreserved Plt S0020-1693 ( 96 ) 05388- I
In this note we report the synthesis and molecular structure of a binuclear complex possessing 16-electron metal centers, otherwise analogous to previously reported cyclopentadienyl complexes of the type shown in Scheme 1.
2. Experimental 2.1. Synthesis of [(PMe'Buz)CIRh(Iz-PMetBu)]z (1) 27 ml of 1.7 M tBuLi in pentane were added slowly with stirring to a solution of 2.0 ml (22.4 retool) PMeCI2 (SU'em Chemicals) dissolved in 20 ml dry pentane in a I00 ml Schlenk flask cooled down to -78°C. The mixture was allowed to warm up slowly after the addition had completed while vigorous stirring was maintained. The white precipitate was filtered off through Celite after 5 h and the solvent was removed in vacuo yielding a light yellow oil. Trap-to-trap distillation gave 2.3 g of a colorless oil, which was mostly PMetBu2 (IH NMR: 80.83 (d, J ( P - H ) = 4 . 5 Hz, 3H), 1.04 (d, J(P-H) = 10.6 Hz, 18H); 31pIH NMR (Ct;D6): 8 11-4 (s)) with about a4% molar ratio of (PMerBu)2 [ 11], identiffed by GCIMS and comparison with reported [ 11 ] spectroscopic data (~H NMR: 80.88 (t, J ( P - H ) =4.8 Hz, 6H), 1.13 (t, J ( P - H ) = 6 A Hz, 18H); 3~PIH NMR (C~D6): 8 - 3 1 . 0 4 (s)). 0.090 g of the above mixture was then added to [Rh(COE)2CI]2 (0.20 g, 0.28 retool), synthesized according to Ent and Ondetdelinden [ 12]. The major product was Rh ( PMetB u2) 2C1 as evidenced by 3ip NMR [ 13 ]. However,
396
K. Wang et aL / hwrganica Chimica Acta 255 (1997) 395-398
recrystallization in t o l u e n e / p e n t a n e at --35°C gave only black crystals of 1. Yields were not optimized although presumably a mixture with a greater ratio of (PMetBu)z:PMe'Buz would afford higher yields of c o m p l e x 1. 2.2. Single crystal structure determination o f complex 1
A crystal ( 0 . 7 0 × 0 . 6 0 × 0 . 3 0 m m ) of complex 1 was m o u n t e d on an Enraf-Nonius C A D 4 diffractometerequipped with a graphite m o n o c h r o m a t o r and Mo K a (A = 0.71073 A.) radiation. The unit cell parameters were obtained by leastsquares refinement o f the setting angles o f 25 reflections in the range 17 < 0 < 2 1 ° at room temperature. The data to O= 23 ° were collected in the to:0 m o d e at room temperature. No significant change was detected in the intensities of the three standard reflections collected every hour, Lorentz, polarization and absorption (numerical, SHELX-76 Gaussian grid [ 14] ) corrections were applied to the data. The crystallographic data are shown in Table 1. The crystal structure was solved by Patterson m e t h o d s using the S H E L X S 8 6 program [ ! 5 ]. Final coordinate and displacement parameters for all non-H atoms are given in Table 2. T h e structure of c o m p l e x 1, s h o w n in the O R T E P [ 16] plot o f Fig. 1, was Table 1 Crystal data and structure rennement for [ (PMetBu.,)CIRh(/t-PMetBu) l z (1) Empirical formula Formula weight Temperature (K) Crystal system Space group No. reflections, 0 range cell detection (°) Unit cell dimensions a(A) b(A) c(A) a(°) B(°) y(°) Volume (/~.