Organometallics 1993,12, 2686-2698
Synthesis, Structure, and Dynamic Behavior of Symmetrical cis- and trans-Alkene Complexes of the Chiral Rhenium Lewis Acid [(q5-C5Hs)Re(NO) (PPha)]+: Binding Selectivities and Isomerization Processes Jiaqi Pu, Tang-Sheng Peng, Charles L. Mayne, Atta M. Arif, and J. A. Gladysz' Department of Chemistry, University of Utah, Salt Lake City, Utah 84112 Received January 22, 1993 Reactions of [(~S-C~H~)Re(NO)(PPh3)(C1CeH~)l+BF4-with cis-alkenes (a,2-butene; b, 3-hexene; c, stilbene; d, 1,2-dichloroethylene; -45 "C to room temperature) give the adducts (2)[($-CsHs)Re(NO) (PPh3)(RHC=CHR)I +BF4- ((2)la-d) in 67-95 % yields after workup. Reactions with trans-alkenes are much slower, and (E)-la-c are isolated in 86-98% yields after 12-24 h a t 85-95 "C. Complexes (2)-la-d are obtained as 70-84:30-16,85:15,93:7, and 5941 equilibrium mixtures of diastereomers that differ by ca. 180" rotations about the Re-(C-C) axes. Variable-temperature and 2D NMR experiments establish rotational barriers of >17.511.0 kcal/mol and exclude alternative isomerization pathways. Complexes (E)-la-care obtained as >99-98:99-98: tram seems aasured from a variety of competition experiments that have appeared in the literature.
3.1%
3 4 4 abs coeff ( p ) , cm-1 % minimum transmission % maximum transmission '2
A/a (max) Ap (max), e/A3
la.( CHzCI2) CZ~H~~BCI~F~NOPR~ 771.44 monoclinic P2dn
(E)-WCdWo.s CB.~H~~BF~NOPR~ 722.59 monoclinic
12.030(1) 22.430(1) 11.385(1) 101.06(1) 3014.99 4 1.699 1.706 0.35 X 0.25 X 0.15 Syntex P1 X(Mo Ka) = 0.710 73 8-28 2.0 0-14,0-26, -13 to +13 Kal-1.3 to Ka2 +1.6 98 5852 5559 43.62 67.30 99.00 353 0.0408 0.0438 3.1606 0.002 1.589 (-0.925 A from Re)
28.703(8) 14.454(3) 14.510(4) 109.64(2) 5669.94 8 1.693 1.685 0.23 X 0.20 X 0.17 Enraf-Nonius CAD-4 X(Mo Ka) = 0.709 30 8-29 variable (1.0-8.0) 0-32,0-16, -15 to +15 0.80 0.34 tan 8 1 X-ray h 4759 2820 44.48 71.87 99.80 353 0.0360 0.0393 0.5873 0.002 0.785
+
cis-stilbene complex (2)-lcgives a IVc/Vc equilibrium ratio (93:7) similar to the IIc/IIIc ratio of the corresponding styrene complex (9010). The diastereomers of trans-alkene complexes (E)-la-c (VI, VII; Scheme 111) interconvert with much higher barriers. Thus, syntheses conducted at lower temperatures give nonequilibrium diastereomer ratios. Possible origins of the lower kinetic selectivities have been discussed earlier.3c The greatest difference is observed with trans3-hexene complex (E)-lb, for which a 52:48 VIb/VIIb mixture is obtained after 25% conversion at 60 "C. The much faster reaction of 2 and trans-stilbene suggests that a phenyl ring may be the kinetic binding site. For all three trans alkene complexes, the VI/VII equilibrium ratios (99:1, >99:1,98:2; Scheme 111)are higher than the II/III equilibrium ratios of the corresponding monosubstituted alkene complexes (96:4, 97:3, 90:10, Scheme I)." Thus, diastereomeric trans-alkene complexes exhibit greater free energy differences. This trend is complementary to that of cis-alkene complexes (2)-la,b, and shows that on the C=C terminus syn to the PPh3 ligand the substituent position in VI1 is destabilizing relative to that in VI. Thus, relative to monosubstituted alkenes, trans-alkenes give slightly enhanced thermodynamic binding selectivities, and cis-alkenes generally give slightly diminished thermodynamic binding selectivities. To our knowledge, I is the only chiral receptor found to date that is capable of binding one enantioface of symmetrical trans-alkenes with high thermodynamic selectivities. Other chiral metal fragments for which diastereomeric trans-2-butene complexes have been reported are illustrated in Chart III.2d+26As explicitly
