1044
Organometallics 1984,3,1044-1050
previously observed that the replacement of a tungsten CO group in the bridging carbene complex (CO),W[p-C(OMe)(a~yl)]Pt(PMe~)~ with a PMe3 ligand shortens the W-C(carbene) bond from 2.48 (1)to 2.37 (1) A. This shortening may be understood in terms of increased a bonding from the W to the carbene carbon, which stabilizes the compound. Such a a bonding must also be responsible in part for the stability of I. One other interesting aspect of the molecular orbital calculations on this compound is the extensive interaction of both iron and cobalt d functions in a single molecular orbital. This admixture is apparent in levels 38 and 44 and can be traced to the near degeneracy of cobalt and iron d functions. Since sizable percentages of iron and cobalt
character are found together, we predict that experimental measurements such as photoelectron spectroscopy would reflect this admixture.
Acknowledgment. This research was supported by the National Science Foundation, Grant No. CHE-8207434 (R.F.F.), and the US.DOE (R.J.A.). Registry No. I, 83043-22-5;N ~ [ C O ( C O ) ~14878-28-5; ], {Cp(CO)(MeCN)Fe[C(SMe)z]]PF6, 77781-29-4; Co, 7440-48-4; Fe, 7439-89-6. Supplementary Material Available: Tables of anisotropic thermal parameters for non-hydrogen atoms and calculated and observed structure factors (15 pages). Ordering information is given on any current masthead page.
Reactivity of Diphosphenes, Phospharsenes, and Diarsenes toward Transition-Metal Carbonyls A. H. Cowley," J. E. Kilduff, J. G. Lasch, N. C. Norman, M. Pakulski, F. Ando, and T. C. Wright Department of Chemistfy, University of Texas at Austin, Austin, Texas 78712 Received December 27, 1983
The reactivity of stable diphosphenes, phospharsenes, and diarsenes toward transition-metal carbonyls has been explored. The diphosphene ( ~ , ~ , ~ - ~ - B U , C2,~forms H ~ ) adducts ~ P ~ , with one Fe(C0)4and one Ni(CO), group from reactions with Fe2(C0I9and Ni(C0I4, respectively. The iron complex (2,4,6-t3, has been structurally characterized by X-ray diffraction. Compound 3 crystallizes in the monoclinic space group P2,/c, with a = 21.251 (6) A, b = 9.793 (2) A, c = 20.99 (2) A, and /3 = 108.73 (6)'. The structure reveals that the diphosphene2 is 9' bonded to the Fe(C0I4group through a phosphorus lone pair. The phospharsene ~ , ~ , ~ - ~ - B U ~ C ~ H ~ A 8, ~= reacts P C with H ( SFez(CO)9 ~ M ~ ~to)give ~ , complexes with an Fe(C0)4 group attached to As, 9, or P, 10. Treatment of the diarsene 2,4,6-t-Bu3C6H2As= ASCH(S~M~,)~, 11, with Cr(CO),(THF) affords the complex ~ , ~ , ~ - ~ - B U ~ C ~ H ~ A ~ = A S C H ( S ~ M ~ ~ ) ~ C ~ ( 12, with the Cr(C0)5unit 9' bonded to the (Me3Si)&H-substitutedarsenic. This was determined by an X-ray diffraction study. Compound 12 crystallizes in the monoclinic space group ml/n with a = 10.710 (3)A, b = 29.770 (3) A, c = 11.984 (1) and 6 = 98.02 (1)'. The structures of and bonding in these complexes are discussed.