~) z Density (calc.) (gcm -3) Absorption coefficient ( mm- 1 ) F(000) Crystal size (ram) ORange data collection (*) Index ranges Reflections collected Max., rain. transmission Independent reflections Observed reflections (/> 2o'(1) ) Data/parameters Goodness-of-fit on F 2 Final R(F), Rw(F 2) (!> 2¢(•) ) Final R( F). Rw( F 2) (all data) Extinction coefficient Largest difference peak, hole (e A- ~)
C2.H~CI:P4Rh2 803+41 293(2) monoclinic P21/c(No. 14) 25,17-20 !1,121(1) 14.887(1) 22.865(2) 90 94.87(!) 90 3771.8(5) 4 1.415 1,203 1672 0.70×0.60×0,30 2-23 0~h~12.0~k~16. -25 ~1~24 5087 0.779,0.722 4803(R(int) =0.024) 4228 4803•348 1.038 0.039,0.096 0.048,0.099 0.0005(1) 2.4.-1.2
Table 2 Atomic coordinates ( × 10a) and equivalent isotropie displacement parameters (A2X 103) for complex I
Rh(l) Rh(2) P(I) P(2) P(3 P(4) Cl(l) C1(2 C(i) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(lO) C(II) C(12) C(13) C(14) C(15) C(16) C(t7) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28)
x
Y
z
U,~ta
2884(1) 924(I) 1786(1) 283t(2) 4744(2) -580(2) 2895(2) -658(I) 907(6) 2180(6) 748(7) 1630(7) - 312(6) 3249(7) 3856(6) 2290(7) 4498(7) 3290(9) 5792(7) 4612(6 5770(8) 6228(7) 6955(8) 5026(9) 3653(11) 4283(12) 5785(9) -204(7) - 1217(7) -1929(6) -1126(8) 1034(7) -183(9) - 1303(8) -357(9) -2490(8)
1423(1) 1850(1) 2655(1) 1836(I) 1346(i) 2493(1) -189(I) 1051(1) 2833(4) 3814(4) 1927(5) 3474(5) 3271(51 978(5) 2759(5 238(5) 577(5) 1419(6) 2304(6) 928(6) 466(5) 2357(6) 2203(9) 3154(6) 222(9) 1666(9) 495(9) 3601(5) 1691(5) 2769(5) 3928(6) 355I(6) 4291(5) 62(5) 1615(6) 1935(6)
7587(I) 6837(i) 7584(I) 6647(1) 8214(!) 6124(1) 7532(1) 7277(1) 8235(3) 7412(3) 8536(3) 8664(3) 8045(3) 6097(3) 6486(3) 6062(3) 6286(4) 5489(3) 8204(4) 8996(3) 7907(4) 7605(4) 8642(4) 8363(6) 8961(5) 9369(5) 9264(5) 5782(3) 5533(3) 6483(3) 5291(4) 5550(4) 6287(4) 5809(3) 5039(3) 5263(4)
43(I) 42(I) 45(i) 52(1) 71(l) 54(1) 76(1) 60(I) 59(2) 64(2) 75(2) 85(2) 82(2) 70(21 70(2) 83(2) 87(2) 102(3) 88(2) 79(2) 94(3) 92(3) 133(4) 146(5) 160(6) 158(5) 151(5) 76(2) 71(2) 74(2) 97(3) 101(3) 106(3) 84(2) 98(3) 101(3)
"U~q is defined as one third of the trace of the orthogonalized Uq tensor.
Fig, 1. Molecular structure and atom labeling scheme of [ ( PMe'Bu2)CIRh(~-PMe'Bu) ]2 ( I ), H atoms have been removed for cl,'wity. The thermal ellipsoids are drawn at the 50% probability level. refined on F 2, using full-matrix least-squares methods and the S H E L X L 9 3 c o m p u t e r program [ 17]. The function minimized was w R ( F 2 ) = { ~ [ W ( F o 2 - F c 2 ) 2 ] /
K. Wang et al. / lnorganica ChimicaActa 255 (I997) 395-398
397
Table 3 Selected bond lengths CA) and angles (°) for [ (PMetBu2)CIRh(/~-PMetBu)]2 (1) Rh(I)-P(l) Rh(I)-CI(I) Rh(I)-Rh(2) Rh(2)-P(I) Rh(2)-P(4)
2.202(2) 2.404(2) 2.7310(7) 2.235(2) 2,431(2)
Rh(I)-P(2) Rh(I)-P(3) Rh(2)-P(2) Rh(2)-CI(2)
2.232(2) 2.417(2) 2.201(2) 2,413(2)
