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The crystal structure of [Rh3(μ3-CO)2(η-C5Me5)3] and reactions of the unsaturated metal clusters [MM′2(μ3-CO)2(η-C5Me5)3] (M = M′ = Rh; M = Co or Ir, M′ = Rh) with hydrogen
Cl2
Journal of Organometallic Chemistry, 281 (1985) Elsevier
Sequoia
S.A.,
Lausanne
-
Printed
C12-4316
in The Netherlands
Preliminary communication
THE CRYSTAL STRUCTURE OF [Rh3(p3 -CO),(v-CSMe,),] AND REACTIONS OF THE UNSATURATED METAL CLUSTERS [MM; (p3 -C0)2(q-CsMe,),] (M = M’ = Rh; M = Co or Ir, M’ = Rh) WITH HYDROGEN*
ALVAR JUDITH
C. BRAY, MICHAEL GREEN, DAVID R. HANKEY, A.K. HOWARD, OWEN JOHNSON, and F. GORDON
A. STONE
Department of Inorganic Chemistry, The University of Bristol, Bristol BSB 1 TS (Great Britain) (Received
July 19th,
1984)
Summary
An X-ray crystallographic study of the complex [ Rh3 (p 3 -CO)? (v-C,Me, )3 ] has revealed that the CO ligands asymmetrically bridge the RhB triangle in accord with theoretical predictions. Treatment of the trirhodium compound, or the related mixed-metal complexes [MRh,(p,-CO),(+5Me,),] (M = Co or Ir), with hydrogen gas gives the species [ MRh, (p-H)z (p-CO)(p3 -CO)(7)-C+Me,),] ; the molecular structure of the dihydridotrirhodium cluster has been established by X-ray diffraction.
The unsaturated dimetal compounds l-5 [l] are known to undergo a variety of interesting reactions, notably in combination with metal-ligand fragments to afford metal clusters [ ld,le,2,3]. Herein we report the synthesis of complex 6, thus completing this family of dimetal compounds. We also describe studies on the trimetal species 7-11. A mixture of equimolar amounts of [Rh(C,H,),(n-&Me,)] and [ Ir(CO), (v-C5MeS )] in refluxing toluene (1 h) affords red purple crystals of 6 (60%) [4]. We have previously shown [Id] that 2 reacts with the mononuclear metal compounds [M(C,H,),(n-&Me,)] (M = Co or Rh) to give the trimetal clusters 9 and 10, respectively. Extension of this procedure to reactions between [Co(C,H,),(q-C,Me,)] and 1 or 4, and between [Rh(C2Hq)2(q-C&Me,)] and 6, affords the complexes 7,8 and 11 [ 51. *Presented in part at the International Symposium on “New Vistas in Organometallic sponsored by INSA held at Jaipur (India), March 1984. 0022-328X/85/$03.30
o 1985
Elsevier Sequoia
S.A.
Chemistry”
M
M’
1 2
co
co
Rh
Rh
3
Ir
Ir
4
Co
Rh
5
Co Rh
Ir Ir
6
I
7 8 9 10 11
M
M’
M”
co
co
co
Co
Co
Rh
Co Rh It-
Rh Rh Rh
Rh Rh Rh
Consideration of the bonding in the hypothetical molecule [ Rh3(ps -CO)2 (Q-C+H~)~] in terms of a combination of frontier orbitals of the fragments Rhz(p-CO)z(q-C5H5)2 and Rh(n-CgH5) has led to the conclusion that the CO ligands would asymmetrically bridge the Rh3 triangle in the tricyclopentadienyltrirhodium compound [6] . We were able to test this prediction by an X-ray crystallographic study of the pentamethylcyclopentadienyl compound 10.The structure is shown in Fig. 1 [ 71, The results show that the two CO ligands adopt bonding modes intermediate between pz and p3, with C(la)
C61
Fig. 1. The molecular structure of IRh,(~,-CO),(q-C,Me,),] (10). Rh(l)-Rh(2) 2.572(2), Rh(l)Rh(3) 2.663(2), Rh(2)-Rh(3) 2.639(2). Rh(l)-C(la) 2.32(2). Rh(2)-_C(la) 1.97(2). Rh(B)-C(la) 1.99(2). Rh(lk-C(lb) 2.37(2), Rh(2)-C(lb) 2.02(2), Rh(3)-C(lb) 1.96(2) A.
