1007
Inorg. Chem. 1982, 21, 1007-1014 Department of Health, Education and Welfare and Faculty Development Grant 7590 from Northeastern University (to G.D.), which are gratefully acknowledged. Registry No. (tmpd),Cu,Cl2CO3, racemic form, 80225-06-5; [(DENC)CUCI],(CO,)~,80105-81-3;[(DENC)CuC1],02, 80105-85-7;
DENC, 59-26-7;C02, 124-38-9;02, 7782-44-7. Supplementary Material Available: Tables of observed and calculated structure factor amplitudes and of least-squares planes (Table VIII) (14 pages). Ordering information is given on any current masthead page.
Contribution from the Research School of Chemistry, The Australian National University, Canberra, A.C.T., 2600,Australia
Resolutions Involving Metal Complexation. Preparation and Resolution of ( R,S )-Methylphenyl(8-quinoly1)phosphine and Its Arsenic Analogue. Crystal and Molecular Structure of (+)589-[ ( R )-Dimethyl(1-ethyl-a-naphthy1)aminato-C2,N][( S )-methylphenyl( 8-quinol y l)phosphine]palladium(11) Hexafluorophosphate DAVID G.ALLEN, GEORGE M. McLAUGHLIN, GLEN B. ROBERTSON, WILLIAM L. STEFFEN, GEOFFREY SALEM, and STANLEY BRUCE WILD* Received August 6, 1981 The asymmetric bidentates (R,S)-methylphenyl(8-quinolyl)phosphine and (R,S)-methylphenyl(8-quinolyl)arsine have been prepared in high yield from 8-chloroquinoline and the respective substituted phosphide or arsenide anion in tetrahydrofuran at -78 OC. Both compounds are air-stable crystalline solids. An efficient and large-scale resolution of both substances is described, which is based upon the fractional crystallization of a pair of internally diastereoisomericpalladium(I1) complexes containing the chiral chelating ligand and an optically active ortho-metalated dimethyl(1-ethyl-a-naphthy1)amine.The optically pure enantiomers of the tertiary phosphine have CY]^ h107" (mp 98 "C) and the corresponding arsine [aIDil15" (mp 75-76 "C) in diethyl ether solution. The molecular structure and absolute configuration of (+)sss- [(R)-dimethyl(l-ethyl-cY-naphthyl)aminato-C?,iVl[(S)-methylphenyl(8-quinolyl)phosphine]palladium(II) hexafluorophosphate has been with a = 25.784 (5) A, determined by a single-crystal X-ray analysis. The complex crystallizes in space group P212121 b = 19.159 (3) A, c = 12.277 (2) A, and Z = 8. The structure was solved by heavy-atom methods and refined by least-squares methods to an R of 0.079 and R.,, of 0.047 for 2955 reflections. The tertiary phosphine liberated from this complex, -107" (diethyl ether), accordingly has the R absolute configuration. Introduction Recent work in our laboratory has shown that palladium(I1) complexes containing optically active ortho-metalated dimethyl(cY-methylbenzy1)amines are exceedingly effective resolving agents for dissymmetric di(tertiary phosphines' and arsines2). For bidentates of lower symmetry, however, the existence of cis-trans isomerism within the internally diastereoisomeric complexes is a potential drawback to the generality of the method. In this article we describe the synthesis and resolution of the asymmetric bidentate (R,S)-methylphenyl(8-quinoly1)phosphine and its arsenic analogue, symmetrical counterparts of which have been known for some time.3 Chiral bidentates of this type, which are unsymmetrical with respect to the arrangement of donor atoms, are of considerable synthetic interest because of the potential of their metal chelates to exercise an electronic, as well as steric, control over the asymmetric synthesis of a chiral molecule from an appropriate coordinated substrate. Moreover, in view of our earlier results concerning the dynamic properties of certain square-planar and square-pyramidal complexes of bivalent nickel,, palladium, and platinum containings dissymmetric di(tertiary phosphines and arsines), it was appropriate to investigate the behavior of related compounds containing asymmetric bidentates. (1) Roberts, N. K.; Wild, S.B. J. Am. Chem. Soc. 1979, ZOZ, 6254. (2) Roberts, N. K.; Wild, S.B. J . Chem. Soc., Dolron Tram. 1979,2015. (3) Barclay, G. A.; Harris, C. M.; Kingston, J. V. Chem. I d . (Lodon) 1965,227. Hudali, H. A.; Kingston, J. V.; Tayim,H.A. Inorg. Chem. 1979, 18, 1391. Issleib, K.; Haftendorn, M. Z . Anorg. Allg. Chem. 1970, 376, 79. (4) Roberts, N. K.; Wild, S.B. Inorg. Chem. 1981, 20, 1892. (5) Roberts, N. K.; Wild, S.B. Inorg. Chem. 1981, 20, 1900.