Introduction The coordination chemistry of compounds featuring double bonds between the heavier group 5A elements existed prior to the isolation of stable uncomplexed systems. Examples of diphosphene complexes include [ (q5C5H5)2M0(t1~-P2H2)l 9' [Pd(~~-Ph2Pz) (Ph2PCH2PPh2)I,2 [Ni(v2-(Me&P2) (EbP)21?and [ p t ( ~ 2 - ( C P ~ 2 P ~ ( P h ~ P ) , 1 ~ In all these complexes and the arsenic analogues [Fe(q2(C85)2Asd(C0)4l5 and [Pt(?2-(C6F5)2As2)(Ph3P)21 ,5 the ML" E F ligands adopt a trans conformation and the q2-bonding D mode A. Another bonding mode, B, has been observed two. The phenyl groups are trans in both cases. in complexes of composition (PhE=EPh)(M(CO),), (E = Recent work by Power et al. has resulted in two new As! Sb;7,M = Cr! W7). Six-electron donation on the part modes of ligation, C and D. Thus, treatment of of the diarsene or distibene ligand is achieved by q2 (Me3Si)2CHPC12with [Fe(C0),l2- afforded [trans-([Febonding to one M(C0)5moiety and 7' bonding to the other (CO)4]2[PCH(SiMe3)2]2]],8 an example of a type C complex in which each phosphorus lone pair bonds to an Fe(C0)4 (1) (a) Green, J. C.; Green, M. L. H.; Morris, G . E. J. Chem. SOC., Chem. Commun. 1974,212. (b) Cannillo, E.; Coda, A; Prout, K.; Daran, group in an 9' fashion. This is the first example of a J.-C. Acta Crystallogr., Sect. E 1977, B33, 2608. diphosphene complex containing an unsupported P=P (2) Chatt, J.; Hitchcock, P. B.; Pidcock, A.; Warrens, C. P.; Dixon, K. double bond. A similar complex of the isoelectronic ligand R. J. Chem. SOC.,Chem. Commun. 1982,932. (Me3Si)2NP=PN(SiMe3)2has also been de~cribed.~ On (3) (a) Jhppisch, B.; Schiifer, H. Acta Crystallogr.,Sect. E 1982, B38, 748. (b) Schder, H. 2.Naturforsch.,B: AGrg. Chem., Org. Chem. 1979, the other hand, the reaction of (2,4,6-t-Bu3C6H20)PC12 34B, 1358. with [Fe(CO),]" resulted in a type D complex featuring (4) Elmes, P. S.; Scudder, M. L.; West, B. 0. J. Organomet. Chem. one 9'- and one s2-bonded Fe(C0)4 group.l0 1976,122, 281. ( 5 ) Elmes, P. S.;Leverett, P.: West, B. 0. J. Chem. SOC.,Chem. Commun. 1971,747. (6) Huttner. G.: Schmid. H.-G.:Frank.. A.:. Orama. 0. Anaew. - Chem.. Inti Ed. Engl. '1976, 15, 234. (7) Huttner, G.; Weber, U.; Sigwarth, B.; Scheidsteger, 0. Angew. Chem., Znt. Ed. Engl. 1982,21, 215. '
(8) Flynn, K. M.; Olmstead, M. M.; Power, P. P. J. Am. Chem. SOC. 1983,105, 2085. (9) Flynn, K. M.; Murray, B. D.; O h b a d , M. M.;Power, P. P. J. Am. Chem. SOC.1983,105, 7460.
0276-7333/84/2303-l044$01.50/00 1984 American Chemical Society
Organometallics, Vol. 3, No. 7, 1984 1045
Reactivity of Diphosphenes, Phospharsenes, and Diarsenes Having ligands with preformed double bonds at our disposal," we realized that new modes of coordination might become possible. In fact, the diphosphene (2,4,6t-BU&H2)2P2 reacts readily with Fe2(CO)9to afford the first example of a type E complex.12 Virtually simultaneously, Power et al.1° reported the synthesis of (Me,Si),CH- or (Me3Si)2N-substitutedCr(CO)5complexes of type E via the reaction of the appropriate phosphorus dichlorides with [Cr(C0),l2-. The group 5A double-bonded compounds can also function as ligands in metal clusters. One type of ligation, F, has been recognized so far. The diiron complex [Fe(11.-s2-(t-B~2P2))(C0)6] features a transverse p-s2 diphosphene geometry and a cis disposition of the t-Bu groups.13 In this paper we report full details of our synthetic approach to the coordination chemistry of diphosphenes and diarsenes using preformed double bonds. We also report the first coordinated phospharsene.
