Volume 32
Inorganic Chemistry
Number 2
January 20, 1993
I
(8
Copyright 1993 by the American Chemical Society
Communications The First Observation of V(Ru,P) in 31PCP/MAS NMR Spectra of Solid Ruthenium Compounds Klaus Eichele,l’ Roderick E. Wasylisherq’J’ John F. Corrigan,lb Simon Doherty,lbYan S q l band Arthur J. Carty’Jb Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 453, and Guelph-Waterloo Centre for Graduate Work in Chemistry, Waterloo Campus, Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1 Received August 20, 1992
Indirect spin-spin coupling constants involving phosphorus31 and metal nuclei provide an important parameter for characterizing metal-phosphorus bonds.2” For example, the magnitude of 1J(195Pt,31P) in square-planar Pt(I1) phosphine complexes provides unambiguousstereochemicalinformation.2-8 One-bond 31P-M spin-spin coupling constants are now available for more than 20 different metal^.^ Most of the data involve metal nuclei which have a spin l / 2 isotope (e.g., lo3Rh,107/109A g, 111/113Cd,117/119Sn, 183W, 187oQ,19sPt, 1*Hg,207Pb),2+ Phosphorus couplingsinvolving quadrupolar metal nuclei (S2 1) are difficult or impossible to observe in solution NMR studies because of the efficiency of the quadrupolar relaxation mechanism in all but the most symmetric metal environments.+I Hence, coupling constants such as J(s9Co,31P)11 and J(99Tc,31P)12 are only observed in relatively symmetric octahedral complexes where the electric field gradient at the quadrupolar s9C0(S= 7/2)or 99Tcnucleus (S= 9 / 2 ) is approximately zero. In 1982 Menger and Veemanl3 demonstrated that analysisof 31PCP/MASspectra of solid Cu(1) phosphine complexes provides J(63Cu,31P)and J(65Cu,3lP), even though both of these naturally occurring copper isotopes are quadrupolar withS = 3/2. Subsequently,several reportsof values
(4)
(5) (6) (7) (8) (9)
(IO) (1 1)
(12) (13)
(a) Dalhousie University. (b) University of Waterloo. Nixon, J. F.; Pidcock, A. Annu. Rev. NMR Spectrosc. 1969, 2, 345. (a) Pregosin, P. S.;Kunz, R. W. In NMR BasicPrinciplesandProgress; Diehl. P., Fluck, E., Kosfeld, R., Us.Springer-Verlag: ; Berlin, 1979; Vol. 16. pp 16153. (b) Pregosin, P. S. In Phosphorus-31 N M R Spectroscopy in Stereochemical Analysis, Organic Compounds and Metal Complexes; Verkade, J. G., Quin, L. D., Eds.; Methods in Stereochemical Analysis 8; VCH Publishers, Inc.: Deerfield Beach, FL. 1987: DD 465-530. (a)’Verkab’e: J. G.; Mosbo, J. A. In Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis, Organic Compoundsand Metal Complexes; Verkade, J. G.,Quin, L. D., Eds.; Methods in Stereochemical Analysis 8; VCH Publishers, Inc.: Deerfield Beach, FL, 1987; pp 425-463. (b) Carty, A. J.; MacLaughlin, S.A.; Nucciarone, D. Ibid., pp 559619. Jameson, C. J. In Multinuclear N M R Mason, J., Ed.; Plenum Press: New York, 1987; pp 89-131. Transition Metal Nuclear Magnetic Resonance; Pregosin, P. S.,Ed.; Studies in Inorganic Chemistry 13; Elsevier: Amsterdam, 1991. Harris, R. K.;McNaught, I. J.; Reams, P.;Packer, K.J. Magn. Reson. Chem. 1991,29, S60. Power, W. P.; Wasylishen, R. E.Inorg. Chem. 1992, 31, 2176. (a) Pople, J. A. Mol. Phys. 1958,1,168. (b) Suzuki, M.; Kubo. R. Ibid. 1967. 7, 201 * Rehder, D.; Bechthold, H. C.; Paulsen, K. J . Magn. Reson. 1980, 40, 305. Socol, S.M.; Lacelle, S.;Verkade, J. G. Inorg. Chem. 1987,26, 3221. Vanderheyden, J.; Ketring, A. R.; Libson, K.; Heeg, M. J.; Roecker, L.; Motz. P.; Whittle, R.; Elder, R. C.; Deutsch, D. Inorg. Chem. 1984,23, 3184. Menger, E. M.; Veeman, W. S. J . Magn. Reson. 1982, 46, 257.