Scheme I No[ EMePh] I
CI
q E
./- pPh Me (R)- I
(Ri-2
The present article describes a direct and efficient synthesis of (R,S)-methylphenyl(8-quinolyl)phosphine,and its arsenic analogue, as well as the resolution of both compounds, which in each case was based upon the fractional crystallization of a pair of internally diastereoisomeric palladium(I1) complexes containing the appropriate bidentate and an optically active ortho-metalated dimethyl( 1-ethyl-a-naphthy1)amine. Results and Discussion
Methylphenyl(8-quinolyl)phosphine, (R,S')-l, and its arsenic analogue, (R,S)-2,were prepared from 8-chloroquinoline and the respective anion in tetrahydrofuran at -78 "C (Scheme I). They distilled as high-boiling viscous oils and were sub-
0020-1669/82/1321-1007$01.25/0 0 1982 American Chemical Society
1008 Inorganic Chemistry, Vol. 21, No. 3, 1982 Scheme I1
Allen et al. Scheme 111
Me
M
y
Me
1
,
,/C' Pd
1 +
/,
\*
% . &< .+ (R
-3
I
1 Me
,Me
fi
Me
lf^"
Me
-
1R.S) 4 1R.S) 5
sequently crystallized from boiling methanol. The tertiary phosphine was isolated as pale yellow prisms, mp 111-1 12 OC, and the arsine as white needles, mp 82-83 O C . Yields in both cases were ca. 80%. The resolutions of (R,S)-1 and (R,S)-2were based upon the separation of a pair of internally diastereoisomer palladium( 11) complexes derived from the resolving agent (+)589-di-p-chloro-bis[@)-dimethyl( 1-ethyl-a-naphthyl)aminato-eNdipalladium(II), (R)-3. The latter was obtained in 95% yield from (+),,,-(R)-dimethyl( 1-ethyl-a-naphthyl)amine and lithium tetrachloropalladate(I1) in methanol. The corresponding derivatives of the more readily available optically active dimethyl(a-methylbenzy1)amineswere not found suitable for the resolution of (R,S)-1 or (R,S)-2although they were most effective for the resolution of (RR,SS)-ophenylenebis(methylpheny1phosphine) and its arsenic analogue.* The partial resolution of certain unidentate mono(tertiary phosphines) has been achieved by use of an analogous palladium(I1) complex containing dimethyl( 1-ethyl+ naphthyl)amine, however.6 The resolutions were performed as illustrated in Schemes 11-IV. The initial step involved the formation of the internally diastereoisomeric palladium(I1) complexes as shown in Scheme 11. The appropriate racemic bidentate was stirred with a suspension of the chloro-bridged dimer (R)-3in methanol, giving, in a short time, a pale yellow solution of the expected cationic chlorides. The addition of an excess of NH4PF6to either of the solutions precipitated the respective mixtures of internally diastereoisomeric hexafluorophosphate salts in high yield. For both ligands the mixture could be satisfactorily separated by fractional crystallization from acetone. The less soluble salts (R,R)-4and (R,R)-5crystallized as fine white needles having [a]D's of -346 and -334O in acetone, respectively. The mother liquors were then evaporated to dryness and the residues dissolved in ethyl methyl ketone. The careful addition of diethyl ether to one or other of these solutions led to the precipitation of the more soluble components of the mixtures, viz., (R,S)-4and (R,S)-S. Both salts crystallized as methyl ethyl ketone solvates in the form of pale yellow prisms. A solution of the tertiary phosphine complex in acetone had [(Y]D +14O and the corresponding arsenic compound gave -34' in the same solvent. The fractional crystallization procedure was carried out twice more to give a ca. 90% overall recovery of the respective internally diastereoisomeric salts. Recrystallization of the ethyl methyl ketone solvates from acetone by the addition of water afforded the solvent free complexes. (6) Tani, K.;Brown, L.D.;Ahmed, J.; Ibers, J. A.; Yokota, M.;Nakamura, A.; Otsuka, S.J . Am. Chem. Soc. 1977, 99, 7876.