demonstrated with the corresponding monosubstituted alkene complexes,3 all of the compounds described herein should be readily available in enantiomerically pure form. Thus, there are numerous possibilities for enantioselective syntheses of organic molecules.27 2. Isomerization of Alkene Complexes. As shown in Table I, the barriers for isomerization of the less stable RRS,SSR diastereomers of cis-alkene complexes (2)-la-c to the more stable RSR,SRS diastereomers increase as the size of the =CHR substituent increases (R = CH3, C2H6, C6H6: 11.0-11.1,12.6-12.8,13.2 kcal/mol). The 2D NMR experiments with cis-2-butene complex (2)-la,and the spin saturation data for cis-1,2-dichloroethylene complex (2)-ld,show that isomerizationoccurs by a simple 180" rotation about the Re(CYC) bond axis.21 In all cases, ?r back-bonding should diminish along the reaction coordinate. Thus, the higher barrier of the cis-l,2dichloroethylene ligand p17.5 kcal/mol) can be attributed to its superior ?F acidity, which stabilizes the ground state more than the transition state. Rotation about the Re(C-C) axis of trans-alkene complexes (E)-1is, in contrast to cis-alkene complexes (a-1, a degenerate process. These barriers also exhibit several interesting trends (Table I). For example, that of the RSS,SRR diastereomer of tram-%-butenecomplex (E)la (18.6 kcal/mol) is much higher than that of cis-Bbutene complex (Z)-la (11.0-11.8 kcal/mol). We propose the following explanation. The interconversion of 2 isomers IV and V in Scheme I1can be accomplished by sequential passage of the =CHR substituents over the medium-sized cyclopentadienyl ligand. No transit over the bulky PPh3 ligand is required. However, the interconversion of
(26) (a) Boucher, H.; Bosnich, B. J. Am. Chem. SOC.1977,99,6253.(b) Shinoda, S.; Yamaguchi, Y.; Saito, Y.Znorg. Chem. 1979,18,673.
J. A. Tetrahedron Lett. 1990,31, 4417.
(27) For additions of alkyl copper nucleophiles,seePeng,T.-S.;Ghdysz,
Pu et al.
2694 Organometallics, Vol. 12,No. 7,1993 CLS
C13
C13
C26
C25 C19
LI
174.09
c2
,1
.
I
f&.Ss\
. 91
0.62 A 0.80 A
Figure 3. Structure of the cation of cis-2-butenecomplex (RSR,SRS)-[(v5-C5HdRe(NO)(PPh3)(H3CHC=CHCHs)I+BF,- ((RSR,SRS)-la):top, numbering diagram; middle, Newman-type projection with phenyl rings omitted; n bottom, view of Re-CuC plane.
degenerate rotamers of tram complexes (Scheme V) requires, at some stage, the passage of a=CHR substituent over the bulky PPh3 ligand. Thus, barriers are generally higher. This comparison holds for stilbene complexes (2)-lc and the RSS,SRR diastereomer of (E)-lc (12.8-13.5 vs >17.6 kcal/mol). However, the rotational barrier of the less stable RRR,SSS diastereomer of (E)-lc (11.6 kcal/ mol) is lower than either of these compounds. Since substituents are forced into the least favorable position on each C-C terminus in RRR,SSS, diastereomers, we suggest that the low barrier is primarily due to groundstate strain. The transition states for the two (E)-lc diastereomers would likely involve comparable repulsive interactions between eclipsing =CH phenyl groups and PPh3 ligands, with the configuration at the opposite =CH terminus of secondary energetic importance. Ground-state strain (and/or ?r acidity effects) may also contribute to the
172.19 f7l.O0\ c2
91
0.69 A 0.73 A
Figure 4. Structure of the cation of trans-2-butene complex (RSS,SRR)-[(v6-C5Hs)Re(NO)(PPh3) (H3CHC=CHCHs)l+BFd- ((RSS,SRR)-la):top, numbering diagram; middle, Newman-type projection with phenyl rings omitted; n bottom, view of Re-CUC plane.