Results and Discussion Initial attempts to use diphosphenes as ligands focussed on the reaction of (Me3Si)3CP=PC(SiMe3)3,14 1, with Fe2(C0)9and Ni(CO)& However, in neither case was any reaction observed even, in the case of Fe2(C0)9,under forcing conditions (THF reflux overnight). It is presumed that this is due to the large steric bulk of the (Me3Si),C groups which prevents access to the phosphorus lone pairs. This lack of reactivity associated with 1 is not peculiar to metal carbonyl systems, it being by far the least reactive of all diphosphenes studied." The aryl-substituted diphosphene (2,4,6-t-B~,C~H;)~p~,', 2, is much more reactive. Examination of models of 1and 2 indicates that, while the ortho t-Bu groups of 2 provide adequate bulk to stabilize the complex, access to the phosphorus atoms is possible between these groups over the c6 ring. The conical symmetry of the (Me,Si),C group precludes such an approach. Treatment of 2 in hexane at 0 "C with Fe2(C0)9for 2 h led to a color change from orange to dark red. Purification and subsequent recrystallization afforded dark red 3, which were crystals of (2,4,6-t-B~~C~H~)~P~Fe(co)~, characterized initially by 31PNMR and IR spectroscopy.
2
3
The ,lP(lH}NMR spectrum of 3 comprised an AB system, (10)Flynn, K. M.; Hope,H.;Murray, B. D.; Olmstead, M. M.; Power, P. P. J. Am. Chem. SOC.1983,105, 7750. (11) Cowley, A. H.Polyhedron 1984, 3, 389. (12) Cowley, A. H.; Kilduff, J. E.; Lasch, J. G.; Norman, N. C.; Pakuleki, M.; Ando, F.; Wright, T. C. J. Am. Chem. SOC.1982,105,7751. (13) Vahrenkamp, H.; Wolters, D. Angew. Chem., Znt. Ed. Engl. 1983, 22, 154. (14) Cowley, A. H.; Kilduff, J. E.; Newman, T. M.; Pakulski, M. J. Am. Chem. SOC.1982,104, 5820. (15) Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotau, K.; Higuchi, T. J. Am. Chem. SOC.1981,103,4587.
t
c9 CB
f
Figure 1. ORTEP view of (2,4,6-t-Bu3C,Hz),PzFe(CO),, 3,showing the atom numbering scheme. Table I. Crystal and Intensity Collection Data for 3 and 13 3 formula fw cryst system space group
C,,FeH58O,P* 720.70 monoclinic p2,I C 21.251 (6) a /A 9.793 (2) b/A 20.99(2) c 1.4 108.73 (6) pldeg 4136 (5) UlA' z 4 1.157 ~(ca1cd)lgcm-' 4.7 p(Mo Ka)/cm-' 0.71069 h(Mo Ka)/A 0.4 X 0.4 X 0.6 cryst size/" w scan angleldeg 0.8 + 0.35 tan0 2.0"G 28 G 50.0" 28 limits/deg 7504 total unique measd data no. of data ohsd 4204 I > 2.50(1) data omission 465 no. of variables R Is 0.0578 0.0824 Rw 1.634 GOF
13
monoclinic P2,In 10.710 (3) 29.770 (3) 11.985 (1) 98.02 (1) 3784 (1) 4 1.311 31.6 0.71069 0.5 X 0.5 X 0.7 0.8 + 0.35tan e 2.0" G 2e G 50.0" 6428
3891
I > 2.50(1) 361 0.0459 0.0721 1.821