Scheme IV (R,R)-5
( R , S )- 5
Me Me
(R)-7
The liberation of the resolved tertiary phosphines from (R,R)-4and (R,S)-4 was accomplished as shown in Scheme 111. The complexes were treated with sulfuric acid (70%), the reaction mixture was hydrolyzed, and lithium chloride was added. This formed the square-planar complexes (R)-6 and (59-6. (The optically active amine was recovered from the mother liquor in each case by neutralization and extraction into diethyl ether.) Removal of the resolved ligands from the dichloropalladium(I1) complexes was fulfilled by treating a dichloromethane solution of the appropriate optically active complex with aqueous potassium cyanide. The pure methylphenyl(8-quinoly1)phosphines were then isolated from the organic layer and recrystallized from dichloromethanemethanol mixture. They formed pale yellow prisms, mp 98 "C, with [(YID'S of -107' and +107O (diethyl ether) for the R and S enantiomers, respectively. The liberation of the resolved tertiary arsine from (R,R)-5 or (R,S)-5was achieved by a method which enabled recovery of the resolving agent (R)-3 rather than the free amine (Scheme IV). Thus, treatment of a dichloromethane solution of either of the pure diastereoisomeric complexes with diamino- 1,Zethane precipitated the salt (R)-7. The free arsines were then isolated from the mother liquor and recrystallized from methanol. The optically pure tertiary arsines (R)-2and (S)-2, mp 75-76 OC,had [a]D's of -1 15 and +115O (diethyl ether), respectively. Conversion of (R)-7 into the resolving agent (R)-3 took place upon the addition of concentrated hydrochloric acid to a solution of the former in acetone. Crystal and Molecular Structure of (R,S)-4. Absolute Configuration of (-)58s-(R)-l. So that the absolute configuration of (-)589-1 could be established, an X-ray crystal structure determination of (+)589-(R,S)-4was undertaken. A suitable crystal for the analysis was obtained by dissolving the ethyl ketone solvate of (R,S)-4 in acetone and reprecipitating
Resolutions Involving Metal Complexation
Inorganic Chemistry, Vol. 21, No. 3, 1982 1009
Table I. Bond Distances (A) with Estimated Standard Deviations (in Parentheses) Pd-P(l) N(1) N(2) C(6) P(l)-C(15) C(24) C(30) N(l)-C(l) C(2) C(3) N(2)-C(20) C(23) C(3)-C(4) C(5) C(5)-C(6) C(10) C(6)-C(7) C(WC(8) C(8)-C(9) C(g)-C(lO) C(11) C(lObC(14) C(ll)-C(12)
a
b
2.202 (5) 2.20 (2) 2.17 (2) 1.99 (2) 1.80 (2) 1.78 (2) 1.83 (2) 1.48 (3) 1.52 (3) 1.54 (3) 1.39 (2) 1.35 (3) 1.53 (3) 1.49 (3) 1-43(3) 1.43 (3) 1.43 (3) 1.34 (3) 1.32 (3) 1.38 (3) 1.48 (3) 1.41 (3) 1.40 (3)
2.216 (6) 2.18 (2) 2.19 (2) 1.99 (2) 1.84 (2) 1.76 (2) 1.79 (2) 1.52 (3) 1.47 (3) 1.51 (3) 1.37 (2) 1.33 (3) 1.52 (3) 1.48 (3) 1.41 (3) 1.54 (3) 1.46 (3) 1.36 (3) 1.22 (4) 1.45 (4) 1.56 (4) 1.47 (3) 1.34 (4)
C(12)-C(13) C(13)-C(14) C(15)-C(16) C(20) C(16)-C(17) C(17)-C(18) C(18)-C(19) C(19)-C(20) C(21) C(21)-C(22) C(22)-C(23) C(24)-C(25) C(29) C(25)-C(26) C(26)-C(27) C(27)-C(28) C(28)-C(29) P(2)-F(1) F(2) F(3) F(4) F(5) F(6)
a
b
1.40 (3) 1.37 (3) 1.38 (2) 1.39 (2) 1.41 (3) 1.34 (3) 1.37 (3) 1.45 (3) 1.39 (3) 1.35 (3) 1.36 (3) 1.39 (3) 1.39 (3) 1.33 (3) 1.37 (3) 1.27 (4) 1.44 (4) 1.53 (2) 1.50 (2) 1.53 (2) 1.46 (2) 1.49 (2) 1.46 (2)
1.34 (5) 1.37 (4) 1.38 (3) 1.36 (3) 1.43 (3) 1.27 (3) 1.33 (3) 1.42 (3) 1.35 (4) 1.27 (4) 1.38 (3) 1.41 (3) 1.39 (3) 1.43 (3) 1.39 (3) 1.34 (3) 1.36 (3) 1.54 (2) 1.54 (2) 1.60 (2) 1.57 (2) 1.51 (2) 1.56 (2)
the complex with water. Under these conditions pure (RS)-4 crystallized as colorless prisms. The asymmetric unit of the crystal consists of a pair of cations (a and b in Tables I and 11) and associated hexafluorophosphate anions. There are no significant differences in the structure of the two complex cations. The stereo-
Figure 1. Molecular geometry and absolute configuration of (+)S89-(%9-4.