Cl4
and C(lb) essentially equidistant from Rh(2) and Rh(3) and significantly further from Rh( 1) [ 81. The uniqueness of Rh( 1) is also reflected in the metal-metal separations with Rh(2)-Rh(3) (2.639(2) a) being longer than Rh(l)--Rh(2) or Rh(l)-Rh(3) (( mean) 2.563(2) a). Moreover, the Rh(l)&Me,\ separations are slightly shorter (mean 2.17(2) a) than those between Rh(2) or Rh(3) and their respective CSMe, groups (mean 2.26(2) a).
Fig. 2. The molecular structure of [Rh,(fi-H),(fi-CO)&-CO)(q-CSMe,),] (12). Atoms labelled with a Prime are related to those not so marked by a crystallographic mirror plane which bisects the positionally disordered C,Me, ring bonded to Rh(2) (only one such ring is shown). Rh(l)-Rh(2) 2.785(l). Rh(l)-Rh(1’) 2.674(l). Rh(l)-C(la) 2.13(l), Rh(S)-C(la) 1.99(l). Rh(l)--C(Za) 1.98(l) A; Rh(l)-C(Pa)O(2a) 137.5(1)O.
Compound 10 in thf reacts readily with hydrogen gas (25°C 1 atm) to give the dihydridotrirhodium complex 12 [ 91, the molecular structure [ 71 of which was established by an X-ray diffraction study (Fig. 2). The three rhodium atoms form an isosceles triangle, and whilst one CO ligand remains essentially triply bridging, the other CO group has been displaced to an edge-bridging site so as to accommodate the two hydrido ligands, which were located on the long Rh-Rh vectors by a low-angle electron density difference map. The reaction between hydrogen and the heteronuclear clusters 9 and 11 afforded the isomeric species 13 and 14, respectively. On warming solutions of these compounds, hydrogen is released and compounds 9 and 11 are regenerated. On the basis of relative peak intensities in the ‘H NMR spectra [ 91, it was observed that 13a and 13b were formed in the ratio ca. 15/85, and 14a and 14b in the ratio ca. 45/55. On the present evidence it is not possible to say whether these are the kinetically or thermodynamically controlled product ratios. Acknowledgement. We thank the S.E.R.C. for support and B.P. Chemicals (Hull) for C.A.S.E. research studentships (A.C.B. and D.R.H.).