lower rotational barriers of (2)-la-c compared to the corresponding ethylene complex (16.4 kcal/mol).3* We presently have no information on the mechanism by which the RRR,SSS diastereomers of (E)-la-cisomerize to RSS,SRR diastereomers. With analogous monosubstituted alkene complexes (11, 111) this process is nondissociative, and based upon an extensive series of experiments an intermediate C-H 'u bond" complex has been proposed.3c The isomerization of trans-stilbene complex (E)-lc is much faster than those of monosubstituted alkene complexes, and a mechanistic study is planned. 3. Other Spectroscopicand Structural Properties. The NMR data presented above establish a number of useful correlations that will be important in studies of complexes of I and other classesof alkenes.'jI6 For example, with all of the diastereomers IV-VI1 in Scheme I (a) the
Alkene Complexes of ~((r15-Cdls)Re(NO)(PPhS)]+
Organometallics, Vol. 12, No. 7, 1993 2695
Table III. Atomic &ordinates for (Z)-la.(CH2C12) and (E)-~~*(CSHIZ)O.S atom
Re P F1 F2 F3 F4 0 N c1 c2 c3 c4 c5 C6 c7 C8 c9 c10 c11 c12 C13 C14 C15 C16 C17 C18 C19 c20 c21 c22 C23 C24 C25 C26 C27 C28 C29 C30 B c11 c12 H1 H2
X
(2) - h (CH&I,) Y
(E)-WC~HIZ)O.S
z
X
Y
z
0.70905(3) 0.8224(2) 0.5029(6) 0.3287(7) 0.4381(8) 0.4666(8) 0.8110(8) 0.7648(7) 0.5638(8) 0.5279(8) 0.497( 1) 0.562( 1) 0.816( 1) 0.753(1) 0.638( 1) 0.627( 1) 0.742( 1) 0.9532(7) 1.0259(8) 1.1247(9) 1.15 20( 9) 1.080( 1) 0.9801(8) 0.763 l(7) 0.7052(8) 0.6640(8) 0.6752(8) 0.7319(9) 0.7763(8) 0.8771(7) 0.9771(8) 1.0176(8) 0.9582(9) 0.8621(9) 0.8219(8) 0.638( 1)
0.78 13l(2) 0.87 12(1) 0.1635(4) 0.1354(5) 0.1556(5) 0.0780(4) 0.7317(4) 0.7549(4) 0.8450(5) 0.7849(6) 0.7568(7) 0.8865(7) 0.7348(5) 0.7780(5) 0.7641( 5 ) 0.7111(5) 0.6930(5) 0.8629(4) 0.8165(5) 0.8079(6) 0.8451(6) 0.8900(6) 0.8992(5) 0.9407(4) 0.9393(4) 0.9919(5) 1.0455(4) 1.0469(5) 0.9945(4) 0.8900(4) 0.9231(4) 0.9409(5) 0.9253(5) 0.8915(5) 0.8735(5) 0.0391(8)
0.94111(3) 0.9778(2) 0.4763(7) 0.4750(7) 0.6429(7) 0.5453(8) 1.1734(6) 1.0839(7) 0.9579(9) 0.961(1) 1.067( 1) 1.056(1) 0.8222(9) 0.7507(9) 0.7401(9) 0.807(1) 0.852(1) 0.9207(8) 0.9659(9) 0.924( 1) 0.838( 1) 0.793( 1) 0.8334(9) 0.9099(8) 0.7905(8) 0.7352(8) 0.797( 1) 0.914(1) 0.9717(8) 1.1355(7) 1.1633(8) 1.2817(9) 1.3696(9) 1.3436(9) 1.2260(8) 0.366(1)
0.4308(6) 0.7670(3) 0.6376(3) 0.5000 0.4707
0.1336(3) 0.0561 (2) 0.0366(2) 0.8613 0.7793
0.5347(6) 0.4519(3) 0.2157(3) 0.8887 0.8594
