Organometallics 1986, 5 , 506-510
506
Properties and the Crystal and Molecular Structure of the Pentaammineruthenium(I I ) Dimethyl Acetylenedicarboxylate Complex [ (NH,),Ru( DMAD)](PF,), Wayne W. Henderson,la Barbara T. Bancroft,lb Rex E. Shepherd,"la and John P. Fackler, Jr.*lb Departments of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and Texas A&M University, College Station, Texas 77843 Received April 24, 1985
T h e crystal and molecular structure of t h e dimethyl acetylenedicarboxylate complex [ (NH,),Ru(DMAD)](PF& has been determined from 4025 reflections (MoKa) to R = 0.0422 (R, = 0.0451); the space group is P2,/c. Unit cell parameters a, b, and c are 10.7103 (8), 11.8553 (ll),and 16.4087 (10) 8,respectively. T h e number of molecules per unit cell, 2, is 4. T h e central CGC bond length is 1.238 (7) -A and exhibits the antici ated increase in distance relative to the free ligand upon coordination to the back-bonding (NH3),Ru moiety. T h e trans NH3-Ru distance is 2.163 (5) A while t h e cis NH3's average 2.139 A. T h e DMAD ligand is found to be rotated by 24.7' relative to the "in-plane" Nl-N3-N4-Ru centers. ASED-MO calculations found a n electronic and steric energy minimization at 30' rotation in good agreement with the observed 24.7' twist. T h e two CH30C(0) groups of the coordinated DMAD ligand are bent back 35.0' and 28.5'. In-plane N H 3 ligands are bent back by 7' in the (NH3),Ru2+moiety. T h e vcEc at 1947 cm-' for DMAD shows the DMAD is a better a-acceptor among substituted alkynes, RC=CR, according to the order R = CH30C(0) > P h t H > C2H5. T h e reduction potential of Ru(NH,),(DMAD)~+is 1.00 V (p = 0.10, T = 25.0 'C) with E" for R~(NH,),(alkyne)~+/*+ series following the order R = C H 3 0 C ( 0 ) (1.00 V) > P h (0.95) > C2H, (0.78 V) > H(0.665 V). T h e trans NH, exhibits its 'H resonance at 4.63 p p m while cis NH3's have their resonance at 3.08 ppm in acetone-dfi. The position of the trans NH3 resonance is sensitive to t h e ligand n-acceptor power, implicating t h e 7-acceptor order for RCECR as R = C H 3 0 C ( 0 ) > H N P h > C,H,. T h e position of t h e cis NH:, 'His also influenced by the ligand r-acceptor power, but less than the trans N H 3 resonance.
PI
Introduction
Experimental Section
The Ru(NH3),2+ moiety is particularly good as a a-donor metal center toward a n-acceptor ligand; t h e pyridine and pyrazine complexes of ( N H 3 ) 5 R ~ 2have + been extensively studied.2 Correlations between spectral and chemical p r o p e r t i e s of these N-heterocyclic c o m p l e x e s of (NH3),Ru2+ to the n-acceptor power of the ligands have been m a d e e 3 T h e use of ( N H 3 ) 5 R ~ 2as + a probe of the n-acceptor nature of olefins and acetylenes would appear t o b e an obvious extension of its chemistry. Yet i t is
[Ru(NH3),(DMAD)](PFS),. The title complex was prepared by the addition of excess dimethyl acetylenedicarboxylate ligand (Aldrich) to an aqueous suspension of Ru(NH3),C13over Zn/Hg, as described in the literature.2 The PF,- salt was precipitated by the addition of a small amount of saturated NH,PF6 solution. The yellow powder was recrystallized from hot water to yield yellow-orange single crystals. An elemental analysis was performed by Galbraith Labs. Anal. Calcd for R U C ~ H ~ ~ O , N (Found): ~P~F,~ Ru, 16.35 (16.58);C, 11.66 (11.45);H, 3.42 (3.38); N, 11.33 (11.13). Instrumentation. UV-visible spectra were obtained on a Varian-Cary 118C spectrophotometer using thermostated quartz cells. IR spectra were obtained on a Beckman Acculab 4 spectrophotometer. The electrochemical studies were carried out with a glassy carbon working electrode vs. a saturated NaCl SCE standard. The El,2values were measured via differential pulse polarography on an IBM 225 Electrochemical Analyzer. The ionic strength was maintained at 0.10 with NaCl, and the temperature was held at 25.0 k 0.1 "C. 13C and 'H nuclear magnetic resonance spectra were obtained on a Bruker WH-300 spectrometer operating at 75.45 and 300.0 MHz, respectively. Dimethyl-d6sulfoxide, acetone-d,, and D 2 0 (Stohler Isotope Chemicals) were used as solvents for both the and 'H methods with p-dioxane and Me,Si as the standards. The I3C resonances are reported vs. external Me,% using the relationship C3ext,Me4Si = C3int,dioxane + 66.5, and the 'H resonances are reported in parts per