0020-1669/93/ 1332-0121S04.00/0
for J(63/6sCu,)1P) haveappeared in the literature.“ More recently, Lindner et al.lsJ6 and Gobetto et al.17 reported observations of 1J(M,31P)from solid-state NMR studies where M = 9WM0, S5Mn, 59C0,and 93Nb. Despite the interest in and catalytic importance of ruthenium complexes,only two reports of coupling constants involving the quadrupolar ruthenium-99 nucleus have appeared, viz., J(99Ru,13C)and J(99Ru,170) in the highly symmetric compounds &[Ru(CN)6] and Ru04, respectively,Is and J(119Sn,99R~) in [Ru(SnCl3)~C1le.l9 Here we wish to report the first observation of 1J(101,99R~,31P) in 31PCP/MAS NMR spectra of solid ruthenium-phosphorus complexes. The center peakin the 8l.0-MHzS1PCP/MASNMRspectnun of the octahedral complex all-trans-Ru(PEt3)z(C0)2(C=CPh)2 (1)20is shown in Figure la. Particularly striking are the small satellite peaks arising from Ru,P spin-spin coupling, which surround the intense isotropic peak,4 ” P ) = 18.7 ppm (enlarged in Figure lb). Since ruthenium-99 (natural abundance 12.7%) and ruthenium- 101 ( 17.1%) both have a nuclear spin of 5/2, 21.22 one might anticipate the high-resolution 31PNMR spectrum of a molecule containing the 101,99R~,31P spin-pairs to consist of six equally spaced peaks, each associated with one of the allowed components of 101,99Ru nuclear spin along the magnetic field, m,. However, it is well-known that in the solid state the Zeeman levels of a quadrupolar nucleus are strongly perturbed by the quadrupolar interaction and hence the quantum numbers, m,, are no longer eigenstates of the Zeeman-quadrupolar Hamilt ~ n i a n . ~One ~ - important ~~ consequence of the so-called breakdown of the high-field approximation is that dipolar interactions (14) (a) Olivieri, A. J . Am. Chem. Soc. 1992, 114, 5758. (b) Attar, S.; Bowmaker, G. A.; Alcock, N. W.; Frye, J. S.;Bearden, W. H.; Nelson, J. H. Inorg. Chem. 1991, 30, 4743. (c) Bowmaker, G. A,; Cotton, J. D.; Healy, P. C.; Kildea, J. D.; Silong, S.B.;Skelton, B. H.; White, A. H. Inorg. Chem. 1989, 28, 1462 and references cited therein. (15) Lindner, E.; Fawzi, R.; Mayer, H. A.; Eichele, K.; Hiller, W. Organometallics 1992, I I , 1033. (16) Lindner, E.; Fawzi, R.; Mayer, H. A,; Eichele, K.; Pohmer, K. Inorg. Chem. 1991,30, 1102. (17) Gobetto, R.; Harris, R. K.; Apperley, D. C. J . Magn. Reson. 1992, 96, 119. (18) Brevard, C.; Granger, P. Inorg. Chem. 1983, 22, 532. (19) Farrugia, L. J.; James, B. R.; Lassigne, C. R.; Wells, E. J. Can.J. Chem. 1982, 60, 1304. (20) Sun, Y.; Taylor, N. J.; Carty, A. J. 1. Organomet. Chem. 1991, 123, c43. (21) Biittgenbach, S.; Dicke, R.; Gebauer, H.; Herschel, M. Z . Phys. A 1977, 280, 217. (22) Brevard, C.; Granger, P. J. Chem. Phys. 1981, 75. 4175. (23) Abragam, A. Principles of Nuclear Magnetism; Clarendon Ress: Oxford, U.K., 1961.