0.13053( 1) 0.10518(9) 0.2280(3) 0.2175(4) 0.1637(4) 0.1686(4) 0.0653(3) 0.0895(3) 0.0822(4) 0.0862(4) 0.0443(4) 0.1063(5) 0.2099(4) 0.2077(4) 0.1963(4) 0.1922(4) 0.2012(4) 0.1165(4) 0.07 8 3(4) 0.0887(5) 0.1356(6) 0.1739(5) 0.1643(4) 0.0401 (3) 0.0043(3) -0,0448 (4) 4.0595(4) 4).0244(4) 0.0244(4) 0.1 366(4) 0.1510(4) 0.1734(5) 0.1808(5) 0.1675( 5 ) 0.1447(4) 0.0533(5) 0.0266(6) -0.0498( 5 ) 0.1953( 5 )
0.1 106l(3) 0.2474(2) 4.1717(7) -0.2944(7) 4,1906(8) 4.268(1) 0.1635(7) 0.1425(6) 0.0414(8) 4 . 0 168(8) -0).0352(9) 0.0 133(9) 0.162 1(9) 0.086( 1) 0.009( 1) 0.039( 1) 0.1 31( 1) 0.2464(8) 0.2459(9) 0.245(1) 0.245( 1) 0.243(1) 0.246(1) 0.2785(7) 0.2221 (8) 0.2492(9) 0.3303(9) 0.387( 1) 0.3624(8) 0.3501 (8) 0.4200(8) 0.4995(9) 0.509( 1) 0.442( 1) 0.3616(8) 0.5 177 (9) 0.584( 1) 0.532( 1) -0.229( 1)
0.49826(3) 0.5654(2) 0.7649(6) 0.6756(9) 0.6327(7) 0.7556(8) 0.3023(5) 0.3832(5) 0.5716(7) 0.4958(8) 0.4036(9) 0.6775(8) 0.557(1) 0.6136(8) 0.554(1) 0.460( 1) 0.4642(8) 0.6964(7) 0.7350(8) 0.8339(9) 0.8954(8) 0.8601(9) 0.7611(9) 0.5139(7) 0.4499(7) 0.4150(8) 0.4433(8) 0.5076(9) 0.5415(8) 0.5453(8) 0.612(1) 0.592(1) 0.506( 1) 0.438(1) 0.456( 1) 0.2747(9) 0.773(1) 0.732( 1) 0.706( 1)
0.0625 -0.0820
0.5625 0.5214
C-C 13C NMR resonance of the carbon syn to the PPh3 ligand is downfield of that anti to the PPh3 ligand, and gives a larger Jcp; (b) the lH NMR resonance of the =CH group syn to the PPh3 ligand is upfield of that anti to the PPh3 ligand, and (when resolved) gives a larger JHP.The lH NMR chemical shifts of the methyl groups in diastereomeric 2-butene, propene, and isobutene complexes of I follow the shielding patterns summarized in X (Chart 11). Many trends other than those explicitly noted above can also be discerned. As expected from the resonance forms in Scheme I, the C-C bond lengths in crystalline 2-butene complexes (2)la and (E)-la [1.417(9), 1.42(2) AI are between those of the CHz-CHz bond in n-butane [1.531(2) and the C=C bonds in the free alkenes [1.348(1), 1.347(3)AI .28 In (Z)-la, the Re-Cl bond is longer than the R e C 2 bond [2.293(7)vs 2.234(6) AI, and the Re-Cl4.72 angle is smaller than the Re-C2-C1 angle [69.5(4)' vs 74.0(4)'1. Thus, the cis-&-buteneligand is not bound symmetrically, but is "slipped" slightly toward C2. However, the correspond(28) Calloman,J. H.; Hirota, E.; Iijima, T.; Kuchitau, K.; Lafferty, W. J. In Landolt-Bbrnatein Numencal Data and Functional RelotLonship in Science and Technology;Madelung, O., Ed. in Chiefi Spring-Verlag: New York, 1987; Vol. 15;Structure Data of Free Polyatomic Molecules; Hellwege, K.-H.; Hellwege, A. M.,volume Eds.; p 428,442,478.