million downfield relative to internal Me& Spectra of the complexes were obtained at concentrations near saturation and at ambient probe temperature. X-ray Crystallography. A crystal from the preparation analyzed by Galbraith was selected having a size ca. 0.2 X 0.2 X 0.1 mm. The crystals appear to be board-like in structure. Data were collected (hkE, hh-l) on a Nicolet R3m-E diffractometer using graphite-monochromated Mo Kcu radiation ( A = 0.71069 A). A total of 4025 reflections having 3.0 < 28 < 50.0 were measured, using the WykoffLO w scan method. During the data collection three standard reflections were monitored every 97 reflections. The intensities were reduced by applying polarization and decay corrections as well as a psi scan empirical absorption correction. Cell parameters and systematic absences were consistent with the
surprising when one considers t h e long history of olefin
and acetylenic complexes that olefin and acetylene complexes of (NHJ5Ru2+ were reported b y L u d i et al. rather late in the development of the Ru(I1)-x-acceptor chemical studies.* The m a i n a t t e n t i o n in the L u d i s t u d y was t h e (NH,),Ru(fumaric acid)2+ complex which exhibited a n increase in the central C=C distance of HO,CCH=CHC02H from 1.348 A in the free ligand t o 1.413 A in the ~ o m p l e x .T~h i s change is typical of t h e s a m e change o n coordination of CzH4in m a n y organometallic comp1exes.j W e report h e r e concerning the coordination of t h e substituted acetylene dimethyl acetylenedicarboxylate ester (DMAD) toward (NH3),R~i". (1) (a) University of Pittsburgh. (b) Texas A&M University.
(2) (a) Ford, P. C.; Rudd, DeF. P.; Gaunder, R.; Taube, H. J . Am. Chem. SOC.1968,90, 1187-1194. (b) Ford, P. C. Coord. Chem. Reo. 1970, 5, 75-99. (c) Taube, H. "Survey of Progress in Chemistry": Scott, A. F. Ed.; Academic Press: New York, 1973; Vol. 6 Chapter 1. (d) Gaunder, R.; Taube, H. Inorg. Chem. 1970, 9, 2627-2637. ( e ) Shepherd, R. E.: Taube, H. Inorg. Chem. 1973, 12, 1392-1401. (3) (a) Wishart, J. F.; Taube, H.; Breslauer, K. J.; Isied, S. S. Inorg. Chem. 1984.23, 2997-3001. (b) Reference 7e. (c) Kuehn, C.; Taube, H. J . Am. Chem. Soc. 1975, 98, 689-702. (d) Drago, R. S.; Cosmano, R.; Tesler, J. Inorg. Chem. 1984, 23, 4514-4518. (4) Lehmann, H.: Shenk, K. J.; Chapuis, G.; Ludi, A. J . A m . Chem. SOC. 1979, 101, 6197-6202. ( 5 ) (a) Ittel, S. D.; Ibers, J. A. Adu. Organomet. Chem. 1976, 14, 33-61; (b) Stalick, J. K.; Ibers. J. A. J . A m . Chem. Soc. 1970. 18, 5333-5338
0276-7333/86/2305-0506$01.50/0
1986 American Chemical Society
Organometallics, Vol. 5, No. 3, 1986 507 Table 11. IR Frequencies of [ Ru(NH,),(DMAD)] (PF,),
Table I formula space group a, A b, A c,
A
62 deg
v, A3
mol wt
z
d(calcd), g/cm3 d(obsd) g/cm3 cryst size color radiatn b, absorptn coeff data range centered on no. of data no. of unique data F: > 3u(F>) no. of parameters refined max transmissn min transmissn g
Ru(NH~)~(C@&) (PFs)2 W
V,
C
cm-'
1947 1935 1708 1695 1648 1640 1443 1362 1325 1252 1038 848 7 50 715 660
10.7103 (8) 11.8553 (11) 16.4087 (10) 107.002 (5) 1992.42 (25) 618.26 4 2.06 2.09 0.20 x 0.20 x 0.10 yellow-orange Mo Kcu 9.3 cm-l 3.0 < 28 < 50.0 25 reflctns, 28 of 20-30' 4025 2621 272 0.807 0.787 0.0005
ligand C S ligand C=O R U ~ I Amoiety ~
ligand Ru"A, moiety ligand ligand PF; ion ligand ligand
1
monoclinic system, space group P2,/a. The data were collected in this space group and transformed to the standard group P2,/c (No. 14). The position of Ru was determined by SHELXTL direct methods. The remaining positions of non-hydrogen atoms were obtained from a difference Fourier synthesis. The positions of the hydrogen atoms were calculated by using an idealized sp3hybridized geometry and fixed bond lengths of 0.96 A. A least-squares refinement of 272 parameters using anisotropic thermal parameters for all atoms except hydrogens gave R = 0.0422 and R, = 0.0451 with quality of fit of 1.599. The SHELXTL program minimized Cwi(lFol- lFc1)2using w i = l / u i values. uivalues were estimated from the diffractometer intensity measurements assuming the errors are from counting statistics after the polarization and decay corrections were included. SHELXTL programs use the International Tables for f ', and f ". scattering factors, f,, Table I summarizes the data collection a t room temperature.
