Monoclinic and triclinic forms of [1,2-bis(diphenylphosphino)propane](η6-methyldiphenylphosphine)(methyldiphenylphosphine)molybdenum(0) benzene solvate

Morris, Robert H.; Sawyer, J. F.; Sella, Andrea

doi:10.1107/s0108270187007352

Cited by 4 publications

(3 citation statements)

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“…The molecular structure of 2 has no crystallographic symmetry, although small conformational changes reveal its C s molecular symmetry. The unremarkable metric data of Table compare to that previously reported for other (η 6 -arene)Mo(P) 3 complexes such as (η 6 -C 6 H 5 (PPhMe))Mo(PPh 2 Me) 3 , [(μ 2 -η 6 -C 6 H 5 (PMe 2 ))Mo(PPhMe 2 ) 2 ] 2 , and (η 6 -C 6 H 5 (PPhMe))Mo(PPh 2 Me)(Ph 2 PCH(Me)CH 2 PPh 2 ) . The molecular structures of 1 − 5 that were computed using the PM3(tm) method are compared in Table with those that were determined by X-ray crystallography for 1 − 4 .…”

Section: Resultssupporting

confidence: 77%

“…The unremarkable metric data of Table 2 compare to that previously reported for other (η 6 -arene)Mo(P) 3 complexes such as (η 6 -C 6 H 5 (PPhMe))Mo(PPh 2 Me) 3 , 28 [(µ 2 -η 6 -C 6 H 5 (PMe 2 ))-Mo(PPhMe 2 ) 2 ] 2 , 29 and (η 6 -C 6 H 5 (PPhMe))Mo(PPh 2 Me)-(Ph 2 PCH(Me)CH 2 PPh 2 ). 30 The molecular structures of 1-5 that were computed using the PM3(tm) method are compared in Table 2 with those that were determined by X-ray crystallography for 1-4. Figure 8 (left) depicts the computed structures of 1-5 as space-filled models.…”

Section: Table 2 Selected Interatomic Distances (å) and Angles (Deg) ...mentioning

confidence: 99%

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Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

et al. 1999

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We have previously reported (J. Am. Chem. Soc. 1995, 117, 12639) the arene complex (η 6 -C 6 H 6 )Mo(TRIPOD) (1), where TRIPOD ) 1,1,1-tris(diphenylphosphinomethyl)ethane, is protonated upon addition of 1 equiv of D + to yield the metal-hydride [(η 6 -C 6 H 5 D)Mo-(TRIPOD)H] + (1H + -d 1 ) via exo addition of D + to the arene ligand followed by migration to the metal of the endo proton of the putative η 5 -cyclohexadienyl complex [(η 5 -C 6 H 6 D)Mo-(TRIPOD)] + (1 ‡ ). The opposite isotopomer is obtained when (η 6 -C 6 D 6 )Mo(TRIPOD) (1-d 6 ) is employed to give [(η 6 -C 6 D 5 H)Mo(TRIPOD)D] + (1D + -d 6 ). Our recent investigation of the electronic structure of 1 and its one-electron oxidized derivative [(η 6 -C 6 H 6 )Mo(TRIPOD)] + (1 + ) suggested the mechanism of protonation is not driven entirely by electronic factors; steric factors are likely important for indirect protonation of 1. Consistent with that conclusion, we report herein that some other phosphine derivatives are protonated directly at the metal center. Thus, under the same reaction conditions the monodentate phosphine derivatives (η 6 -C 6 D 6 )Mo(PR 3 ) 3 , where PR 3 ) PPh 2 Me (3-d 6 ), PPhMe 2 (4-d 6 ), and PMe 3 (5-d 6 ), are protonated directly at the metal 0%, 20%, and 40% of the time, respectively. The remainder of the protonations take place via the aforementioned indirect protonation of the arene ligand. Surprisingly, (η 6 -C 6 D 6 )Mo(TRIPHOS) (2-d 6 ), where TRIPHOS ) bis(2-diphenylphosphinoethyl)phenylphosphine, reacts with H + by direct protonation of the metal center 80% of the time to give a C 1 -symmetric kinetic hydride [(η 6 -C 6 D 6 )Mo(TRIPHOS)H] + (2 K H + -d 6 ). The other 20% of the time 2-d 6 reacts via the arene mechanism to give [(η 6 -C 6 D 5 H)Mo(TRIPHOS)D] + (2 K D + -d 6 ). The two enantiomeric forms of 2 K H + are observed to be in rapid equilibrium (k ) 6.4 × 10 3 s -1 at -87°C). Compound 2 K H + eventually isomerizes (k ) 6.1 × 10 -4 s -1 at -60°C) to the C s -symmetric thermodynamic hydride [(η 6 -C 6 H 6 )Mo-(TRIPHOS)H] + (2 T H + ). We conclude from the crystal structures of 1-4, tracer studies, and electronic structure calculations of the five derivatives 1-5 presented herein that indirect protonation does not represent a general mechanism for this class of compounds. In addition to electronic factors that favor direct protonation of the metal center from an equatorial trajectory, subtle steric demands of the phosphine ligands play an important role in dictating whether a proton initially attacks the arene ligand or the metal of 1-5. The semiempirical PM3(tm) method may be used to map metal-based frontier orbitals of the complexes 1-5 onto plots of their surface electron densities, thereby revealing sterically accessible metal electron density. Such plots provide straightforward models that predict the mechanisms of protonation.