Q 1993 American Chemical Society
Communications
122 Inorganic Chemistry, Vol. 32, No.2, 1993
P
I
24
20 16 ppm
12
.
’
’
’
500
,
.
0
,
.
.
.
I
*
.
,
.
228
-500
,
.
220
,
*
,
I
212
228
ppm
Hz
Figure 1. (a) Isotropic region of the 81.0-MHz 31P CP/MAS N M R spectrumofall-t-Ru(PEt,)2(CO)~(OW!Ph)z(1). (b) Amplification of the satellite pcab shown in (a). (c) Calculated spectrum due to 70% of uncoupled phosphorus-31 and 13% coupled to ruthenium-99 (J= 104 Hz,d = -46 Hz). (d) Schematic representation of the ruthenium-99
220
212
ppm
Fig1~e2.Isotropic region of the S ~ . ~ - M H Z ~ ~ P C P / M NMR A S spectrum of the butterfly cluster (~~-H)R~~(CO)IO(~-PP~~)[C~~-PP~(C~H*) (2) in the p-PPh2 region: (a) experimental spectrum; (b) calculated spectrum. The skeletal framework of 2 is shown in the insert.
satellites.
involving quadrupolar nuclei are not completely eliminated by magic angle spinning.2’ As a result, high-resolution MAS NMR spcctra of spin 1/2 nuclei which are J-coupled to quadrupolar nuclei are not generally symmetrical. Instead, the separations between peaks are ysqueezbdwat one end and “stretchedmat the other (Figure ld).28 Two parameters, Jand the residual dipolar coupling d, are required to describe these multiplets. Despite the apparent complexity of the spin 1/2, spin Ssystem, itisimportant torecognize28thatJanddcanbereadilydetermined from an analysis of the high-resolution MAS NMR spectrum of thespin1/2nucleus. Adjacentpeahinthe”PCP/MASspectnun of 101.99R~,31P spin-pairs will be separated by M - 6d/5, M 3d/5, lJl, lJl + 3d/5, and IJI 6d/5, starting at the low frequency end and assuming M > W. Note that despite the asymmetry of the multiplet (Figure Id), the separation between the outermost peaks still equals 154. For the octahedral compound 1, the 3IP NMR line shape in Figure l b was simulated (Figure IC)with J = 104 Hz and d = -46 Hz. The parameter d is related to the
+
. . . . . . . . . . . . . . . . . . . . .
(24) Caaabella, P. A. J. Chem. Phys. 1964,41, 3793. (25) VanderHart, D.L.;Gutowsky, H.S.;Farrar, T. C. J . Am. Chem. Soc. 1%7,89, 5056. (26) . . Stoll, M. E.; Vaughan, - R. W.;Saillant. R. B.;Cole, T. J. Chem. Phys. 1914,61t2896. (27) Olivieri, A. C. 1.Magn. Reson. 1989,81,201. ( 2 8 ) To first order, the spin I 2 (”P) MAS N M R transitions of a spin l / 2 , spin S pair are given byb v,(”P) = -mlJI
- (S(S + 1) - 3m2]d/S(2S - 1)
when is the Iol**Ruindirect spin-spin coupling constant, S = m= 101.99Ru. )/2, ..., - S I 2 , and d is given by
d = -(3xD/20u,)[(3 cos2d - 1)
+
r)
for
sin2@00s 2a]
D is the Ru-P direct dipolar coupling constant, dependent on the inverse
cube internuclear separation, v, is the ~ R orUIolRu Larmor frequency (9.23 and 10.34 MHz at BO = 4.7 T), x is the 9PRuor ‘OIRu nuclear quadrupolar coupling constant, e29,,Q/h, and r) is a parameter which
dacriba the asymmetry of the elcctnc field gradient (EFG) tensor at the nucleus S , (e9x,- e9yy)/e9zz,with bzJf b,.J 2 kxd. The azimuthal and polar angla aand Bdefine theonentationof the 101.99Ru,”Pdipolar vector in the principal axis system of the EFG tensor. Note that. to first order, the appearance of the spectrum is independent of the sign of J .