Results and Discussion Infrared Spectrum. The following IR vibrations (cm-l) are observed for [Ru(NH,),(DMAD)](PF,), in KBr: VC-C = 1947, 1935 sh; VC=O = 1708, 1695; ddegNHB= 1648, 1640; = 1325; vp-F = 848. The vCEC of DMAD is lowered 310 cm-' in the complex relative to the free ligand. The extent of the a-back-bonding to DMAD and other acetylenes has been discussed in terms of the lowering of the uczc;6 as much as a 500 cm-' decrease has been observed depending on the metal and other ligands.&l0 If L = acetylene, the lowering of vcSc from the free ligand value to that of the complex is 199 cm-', for phenylacetylene the lowering is 229 cm-l, and for 3-hexyne the lowering is 123 ~ m - l .The ~ change is much larger for the dimethyl acetylenedicarboxylate case, indicating that DMAD is a better a-acceptor than other alkynes. A rough order of a-acid strength would be DMAD > PhC=CH HC=CH > EtCGCEt. Electrochemistry. The reduction potential of [Ru(NHJ5(DMAD)l3+I2+was measured to be +1.00 V vs. the
-
(6) (a) Davidson, G. Organomet. Chem. Reo., Sect. A 1972, 303. (b) Nakamoto, K. "The Infrared and Raman Spectra of Inorganic and Coordination Compounds", 3rd. ed.; Wiley: New York, 1978; p 387. (7) Sullivan, B. P.; Kober, E. M.; Meyer, T. J. Organometallics 1982,
I
I
I 300
I
I
I
400
I
I
500
W A V E L E N G T H [nm]
Figure 1. UV-visible spectrum of (NH3)5Ru(DMAD)2+(3.88 X M in HzO at 25 "C).
NHE. Electrochemical studies by Anson et al.," Taube et al.,3cand Shepherd et a1.I2 have previously shown that a large positive value for E", Ru(III)/Ru(II) is indicative of significant a-back-bonding to the ligand which stabilizes the Ru(1I) oxidation state. A comparison of Ru(NH,)~(DMAD),+12+with other R ~ ( N H ~ ) ~ ( a l k y n ecomplexes )~+/~+ shows the reduction potential to decrease as L = DMAD (1.00 V) > phenylacetylene (0.95 V) > 3-hexyne (0.78 V) > acetylene (0.665 UV-Visible Spectra. The spectrum of Ru(NH3),(DMAD)2+in H 2 0 is shown in Figure 1. The peak at 460 nm (E 1025) is assigned to the MLCT and the peaks at 400, 335, and 275 nm are most likely d-d transitions superimposed upon the charge-transfer absorption envelopes. The MLCT is shifted toward lower energy as the energy of the ligand a*-orbital is decreased. The dimethyl acetylenedicarboxylate complex has a larger bathochromic shift of the MLCT compared to a ~ e t y l e n e . This ~ suggests that a-back-donation is relatively more important for the complex with L = DMAD, in agreement with the infrared evidence and the electrochemistry of the complex.
1, 1011-1013.
(8) Sullivan, B. P.; Smythe, R. S.; Kober, E. M.; Meyer, T. J. J . Am. Chem. SOC.1982,104, 4701-4703. (9) Bruce, M. I.; Hambley, T. W.; Rodgers, J. R.; Snow, M. R.; Wong, F. S. Aust. J. Chem. 1982, 35, 1323-1333. (10) Herrick, R. S.; Templeton, J. L. Organometallics 1982, I, 842-851.
(11) Lim, H. S.; Barclay, D. J.; Anson, F. C. Inorg. Chem. 1972, 11, 1460-1466. (12) Johnson, C. R.; Shepherd, R. E. Synth. React. Inorg. Met.-Org. Chem. 1984, 14(3), 339-353.
