J. Am. Chem. SOC.1983, 105, 7752-7754
7752
and diarsenes (RAs=AsR)~ have been isolated, four of which have now been structurally c h a r a c t e r i ~ e d . ~ " , " ,We ~ , ~ now ~ report (i) the first indication that compounds with P==Pand P=As bonds will react with organometallic reagents, (ii) a new mode of coordination for a diphosphene, and (iii) the first phosphaarsene complexes. In a typical reaction, 0.563 g (1.02 mmol) of (2,4,6-tB u ~ C ~ H ~ ) ~was P ~treated with 0.51 g (1.40 mmol) of Fez(CO), in 45 mL of n-hexane at 0 OC. The dark-red reaction mixture was allowed to warm to ambient temperature, and stirring was continued for 6 h. After filtration, the solvent and volatiles were removed by pumping in vacuo. Purification was effected by chromatography at -78 OC (n-hexane/Florisil). Red-brown (2) (mp 168-170 OC crystals of (2,4,6-t-B~~c~H~)~P~Fe(Co)~
1
2, M = F e ; n = 4 3, M = N i ; n = 3
dec) formed from n-hexane solutions held at -20 OC (yield 65%). 2: 31P('HJNMR (AB pattern) BA +423.6,68 +396.4, 'Jpp = 578.0 Hz; IR (n-hexane) vco 1940, 1915, 1895, 1880 cm-'; UV-vis (CH2C12) A, 486 (e = 5200), 288 (e = 18700), 244 nm (e = 26 000). The X-ray structure of Z5 (Figure 1) reveals a P(l)-P(2) bond length of 2.050 (1) A, which is comparable to those reported for other compounds with P=P bonds.2a,mqs Furthermore, within experimental error the C2P2Feframework is planar. The P-P-C bond angles in 2 are 6' larger than those in the free ligand, 1.2a Steric crowding is also evidenced by the fact that the P( 1)-C( 1) bond is 0.03 A longer than the P(2)-C(7) bond. Compound 2 represents a new mode of coordination for a diphosphene. Previously reported complexes were of type I9 or 11.8 P-P
\ML,/ 1
LnM
R
11
Compound 2 is also formed (along with 1) when (2,4,6-tBu&H2)PC12 is treated with Na,Fe(CO), in THF solution. The (3) Cowley, A. H.; Lasch, J. G.; Norman, N. C.; Pakulski, M.; Whittlesey, B. R. J . Chem. SOC.,Chem. Commun. 1983, 881. (4) (a) Couret, C.; Escudie, J.; Madaule, Y.; Ranaivorjatovo, H.; Wolf, J.-G.; Tefrahedron Lett. 1983, 24, 2769. (b) Cowley, A. H.; Lasch, J. G.; Norman, N. C.; Pakulski, M. J. Am. Chem. SOC.1983, 105, 5506. (5) Crystal data for (2): C40FeH5804P2. M = 720.7 monoclinic, space group P2,/c (No. 14), a = 21.251 (6) A, b = 9.793 (2) A, c = 20.99 (2) A, @ = 108.73 ( 6 ) O , Li= 4136 (5) A,'& = 1.157 g cm-', Z = 4, X(Mo Ka) = 0.71069 A (graphite monochromator), p(Mo Ka) = 4.7 cm-'. From a total of 7504 unique reflections, measured on an Enraf-Nonius CAD-4F diffractometer, 4204 (I > 2.5u(I)) were used to solve ( M U L T A N ~and difference Fourier) and refine (full matrix, least squares) the structure of 2. All nonhydrogen atoms were refined with anisotropic thermal parameters. However, under these conditions, the methyl carbon C(41) did not refine well and in the final cycle was given an isotropic tem rature factor. All hydrogen atoms were fixed in idealized geometries 0.95 f i r o m their respective carbon atom. These were included in the structure factor calculation but not refined due to insufficient data. Refinement with a weighting scheme' converged smoothly to give final residuals R = 0.0578, R, = 0.0824, GOF = 1.634. (6) Germain, G.; Main, P.; Woolfson, M. M. Acta Crystallogr., Sec. A 1971, A27, 368. Main, P. MULTAN 82, University of York, York, England, 1982. (7) The weighting scheme used was of the form w = (41"/$(1") + P2P) with P = 0.08. (8) Flynn, K. M.; Olmstead, M. M.; Power, P. P. J . Am. Chem. SOC.1983, 105, 2085. (9) (a) Elmes, P. S.; Scudder, M. L.; West, B. 0. J . Organomet. Chem. 1976, 122, 281. (b) Cannillo, E.; Coda, A.; Prout, K.;Daran, J. C. Acta Crysfallogr.,Sect. B, 1977, 833, 2608. (c) Deppisch, B.; Schafer, H. Ibid. 1982, B38, 748. (d) Chatt, J.; Hitchcock, P. B.; Pidcock, A,; Warrens, P. W.; Dixon, K. R. J. Chem. SOC.,Chem. Commun. 1982, 932.