References
M
M’
M
M’
12
Rh
Rh
13b
Co
Rh
130
Co
Rh
14b
Ir
Rh
14a
Ir
Rh
and notes
(a) Compound 1. L.M. Cirjak, R.E. Ginsburg, and L.F. Dahl, Inorg. Chem.. 21 (1982) 940: W.I. Bailey, D.M. Collins, F.A. Cotton, J.C. Baldwin, and W.C. Kaska, J. Organomet. Chem., 166 (1979) 373: (b) Compound 2, A. Nutton and P.M. Maiths, ibid., 166 (1979) C21; (c) Compound 3. W.A.G. Graham and J.K. Ho~ano, unpublished work; (d) Compound 4. M. Green, D.R. Hankey, J.A.K. Howard. P. Louca. and F.G.A. Stone, J. Chem. Sot.. Chem. Commun., (1983) 757: ‘(e) Compound 5. W.A. Herrmann, C.E. Barnes, R. Serrano. and B. Koumbouris. J. Organomet. Chem.. 256 (1983) C30. (a) N.M. Bow, M. Green, R.M. Mills. G.N. Pain, F.G.A. Stone, and P. Woodward. J. Chem. Sot.. Chem. Commun., (1980) 1171; (b) M. Green, R.M. Mills, G.N. Pain, F.G.A. Stone, and P. Woodward, J. Chem. Sot., Dalton Trans., (1982) 1309; (c) M. Green, J.A.K. Howard, G.N. Pain, and F.G.A. Stone, ibid., (1982) 1327; (d) M.L. AIdridge. M. Green, J.A.K. Howard, G.N. Pain, S.J. Porter, F.G.A. Stone. and P. Woodward. ibid., (1982) 1333: (e) R.D. Barr, M. Green, K. Marsden. F.G.A. Stone, and P. Woodward. ibid., (1983) 507. L.M. Cidak. J-S. Huang, Z-H. Zhu, and L.F. Dahl, J. Am. Chem. Sot., 102 (11980) 6626. Selected spectroscopic data for 6: urnax at 1713 cm-’ (PhMe). NMR: H (in C,D, for % cTn> Cplexes reported), 6 1.46 (d. 16 H. RhC,Me,, J(RhH) 0.5 Hz). and 1.65 (s, 16 H, IrCsMe,); (in C,D,CDs for all complexes reported), b 239.8 (d. CO, J(RhC) 48 Hz), 96.6 (IrC,Me,), 100.6 (d, RhCsMe,. J(RhC) 7 Hz), 9.1 (CsMe,), and 8.5 ppm (C&e,). Selected spectroscopic data: Compound 7, u,a,(CO) 1675 cm-’ (thf). NMR: ‘H. 6 3.38 (s, 46 H, C,Mes); Compound 8, v,,(CO) 1677cm-’ (thf). NMR: ‘H. 6 0.98 (s. 16 H. RhCsMe,), ‘sC- VH}. S 94.6 (d, RhCsMe,, J(RhC) 6 Hz), 94.3 (CoCsMe,). 11.1 and 1.95 (s, 30 H. CoCsMe,); (RhCsMe,), and 9.8 ppm (CoCsiVZe,); Compound 11, urnax(CO) 1661 c -’ (PhMe). NMR: ‘H, 6 1.63 (d, 30 H. RhCsMe,, J(RhH) 0.5 Hz), and 2.08 (s. 16 H, IrCsMe,); 13C- t? H}, 6 94.9 (d. RhCsMe,, J(RhC) 6 Hz), 94.4 (IrCsMe,), 10.4 (RhCsMe,), and 9.5 ppm (IrCsMe,). A.R. Pinhas, T.A. Albright, P. Hofmsnn. and R. Hoffmann, Helv. Chim. Acta. 63 (1980) 29. For 10, crystal data. C,,H,,O,Rh, M = 770.4, orthorhombic. space group Pbca (no. 61). o 17.86(4), F(000) = 3104. MO-K,(graphite monob 21.85(1)A,c15.46(1), U6028A3, Z= 8.D,1.70gcm-3, chromator) h 0.71069 A, p(Mo-K,) 16.2 cm-‘. Current R = 0.05 CR,., = 0.06) for 2067 absorptioncorrected intensities (293 K, w scans, 28 < 50’. F > 4o(F). Nicolet P3m diffractometer. For 