508 Organometallics, Vol. 5, No. 3, 1986 The MLCT transition is a function of solvent and shows a bathochromic shift as the Gutmann donor number of the solvent increases. The absorption band shifts from 452 nm in acetonitrile (donor number = 14.1) to 455 nm in acetone (17.01, 460 nm in H 2 0 (18.0), and 469 nm in dimethyl sulfoxide (29.8). This trend has been explained for Ru(I1) and Ru(II1) ammines in terms of greater solventNH, hydrogen bonding.13J4 The sensitivity of the Ru(NH3)5(DMAD)2+visible and UV spectrum to the choice of solvent establishes the charge-transfer character of these bands as metal to ligand, being more complete in the excited state with the ruthenium center taking on more Ru(II1) character. NMR Spectra. The proton signals of the ammonia ligands in R u ( N H ~ ) ~ L complexes ~+ can be seen in acetone-d, or dimethyl-d, sulfoxide and appear as two absorptions of relative ratio 12:3 (cis:trans). Ludi supports the view that the cis NH3 peak is independent of the sixth ligand, while the trans NH3 peak is shifted downfield as the a-back-bonding capacity of L increase^.^ Presumably the synergistic effect of increased a-donation, a-acceptance from the metal to the ligand L causes the metal-trans NH3 a-bonding to be more polarized, resulting in lower field trans NH3 'H resonances. For DMAD this trend continues: the cis resonance is 3.07 ppm and the trans resonance is 4.63 ppm in acetone-d,. The trans NH3 resonances establish an order of a-back-bonding in R u ( N H ~ ) ~ of L~+ CH3CH2C=CCH2CH34(3.40 ppm) < C6H5CrCH4(3.97 ppm) ^I HC=CH4 (3.98 ppm) < DMAD (4.63 pprn). The cis NH, resonances do vary from 2.40 ppm for 3-hexyne to 3.07 ppm for DMAD and thus are not completely invariant with the nature of 1, as suggested by Ludi et ale4 The ligand 'H and 13C resonances have been used to measure a-back-bonding in these types of complexes a l ~ 0 . l ~ Donation of electron density to the metal occurs via uinteraction and causes downfield shifts; a-back-bonding can replace the electron density on the ligand, attenuating or even cancelling the downfield effect. In addition, for acetylenes, the loss of axial symmetry in the ligand by coordination can cause a downfield shift.16 For DMAD there is essentially no shift of the methyl 'H resonances upon coordination: 6 3.88 (free ligand) and 6 3.91 (complex in acetone-d,). Whether this is a consequence of the several factors effectively cancelling or isolation of the methyl groups from the changes in electron density by the -OC(O)- groups cannot be determined from the 'H NMR spectra. 13C NMR spectra were measured in an attempt to resolve these questions about a-back-donation. The Ru(NH3)5(DMAD)2+complex showed only two resonances in D 2 0 / H 2 0solvent: a singlet a t 98.46 ppm assigned to the acetylene carbons and a quartet centered at 53.65 ppm assigned to the methyl carbons. The carbonyl carbon resonance was not observed; the carbonyl C appears at 151.83 ppm for the free ligand in Me,SO. The free ligand value of the acetylene carbon is 74.35 ppm (Me2S0 sol(13) Curtis, J. C.; Sullivan, B. P.; Meyer. T. J. Inorg. Chem. 1983,22, 224-236. (14) Shepherd, R. E.; Hoq, M. F.; Hoblack, N.; Johnson, C. R. Inorg. Chem. 1984,23, 3249-3252. (15) (a) McDonald, J. W.; Corbin, J. L.; Newton, W. E. J . Am. Chem. SOC.1975,97, 1970-1971. (b) McDonald, J. W.; Newton, W. E.; Creedy, C. T. C.; Corbin, J. L. J. Organomet. Chem. 1975, 92, C25. (c) Ricard, L.; Weiss, R.; Newton, W. E.; Chen, G . J.-J.; McDonald, J. W. J . Am. Chem. SOC.1978, 100, 1318-1320. (d) Templeton, J. L.; Ward, B. C.; Chen, G. J.-J.;McDonald, J. W.; Newton, W. E. Inorg. Chem. 1981,20, 1248-1253. (e) Templeton, J. L.; Ward, B. C. J . Am. Chem. SOC.1980, 102, 3288-3290. (fl Chisholm, M. H.; Clark, H. C.; Manzer, L. E.; Stothers, J. B. J . Am. Chpm. SOC.1972, 94, 5087-5089. (16) (a) Borg, A.; Lindblom, T.; Vestin, R. Acta Chem. Scand., Ser. A 1975, A29. 475. (b) Reference 9.