chemical arrangement of the atoms in the cation is depicted in Figure 1, and the corresponding distances and angles for both cations and anions are presented in Tables I and 11. The
Table 11. Selected Bond Angles (Deg) with Estimated Standard Deviations (in Parentheses) P( l)-Pd-N(l) Ni2j (36) N( l)-Pd-N( 2) C(6) N( 2)-Pd-C(6) Pd-P(l)-C( 15) C( 24) C(30) C(15)-P( 1)-C(24) C(W c(24)-P( 1)-C(3 0) Pd-N(l)-C(l) C(l)-N( 1 ) 2 ( 2 ) C(3) C(2)-N( 1)-C(3) Pd-N(2)-C( 20) N(l)-C(3)2(4) . (35) C(4)-C(3)-C(5) C(3)-C(5)-C(6) C( 10) C(6)-C(S)-C( 10) Pd-C(6)-C( 5) C(7) C(5)-C( 6)-C( 7) C(6)-C(7)-C(8) C(7)-C( 8)-C(9) C(8)-C( 9)-C( 10) C(11) C(10)-C(9)-C(11) C( 9)-C( 1O)-C( 5) (314) C(5)-C( 10)-C( 14) C(9)-C( 1l)-C(12) C(ll)-C(l2)-C(13)
a
b
161.8 (5) 83.6 (4) 92.9 (5) 101.2 (6) 82.5 (7) 176.3 (7) 100.3 (6) 120.3 (7) 115.8 (6) 106.3 (9) 106.5 (8) 106.4 (9) 118 (1) 108 (1) 99 (1) 112 (2) 113 (2) 106 (2) 116 (1) 124 (1) 120 (2) 113 (2) 110 (2) 111 (2) 115 (2) 128 (2) 117 (2) 113 (1) 128 (1) 119 (2) 119 (2) 124 (2) 120 (2) 121 (2) 119 (2) 120 (2) 124 (2) 116 (2) 114 (2) 125 (2)
165.2 (4) 82.3 i4j 95.2 (6) 100.9 (6) 81.0 (7) 176.7 (7) 99.5 (7) 120.6 (7) 118.5 (7) 106.0 (9) 107.0 (9) 103.8 (9) 119 (1) 112 (1) 98 (1) 108 (2) 107 (2) 113 (2) 114 (1) 124 (1) 121 (2) 120 (2) 107 (2) 111 (2) 116 (2) 129 (2) 115 (2) 111 (1) 126 (1)
122 (2) 119 (2) 121 (3) 129 (3) 128 (3) 102 (2) 113 (2) 133 (2) 114 (2) 120 (2) 134 (3)
C(12)-C(13)-C(14) cii 3j-c(i4 j-c(ioj P(l)-C(lS)-C(l6) C(20) C( 16)-C( 15)-C(20) C(15)-C(16)-C(17) C(16)-C(17)-C(18) C(17)-C( 18)-C(19) C( 18)-C( 19)-C(20) C(21) C(20)-C( 19)-C(2 1) C( 19)-C(20)-C( 15) NO) C( 15)-C( 20)-N( 2) C(19)-C(21)-C(22) C(21)-C(22)-C(23) C(22)