P(I)-Rh(l)-P(2) P(2)-Rh(I)-CI(I) P(2)-Rh(I)-P(3) P(I)-Rh(I)-Rh(2) CI(I)-Rh(I)-Rh(2) P(2)-Rh(2)-P(I) P(I)-Rh(2)-CI(2) P(I)-Rh(2)-P(4) P(2)-Rh(2)-Rh(I) Ci(2)-Rh(2)-Rb(I) Rh(l)-P(l)-Rh(2)
78A0(6) 102.98(7) 122.36(6) 52.55(4) 101.94(5) 78.35(6) 103.08(6) 121.86(6) 52.47(5) 101.2314) 75.98(5)
P(I)-Rh(I)-CI(I) P(l)-Rh(I)-P(3) CI(I)-Rh(IF-P(3) P(2)-Rh(I)-Rh(2) P(3)-Rh~I)-Rh(2) P(2)-Rh(2)-CI(2) P(2)-Rh(2)-P(4) CI(2)-Rh(2)-P(4) P(I)-Rh(2)-Rh(l) P(4)-Rh(2)-Rh(I) Rh(2)-P(2)-Rb(I)
146,76(7) i 19,20(7) 88,58(7)
51.46(4) 168.6615) 145.74(6) 119,44(6) 89.35(6) 51.47{4)
168.45{5) 76.07(5)
Table 4 Selected torsion angles (°) for [ (PMe'Bu_,)CIRh(/.t-PMetR~l) I, ( 1) P( I )-Rh( I )-Rh(2)-P(2) P(3)-Rh( I)-Rh(2 )-P(2)
106.63(7) 60,5(3)
Ci( I )-Rh( I )-Rh(2)-P( i ) PCI )-Rh( I )-Rh(2)-CI(2) CI( I )-Rh( I )-Rh(2)--CI(2) P( ! )-Rh( 1)-Rh(2)-P(4) CI( I )-Rh( I )-Rh(2)-P(4) P(2)-Rh( 1)-P( 1)-Rh(2)
156.19(7) -97.87(7) 58.32(7) 58.2(2) - 145.6(2) 49.92(5)
P(3)-Rh( I )-P( I )-Rh(2) CI(2)-Rh( 2)-P( I )-Rh( 1 ) P( I )-Rh(2)-P(2)-Rh( I ) P(4)-Rh(2)-P(2)-Rh( I ) CI( 1 )-Rh( I )-P(2)-Rh(2)
170,66(6) 94.04(5) 49.93(5) 170,10(5) 95,04(6)
E[w(F,, 2)2] }o.s with G O F = {E[wFo 2 - F ~ "-)2]/(N,,b~-Nparam) }o.5 and weights: w = I / [ o 2 ( F o -') + (0.0434P):+ 12.65P], where P - [0.33333max(0,F. 2) +0.66667F~ '1. An extinction correction, x = 0 . 0 0 0 5 ( l ) was refined (SHELXL93) such that F,: was multiplied by the overall scale factor and the term [1 +0.001xF~ 2A3/sin(2~9)]-o.~. The torsion angles of the H atoms in each of the 22 methyl groups were refined as a rotating group (SHELXL93), but constrained to idealized CH3 group geometry (tetrahedrai angles). The motion of the H atoms of this 'rotating group' is a combination of riding motion on the C atom and a tangential component perpendicular to the C'--C and C - H bonds, so that the C - H distances and C'--C-H and H--C-H angles remain constant. The displacement parameters of the H atoms were held equal to !.5 times the displacement parameters of the C atoms to which they were bonded. The final R(F) factor was 0.039 (Rw(F2)=0.096) for the 4228 data with 1>2o'(1); R ( F ) =0.048, Rw(F 2) = 0.099 and G O F = 1.038 for all 4803 data. The number of parameters varied was 348 and all final maximum shift/error values were less than 0.01. The maximum peak and valley on the final difference-Fourier map were + 2.4 and - 1.2 e ,g,- 3, respectively. Selected final
CI( I)-Rh( I )-Rh (2)-P( 2 } P(2)-Rh( I )-Rh(2)-P( I ) P( 3)-Rh( I )-Rh(2)-P( I ) P(2)-Rh( I )-Rh(2)-CI(2) P(3 )-Rh{ I )-Rh{2)-CI(2) P(2)-Rh( I )-Rh(2)-P(4)
-97.18(7) - 106,63(7) -46.1 (3) 155.50{7) - 144.0(3) -48.4(2)
P{3)-Rh ( 1)-Rh{2)-P(4) O11 )-Rh( ! )-P( 1)-Rh(2) P( 2)-Rh{ 2)-P( 1)-Rh( ! )
12.1(4) -46.11 {131 -50.88(5)
P(4)-Rh(2)-P( I )-Rh(I) CI(2)-Rh(2)-P( 2)-Rh( I )
- !68.44{5) -46.26{ 12}
P( I )-Rh( 1)-P(2)-Rh(2) P( 3 )-Rh( I )-P( 2 )-Rh (2)
-50.95(5) - 168.30(7)
bond lengths and angles and torsion angles for complex I are given in Tables 3 and 4, respectively.