Henderson et al.
Figure 2. Thermal ellipsoid drawing of [ (NH&Ru(DMAD)](PF6)2.
Table 111. Atom Coordinates (XlO') and Temperature Factors (A2X lo3) for R U ( " ~ ) ~ ( C , H , ~ ~ ) ( P F , ) ~ atom
RU N(1) N(2) N(3) N(4)
N(5) C(1) C(2) C(3) C(4)
C(5) C(6) O(1) O(2) O(3) O(4) P(1) F(11) F(12) F(13) F(14) F(15) F(16) P(2) F(21) F(22) F(23) F(24) F(25) F(26)
X
2519 (1) 2109 (3) 3759 (3) 2781 (3) 2149 (3) 1285 (3) 2658 (3) 3137 (4) 2228 (4) 1232 (5) 4681 (4) 3739 (4) 2315 (3) 1710 (3) 3876 (3) 4110 (3) 3599 (1) 3315 (3) 2675 (3) 3856 (3) 3848 (5) 4516 (3) 3334 (5) 334 (1) 2 (4) 1226 (3) 653 (3) -550 (3) 640 (8) 43 (7)
Y
-9534 -11183 -9877 -10397 -9070 -9202 -7764 -8178 -6793 -5312 -8634 -7931 -6513 -6293 -6983 -8837 -3584 -4810 -3177 -2312 -3413 -3936 -3719 -2096 -844 -1681 -3326 -2470 -1859 -2206
(1) (4) (4) (4) (4) (4) (5) (4) (5) (6) (6)
(5) (4) (4) (4) (3) (1) (4) (5) (3) (5) (5) (5) (2) (4) (6) (4)
(5) (10) (10)
2
ut,,A=
949 (1) 144 (5) 772 (5) 2778 (4) -1066 (4) 1170 (6) 1183 (5) 2194 (5) 411 (5) 327 (7) 5388 (7) 3456 (5) -613 (4) 989 (4) 3874 (4) 4108 (4) 2199 (2) 2371 (5) 2108 (7) 2070 (5) 3709 (4) 2355 (9) 719 (4) 2314 (2) 2153 (8) 3133 (7) 2472 (9) 1457 (8) 1123 (8) 3509 (8)
22 (1)" 40 (2)' 34 (2)" 32 (2)" 35 (2)" 43 (2)" 27 (2) 27 (2) 26 (2)" 49 (3)" 53 (3) 30 (2)' 40 (2) 38 (2) 48 (2IQ 36 (1)' 40 (1)' 108 (3) 143 (4) 80 (2In 166 (5) 144 (4)" 140 (4)' 38 (1)' 127 (4) 134 (3)' 147 (4)O 146 (4)' 216 (7) 222 (7)'
a Equivalent isotropic U defined as one-third of the trace of the orthogonalized U,, tensor.
vent), giving a A6 of 24 ppm downfield upon coordination. Clearly this shift indicates that 0-donation and loss of axial symmetry are important effects. The methyl value of 53.65 ppm (H20solvent) is close to the value of the resonances in other DMAD complexes and 54.07 ppm (Me2S0solvent) for the free ligand. It suggests the effect of a-back-bonding is not very important at positions 4 atoms remote to the metal. Structure of [RU(NH,),(DMAD)](PF~)~. The thermal ellipsoid drawing of the RU(NH,),(DMAD)~+complex as determined by the crystal structure of its PF6-salt is shown in Figure 2. The molecular packing is available in supplementary materials (Figure A). The PF6- anions are
Organometallics, Vol. 5, No. 3, 1986 509 Table IV. Energy Minimization by ASED Calculation 0, deg energy, eV 0, deg energy, eV 0 0.1552 50 0.1250 5 10 15 20 25 30 35 40 45
0.1401 0.1024 0.0588 0.0240 0.0042 0.0 0.0102 0.0340 0.0718
55 60 65 70 75 80
85 90
Table V. Bond Lengths (A) 2.163 (5) Ru-N(2) Ru-N(4) 2.140 (5) 2.143 (6) 2.144 (5) 1.238 (7) 1.452 (7) 1.329 (8) 1.437 (7) 1.328 (7)
0.1971 0.2935 0.4168 0.5584 0.6959 0.803 0.8657 0.8853
