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OSU – June – 2010 - SGK 1
STEVE KUKOLICH, Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721
MICROWAVE MEASUREMENTS OF STRUCTURE CHANGES FOR LIGAND MOLECULES BOUND TO TRANSITION METALS†
† This material is based on work supported by the National Science Foundation under Grant Nos. CHE-0809053, CHE-0304969, CHE-9634130.
OSU – June – 2010 - SGK 2
Structural changes on complex formation & CATALYSIS
FORMATION OF TRANSITION METAL COMPLEXES WITH SMALL ORGANIC MOLECULES CAUSES CHANGES IN:
A) REACTIVITY OF THE ORGANIC LIGANDS B) ELECTRONIC STRUCTUREC) MOLECULAR STRUCTURE
C7H7-Ti-C5H5 (Cycloheptatriene…C2H4-M-(CO)4 (Ethylene-M, M = Osmium, Iron)C2H2-Re-CH3-O2 (Acetylene Methyl Dioxo Rhenium)C6H6-Cr-(CO)3 (Benzene Chromium Tricarbonyl)C4H6-Fe-(CO)3 (Butadiene Iron Tricarbonyl)
OSU – June – 2010 - SGK 3
Transition Metal Complexes
C7H7-Ti-C5H5 C2H4-Os-(CO)4 C2H2-Re-CH3-O2
C1C2
C3C4
C5C6
C7
Ti
C8
C9C10
C11
C12
ReO1
O2
C1C2
C3
H1
H2
H5
H3
H4
b
a
OSU – June – 2010 - SGK 4
C7H7-Ti-C5H5
(7-C7H7)Ti (5-C5H5) normal isotopomer reported in 2004[i]
Calculations predict a droop of the CHT hydrogens toward the titanium atom.
To measure angle and other structural parameters:
Study with13C substitution, single-D substitution on cycloheptatriene
New Structrural Parameters obtained
[i] Keck, K.S.; Tanjaroon C. and Kukolich, S. G. J. Mol. Spec. (2005) 232 55-60. PRESENT WORK > Adam Daly, Erika Weidenschilling
OSU – June – 2010 - SGK 5
MOLECULAR CONSTANTS: Transitions were measured and the following B and C rotational constants were obtained and used in a structure fit
ISOTOPOMER MEASURED FIT VALUE DEV. No. OF LINES
12C - B 771.7891 771.8240 -0.0349 14 - C 771.7891 771.7745 0.0146 13C - C7H7 - B 769.2680 769.2427 0.0253 12 - C 766.1320 766.1463 -0.0143 13C - C5H5 - B 767.0140 767.0210 -0.0070 9 - C 765.3230 765.3072 0.0158 C7H6D - B 769.6930 769.6790 0.0140 16 - C 761.1780 761.1918 -0.0138
OSU – June – 2010 - SGK 6
Ring Parameter Value C (C7H7) R(C(center)-Ti) -1.48(1) H (C7H7) R(H(center)-Ti) -1.33 (1)
C5H5 R(C(center)-Ti)* 2.01(1)
Angle determined from the fit: 8.6˚, S. D. fit = 24 kHz * Note that C5H5 assumed planar.
A least squares fit was performed using a model with the C-C and C-H distances fixed to DFT values
OSU – June – 2010 - SGK 7
Ethylene Structure Changes on Complex Formation
Ethylene-Os: JOE TAKATS – U. ALBERTA, C. Karunatilaka, B. S. Tackett, J. Washington, and S. G. Kukolich, J. Am. Chem. Soc. 129(34), 10522-10530 (2007)
OSU – June – 2010 - SGK 8
DFT-calculated rotational constants agree remarkably well with the experimental values > First transition measured ( 616 505) at 9197.8522 MHz deviated only 1.5 MHz from the predicted frequency.
The 414 303 transitions at ~6195 MHz observed for Os(CO)4(2-C2H4). Similar 3-line patterns, arising from 3 Os isotopes (188Os, 190Os and 192Os). were observed for most of the Ka = +1 transitions.
OSU – June – 2010 - SGK 9
Rotational and distortion constants obtained from the least-squares fits to determine rotational constants for 7 isotopomers. DFT calculated parameter values are also presented.