12, C,,H,,O,Rh,, M = 772.5, orthorhombic, space groupPnam (no. 62 non-standard setting), LI12.029(3). b 13.403(3). c 19.031(5) A, U 3068(l) As, 2 = 4. D, 1.68 g cm-s, F(000) = 1560. ).I(Mo-I&) 15.96 cm-‘. Current R = 0.043 (R, = 0.047) for 3221 absorption corrected intensities, 200 K, 28 $ 60°, F > 5o(F). The atomic coordinates for this work are avaflable on request from the Director of the Cambridge CrystaBographic Data Centre, University Chemical Laboratory. Lensfield Road, Cambridge CB2 1EW (Great Britain). Any request should be accompanied by the full literature citation for this communication. Using the terminology of ref. 6, the dihedral angles $6) between the Rh(l)Rh(S)Rh(3) plane and the two Rh(2)Rh(3)C(l) planes in 10 are 76.6 and 77.6 , respectively, compared with 6 90 for an unsymmetrical trimer and 6 SO” for a symmetrical trimer. Calculations [Sl suggest 8 65” for a structure
Cl6 Of wtimum an
NMR 9
minimal change
energy
studies
energy,
[Id]
reveal
Selected
spectroscopic
-21. BI 0
d of d, 2 H, p-H,
“C-
,6
H
(C,Me,), ‘H, 13b. 31
98.5
(d,
NMR: and
(d. ‘H,
21 Hz),
14a,
NMR:
(s. 30
H. CsMe,):
that
data:
10 adopts
between
surprising,
the symmetrical
Compound
12,
vmax(CO)
1762
20 Hz),
1.73
&-CO,
39 and
26 Hz),
CsMes,
J(RhC)
6 -26.33 6
(s, 15
(d.
-21.67
(d, 32
11.1
1.69
2
1.71 H.
J(RhH)
NMR:
and
21 Hz),
and 20.8
‘H, 1.88
JOURNAL OF ORGANOMETALLIC
J(RhH) 6 -22.4 (br,
(d,
ppm
cm-’
-22.90
and Hz),
CHEMISTRY,
1.83
J(RhC)
(s, 15
Dory, T.S., Cl, C8 Ebsworth, E.A.V., 63 Erdik, E., 15 Green, M., Cl2 Hankey, D.R., Cl2 Howard, J.A.K., Cl2 Huntley, C.M., 63 Hurst, G.D., 15 Jesthi, P.K., 15 Johnson, O., Cl2 Kiwan, AM., 111 Kunze, U.R., 79 Lauteschliiger, S., 25, 33
(s. 15 41
Hz),
Compound H, C,Me,).
(s,
1.88 1.78
r qu’ring pHj
‘H, 6 H. C,Me,); 101.7 13a,
(br,
15
J(RhH)
H, 21
C,Me,), -21.21
(s, 15 H. C,Me,),
and
VOL. 281, NO. 2
Peterson, M.L., 15 Rankin, D.W.H., 63 Rausch, M.D., C8 Ray, R., 15 Riess, J.G., 1 Roesky, H.W., 69 Sadhu, K.M., 15 Schmidbaur, H., 25, 33 Schumann, H., 95 Seyferth, D., 111 Sinn, E., 111 Stone, F.G.A., Cl2 Tsai, D.J.S., 15 Zuckerman, J.J., Cl, C8
J(RhH)
Compound
Hz).
Maire, J.C., 45 Majumdar, D., 15 Matteson, D.S., 15 Miiller, G., 25, 33
NMR:
Compound
15 H, C,Me,).
AUTHOR INDEX Barnes, C.L., Cl Bray, AC., Cl2
“C-
(d of d, 1 H, pu-HRh,,
1.80
1 H, /I-HIrRh,
15 H, C,Me,),
6 60’
NMR:
(thf).
and
(C,Me,).
1.80
with
temperature
at -8O’C.
1634
and
Hz). 27
even
(t. p-CO,
9.6
C,Me,),
and that
variable
H. C,Me,).
237.5
(s, 15 H, C,Me,),
p-HIrRh,
14b,
H,
and
(s. 30
(C,Me,).
(s. 30
1 H, fi-HCoRh.
H, C,Me,).