considerably disordered. Positional parameters are listed in Table 111. The dimethyl acetylenedicarboxylate ligand is seen to be twisted with respect to the two planes created by N(2)-N(l)-N(5)-Ru and N(3)-N(l)-N(4)-Ru, but it is not in the position of equilibrium (45') arising from steric interactions with the NH3 groups. It is at 24.7' to the N(3)-N(l)-N(4)-Ru plane and 68.6' to the N(2)-N(l)-N(5)-Ru plane. The two nitrogens closest to the RuC(l)-C(2) plane (N(3), N(4)) are bent back by 7' each, forming an N(3)-Ru-N(4) angle of 165.9'. The C(l)-C(2)-C(6) and C(2)-C(l)-C(3) bonds are bent back forming angles of 151.5' and 145.6', respectively. This combined with the lengthening of the C(l)-C(2) acetylene bond to 1.238 (7) 8, supports the anticipated intermediate bond order between the acetylene carbon atoms, lower than ca. 1.20 8, of C=C and higher than 1.34 8, of C=C. The Ru-C(l) and Ru-C(2) bond lengths vary slightly since they are not required by the symmetry to be identical, but this variation is statistically insignificant. No hydrogen bonding has been observed. ASED-MO calculations were carried out to seek the electronic and steric energy minimization of the (NH3)5R~2+ and DMAD ligand fragments. Details of the program and the methods have been given elsewhere." ASED-MO calculations do not suggest anything unusual about the twist of 25', other than that it indeed is the sterically preferred orientation when only two nitrogens are bent back. Parameters used in the ASED calculations are specified in supplementary materials (Table A). The difference in total energy of the (NH3)5Ru(DMAD)2+ complex as DMAD is rotated about the Ru to C=C axis is given in Table IV. In these calculations 0 = 0' corresponds to the plane containing Ru-N(3)-N(4) with the nitrogens bent back; 0 = 90' corresponds to the Ru-N(2)-N(5) plane which has nondistorted NH, ligands. The equilibrium position by the ASED calculation (E = 0) occurs at 30' which is close to the experimental value of 24.7'. Since the ASED-MO calculations find the minimum at about 30' instead of 0' or 45' for the twist, symmetry requires 0-donation from the filled a-level of the C=C bond of DMAD into the d+z, d,n-hybridized metal orbitals together with n-bonding interaction between the d,, and d,, metal orbitals and the ligand a*-level. Steric perturbations occur as well. The argument for a steric effect is supported by the N(3)-Ru-N(5) angle of 85.9' and N(2)-Ru-N(4) angle of 87.5' while the other angles bisected (17) Trzcinska, B. M.; Fackler, J. P., Jr.; Anderson, A. B. Organometallics 1984, 3, 319-323. (18) (a) Johnson, C. R.; Shepherd, R. E. Inorg. Chem. 1983, 22, 2439-2444. (b) Johnson, C. R.; Shepherd, R. E. Inorg. Chem. 1983,22, 1117-1123. (c) Johnson, C. R.; Shepherd, R. E. Inorg. Chem. 1983,22, 3506-3513. (d) Henderson, W. W.; Shepherd, R. E. Inorg. Chem. 1985, 24, 2398-2404. (19) (a) Isied, S. S.; Taube, H. Inorg. Chem. 1976, 15, 307G3075. (b) Isied, S. S.; Taube, H. Inorg. Chem. 1974, 13, 1545-1551. (c) Isied, S. S.; Taube, H. Inorg. Chem. 1975, 14, 2561-2562. (20) Wycoff, H. W.; Tsenaglou, D.; Hanson, A. W.; Knox, J. R.; Lee, B.; Richards, F. M. J . Biol. Chem. 1970, 245, 305-328.