ParameterC2H4Os(CO)4
(192Os)
DFT a
(192Os)
C2H4Os(CO)4
(190Os)
C2H4Os(CO)4
(188Os)
C2D4Os(CO)4
(192Os)
13C axial(192Os)
13C equatorial
(192Os)
13C ethylene(192Os)
A (MHz) 929.3256(6) 930.85 929.3328(5) 929.3407(7) 881.4489(1) 929.2751(3) 923.1201(10) 920.6996(5)
B (MHz) 755.1707(3) 754.62 755.1689(2) 755.1666(7) 744.4294(1) 750.9077(2) 753.9757(4) 754.9994(3)
C (MHz) 752.7446(3) 752.56 752.7494(2) 752.7545(3) 724.3714(2) 748.4802(2) 749.8525(8) 747.2494(3)
DJ (kHz) 0.037(3) 0.05 0.033(3) 0.033(3) 0.035(1) 0.037(3)b 0.037(3)b 0.037(3)b
DJK (kHz) 0.227(17) 0.21 0.227b 0.227b 0.227b 0.227b 0.227b 0.227b
DK (kHz) - 0.29(3) - 0.24 - 0.24(3) - 0.23(4) - 0.21(1) - 0.29b - 0.29b - 0.29b
d1 (kHz) - 0.002(2) - 0.002 - 0.002b - 0.002b - 0.002b - 0.002b - 0.002b - 0.002b
d2 (kHz) 0.0073(8) - 0.0066 0.0073b 0.0073b 0.0073b 0.0073b 0.0073b 0.0073b
σFIT (kHz) 4.7 - 3.2 3.6 3.3 2.5 5.7 3.4
N 42 - 24 18 27 8 7 9
OSU – June – 2010 - SGK 10
Ethylene Iron tetracarbonyl (EtFe)*
*B. J. Drouin and S. G. Kukolich, J. Am. Chem Soc. 121, 4023-4030 (1999)
OH
C
H
O
C
C
C
O
C
H
H
C
O
o1.073 A
1.812 A
o
2.097 Ao
Fe
1.144 A
1.152 Ao
o
110.9
o
The deformation of the ethylene ligand upon coordination to osmium is large, well-determined. The experimental ethylene C—C bond length of 1.43 Å for the complex falls between the free ethylene average rz (C=C) value of 1.339(1) Å and the r0(C—C) bond length of 1.534(2) Å for ethane. The C—C bond length for the Fe congener is 1.421(7) Å.
The angle between the plane of the CH2 group and the C—C bond (out-of-plane) is 26°. This angle is 22° for Fe(CO)4(C2H4), indicating that the degree of metal (d) olefin (*) back-bonding is greater for the Os complex.
OSU – June – 2010 - SGK 11
Acetylenemethyldioxorhenium (ACMDO),
a metalacyclopropane [i]
The molecular structure for ACMDO] was obtained by measuring and analyzing the rotational spectra for 14 isotopomers.
[i] S. G. Kukolich, B. J. Drouin, O. Indris, J. J.
Dannemiller, J. P. Zoller and W. A. Herrmann, J. Chem. Phys. 113, 7891-7900 (2000)
ReO1
O2
C1C2
C3
H1
H2
H5
H3
H4
b
a
Motivation-K. Barry Sharpless developed highly efficient, enantioselective oxidation reactions using Osmium Tetroxide and Methyl Rhenium Trioxide.
OSU – June – 2010 - SGK 12
A, B, C’s & eqQ’s
OSU – June – 2010 - SGK 13
Structural parameters for ACMDO
H5
H1
C3
H2
C1
Re
C2
H4
O1
z
2.116 A
1.710 A
2.043 A2.067 A
81.9
100.8
146 1471.294 A
1.072 A1.075 A
ACETYLENE C-C BOND LENGTH 1.207 Å ETHYLENE C-C BOND LENGTH 1.339 Å
The C-C bond length is increased by 0.08 Å to 1.29 Å. The H-C-C interbond angles are reduced from 180 to 146, and 147.
The experimental structural parameters indicate that this compound is better described as a metallacyclopropene rather than as an 2-type, -bonded complex.
OSU – June – 2010 - SGK 14
Benzene Chromium Tricarbonyl• Bonded Cr(CO)3
reduces the symmetry of Benzene to C3v
• 2 RESONANCE structures no longer equivalent
• ACTIVATES arenes toward nucleophillic attack at H sites
C3v SYMMETRIC TOP WITH ALTERNATING C-C BOND
LENGTHS, STILL A SYMMETRIC TOP - ONLY 1 MOMENT OF INERTIA from microwave spectrum ISOTOPIC SUBSTITUTION!