Compound J(RhH>
6 Hz), Hz),
that
structure
28 and
32
this geometry
therefore,
J(RhC)
1.60
ofd. 1 H.wHRh,, (s. 15 H, C,Me,).
is not
J(RhC)
2 H, J(RhH)
‘H,
transformation
(d oft,
245.2
5 -25.54
with
mol-' . It
of 10 kJ
and (d 1.77
1.76
Journal of Organometallic Chemistry, 281 (1985) Elsevier
Sequoia
S.A.,
Lausanne
-
Printed
C12-4316
in The Netherlands
Preliminary communication
THE CRYSTAL STRUCTURE OF [Rh3(p3 -CO),(v-CSMe,),] AND REACTIONS OF THE UNSATURATED METAL CLUSTERS [MM; (p3 -C0)2(q-CsMe,),] (M = M’ = Rh; M = Co or Ir, M’ = Rh) WITH HYDROGEN*
ALVAR JUDITH
C. BRAY, MICHAEL GREEN, DAVID R. HANKEY, A.K. HOWARD, OWEN JOHNSON, and F. GORDON
A. STONE
Department of Inorganic Chemistry, The University of Bristol, Bristol BSB 1 TS (Great Britain) (Received
July 19th,
1984)
Summary
An X-ray crystallographic study of the complex [ Rh3 (p 3 -CO)? (v-C,Me, )3 ] has revealed that the CO ligands asymmetrically bridge the RhB triangle in accord with theoretical predictions. Treatment of the trirhodium compound, or the related mixed-metal complexes [MRh,(p,-CO),(+5Me,),] (M = Co or Ir), with hydrogen gas gives the species [ MRh, (p-H)z (p-CO)(p3 -CO)(7)-C+Me,),] ; the molecular structure of the dihydridotrirhodium cluster has been established by X-ray diffraction.
The unsaturated dimetal compounds l-5 [l] are known to undergo a variety of interesting reactions, notably in combination with metal-ligand fragments to afford metal clusters [ ld,le,2,3]. Herein we report the synthesis of complex 6, thus completing this family of dimetal compounds. We also describe studies on the trimetal species 7-11. A mixture of equimolar amounts of [Rh(C,H,),(n-&Me,)] and [ Ir(CO), (v-C5MeS )] in refluxing toluene (1 h) affords red purple crystals of 6 (60%) [4]. We have previously shown [Id] that 2 reacts with the mononuclear metal compounds [M(C,H,),(n-&Me,)] (M = Co or Rh) to give the trimetal clusters 9 and 10, respectively. Extension of this procedure to reactions between [Co(C,H,),(q-C,Me,)] and 1 or 4, and between [Rh(C2Hq)2(q-C&Me,)] and 6, affords the complexes 7,8 and 11 [ 51. *Presented in part at the International Symposium on “New Vistas in Organometallic sponsored by INSA held at Jaipur (India), March 1984. 0022-328X/85/$03.30
o 1985
Elsevier Sequoia
S.A.
Chemistry”
M
M’
1 2
co
co
Rh
Rh
3
Ir
Ir
4
Co
Rh
5
Co Rh
Ir Ir
6
I
7 8 9 10 11
M
M’
M”
co
co
co
Co
Co
Rh
Co Rh It-
Rh Rh Rh
Rh Rh Rh
Consideration of the bonding in the hypothetical molecule [ Rh3(ps -CO)2 (Q-C+H~)~] in terms of a combination of frontier orbitals of the fragments Rhz(p-CO)z(q-C5H5)2 and Rh(n-CgH5) has led to the conclusion that the CO ligands would asymmetrically bridge the Rh3 triangle in the tricyclopentadienyltrirhodium compound [6] . We were able to test this prediction by an X-ray crystallographic study of the pentamethylcyclopentadienyl compound 10.The structure is shown in Fig. 1 [ 71, The results show that the two CO ligands adopt bonding modes intermediate between pz and p3, with C(la)
C61
Fig. 1. The molecular structure of IRh,(~,-CO),(q-C,Me,),] (10). Rh(l)-Rh(2) 2.572(2), Rh(l)Rh(3) 2.663(2), Rh(2)-Rh(3) 2.639(2). Rh(l)-C(la) 2.32(2). Rh(2)-_C(la) 1.97(2). Rh(B)-C(la) 1.99(2). Rh(lk-C(lb) 2.37(2), Rh(2)-C(lb) 2.02(2), Rh(3)-C(lb) 1.96(2) A.