1000
100
0
-600
-1000
HZ
figure 3. (a, b) Calculated
N M R spectra of the 99Ru,31Pand 1°IRu,”P spin pairs a t each of the two sites, respectively, of the butterfly cluster 2. (c) Sum of the spectra shown in (a) and (b). This sum corresponds to the satellite pcaks shown in Figure 2b. IlP
characteristics of the electric field gradient (EFG) at the ruthenium nucleus and hence to the ruthenium quadrupolar couplingconstant x and itsasymmetry.28 If the largest component of the EFG tensor in 1 is along the P-Ru-P bond axis, B = Oo and x = 8.5 MHz, independent of the value of q. On the other hand, if the largest component of the EFG tensor is along either the Ph--Ru--CnCPh or OIC-Ruaxis, then = 90° and a = 0 or 90°; therefore, it is impassible to obtain x and q independently. There is no firm experimental information regarding the orientation of the EFG tensor; however, M(lssbnuer studiea have indicated sirllilar partial quadrupolar splittings for
Inorganic Chemistry, Vol. 32,No.2, 1993 123
Communications
Tabk I. Magnetogyric Ratios and Typical Values of Indirect and PR3 and CO ligands,29implying that the largest component of Reduced SpinSpin Coupling Constants, I and K, Respectively the EFG tensor is along the acttylide-Ru bonding axis. If one further assumes that q = 0, then x = -1 7 MHz. We believe that nucleus y, lo7 rad s-l T I I(M,”P), Hz K(M,)IP), IOi9 N A-2 m-3 this is the correct order of magnitude for x(Ru) in 1, although s7Fe 0.8687 26-147O.b 164930 the error in this value might beconsiderable. Interestingly,direct 99Ru -1.2286 100-174 441-196 measurements of x values for 99Ruvia NQR spectroscopy have l*70s 0.6193 71-317**‘ 630-2813 WO 6.3015 414-1222’ 361-1066 not been reported.31 Note that, in principle>* the NMR lopRh -0.8468 21-374‘J 136-2427 experimentcontains information on both the magnitude and sign of x. Goodfellow, R. J. In ref 5, pp 521-561. Reference 6. Benn, R.; The 3lP CP/MAS NMR spectrum of 1 (Figure 1) gives no Brenneke, H.; Joussen, E.; Lchmhhl, H.; Ortiz, F. L. Orgommctullfcs 1990, 9, 756. Reference 4. evidence for lOlRu,3lP spin-spin coupling. Signal intensity from the IOIRu,31P spin-pair appears to be absent from the spectrum. reveals that (i) the tworutheniumsitesRu(2)andRu(l) incluster Although the magnetogyric ratios are similar [ ~ ( I O I R U ) / ~ ( ~ ~2- differ widely, indicating distinct structural and bonding Ru) = 1.1211, thequadrupolar moment, Q,of lolRu is 5.8 times differencesfor the wingtip and hinge ruthenium atoms in the Ru., that of 99Ru. Three consequences of the large Q for IolRu are butterfly, and (ii) thevalues of d for 2 haveoppositesignscumpared as follows: (i) The value of d for the lOlRu,3lP spin-pair will be to that for the octahedral complex 1. Since the orientation of the -5.8 times the corresponding value for the 99R~,31P spin-pair. EFG tensor for 2 is unknown, the change in sign may be due to Simulations show that while J(101R~,31P) and J(99Ru,31P)are a change in the sign of x or the sign of the orientational term.28 similar, the distortions of the six-line multiplets due to d( lOlRu) However, since both spin-pairs, Io1Ru,JIPand *Ru,3IP, were and d(*Ru) are sufficientlydifferent to produce additional peaks observed in the CP/MAS NMR spectrum of the cluster 2, in the spectrum. Absence of these features indicates that only x is assumed to be significantly smaller than for