3. Results and discussion Although (PMe~Bu)2 was an unanticipated byproductof an attempted synthesis of PMe'Bu2, its formation led to a convenient method for the preparation of complex 1 (Eq. (l)). [ (COE) 2Rh ( IX- CI) ] 2 + 2PMetBu: + (PMetBu) 2 (PMetBu2)CIRh(P--PMetBu) ]2 1
(1)
The synthesis of phosphido-bridged dimers using diphosphines is well precedented. Indeed, diphosphines were used by Hayter to synthesize the first such complexes [~-10], including [Cl3CO(/.~-PPh2)]-, [ 10], although other re,agents have since proven more convenient [7]. The molecular structure of complex 1 is shown in Fig. 1 with the atom labelling scheme. Crystallographic details,
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K. Wang et al. / lnorganica Chimica Acta 255 (19971395-398
Table 5 Comparison of the butterfly Rh:(/z.-P), cores of [ (PMetBu_~)CIRh(p.-PMe*Bu)12 (1) and [Cp*Rh(/.t-PMe2)(/.t-PPh~) ]~_(2) "1.Selected bond lengths (A) and angles ( -~1 1
2 "~
Rh(l)-Rh(2) Rh(l)-P(i) Rh(Ij-P(2)
2.7310 2.202 2.232
2.7952 2.230 2.240
Rh(l)-P(I)-Rh(2) P(I)-Rh(I)-P(2) P(2)-Rh(I)-Rh(2)
75.98 78.40 51.46
77,81 80,01P 51.13 "
P(l)-Rh(l)-Rh(2)-P(2)
106.63
111.5
1
2 "~
Rh(2)-P(2) Rh(2)-P(I)
2.201 2.235
2.230 2.221
Rh(2)-P(2)-Rh(I) (2).-Rh(2)-P(I) P(t)-Rh(I)-Rh(2)
76.07 78.35 52.55
77.39 80.39 50.95 "
•" From ReL 6. Atom labeling scheme for complex I and for the l Rh(/-tP) ] z core of complex 2 is as given in Fig. 1. t, Calculated based on angles reported in Ref. 6. selected bond distances, angles and torsion angles are listed in Tables 1-4. The R h - R h distance of 2.731 .A falls in the range of a typical R h - R h single bond. A comparison with ~he previously reported structure of (Cp*Rh),(/x-PMe2)(/.tPPh2) (2; Cp* = C.~Mes) is shown in Table 5 [6]. The similarity of the butterfly Rh2(/z-P) 2 cores of complexes 1 and 2 is striking in view of the very different sets of ancillary Iigands on the Rh centers of each complex (i.e., PMetBu, and C! versus C p * ) and their different electron-counts ( 16 and 18, respectively). Note also that the the 18-electron rhodium center of Cp*Rh(/.t-PMez)-,Mo(CO)4 is approximately isostructural to those of complex 2 [2]. Each rhodium atom in complex 1 is approximately coplanar with four of the five atoms to which it is bound; Rh I lies within the plane approximated by PI, Rh2, C! I and P3, while Rh2 is found in the corresponding approximate plane containing P2, R h l , Cl2 and P4. The total of the four X - R h - Y angles of each of these groups is 362.3 and 362,5 ° , respectively. Thus the vacant coordination sites on RhI and Rh2 may be viewed as being trans to the bridging phosphorus atoms P2 and PI, respectively. If the R h - R h bond is viewed as related to a R h - X bond, then the rhodium centers of compound I are analogous to those of five-coordinate Rh (III) complexes. Most such complexes, like 1, possess very bulky phosphines which presumably protect the vacant coordination sites (though only weakly enough so that the chemistry expected of unsaturated species can be observed). It is our hope that complex 1 will possess enough shared characteristics of unsaturated complexes and phosphido-bridged complexes to result in a display of novel, possibly catalytic, reactivity.
4. S u p p l e m e n t a r y m a t e r i a l
Further data including complele intramolecular distances and angles, torsion angles, anisotropic displacement parameters and H atom parameters can be obtained on request from
the Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road Cambridge CB2 1EW, UK,
Acknowledgements
We thank the Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research, U.S. Department of Energy for support of this work. A.S,G. thanks the Camille and Henry Dreyfus Foundation for a Teacher Scholar Award and the Alfred P. Sloan Foundation for a Research Fellowship,
References
[ll A.D. Harley, G.J. Guskey and G.L. Geoffroy, Organometallics. 2 (1983) 53. [21 R,G. Finke, G. Gaughan. C, Pierpont and J.H. Noordik, Organometallics. 2 (1983) 148 I. [3] L. Chen, D.I. Kountz and D.W. Meek, Organomemllics. 4 (1985) 598. [4] H. Wemer and R. Zolk, Organometallics, 4 (1985) 601. [5] B. Klingert, A.L. Rheingoldand H. Werner, hzorg. Chem.. 27 ( 19881 1354. 16] H. Werner and B. Klingert, Organometallics. 7 (1988) 911. 17] H. Wemer, Comments Inorg. Chem.. !0 (1990) 267. [8] R,G. Hayter,Z Am. Chem. Soc.. 85 (1963) 3120. [91 R,G, Hayter, lnorg, Chem., 2 (1963) 1031. [ 10] R,G. Hayter,J. lnorg. Nucl. Chem., 26 (1964) 1977, [ I l ] (a) H.C.E. McFarlane, W. McFarlane and J.A. Nash, Z Chen~. Sot.. Dalton Trans,, (1980) 240; (b) O. Scherer and W, Gick, Chem. Bet., I03 (1970) 71. [ 12l A.v.d. Ent and A.L. Onderdelinden,Inorg, Synth., 14 ( 19731 92. [ 13] K, Wang, M.E. Goldman,T,J. Emgeand A.S. Goldman,,/. Organomet. Chem., 518 (1996) 55. 114] G.M. Sheldrick, SHELX76, program for crystal structure determination, Universityof Cambridge, UK, 1976. [15] G.M Sheldriek, SHELXS86, program for the solution of crystal structures. Universityof G6ttingen, G6ttingen, Germany, 1986, [16] C.K. Johnson, ORTEP !1, Rep. ORNL-513& Oak Ridge National Laboratory, Oak Ridge, TN, 1976. [ 17] G.M. Sheldrick,SHELXL93, program for crystal structure refinement, University of G6ttingea, G6ttingen, Germany, 1993.