aP, +423.6, Bp, +396.4, and lJPp= 578.0 Hz. The low-field chemical shifts and large coupling constant are consistent with the retention of a P=P double bond and chemically inequivalent phosphorus atoms. The IR spectrum showed three terminal CO absorptions at 2046,1981, and 1965 cm-' indicative of one Fe(C0)4group. From this information the structure drawn for 3 was postulated and this was confirmed by an X-ray crystallographic study. The structural study revealed the compound 3 as shown in Figure 1. Tables of atomic positional parameters, bond lengths, and bond angles are given in Tables II-IV, respectively, while pertinent crystallographic data are collected in Table I. The P-P bond length of 2.050 (1)A is consistent with a double bond and compares with that in the uncoordinated system of 2.034 (2) A,15 i.e., 0.016 A longer. The phosphorus atom P(1) bonds to the iron (Fe(l)-P(l) = 2.215 (1)A) and forms one of the equatorial ligands in the trigonal-bipyramidal geometry about the iron, the remaining four ligands being carbonyls. Equatorial coordination of the large diphosphene ligand is expected on steric arguments alone since only two and not three 90' angles occur between ligands. In a related complex,
1046 Organometallics, Vol. 3, No. 7, 1984
Cowley et al. Table 111. Bond Lengths ( A ) for (2,4,6-t-Bu3C,H,),P,Fe(CO),, 3"
Table 11. Atomic Coordinates for
(2,4,6-t-Bu,C,H,),PlFe(CO), ,3
atom
X
Y
oi02j O(03) O(04) C(O1) C(02) C(03) C(04) C(l) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(20) C(21) C(22) C(23) C(30) C(31) C(32) C(33) C(40) C(41) C(42) C(43) C(50) C(51) C(52) C(53) C(60) C(61) C(62) C(63) C(70) C(71) C(72) C(73)
0.81810 ( 4 ) 0.73845 ( 6 ) 0.72215 ( 7 ) 0.7500 (3) 0.9316 ( 2 j 0.8206 (3) 0.8962 (3) 0.7752 (3) 0.8871 (3) 0.8177 ( 3 ) 0.8635 ( 4 ) 0.6685 ( 2 ) 0.6161 (2) 0.5826 (3) 0.5949 (3) 0.6401 (3) 0.6765 (3) 0.7915 (2) 0.7849 (3) 0.8415 (3) 0.9029 (3) 0.9043 (2) 0.8509 (3) 0.5903 (3) 0.5720 ( 3 ) 0.6393 (3) 0.5255 (3) 0.5598 (3) 0.5140 ( 6 ) 0.6095 ( 6 ) 0.5208 ( 5 ) 0.7191 (3) 0.7105 (5) 0.7926 ( 4 ) 0.6948 ( 4 ) 0.7199 (3) 0.6620 (3) 0.7237 (3) 0.7048 (4) 0.9651 ( 3 ) 0.9536 ( 4 ) 0.9888 (3) 1.0189 ( 4 ) 0.8630 (3) 0.8984 ( 4 ) 0.8022 (4) 0.9081 ( 5 )
0.23615 (8) 0.3646 (1) 0.5702 (1) -0.0088 ( 4 ) 0.1703 ( 7 ) 0.1143 (6) 0.4509 (5) 0.0871 (6) 0.1966 (8) 0.1622 ( 6 ) 0.3743 ( 7 ) 0.2673 (5) 0.2123 ( 5 ) 0.0991 ( 6 ) 0.0369 ( 5 ) 0.1035 (6) 0.2168 ( 6 ) 0.6632 ( 5 ) 0.7096 ( 5 ) 0.7595 (5) 0.7728 ( 5 ) 0.7488 (5) 0.6979 ( 5 ) 0.2708 ( 6 ) 0.4204 ( 7 ) 0.2470 (7) 0.2035 (8) -0.0923 (6) -0.0635 (9) -0.1927 ( 9 ) -0.162 (1) 0.2810 ( 7 ) 0.2114 ( 9 ) 0.283 (1) 0.4246 (8) 0.7114 ( 6 ) 0.7624 (8) 0.8065 ( 9 ) 0.5712 (8) 0.8168 ( 6 ) 0.8289 (8) 0.9551 (7) 0.7096 (8) 0.6898 ( 6 ) 0.820 (1) 0.694 (1) 0.565 (1)
2
B,b A'