Cl4
and C(lb) essentially equidistant from Rh(2) and Rh(3) and significantly further from Rh( 1) [ 81. The uniqueness of Rh( 1) is also reflected in the metal-metal separations with Rh(2)-Rh(3) (2.639(2) a) being longer than Rh(l)--Rh(2) or Rh(l)-Rh(3) (( mean) 2.563(2) a). Moreover, the Rh(l)&Me,\ separations are slightly shorter (mean 2.17(2) a) than those between Rh(2) or Rh(3) and their respective CSMe, groups (mean 2.26(2) a).
Fig. 2. The molecular structure of [Rh,(fi-H),(fi-CO)&-CO)(q-CSMe,),] (12). Atoms labelled with a Prime are related to those not so marked by a crystallographic mirror plane which bisects the positionally disordered C,Me, ring bonded to Rh(2) (only one such ring is shown). Rh(l)-Rh(2) 2.785(l). Rh(l)-Rh(1’) 2.674(l). Rh(l)-C(la) 2.13(l), Rh(S)-C(la) 1.99(l). Rh(l)--C(Za) 1.98(l) A; Rh(l)-C(Pa)O(2a) 137.5(1)O.
Compound 10 in thf reacts readily with hydrogen gas (25°C 1 atm) to give the dihydridotrirhodium complex 12 [ 91, the molecular structure [ 71 of which was established by an X-ray diffraction study (Fig. 2). The three rhodium atoms form an isosceles triangle, and whilst one CO ligand remains essentially triply bridging, the other CO group has been displaced to an edge-bridging site so as to accommodate the two hydrido ligands, which were located on the long Rh-Rh vectors by a low-angle electron density difference map. The reaction between hydrogen and the heteronuclear clusters 9 and 11 afforded the isomeric species 13 and 14, respectively. On warming solutions of these compounds, hydrogen is released and compounds 9 and 11 are regenerated. On the basis of relative peak intensities in the ‘H NMR spectra [ 91, it was observed that 13a and 13b were formed in the ratio ca. 15/85, and 14a and 14b in the ratio ca. 45/55. On the present evidence it is not possible to say whether these are the kinetically or thermodynamically controlled product ratios. Acknowledgement. We thank the S.E.R.C. for support and B.P. Chemicals (Hull) for C.A.S.E. research studentships (A.C.B. and D.R.H.).
References
M
M’
M
M’
12
Rh
Rh
13b
Co
Rh
130
Co
Rh
14b
Ir
Rh
14a
Ir
Rh
and notes
(a) Compound 1. L.M. Cirjak, R.E. Ginsburg, and L.F. Dahl, Inorg. Chem.. 21 (1982) 940: W.I. Bailey, D.M. Collins, F.A. Cotton, J.C. Baldwin, and W.C. Kaska, J. Organomet. Chem., 166 (1979) 373: (b) Compound 2, A. Nutton and P.M. Maiths, ibid., 166 (1979) C21; (c) Compound 3. W.A.G. Graham and J.K. Ho~ano, unpublished work; (d) Compound 4. M. Green, D.R. Hankey, J.A.K. Howard. P. Louca. and F.G.A. Stone, J. Chem. Sot.. Chem. Commun., (1983) 757: ‘(e) Compound 5. W.A. Herrmann, C.E. Barnes, R. Serrano. and B. Koumbouris. J. Organomet. Chem.. 256 (1983) C30. (a) N.M. Bow, M. Green, R.M. Mills. G.N. Pain, F.G.A. Stone, and P. Woodward. J. Chem. Sot.. Chem. Commun., (1980) 1171; (b) M. Green, R.M. Mills, G.N. Pain, F.G.A. Stone, and P. Woodward, J. Chem. Sot., Dalton Trans., (1982) 