|norganica Chimica Acta 255 (1997) 395-398
Note
Crystal and molecular structure of a novel coordinatively unsaturated rhodium(II) dimer Kun Wang, Thomas J. Emge, Alan S. Goldman * Department of Chemistry. Rutgers-The State University of New Jersey. New Brunswick. NJ 08855-0939, USA Received g February 1996; revised 22 May 1996
Abstract
A novel, coordinatively unsaturated, phosphido-bfidged Rh (i I) dimer [ ( PMe'Bu2)CIRh(/.t-PMetBu) 12 (1) has been characterized. Complex 1 crystallizes in the monoclinic system, space group P2,/c, a = l l . 1 2 1 ( i ) , b=14.887(1), c=22.865(2) A, /3=94.87(1)0, V-- 3771.8( 5 ) A3, Z--4, R(F) = 0.039 and R,~(F -~)= 0.096 for I> 2o'(I). Keyword¢: Crystalstructures; Rhodiumcomplexes;Phosphido-bridgedcomplexes;Unsaturatedcomplexes
1. Introduction A rich and fascinating chemistry of phosphido-bridged Rh(II) and Co(II) dimers has been developed in recent years [ 1-7]. It includes, inter alia, the insertion ofchalcogen atoms [5], CH~ groups (from dihalomethanes) [4], SO~, [3] or acetylenes [5] into the M-M and M-P bonds (Scheme I) [7]. The hope that such complexes might display catalytic reactivity based on cooperative behavior between the metal centers, however, has yet to be realized. In the most general sense, catalysis by transition metal complexes typically requires the presence of vacant coordination sites. The known phosphido-bridged M(II) dimers contain 18-electron metal centers [ I-6,8-10]; although substrate coordination is permitted by the loss of a metal-metal bond, even while maintaining binuclearity [ !-6], it is still reasonable to expect that a vacant coordination site could facilitate catalytic activity. * Corresponding author,
PMe~/
PM~
~zR2
PMe~" R
~e~
R
Scheme I. 0020-1693/97/$17.00 © 1997EIsevie,ScienceS.A. All rightsreserved Plt S0020-1693 ( 96 ) 05388- I
In this note we report the synthesis and molecular structure of a binuclear complex possessing 16-electron metal centers, otherwise analogous to previously reported cyclopentadienyl complexes of the type shown in Scheme 1.
2. Experimental 2.1. Synthesis of [(PMe'Buz)CIRh(Iz-PMetBu)]z (1) 27 ml of 1.7 M tBuLi in pentane were added slowly with stirring to a solution of 2.0 ml (22.4 retool) PMeCI2 (SU'em Chemicals) dissolved in 20 ml dry pentane in a I00 ml Schlenk flask cooled down to -78°C. The mixture was allowed to warm up slowly after the addition had completed while vigorous stirring was maintained. The white precipitate was filtered off through Celite after 5 h and the solvent was removed in vacuo yielding a light yellow oil. Trap-to-trap distillation gave 2.3 g of a colorless oil, which was mostly PMetBu2 (IH NMR: 80.83 (d, J ( P - H ) = 4 . 5 Hz, 3H), 1.04 (d, J(P-H) = 10.6 Hz, 18H); 31pIH NMR (Ct;D6): 8 11-4 (s)) with about a4% molar ratio of (PMerBu)2 [ 11], identiffed by GCIMS and comparison with reported [ 11 ] spectroscopic data (~H NMR: 80.88 (t, J ( P - H ) =4.8 Hz, 6H), 1.13 (t, J ( P - H ) = 6 A Hz, 18H); 3~PIH NMR (C~D6): 8 - 3 1 . 0 4 (s)). 0.090 g of the above mixture was then added to [Rh(COE)2CI]2 (0.20 g, 0.28 retool), synthesized according to Ent and Ondetdelinden [ 12]. The major product was Rh ( PMetB u2) 2C1 as evidenced by 3ip NMR [ 13 ]. However,
396
K. Wang et aL / hwrganica Chimica Acta 255 (1997) 395-398
recrystallization in t o l u e n e / p e n t a n e at --35°C gave only black crystals of 1. Yields were not optimized although presumably a mixture with a greater ratio of (PMetBu)z:PMe'Buz would afford higher yields of c o m p l e x 1. 2.2. Single crystal structure determination o f complex 1