the octahedral the *Ru,3IP spin-pair is present. (ii) Because of the large value complex 1. This is at first sight surprising,but Mhbauer studies of x ( ~ ~ R derived u) for 1 (-17 MHz), we estimate x(IO1Ru) >> have shown that the iron cluster Feo(CO)l2 exhibits significantly v(lolRu). The first-order perturbation approach used here for smaller quadrupolar splittings than octahedral iron complexes of 99Ru,31Pcouplings will not be valid for IOIRU,~IP couplings.27(iii) low sy”etry.3h Since the relaxation rate of quadrupolar nuclei depends on xz, Peaks due to the w-PPh(C&) group of 2 showed satellite lolRurelaxation will be approximately 33.5 times more efficient peaks due to lO1*99Ru,31Pcouplings,but they werenot well resolved than that of 99Ru. This could result in self-decoupling of lolRu due to coupling to three nonequivalent ruthenium sites. Nevfrom 3lP. ertheless, it is possible to estimate the largest coupling constant We have observed 99J01Rusatellites in the 31P CP/MAS 1J(101q99Ru,31P) = 110 Hz on the basis of the 31P CP/MAS line spectrum of the ruthenium-phosphido butterfly cluster (pH)widths. Rud(CO)lo(p-PPh2)[p4-PPh(CaH4)] (2).32 An expansion of the The values obtained here for the one-bond ruthenium31P CP/MAS peaks due to the p-PPh2 group is shown (Figure phosphorusindirect spin-spin couplingconstantscan be compand 2) together with the calculated spectrum. To obtain a satisfactory with other transition metal phosphorus coupling constants by simulation, two different nonequivalent ruthenium sites were expressing them as reduced couplings: introduced (Figure 3), in agreement with the known structure,32 and both isotopes, lolRu and 9 9 R ~taken , into account. Ratios K(M,31P)= ( 4 ~ * / h 7 ~ 7 & ( M , ~ ’ P ) of J(101R~,31P)/J(99R~,31P) and d(101Ru)/d(99Ru)were fixed which are independent of the magnetogyric ratios (Table I). for each site to 1.121 and 5.8, respectively. The spectrum shown Clearly, thevaluesofK(99Ru,31P)arecomparable to typicalvalues (Figure 2b) was calculated using J(IOIRU,~IP)= 174, d(l0lRu) of K(57Fe,31P)and K(1*70s,31P). = +24, J ( ~ ~ R u , ~=’ P159, ) and d(99Ru) = +4 Hz for site 1 and J(lo1Ru,31P)= 145, d(lolRu) = +108, J(99Ru,31P)= 129, and In summary, we have demonstrated that indirect spin+pin d(99Ru) = +19 Hz for site 2. A comparison of these d values coupling constants J(101*99Ru,31P) can be obtained from 3lP CP/ MAS NMR spectra of solid ruthenium phosphine complexes (29) Typically, partial quadrupolar splittings are -0.43 to -0.55 for CO and and measured the first values for J(Ru,P). These coupling -0.53 for PPhj, while ligands involving other carbon multiple bonds constants and the residual dipolar interaction, d, are potentially exhibit more negative splittings, Le. -0.84 for CN, -0.69 for CNR, or powerful tools for probing structure and bonding in solid -0.96 mm/s for CH2=CH.’0 (30) (a) Bancroft, G. M.; Platt, R. H.Adv. Inorg. Chem. Radiochem. 1972, ruthenium complexes. (I
15,59. (b) Ireland, P. S.;Deckert, C. A.; Brown, T. L. J . Mugn. Reson. 1976, 23, 485. (31) Carter, J. C.; Good, M. L. J . Mol. Srrucr. 1980, 58, 415. (32) Corrigan, J. F.; Doherty, S.;Taylor, N. J.; Carty, A. J. J . Am. Chem. Soc. 1992, 114,1551.
Achwledgmeat. We are grateful to the NSERC of Canada for financial support. K.E. gratefully acknowledges the award of an Izaak Walton Killam Postdoctoral Fellowship.