Ru-C(l)
2.136 (5) 2.136 (5) 2.117 (6)
C(l)-C(3) C(3)-0(1) C(4)-0(2) C(6)-0(3) P-F(av)
1.472 (7) 1.193 (8) 1.464 (8) 1.205 (7) 1.545 (25)
-
Table VI. Bond Andes ( d e d 89.2 (2) N( l)-Ru-N( 3)
N(l)-Ru-N(2) N(2)-Ru-N(3) N (2)-Ru-N (4) N(l)-Ru-N(5) N(3)-Ru-N(5) N(l)-Ru-C(l) N(3)-Ru-C( 1) N(5)-Ru-C( 1) N (2)-Ru-C (2) N(4)-Ru-C(2) C(1)-Ru-C (2) Ru-C( 1)-C(3) Ru-C (2)-C (1) C (1)-C(2)-C (6) C(l)-C(3)-0(2) C(2)-C(6)-0(3) 0(3)-C (6)-0 (4) C (5)-0(4)-C (6)
92.8 (2) 87.5 (2) 90.9 (2) 85.9 (2) 162.4 (2) 112.3 (2) 83.0 (2) 84.8 (2) 112.3 (2) 33.8 (2) 133.7 (4) 71.9 (3) 145.0 (5) 110.7 (5) 122.4 (5) 123.5 (5) 115.9 (5)
~
- I
N( l)-Ru-N (4) N( 3)-Ru-N( 4) N( 2)-Ru-N (5) N(4)-Ru-N (5) N(2)-Ru-C(1) N(4)-Ru-C (1) N ( l )-Ru-C(2) N(3)-Ru-C (2) N (5)-Ru-C (2) Ru-C( 1)-C( 2) C(2)-C(l)-C(3) Ru-C (2)-C (6) C( l)-C(3)-0( 1) 0 (l)-C (3)-0 (2) C(2)-C(6)-0(4) C (3)-0( 2)-C (4) F-P-F(av)
83.6 (2) 82.4 (2) 165.9 (2) 178.7 (2) 93.8 (2) 97.3 (2) 81.6 (2) 163.9 (2) 81.8 (2) 94.8 (2) 74.3 (4) 151.5 (5) 143.1 (4) 124.6 (6) 124.7 ( 5 ) 114.1 (5) 117.0 (5) 90.0 (21)
by DMAD are 93.8' and 92.8". The twist of one of the carboxylate groups of 69' with respect to the RuC(l)C(2) plane seems to be a result of a random orientation. The theoretical calculations are not influenced significantly by rotation of this group. The anisotropic temperature factors (Table B), hydrogen coordinates and temperature factors (Table C), and the observed and calculated structure factors (Table D) used to refine the structure leading to the ORTEP drawing in Figure 2 are available as supplementary material on microfilm. Ordering information is given below. Bond lengths for [(NH3)5Ru(DMAD)](PF6)2 are given in Table V; bond angles are supplied in Table VI. The trans NH,, N(1), at 2.163 (5) 8, is slightly longer than the cis NH, ligands which average 2.139 8,. This is consistent with the IH NMR results mentioned above and the known labilization of the trans NH3 position when a strong n-acceptor ligand coordinates to (NH3)5R~2+.19 The crucial C(l)-C(2) distance of 1.238 (7) A. is indeed longer than the free ligand value (ca. 1.20 A) while the average of the C(4)-0(2) and C(5)-0(4) of 1.450 8,is slightly perturbed from the normal C-0 single bond value of 1.43 8,. A slight difference in the Ru-C(l) distance (2.117 (6) A) vs. Ru-C(2) (2.144 (5) A) as well as the modest difference for the Ru-C(1)-C(3) angle of 133.7 (4)' compared to Ru-C(2)-C(6) of 143.1 (4)' reinforces the idea that packing distortions are present in the structure.
Conclusions The most substantial influence of R = CH30C(0)in the (NH,),RU(DMAD)~+complex is manifest in its strong stabilization of the Ru(I1) half of the (III/II) reduction potential. The electrochemistry shows that for Ru(NH3),(alky n e ~ ) ~ +complexes, /~+ R = CH,OC(O) > P h > C2H5 > H in tuning the reduction potential over a 0.34 V range. For comparison with other (NH3)5R~L2+ complexes, a 0.43 V more favorable reduction potential is achieved by changing L from NH, (no a-acceptor power) to L = p y r a ~ i n e ~or~ J ~ a 0.51 V change is achieved on changing from L = pyrazine to L = MezS0.3cJ1These are considered to be dramatic
510
Organometallics 1986, 5 , 510-513
differences in n-acceptor power, contributing factors of about 3 kcal/mol stabilization per ligand ~ h a n g e . ~ ” Therefore the modest changes in R substituents in RC= CR appear to create major differences in the n-acceptor ability of DMAD vs. acetylene, for example, as detected by the measured reduction potentials. The substituent effect of R in various acetylenes is much greater than R groups attached to the pyridine ring. For example, R = (0)CNH2vs. H in the para position of the pyridine ring raises the reduction potential by 0.135 V12 compared to the R = (0)COCH3vs. H shift of 0.34 V for coordinated acetylenes. The same order of the influence of R in R C r C R on the trans NH3 ‘H resonance is observed (CH,OC(O) > P h > H > C2H5) as determined by infrared and approximately so by differential pulse voltammetry of the (III/II) complexes. The acetylenic carbons exhibit a 24 ppm downfield 13C shift upon coordination of DMAD in (NH,),Ru(DMAD12+,indicative of good cr-donation of DMAD to Ru(I1). The other observed shift for the CH, groups of DMAD is virtually unchanged, indicative of a rapid diminution of the influence of the metal’s *-donation in DMAD over three more atom positions from the site of coordination. Interestingly enough, a small difference is still observed in the CH,-0 bond distance in the coordinated ligand for the struckre of [ (NH,),Ru(DMAD)] (PF& ‘Ompared to CH3-0 bonds. The key features Of this structure appear to be as the CrC bond is increased ca. 0.04 A upon coordination; (2) the structure about the Ru(I1) center is approximately seven-coordinate with the C 4 ! donor occupying one position of an octa-