0.0488 0.1074
ing bond lengths and angles are identical within experimental error in the trans complex (E)-la. Monosubstituted alkene complexes of I usually show a small amount of slippage in the opposite d i r e c t i ~ n . @ ~ # ~ We speculate that in 1,2-disubstituted alkene complexes of I, steric repulsion between the PPhs ligand and syn = C H R terminus serves to slightly lengthen the corresponding R e 4 bond. The crystal structure of the methy lcyclopentadienylcyclopentene complex [($-C&
-
CHs)Re(NO)(PPhs)CH=CH(CH2)31+BF4-(4) has also been determined! It exhibits equal Re-C bond lengths. The 2-butene ligand conformations in crystalline (2)la and @)-la deviate from those shown in idealized n
structures IV and VI. The angles of the Re4-C planes with the Re-P and Re-N bonds, which are Oo and f90° in IV and VI, provide one of several measures. In (,@la, these angles (12.3O, 69.5O) are comparable to those of cyclopentene complex 4 (8.8O, 73.6'), and monosubstituted alkene complexes of I (15-18', 71-70°).*b*6 In all cases, the deviation is in a counterclockwise torsional direction from the projections in Scheme I. The distortion in (E)la (22.6O, 66.4O) isthelargestobservedtodate. Wesuggest that this is driven by repulsion between the PPh3 ligand and the syn = C H methyl group (C4). Indeed, when (2)-
Pu et al.
2696 Organometallics, Vol. 12, No. 7, 1993
Table IV. Selected Bond Lengths (A), Bond Angles (des), and Torsion Angles (deg) in (Z)-la.(CH2Cl2and ) (E~-~~Q(C~HI~)OJ Re-P Re-N ReCl ReC2 RGC5 ReC6 Re47 Re48 Re49 P-ClO P-Cl6 P-C22
2.293(7) 2.234(6) 2.286(7) 2.329 (6) 2.317(6) 2.286(7) 2.291(6) 1.824(5) 1.823(5) 1.839(5) 1.184(6) 1.417(9) 1.454(9) 1.471(9) 1.39l(9) 1.377(9) 1.406(9) 1.428(9) 1.44(1)
0-N Cl-c2 C1-C4 C2-C3 C5-C6 c549 cdc7 C7-C8 C8-C9 P-RGN P-ReC 1 P-RGC2 N-ReC 1 N-Re-C2 Cl-ReC2 Re-P-ClO Re-Pa16 ReP-C22 Re-N-O R&l-C2 Re-Cl-C4 C2-Cl-C4 Re4241 RGC2-C3 Cl-C2-C3 cdc5-C9 c5-c6-c7 C6-C7-C8 C7-C8-C9 C5-C9-C8 C4-C 1-C2-C3 C4-C 1-C2-H2 H 1-C1-C2-C3 Hl-Cl-C2-H2
9 1.1(2) 83.1(2) 118.7(2) 107.3( 2) 97.3(2) 36.4(2) 110.4(2) 118.5(2) 116.3(2) 170.9(5) 69.5(4) 125.8(5) 122.8(6) 74.0(4) 118.0(5) 123.5(7) 108.6(7) 108.0(6) 109.2(6) 104.4(6) 109.7(6) - 7 136 -120 23
2.25( 1) 2.23(1) 2.27(2) 2.31( 1) 2.31(2) 2.27(2) 2.26(2) 1.82(1) 1.82(1) 1.81(2) 1.18(1) 1.42(2) 1.51(2) 1.49(2) 1.39(2) 1.36(3) 1.38(3) 1.40(3) 1.35(3) 88.4(4) 81.7(4) 115.7(4) 104.2(6) 90.3(6) 37 .O(5) 1 l6.2(5) 116.3(5) 1 1 1.8(5) 174(1) 71.0(8) 117(1) 120(1) 72.1(8) 116(1) 123(1) 107(2) 109(2) 106(2) 108(2) 1 lO(2)
~
-139(1) 0 -7 131
Chart 111. Binding Selectivities of Other Chiral Metal Fragments and trans-2-Butenea6
60 : 40
50 : 50
53 : 47
la and @)-laare superimposed via their N-Rep linkages in stereo, the conformational "response" of the P P b ligand to this C4 methyl group is vividly illustrated. 4. Conclusion. This study has provided efficient syntheses of symmetrical cis-and trans-alkene complexes of the chiral rhenium Lewis acid I. Four configurational diastereomers are observed, and their NMR properties have been carefully defined. Rotation about the Re(CYC) axis interconverts cis-alkene complex diastereomers, and makes equivalent the = C H R termini within each trans-alkene complex diastereomer. Diastereomeric trans-alkene complexes interconvert by a higher energy process, the mechanism of which remains to be probed.