1309; (c) M. Green, J.A.K. Howard, G.N. Pain, and F.G.A. Stone, ibid., (1982) 1327; (d) M.L. AIdridge. M. Green, J.A.K. Howard, G.N. Pain, S.J. Porter, F.G.A. Stone. and P. Woodward. ibid., (1982) 1333: (e) R.D. Barr, M. Green, K. Marsden. F.G.A. Stone, and P. Woodward. ibid., (1983) 507. L.M. Cidak. J-S. Huang, Z-H. Zhu, and L.F. Dahl, J. Am. Chem. Sot., 102 (11980) 6626. Selected spectroscopic data for 6: urnax at 1713 cm-’ (PhMe). NMR: H (in C,D, for % cTn> Cplexes reported), 6 1.46 (d. 16 H. RhC,Me,, J(RhH) 0.5 Hz). and 1.65 (s, 16 H, IrCsMe,); (in C,D,CDs for all complexes reported), b 239.8 (d. CO, J(RhC) 48 Hz), 96.6 (IrC,Me,), 100.6 (d, RhCsMe,. J(RhC) 7 Hz), 9.1 (CsMe,), and 8.5 ppm (C&e,). Selected spectroscopic data: Compound 7, u,a,(CO) 1675 cm-’ (thf). NMR: ‘H. 6 3.38 (s, 46 H, C,Mes); Compound 8, v,,(CO) 1677cm-’ (thf). NMR: ‘H. 6 0.98 (s. 16 H. RhCsMe,), ‘sC- VH}. S 94.6 (d, RhCsMe,, J(RhC) 6 Hz), 94.3 (CoCsMe,). 11.1 and 1.95 (s, 30 H. CoCsMe,); (RhCsMe,), and 9.8 ppm (CoCsiVZe,); Compound 11, urnax(CO) 1661 c -’ (PhMe). NMR: ‘H, 6 1.63 (d, 30 H. RhCsMe,, J(RhH) 0.5 Hz), and 2.08 (s. 16 H, IrCsMe,); 13C- t? H}, 6 94.9 (d. RhCsMe,, J(RhC) 6 Hz), 94.4 (IrCsMe,), 10.4 (RhCsMe,), and 9.5 ppm (IrCsMe,). A.R. Pinhas, T.A. Albright, P. Hofmsnn. and R. Hoffmann, Helv. Chim. Acta. 63 (1980) 29. For 10, crystal data. C,,H,,O,Rh, M = 770.4, orthorhombic. space group Pbca (no. 61). o 17.86(4), F(000) = 3104. MO-K,(graphite monob 21.85(1)A,c15.46(1), U6028A3, Z= 8.D,1.70gcm-3, chromator) h 0.71069 A, p(Mo-K,) 16.2 cm-‘. Current R = 0.05 CR,., = 0.06) for 2067 absorptioncorrected intensities (293 K, w scans, 28 < 50’. F > 4o(F). Nicolet P3m diffractometer. For 12, C,,H,,O,Rh,, M = 772.5, orthorhombic, space groupPnam (no. 62 non-standard setting), LI12.029(3). b 13.403(3). c 19.031(5) A, U 3068(l) As, 2 = 4. D, 1.68 g cm-s, F(000) = 1560. ).I(Mo-I&) 15.96 cm-‘. Current R = 0.043 (R, = 0.047) for 3221 absorption corrected intensities, 200 K, 28 $ 60°, F > 5o(F). The atomic coordinates for this work are avaflable on request from the Director of the Cambridge CrystaBographic Data Centre, University Chemical Laboratory. Lensfield Road, Cambridge CB2 1EW (Great Britain). Any request should be accompanied by the full literature citation for this communication. Using the terminology of ref. 6, the dihedral angles $6) between the Rh(l)Rh(S)Rh(3) plane and the two Rh(2)Rh(3)C(l) planes in 10 are 76.6 and 77.6 , respectively, compared with 6 90 for an unsymmetrical trimer and 6 SO” for a symmetrical trimer. Calculations [Sl suggest 8 65” for a structure
Cl6 Of wtimum an
NMR 9
minimal change
energy
studies
energy,
[Id]
reveal
Selected
spectroscopic
-21. BI 0
d of d, 2 H, p-H,
“C-
,6
H
(C,Me,), ‘H, 13b. 31
98.5
(d,
NMR: and
(d. ‘H,
21 Hz),
14a,
NMR:
(s. 30
H. CsMe,):
that
data:
10 adopts
between
surprising,
the symmetrical
Compound
12,
vmax(CO)
1762
20 Hz),
1.73
&-CO,
39 and
26 Hz),
CsMes,
J(RhC)
6 -26.33 6
(s, 15
(d.