0002-7863/83/ 1505-7752$01.50/0
Figure 1. View of the ( ~ , ~ , ~ - ~ - B u ~ C ~ H(2)~ ) molecule ~P~F~(CO)~ showing the atom numbering scheme. Important parameters: P( 1)-P(2) 2.050 ( l ) , P(1)-Fe(1) 2.215 ( l ) , P(1)-C(1) 1.893 (4), P ( 2 ) C ( 7 ) 1.859 (4) A; P(l)-P(2)-C(7) 108.4 (l)', P(2)-P(1)-Fe(1) 135.52 ( 6 ) O , P(2)-P(1)-C(1) 109.3 (l)', C(1)-P(1)-Fe(1) 115.1 (1)'.
fact that only one Fe(CO), attaches is a consequence of steric effects. Likewise, only one Ni(CO), group attaches even when 1 is treated with excess Ni(CO), (in E t 2 0 ) . [2,4,6-tBU~C~H~]~P~N (3): ~(C 31P O ('HI ) ~ N M R (AB pattern) BA +449.0, BB +422.0, ' J p p = 540.3 Hz; IR (n-hexane) vco 1800, 1860, 1955 cm-I. The very bulky diphosphene (Me3Si)&P= PC(SiMe3)32b,f,m does not react with Ni(CO), at 25 OC. The unsymmetrical diphosphene, (2,4,6-t-Bu3C6H2)P=PCH(SiMe3)2also reacts with Fe2(C0)9to afford the corresponding (Me3Si)2CHP-boundFe(CO), complex 4 in 63% yield. 4: 31P N M R (ABX system) 6A +424, BB +416, ' J p p = 519.0, 2JpH = 30.0, 3JpH = -3.2 Hz; IR (n-hexane) vco = 1970 (br), 2060 cm-'. Preliminary studies of the reaction of the phosphaarsene (2,4,6~-BU~C~H~)AS=PCH(S~M~~)~) indicate the formation of two products, 5a and 5b, in which the Fe(C0)4 moiety is attached to phosphorus and arsenic atoms, respectively. 31PNMR: 5a, s +390; 5b, s +429 ppm. Acknowledgment. Generous financial support from the National Science Foundation (Grant CHE-8205871) and the Robert A. Welch Foundation is acknowledged. We are also grateful to Professor Philip P. Power for discussing his work prior to publication. Registry No. 1, 79073-99-7; 2, 87937-39-1; 3, 87937-40-4; 4, 87937-
SupplementaryMaterial Available: Tables of bond lengths, bond angles, atomic coordinates, and thermal parameters (8 pages). Ordering information is given on any current masthead page.
Six-Membered Ring Phosphites in Twist Conformations. The Methyl and Phenyl Trans-Y,S'-Cyclic Phosphites of Thymidine Keith A. Nelson, Alan E. Sopchik, and Wesley G. Bentrude* Department of Chemistry, University of Utah Salt Lake City, Utah 84112 Received July 1 I I983 ~
The replacement of the ring carbons of cyclohexane with heteroatoms containing electron lone pairs may greatly affect the relative free energies of potentially populated conformations as 0 1983 American Chemical Society
J. Am. Chem. SOC.,Vol. 105, No. 26, 1983 7753
Communications to the Editor Table I. ' H NMR Parameters for 3 and 4 a t 300 MHzQ
J , Hz compound
cis-36 trans-3d
cis4 trans4 a
solvent acetone-d, acetone-d, acetone-d, ace t one-d,
S'a5'b
5'a4'
5'aP
5'bP
5'b4'
3'4'
3 'P
-9.1 -9.6 -9.2 -9.7
10.8 9.7 10.7
2.4 7.7 2.6 9.2
10.6 3.0 10.8 1.4
4.3 6.2 4.4 6.6
9.5
1.8 1.1 -2 1.1
9.8
9.5 9.1 9.1
4 'P C
-0.8
c -1.0
At -25 "C. bFirst-order analysis. C