0.53005 ( 4 ) 3.52 ( 2 ) 0.46282 ( 6 ) 2.67 ( 3 ) 0.44754 ( 7 ) 3.05 ( 3 ) 7.2 ( 2 ) 0.4602 ( 3 ) 9.1 ( 2 ) 0.4849 ( 3 ) 7.3 (1) 0.6589 ( 2 ) 0.6149 ( 3 ) 11.2 ( 2 ) 4.6 ( 2 ) 0.4866 ( 3 ) 5.6 ( 2 ) 0.5024 ( 4 ) 4.8 ( 2 ) 0.6086 (3) 6.5 (2) 0.5796 ( 4 ) 3.0 (1) 0.4004 ( 2 ) 3.2 (1) 0.4212 ( 3 ) 3.9 (1) 0.3868 (3) 3.5 (1) 0.3330 ( 3 ) 4.0 (1) 0.3096 ( 3 ) 3.6 (1) 0.3386 (3) 2.7 (1) 0.5094 ( 2 ) 3.2 (1) 0.5722 ( 3 ) 3.4 (1) 0.6211 ( 3 ) 3.1 (1) 0.6121 ( 3 ) 3.3 (1) 0.5474 ( 3 ) 3.1 (1) 0.4948 ( 2 ) 4.0 (1) 0.4780 ( 3 ) 0.4642 ( 3 ) 5.5 ( 2 ) 5.2 ( 2 ) 0.5477 ( 3 ) 7.0 ( 2 ) 0.4790 ( 4 ) 0.2998 ( 3 j 3.9 ( i j 0.2327 ( 5 ) 10.4 (3) 0.2945 ( 6 ) 9.0 ( 3 ) 0.3402 ( 5 ) 6.2 ( 3 ) 0.2992 ( 3 ) 5.2 (1) 0.2324 ( 4 ) 11.6 ( 2 ) 0.3378 ( 4 ) 7.5 ( 2 ) 0.2794 ( 3 ) 7.5 ( 2 ) 0.5903 ( 3 ) 4.3 (1) 0.5325 ( 4 ) 6.8 ( 2 ) 0.6496 ( 4 ) 8.0 ( 2 ) 0.6108 ( 4 ) 7.1 ( 2 ) 0.6688 ( 3 ) 3.9 (1) 0.7368 ( 3 ) 6.4 ( 2 ) 0.6515 ( 4 ) 5.9 ( 2 ) 0.6754 ( 4 ) 6.5 ( 2 ) 0.4255 ( 3 ) 3.8 (1) 0.4147 ( 4 ) 5.5 ( 2 ) 0.3653 ( 3 ) 7.8 ( 2 ) 0.4270 ( 4 ) 8.3 ( 3 )
Anisotropically refined a t o m are given in the form of the isotropic equivalent thermal parameter defined as ( 4 / 3 ) [ a z B ( l , l+) b2B(2,2)=czB(3,3)t ab(cos r)B(1,2) + ac(cos p)B(1,3) + bc(cos a)B(2,3)].
[trans-([Fe(CO)4]2[PCH(SiMe3)2]2)], 4: a similar equatorial coordination geometry about each iron is observed. However, in this complex the Fe2P2plane extends to include each of the two seta of equatorial CO ligands. In 3 the reverse is true with the equatorial carbonyls lying perpendicular to the FeP2 plane. This difference appears to result from the different steric requirements of the (Me3SQ2CHand 2,4,6-t-Bu3C6H2groups. One remaining point of interest from comparing the structures of 2 and 3 concerns the P-P-C angles. In diphosphene 2 this angle is 102.8 (l)'.15 The corresponding angles in 3 P(2)-P(l)-C(l) = 109.3 (1)' and P(l)-P(2)-C(7) = 108.4 (1)' are larger by about '6 in each case. This trend may result from rehybridization a t each phosphorus atom. In an uncomplexed diphosphene, R2P2,with idealized P-P-C bond angles of 90°, the dP-P) and u(P-R) bonds are formed by overlaps using pure P(3p) AO's. In this model the u(P-P) bond can be formed via pure P(3p) overlap or by use of sp hybrid orbitals. In either case, the phosphorus lone pairs, sp or s, are not well oriented to interact with
Fe( 1)-P( 1) Fe( 1)-C( 01) Fe( 1)-C( 02) Fe( 1)-C(03) Fe(l)-C(04) P(i)-p(i) ' P(1)-C(l) P(2)-C(7) O(Ol)-C(Ol) 0(02)4(02) 0(03)-C(03) 0(04)4(04) C(l)-C(2) C(l)-C(6) C(2)-C(3) C(2)-C(20) C(3)-C(4) C(3)-H(3) C(4)-C(5) C(4)-C(30) c ( 5 j-c(6 ) C(5 1-H( 5 1 C(6)-C (4 0) C(7)-C(8) C(7 )-C ( 12) C(8)-C(9) C(8 )-C (50) C(9)-e( 1 0 )
2.215 (1) 1.805 (6) 1.785 (6) 1.803 (6) 1.788 (6) 2.050 (1) 1.893 (4) 1.859 ( 4 ) 1.133 (6) 1.147 ( 6 ) 1.138 (6) 1.124 (6) 1.426 (5) 1.448 (6) 1.388 (6) 1.571 (6) 1.380 (6) 0.71 (4) 1.375 (6) 1.520 (6) 1.377 (6) 0.80 ( 4 ) 1.543 ( 6 ) 1.444 ( 6 ) 1.433 ( 5 ) 1.394 ( 6 ) 1.546 ( 6 ) 1.384 (6)
C(9)-H(9) C(lO)-C(ll) C( lo)