These efforta also lay the needed groundwork for (1) studies of analogous optically active complexes, which may have use in enantioselective organic syntheses, (2) syntheses and structural analyses of adducts of I and unsymmetrical cis- and trans-alkenes, where there is the potential for twice as many configurational diastereomers, and (3) investigations of complexes of I and @-unsaturated organic carbonyl compounds. The first two are in progress, and the third is described in the followingpaper.6
Experimental Section" (z) 4 (+-CsHs)WNOW P 4 )(CWC=CHC&)I+BFi ((0
la). A Schlenk tube with an 0-ring-sealed Teflon stopcock was charged with (~6-CaHa)Re(NO)(PPhs)(CH3) (5, 0.172 g, 0.310
mmol),%C&ISCl(9 mL), and a stirbar. The tube was cooled to O C (CH&N/COz bath) and HBF40OEta (33 pL, 0.31 mmol) was added with stirring. After 0.5 h, excess cis-2-butene was added and the stopcock was closed. The cold bath was removed and the solution was stirred for 6 h. The mixture was fiitered and solvent was removed in uacuo. The residue was dissolved in CHzClz (2 mL) and the solution was added dropwiseto stirring hexane (80 mL). The resulting tan powder was collected by fiitration,washed with pentane (2 x 1mL), and dried in uacuo to give (Z)-la (0.179 g, 0.260 mmol, 84%). Dec pt: 97-98 O C . A CHzClz solution of (Z)-la was layered with ether. This gave (Z)-la.(CH2C12)as red-brown prisms that were used for X-ray analysis. Anal. Calcd for CnH&F,NOPReCH2Clz: C, 43.59; H, 3.92. Found: C, 43.46; H, 3.83. IR (cm-', thin film):VNO 1717 vs. NMR, (Z)-la:sl lH (6) 7.78-7.26 (m, PPb), 5.70 (8, CaH& 4.29 (m, =CH anti to PPb), 3.51 (m, =CH syn to PPb), 1.89 (d, J a = 5.1, CHSanti to PPhS), 1.70 (d, JHH= 5.1, CH3 ~ y to n PPb); 13C(lH)(ppm) 133.4 (d, Jcp = 9.8, o-Ph), 132.0 (8, p-Ph), 130.3 (d, Jcp = 56.3, i-Ph), 129.4 (d, Jcp = 10.7, m-Ph),97.6 (8, CsHs), 53.4 (d, JCP= 3.3, =C syn to PPhs), 50.4 (8, =C anti to PPb), 18.3 ( 8 , CHSanti to PPhS), 16.2 (8, CH3 syn to PPh3); alP(1H)(ppm) 8.0 ( 8 ) . NMR (CDzClz, -100 OC), RSR,SRS diastereomer: 'H (6, referenced to CHDC12) 7.76-6.88 (m, PPb), 5.62 (8, CsHs), 4.18 (m,=CH anti to PPb), 2.86 (m, =CH syn to PPha), 2.04 (d, JHH = 5.1, CH3 anti to PPb), 1.58 (d, JHH = 5.0, CH3 syn to PPb); 31P(1H)(ppm, referenced to H8Ol at 25 O C ) 8.2 ( 8 ) . RRS,SSR diastereomer: lH (6) 5.64(s, Cas), 3.91 (m,=CHantitoPPb),82 3.79 (m,=CH y n to PPha)t2 2.28 (d, JHH= 4.9, CHs anti to PPb), 0.65 (d, JHH= 4.9, CH3 syn to PPhs); slP(lH)(ppm) 10.8
-45
(8).