OSU – June – 2010 - SGK 15
Experiment.
view down a-axis of molecule
• 1,2(ortho) D2 substituted Benzene
• C-C bond with D’s can be E(eclipsed), or S(staggered) W.R.T. CO ligand
• For E, distance between D’s is SHORTER, for S – LONGER than normal
• Now we have ASYMMETRIC top, same A, but different B, C
Experimental values for B-C are used to find (C-C) = 0.016 Ǻ(0.017 Ǻ -xray, Rees &Coppens, Acta Crystallogr., Sect. B 1973, 29, 2515)
Parameter E isomer S isomer
A 900.05(5) 900.02(5)
B 723.9167(2) 723.8423(2)
C 717.8598(2) 717.9305(2)
B - C 6.057 5.912
0.145
OSU – June – 2010 - SGK 16
Part of the spectrum (J = 3 4)
OSU – June – 2010 - SGK 17
Butadiene iron tricarbonyl
10 isotopomers measured, including 13C and single and triple D substitutions
Increase in the butadiene C1-C2 bond length (0.08 Å)
Decrease in the butadiene C2-C3 bond length (-0.06 Å)
OSU – June – 2010 - SGK 18
Substantial structure changes
Free butadiene in a planar-trans conformation
Changes to cisterminal CH2 groups are rotated by 28 out of the butadiene plane CH2 plane is folded away from the butadiene C1-C2 axis by 27HYBRIDIZATION now looks more like sp3 than sp2
OSU – June – 2010 - SGK 19
Acknowledgements
This material is based upon work supported by the National Science Foundation under Grant Nos. CHE-0809053, CHE-0304969, CHE-9634130. This support from the National Science Foundation is gratefully acknowledged
Adam Daly, Erika Weidenschilling, Kristen Keck, Chakree Tanjaroon, Chandana Karunatilaka, Brandon Tackett, John Washington, Brian Drouin, Oliver Indris, J. P. Zoller, Shane Sickafoose, Jennifer Dannemiller, Mark Roehrig, Giles Henderson (EIU), Wolfgang Herrmann (T.U.M), Joe Takats (Alberta)
•Department of Chemistry and Biochemistry, U. of Arizona.
OSU – June – 2010 - SGK 20
X-Ray and DFT-calculated charge densities for [Ni(2-CH2CH2)dbpe] reported by Scherer et al.,[1] illustrating charge redistribution for ethylene-nickel bonding, in support of the DCD model.
x) y)Above, X-ray(x), and DFT(y)
charge density plots. Right, DFT-calculated,
donation and back- donation contributions to bonding
[1] Scherer, Wolfgang; Eickerling, Georg; Shorokhov, Dmitry; Gullo, Emanuel; McGrady, G. Sean; Sirsch, Peter. New Journal of Chemistry 2006, 30(3), 309-312.
OSU – June – 2010 - SGK 21
RESULTS
• H-atoms out of plane by 8º
• C-C bond – Free C2H4 1.339Ǻ, C3H6 1.54Ǻ
• C-C bond – GED 1.46(6) Ǻ, DFT Calculation 1.4186Ǻ• J. A. C. S. 121, 4203 (1999)
OSU – June – 2010 - SGK 22
Experiment.
view down z-axis of molecule
• 1,2(ortho) D2 substituted Benzene
• C-C bond with D’s can be E(eclipsed), or S(staggered) W.R.T. CO ligand
• For E, distance between D’s is SHORTER, for S – LONGER than normal
• Now we have ASYMMETRIC top, same A, but different B, C
Parameter E isomer S isomer A (MHz) 900.05(5) 900.02(5) B (MHz) 723.9167(2) 723.8423(2) C (MHz) 7 17.8598(2) 717.9305(2) DJ (kHz) 0.046(2) 0.048(2) DJK (kHz ) -0.10(6) -0.11(5)
The experimental values for B-C are used to find (C-C) = 0.016 Ǻ
OSU – June – 2010 - SGK 23
Ethylene Iron tetracarbonyl (EtFe)*
• Olefin activation on metal catalysts is used in synthesis. Accepted mechanisms involve metalocyclopropane intermediates.
• Simplest “stable” olefin-iron complex
• Example of a “one-on-one” complex → EASIER TO STUDY.
*B. J. Drouin and S. G. Kukolich, J. Am. Chem Soc. 121, 4023-4030 (1999)
OH
C
H
O
C
C
C
O
C
H
H
C
O
o1.073 A
1.812 A
o
2.097 Ao
Fe
1.144 A
1.152 Ao
o
110.9
o