A crystal ( 0 . 7 0 × 0 . 6 0 × 0 . 3 0 m m ) of complex 1 was m o u n t e d on an Enraf-Nonius C A D 4 diffractometerequipped with a graphite m o n o c h r o m a t o r and Mo K a (A = 0.71073 A.) radiation. The unit cell parameters were obtained by leastsquares refinement o f the setting angles o f 25 reflections in the range 17 < 0 < 2 1 ° at room temperature. The data to O= 23 ° were collected in the to:0 m o d e at room temperature. No significant change was detected in the intensities of the three standard reflections collected every hour, Lorentz, polarization and absorption (numerical, SHELX-76 Gaussian grid [ 14] ) corrections were applied to the data. The crystallographic data are shown in Table 1. The crystal structure was solved by Patterson m e t h o d s using the S H E L X S 8 6 program [ ! 5 ]. Final coordinate and displacement parameters for all non-H atoms are given in Table 2. T h e structure of c o m p l e x 1, s h o w n in the O R T E P [ 16] plot o f Fig. 1, was Table 1 Crystal data and structure rennement for [ (PMetBu.,)CIRh(/t-PMetBu) l z (1) Empirical formula Formula weight Temperature (K) Crystal system Space group No. reflections, 0 range cell detection (°) Unit cell dimensions a(A) b(A) c(A) a(°) B(°) y(°) Volume (/~.~) z Density (calc.) (gcm -3) Absorption coefficient ( mm- 1 ) F(000) Crystal size (ram) ORange data collection (*) Index ranges Reflections collected Max., rain. transmission Independent reflections Observed reflections (/> 2o'(1) ) Data/parameters Goodness-of-fit on F 2 Final R(F), Rw(F 2) (!> 2¢(•) ) Final R( F). Rw( F 2) (all data) Extinction coefficient Largest difference peak, hole (e A- ~)
C2.H~CI:P4Rh2 803+41 293(2) monoclinic P21/c(No. 14) 25,17-20 !1,121(1) 14.887(1) 22.865(2) 90 94.87(!) 90 3771.8(5) 4 1.415 1,203 1672 0.70×0.60×0,30 2-23 0~h~12.0~k~16. -25 ~1~24 5087 0.779,0.722 4803(R(int) =0.024) 4228 4803•348 1.038 0.039,0.096 0.048,0.099 0.0005(1) 2.4.-1.2
Table 2 Atomic coordinates ( × 10a) and equivalent isotropie displacement parameters (A2X 103) for complex I
Rh(l) Rh(2) P(I) P(2) P(3 P(4) Cl(l) C1(2 C(i) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(lO) C(II) C(12) C(13) C(14) C(15) C(16) C(t7) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28)
x
Y
z
U,~ta
2884(1) 924(I) 1786(1) 283t(2) 4744(2) -580(2) 2895(2) -658(I) 907(6) 2180(6) 748(7) 1630(7) - 312(6) 3249(7) 3856(6) 2290(7) 4498(7) 3290(9) 5792(7) 4612(6 5770(8) 6228(7) 6955(8) 5026(9) 3653(11) 4283(12) 5785(9) -204(7) - 1217(7) -1929(6) -1126(8) 1034(7) -183(9) - 1303(8) -357(9) -2490(8)
1423(1) 1850(1) 2655(1) 1836(I) 1346(i) 2493(1) -189(I) 1051(1) 2833(4) 3814(4) 1927(5) 3474(5) 3271(51 978(5) 2759(5 238(5) 577(5) 1419(6) 2304(6) 928(6) 466(5) 2357(6) 2203(9) 3154(6) 222(9) 1666(9) 495(9) 3601(5) 1691(5) 2769(5) 3928(6) 355I(6) 4291(5) 62(5) 1615(6) 1935(6)
7587(I) 6837(i) 7584(I) 6647(1) 8214(!) 6124(1) 7532(1) 7277(1) 8235(3) 7412(3) 8536(3) 8664(3) 8045(3) 6097(3) 6486(3) 6062(3) 6286(4) 5489(3) 8204(4) 8996(3) 7907(4) 7605(4) 8642(4) 8363(6) 8961(5) 9369(5) 9264(5) 5782(3) 5533(3) 6483(3) 5291(4) 5550(4) 6287(4) 5809(3) 5039(3) 5263(4)
43(I) 42(I) 45(i) 52(1) 71(l) 54(1) 76(1) 60(I) 59(2) 64(2) 75(2) 85(2) 82(2) 70(21 70(2) 83(2) 87(2) 102(3) 88(2) 79(2) 94(3) 92(3) 133(4) 146(5) 160(6) 158(5) 151(5) 76(2) 71(2) 74(2) 97(3) 101(3) 106(3) 84(2) 98(3) 101(3)
"U~q is defined as one third of the trace of the orthogonalized Uq tensor.