hedral set of ligands; (3) the “trans” NH, is about 0.024 8, further away from Ru(I1) than the “cis” set. The two “3’s nearest the C r C donor are bent away toward the trans NH3 by 7” while two other NH,’s are nearly axial; (4) the DMAD is off a strict plane containing the trans NH3, Ru(II), and the in-plane cis NH3 ligands with a twist to about 24’ instead of a 45” bisection of all adjacent NH3’s; ( 5 ) the ligand bend-back angles of the R group average 31’ in (NH3)5Ru(DMAD)2+ which is about normal for other coordinated acetylene^.^ (Bend-back angles usually fall in the range of 12’ to 40°5.) Curiously enough, the activated C=C unit in (NH3)5Ru(DMAD)2+ has resisted attack by external electrophiles and nucleophiles in several tests. We believe that this result once again emphasizes the importance of synergism in describing the n-back-bonding situation with Ru(I1) and “small atom” units such as CO, NS, CN-, and Rc~CR.3C,12,18
Acknowledgment. We gratefully acknowledge support of this work via NSF Grant CHE 802183 (Pittsburgh) and NSF Grant CHE8408414 (Texas A&M). The center for Energy and Minerals Research (Texas A&M) also has supported this study. Registry No. [RU(NH,)~(DMAD)] (PF& 99642-84-9. Supplementary Material Available: Figure A, molecular packing of RU(NH~)~(DMAD)*+, Table A, parameters used in ASED calculations, Table B, anisotropic temperature factors, Table C, hydrogen coordinates and temperature factors, and Table D, observed and calculated structure factors (22 pages). Ordering information is given on any current masthead page.
Cobaltadihydroquinoline Derivatives from Carbenoid Cobalt Precursors. X-ray Crystal Structure of C,H,(PMe3)CoCH,-2-C,H,( 4-CH,)N=C(OCH3)’ Helmut Werner’ and Lothar Hofmann Institut fur Anorganische Chemie der Universitat, Am Hubland, 0-8700 Wurzburg, Germany
Manfred L. Ziegler and Thomas Zahn Anorganisch-chemisches Institut der Universitat, I m Neuenheimer Feld 270, 0-6900 Heidelberg 1, Germany Received May 3 1, 1985
The reaction of C5H5Co(PMe3)C0with aryl isocyanides CNAr (Ar = CsH5, C6H,-4-CH3)and CHzCII in benzene produces the cationic carbenoid cobalt complexes [C5H5CoCH2Cl(PMe3)CNAr]+ which are isolated as the PFs salts 4 and 5. Addition of KOH to a suspension of 4 or 5 in methanol leads to the formation , of the cobaltadihydroquinoline derivatives C5H5(PMe3)CoCH2-2-C6H3(4-R)N=C(OCH3) (6, R = H; 7, R = CH3) in ca. 70% yield. The molecular structure of 7 has been determined by an X-ray investigation. 7 crystallizes in the space group P 2 J c with a = 8.776 (3)A, b = 14.285 (5) A, c = 14.758 ( 7 ) A, and /3 = 91.38 (3)”. The bicyclic ring system is nonplanar and bent along the N-C axis of the 1-aza-3-cobaltacyclohexadiene ring. The coordination geometry of the metal is slightly distorted octahedral with bond angles between 84.0 and 95.0’. Under mass spectroscopic conditions, 6 and 7 decompose to give [CSH,Co(PMe,)]+and the corresponding 2-methoxyindolenine derivative, thus suggesting the possibility of using the new complexes as precursors for these heterocycles. Introduction Cyclopentadienylcobalt(1) and -rhodium(I) complexes of the general type C5H,M(PMe3)L (M = CO,Rh; L = PR3, P(OR)3,CO, CNR, CzH4,etc.) are strong metal bases and
react with various electrophiles by oxidative addition or oxidative substitution to form the corresponding cobalt(II1) and rhodium(II1) derivativesS2 By using dihalomethanes CHzXX’ as electrophiles, either cationic or neutral car-
(1) Part 55 of the series ‘Basic Metals”. Part 54: Werner, H.; Scholz,
(2) Werner, H. Angew. Chem. 1983,95, 932; Angeu,. Chem., Int. Ed. Engl. 1983, 22, 927.
H.J.; Zolk, R. Chem. Rer. 1985, 118, 4531.
0276-7333/86/2305-0510$01.50/0
0 1986 American Chemical Society