( Z ) - [(s6-C,H6)Re(NO)(PPha)(CIH~HC==CHCIH~)]+BF~((2)-lb). Complex 5 (0.129 g, 0.230 mmol), CeH&l (4 mL), HBFrOEb (26 pL, 0.24 mmol), and cis-3-hexene (85 pL, 0.69 mmol) were combined in a procedure analogous to that given for (Z)-la.After 5 h, an identical workup gave (Z)-lb (0.156g, 0.220 mmol, 95%) as atan powder. Mp: 174-176 O C dec. Anal. Calcd for Cd32BFdNOPRe: C, 48.75; H, 4.51. Found: C, 48.71; H, 4.49. IR (cm-1, thin film): mo 1716 vs. NMR, (Z)-lb31 lH (6, 56 "C) 7.56-7.31 (m, PPb), 5.73 (8, CsHa), 4.36 (m,=CH anti to PPb), 2.97 (m, =CH syn to PPb), 2.18 (m, CHz), 1.79 (m, CH& 1.11 (t, JHH = 7.0, CHs), 0.81 (t, Jm = 7.0, CH3'); I3Cl1H)(ppm) 133.5 (d, Jcp = 9.7, o-Ph), 132.0 (29) General procedures were identical with thoee described in a previous papernabThecis-3-hexene(TCI:TokyoKasei)andotheralkenea (Aldrich) were used as received. (30) Agboaeou, F.; OConnor, E. J.; Garner, C. M.; QuirC Mbndez, N.; Ferntlndez, J. M.; Patton, A. T.; Ramsden, J. A.; Gladysz, J. A. Znorg. Syn. 1992,29, 211. (31) NMR spectra were recorded in CDC1, at ambient probe temperature and referenced to Si(CHs)d (IH, 6 0.00), CDC1, (W, 77.0 ppm), or external85 7% I&F'O, (SIP, 0.00ppm) unless noted. AU coupling constante (J) are in Hz. (32)Aesigned by analogy to the chemical shift trend rigorously established for the RRS,SSR diastereomer of (.%la.
Alkene Complexes of Mt15-CsHs)Re(NO)(PPh3)~+ (s, P P h ) , 130.2 (8, part of i-Ph),= 129.4 (d, Jcp = 11.3, m-Ph), 97.5 (e, C a s ) , 58.4 (br a, =C syn to PPhs), 55.7 (a, =C anti to PPha), 25.7 (8, CH2), 25.1 (s, CH2'), 19.2 (8, CH3), 17.0 (s, CH3'); slP(lH) (ppm) 9.9 (a). 1H NMR (6, -62 OC), RSR,SRS diastereomer: 7.70-7.11 (m, PPhs), 5.77 (a, CsHs), 4.38 (m, =CH anti to PPhs),M 2.67 (m, = C H syn to PPhg),M2.47,2.03 (2m, =CHCHz anti to PPh3),M 1.76 (m, =CHCH2 syn to PPh3),M1.24 (t, JHH= 6.7, CH3 anti to P P ~ s )0.60 , ~ (t, JHH= 6.7, CH3 syn to PPh3).% RRS,SSR diastereomer (partial): 5.73 (a, C&,), 3.86 (m, =CH anti to PPh),g2 3.48 (m, =CH syn to PPh3),821.35 (t,JHH= 6.6, CH3 anti to PPhs),%0.88 (t, JHH= 6.8, CH3 syn to PPha).a (z)([ q6-C6H6)b(NO) (PPhs) (C&HC