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Section: Resultssupporting

confidence: 77%

Section: Table 2 Selected Interatomic Distances (å) and Angles (Deg) ...mentioning

confidence: 99%

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

et al. 1999

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“…The computed molecular structure of (η 6 -C 6 H 6 )Mo(PH 3 ) 3 gives bond distances that are within 0.03 Å and angles that are within 3° of the crystal structure of (η 6 -C 6 H 6 )Mo(TRIPOD) . The computed distances of Mo−C(arene) av = 2.33 Å and Mo−P = 2.41 Å are comparable with the distances of Mo−C(arene) av = 2.29 Å and Mo−P = 2.42 Å which have been determined for several (η 6 -arene)Mo(phosphine) 3 complexes that bear a variety of phosphine ligands. ,, The structure from the Hartree−Fock calculation is also reasonable except for the Mo−P distance, which is 0.2 Å too long.…”

Section: Computational Results and Discussionsupporting

confidence: 73%

Electronic Factors for Protonation of an Organometallic Molecule. Photoelectron Spectroscopy and Electron Paramagnetic Resonance Study of [(η⁶-C₆H₆)Mo(TRIPOD)]^0/+

et al. 2000

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We have previously shown that the arene complex (η 6 -C 6 H 6 )Mo(TRIPOD), where TRIPOD ) 1,1,1-tris((diphenylphosphino)methyl)ethane, is protonated by exo addition of H + to the arene ring to give the transient cyclohexadienyl complex [(η 5 -C 6 H 7 )Mo(TRIPOD)] + , which eventually yields the thermodynamic molybdenum hydride [(η 6 -C 6 H 6 )Mo(TRIPOD)(H)] + . The present study is a combined experimental and theoretical investigation that reveals the fundamental basis for this mechanism. Photoelectron spectroscopy (PES) is used to probe the electronic structure of (η 6 -C 6 H 6 )Mo(TRIPOD) and the production of the [(η 6 -C 6 H 6 )Mo-(TRIPOD)] + cation in the gas phase. The initial ionizations of (η 6 -C 6 H 6 )Mo(TRIPOD) are from energetically closely spaced orbitals of predominantly metal d character ( 2 A 1 and 2 E cation states using C 3v symmetry) that are shifted over 2 eV to lower energy with respect to the comparable ionizations of (η 6 -C 6 H 6 )Mo(CO) 3 . The oxidized species [(η 6 -C 6 H 6 )Mo-(TRIPOD)] + is also prepared in solution by electrochemical means and through the use of chemical oxidants. The electron paramagnetic resonance (EPR) spectrum of this cation shows arene-proton hyperfine coupling that indicates substantial arene character in the highest occupied orbital. The photoelectron and EPR spectra both provide evidence for Jahn-Teller distortion of the 2 E positive ion states. Electronic structure calculations show that this distortion involves opening of one L-Mo-L angle, which effectively creates an open coordination site on the metal for the hydride to occupy in the final thermodynamic product. These experimental and computational results show that, in terms of their energy, the e symmetry and a 1 symmetry metal-based orbitals are similarly favored for oxidative protonation directly at the metal. The e symmetry orbital has a portion of its density on the arene ring, making access to this orbital by proton approach to the exo position of the arene ring possible. For (η 6 -C 6 H 6 )Mo(TRIPOD), exo attack at the arene is favored because the TRIPOD ligand shields the e symmetry orbital from direct attack at the metal by the solvated proton. Thus, exo attack is not initiated by proton interaction with an arene-based orbital but is initiated by proton interaction with the arene portion of the same e symmetry orbital that directs attack at the metal. Calculations predict low barriers for both direct attack at the metal and exo attack at the arene, with attack at the arene favored for longer metalproton distances.

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Arene and Heteroarene Complexes of Chromium, Molybdenum and Tungsten

Morris

1995

Comprehensive Organometallic Chemistry II

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Monoclinic and triclinic forms of [1,2-bis(diphenylphosphino)propane](η6-methyldiphenylphosphine)(methyldiphenylphosphine)molybdenum(0) benzene solvate

Cited by 4 publications

References 5 publications

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Electronic Factors for Protonation of an Organometallic Molecule. Photoelectron Spectroscopy and Electron Paramagnetic Resonance Study of [(η⁶-C₆H₆)Mo(TRIPOD)]^0/+

Arene and Heteroarene Complexes of Chromium, Molybdenum and Tungsten

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Monoclinic and triclinic forms of [1,2-bis(diphenylphosphino)propane](η6-methyldiphenylphosphine)(methyldiphenylphosphine)molybdenum(0) benzene solvate

Cited by 4 publications

References 5 publications

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η6-Arene)molybdenum(phosphine)3Complexes

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η6-Arene)molybdenum(phosphine)3Complexes

Electronic Factors for Protonation of an Organometallic Molecule. Photoelectron Spectroscopy and Electron Paramagnetic Resonance Study of [(η6-C6H6)Mo(TRIPOD)]0/+

Arene and Heteroarene Complexes of Chromium, Molybdenum and Tungsten

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Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Electronic Factors for Protonation of an Organometallic Molecule. Photoelectron Spectroscopy and Electron Paramagnetic Resonance Study of [(η⁶-C₆H₆)Mo(TRIPOD)]^0/+