Fig, 1. Molecular structure and atom labeling scheme of [ ( PMe'Bu2)CIRh(~-PMe'Bu) ]2 ( I ), H atoms have been removed for cl,'wity. The thermal ellipsoids are drawn at the 50% probability level. refined on F 2, using full-matrix least-squares methods and the S H E L X L 9 3 c o m p u t e r program [ 17]. The function minimized was w R ( F 2 ) = { ~ [ W ( F o 2 - F c 2 ) 2 ] /
K. Wang et al. / lnorganica ChimicaActa 255 (I997) 395-398
397
Table 3 Selected bond lengths CA) and angles (°) for [ (PMetBu2)CIRh(/~-PMetBu)]2 (1) Rh(I)-P(l) Rh(I)-CI(I) Rh(I)-Rh(2) Rh(2)-P(I) Rh(2)-P(4)
2.202(2) 2.404(2) 2.7310(7) 2.235(2) 2,431(2)
Rh(I)-P(2) Rh(I)-P(3) Rh(2)-P(2) Rh(2)-CI(2)
2.232(2) 2.417(2) 2.201(2) 2,413(2)
P(I)-Rh(l)-P(2) P(2)-Rh(I)-CI(I) P(2)-Rh(I)-P(3) P(I)-Rh(I)-Rh(2) CI(I)-Rh(I)-Rh(2) P(2)-Rh(2)-P(I) P(I)-Rh(2)-CI(2) P(I)-Rh(2)-P(4) P(2)-Rh(2)-Rh(I) Ci(2)-Rh(2)-Rb(I) Rh(l)-P(l)-Rh(2)
78A0(6) 102.98(7) 122.36(6) 52.55(4) 101.94(5) 78.35(6) 103.08(6) 121.86(6) 52.47(5) 101.2314) 75.98(5)
P(I)-Rh(I)-CI(I) P(l)-Rh(I)-P(3) CI(I)-Rh(IF-P(3) P(2)-Rh(I)-Rh(2) P(3)-Rh~I)-Rh(2) P(2)-Rh(2)-CI(2) P(2)-Rh(2)-P(4) CI(2)-Rh(2)-P(4) P(I)-Rh(2)-Rh(l) P(4)-Rh(2)-Rh(I) Rh(2)-P(2)-Rb(I)
146,76(7) i 19,20(7) 88,58(7)
51.46(4) 168.6615) 145.74(6) 119,44(6) 89.35(6) 51.47{4)
168.45{5) 76.07(5)
Table 4 Selected torsion angles (°) for [ (PMe'Bu_,)CIRh(/.t-PMetR~l) I, ( 1) P( I )-Rh( I )-Rh(2)-P(2) P(3)-Rh( I)-Rh(2 )-P(2)
106.63(7) 60,5(3)
Ci( I )-Rh( I )-Rh(2)-P( i ) PCI )-Rh( I )-Rh(2)-CI(2) CI( I )-Rh( I )-Rh(2)--CI(2) P( ! )-Rh( 1)-Rh(2)-P(4) CI( I )-Rh( I )-Rh(2)-P(4) P(2)-Rh( 1)-P( 1)-Rh(2)
156.19(7) -97.87(7) 58.32(7) 58.2(2) - 145.6(2) 49.92(5)
P(3)-Rh( I )-P( I )-Rh(2) CI(2)-Rh( 2)-P( I )-Rh( 1 ) P( I )-Rh(2)-P(2)-Rh( I ) P(4)-Rh(2)-P(2)-Rh( I ) CI( 1 )-Rh( I )-P(2)-Rh(2)
170,66(6) 94.04(5) 49.93(5) 170,10(5) 95,04(6)
E[w(F,, 2)2] }o.s with G O F = {E[wFo 2 - F ~ "-)2]/(N,,b~-Nparam) }o.5 and weights: w = I / [ o 2 ( F o -') + (0.0434P):+ 12.65P], where P - [0.33333max(0,F. 2) +0.66667F~ '1. An extinction correction, x = 0 . 0 0 0 5 ( l ) was refined (SHELXL93) such that F,: was multiplied by the overall scale factor and the term [1 +0.001xF~ 2A3/sin(2~9)]-o.~. The torsion angles of the H atoms in each of the 22 methyl groups were refined as a rotating group (SHELXL93), but constrained to idealized CH3 group geometry (tetrahedrai angles). The motion of the H atoms of this 'rotating group' is a combination of riding motion on the C atom and a tangential component perpendicular to the C'--C and C - H bonds, so that the C - H distances and C'--C-H and H--C-H angles remain constant. The displacement parameters of the H atoms were held equal to !.5 times the displacement parameters of the C atoms to which they were bonded. The final R(F) factor was 0.039 (Rw(F2)=0.096) for the 4228 data with 1>2o'(1); R ( F ) =0.048, Rw(F 2) = 0.099 and G O F = 1.038 for all 4803 data. The number of parameters varied was 348 and all final maximum shift/error values were less than 0.01. The maximum peak and valley on the final difference-Fourier map were + 2.4 and - 1.2 e ,g,- 3, respectively. Selected final
CI( I)-Rh( I )-Rh (2)-P( 2 } P(2)-Rh( I )-Rh(2)-P( I ) P( 3)-Rh( I )-Rh(2)-P( I ) P(2)-Rh( I )-Rh(2)-CI(2) P(3 )-Rh{ I )-Rh{2)-CI(2) P(2)-Rh( I )-Rh(2)-P(4)
-97.18(7) - 106,63(7) -46.1 (3) 155.50{7) - 144.0(3) -48.4(2)
P{3)-Rh ( 1)-Rh{2)-P(4) O11 )-Rh( ! )-P( 1)-Rh(2) P( 2)-Rh{ 2)-P( 1)-Rh( ! )
12.1(4) -46.11 {131 -50.88(5)
P(4)-Rh(2)-P( I )-Rh(I) CI(2)-Rh(2)-P( 2)-Rh( I )
- !68.44{5) -46.26{ 12}
P( I )-Rh( 1)-P(2)-Rh(2) P( 3 )-Rh( I )-P( 2 )-Rh (2)
-50.95(5) - 168.30(7)
bond lengths and angles and torsion angles for complex I are given in Tables 3 and 4, respectively.