-21.67
(d, 32
11.1
1.69
2
1.71 H.
J(RhH)
NMR:
and
21 Hz),
and 20.8
‘H, 1.88
JOURNAL OF ORGANOMETALLIC
J(RhH) 6 -22.4 (br,
(d,
ppm
cm-’
-22.90
and Hz),
CHEMISTRY,
1.83
J(RhC)
(s, 15
Dory, T.S., Cl, C8 Ebsworth, E.A.V., 63 Erdik, E., 15 Green, M., Cl2 Hankey, D.R., Cl2 Howard, J.A.K., Cl2 Huntley, C.M., 63 Hurst, G.D., 15 Jesthi, P.K., 15 Johnson, O., Cl2 Kiwan, AM., 111 Kunze, U.R., 79 Lauteschliiger, S., 25, 33
(s. 15 41
Hz),
Compound H, C,Me,).
(s,
1.88 1.78
r qu’ring pHj
‘H, 6 H. C,Me,); 101.7 13a,
(br,
15
J(RhH)
H, 21
C,Me,), -21.21
(s, 15 H. C,Me,),
and
VOL. 281, NO. 2
Peterson, M.L., 15 Rankin, D.W.H., 63 Rausch, M.D., C8 Ray, R., 15 Riess, J.G., 1 Roesky, H.W., 69 Sadhu, K.M., 15 Schmidbaur, H., 25, 33 Schumann, H., 95 Seyferth, D., 111 Sinn, E., 111 Stone, F.G.A., Cl2 Tsai, D.J.S., 15 Zuckerman, J.J., Cl, C8
J(RhH)
Compound
Hz).
Maire, J.C., 45 Majumdar, D., 15 Matteson, D.S., 15 Miiller, G., 25, 33
NMR:
Compound
15 H, C,Me,).
AUTHOR INDEX Barnes, C.L., Cl Bray, AC., Cl2
“C-
(d of d, 1 H, pu-HRh,,
1.80
1 H, /I-HIrRh,
15 H, C,Me,),
6 60’
NMR:
(thf).
and
(C,Me,).
1.80
with
temperature
at -8O’C.
1634
and
Hz). 27
even
(t. p-CO,
9.6
C,Me,),
and that
variable
H. C,Me,).
237.5
(s, 15 H, C,Me,),
p-HIrRh,
14b,
H,
and
(s. 30
(C,Me,).
(s. 30
1 H, fi-HCoRh.
H, C,Me,).
Compound J(RhH>
6 Hz), Hz),
that
structure
28 and
32
this geometry
therefore,
J(RhC)
1.60
ofd. 1 H.wHRh,, (s. 15 H, C,Me,).
is not
J(RhC)
2 H, J(RhH)
‘H,
transformation
(d oft,
245.2
5 -25.54
with
mol-' . It
of 10 kJ
and (d 1.77
1.76