3. Results and discussion Although (PMe~Bu)2 was an unanticipated byproductof an attempted synthesis of PMe'Bu2, its formation led to a convenient method for the preparation of complex 1 (Eq. (l)). [ (COE) 2Rh ( IX- CI) ] 2 + 2PMetBu: + (PMetBu) 2 (PMetBu2)CIRh(P--PMetBu) ]2 1
(1)
The synthesis of phosphido-bridged dimers using diphosphines is well precedented. Indeed, diphosphines were used by Hayter to synthesize the first such complexes [~-10], including [Cl3CO(/.~-PPh2)]-, [ 10], although other re,agents have since proven more convenient [7]. The molecular structure of complex 1 is shown in Fig. 1 with the atom labelling scheme. Crystallographic details,
398
K. Wang et al. / lnorganica Chimica Acta 255 (19971395-398
Table 5 Comparison of the butterfly Rh:(/z.-P), cores of [ (PMetBu_~)CIRh(p.-PMe*Bu)12 (1) and [Cp*Rh(/.t-PMe2)(/.t-PPh~) ]~_(2) "1.Selected bond lengths (A) and angles ( -~1 1
2 "~
Rh(l)-Rh(2) Rh(l)-P(i) Rh(Ij-P(2)
2.7310 2.202 2.232
2.7952 2.230 2.240
Rh(l)-P(I)-Rh(2) P(I)-Rh(I)-P(2) P(2)-Rh(I)-Rh(2)
75.98 78.40 51.46
77,81 80,01P 51.13 "
P(l)-Rh(l)-Rh(2)-P(2)
106.63
111.5
1
2 "~
Rh(2)-P(2) Rh(2)-P(I)
2.201 2.235
2.230 2.221
Rh(2)-P(2)-Rh(I) (2).-Rh(2)-P(I) P(t)-Rh(I)-Rh(2)
76.07 78.35 52.55
77.39 80.39 50.95 "
•" From ReL 6. Atom labeling scheme for complex I and for the l Rh(/-tP) ] z core of complex 2 is as given in Fig. 1. t, Calculated based on angles reported in Ref. 6. selected bond distances, angles and torsion angles are listed in Tables 1-4. The R h - R h distance of 2.731 .A falls in the range of a typical R h - R h single bond. A comparison with ~he previously reported structure of (Cp*Rh),(/x-PMe2)(/.tPPh2) (2; Cp* = C.~Mes) is shown in Table 5 [6]. The similarity of the butterfly Rh2(/z-P) 2 cores of complexes 1 and 2 is striking in view of the very different sets of ancillary Iigands on the Rh centers of each complex (i.e., PMetBu, and C! versus C p * ) and their different electron-counts ( 16 and 18, respectively). Note also that the the 18-electron rhodium center of Cp*Rh(/.t-PMez)-,Mo(CO)4 is approximately isostructural to those of complex 2 [2]. Each rhodium atom in complex 1 is approximately coplanar with four of the five atoms to which it is bound; Rh I lies within the plane approximated by PI, Rh2, C! I and P3, while Rh2 is found in the corresponding approximate plane containing P2, R h l , Cl2 and P4. The total of the four X - R h - Y angles of each of these groups is 362.3 and 362,5 ° , respectively. Thus the vacant coordination sites on RhI and Rh2 may be viewed as being trans to the bridging phosphorus atoms P2 and PI, respectively. If the R h - R h bond is viewed as related to a R h - X bond, then the rhodium centers of compound I are analogous to those of five-coordinate Rh (III) complexes. Most such complexes, like 1, possess very bulky phosphines which presumably protect the vacant coordination sites (though only weakly enough so that the chemistry expected of unsaturated species can be observed). It is our hope that complex 1 will possess enough shared characteristics of unsaturated complexes and phosphido-bridged complexes to result in a display of novel, possibly catalytic, reactivity.
4. S u p p l e m e n t a r y m a t e r i a l
Further data including complele intramolecular distances and angles, torsion angles, anisotropic displacement parameters and H atom parameters can be obtained on request from
the Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road Cambridge CB2 1EW, UK,
Acknowledgements
We thank the Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research, U.S. Department of Energy for support of this work. A.S,G. thanks the Camille and Henry Dreyfus Foundation for a Teacher Scholar Award and the Alfred P. Sloan Foundation for a Research Fellowship,
References
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