The reaction of [BrRe(CO)₄]₂ with 2-(diphenylphosphino)pyridine (PN) and 6-(diphenylphosphino)-2-formylpyridine (PON) was investigated. The reactions were regiospecific and exclusively produced the phosphorus-coordinated products, BrRe(CO)₄(κᵖ-PN) and BrRe(CO)₄(κᴾ-PON). The kinetics for the chelate ring closure (κᴾ→ κᴾᴺ) in BrRe(CO)₄(κᴾ-PN) were confirmed to occur by dissociative CO loss. The reaction of [BrRe(CO)₄]₂ with 2-(diphenylphosphino)pyridine (PN) was modeled computationally by DFT calculations. The preferred reaction pathway for the substitution reaction was determined to occur by direct attack of the pnictogen donor on the dimer and formation of the κᴺ isomer as the kinetic substitution product occurs. The κᴺ kinetic product then rapidly isomerizes to the κᴾ thermodynamic product by way of a reversible ligand dissociation. Treatment of the tetrahedral cluster H₂Ru₃(CO)₃(μ₃-S) (1) with 2-(diphenylphosphino)thioanisole (PS) furnishes the cluster H₂Ru₃(CO)₇(κ²-PS)(μ₃-S) (2). Cluster 2, which exhibits a chelated thiophosphine ligand (κ²-PS), exists as a pair of diastereomers with Keq = 1.55 at 298 K that differ in their disposition of ligands at the Ru(CO)(κ²-PS) center. The PS ligand occupies the equatorial sites (Peq, Seq) in the kinetic isomer and axial and equatorial sites (Pax, Seq) in the thermodynamically favored species. The reversible first-order kinetics to equilibrium have been measured experimentally by NMR spectroscopy and HPLC over the temperature range 293-323 K. The substitution reaction involving 1 and the isomerization of the PS ligand in 2 were investigated by DFT calculations. The computational results support a phosphine-induced expansion of the cluster polyhedron that is triggered by the associative addition of the PS donor to 1. The observed isomerization of the PS ligand in 2 is best explained by a tripodal rotation of the CO and PS groups at the Ru(CO)(κ²-PS) center that is preceded by a regiospecific migration of one of the edge-bridging hydrides to the non-hydride-bridged Ru-Ru bond in 2. The chiral clusters 1,2-Ru₃(μ-H)₂(μ₃-S)(CO)₇(μ-1p1,2p2-POP) (A) and 1,2-Ru₃(μ-H)₂(μ₃-S)(CO)₇(μ-1p2,2p1-POP) (B) were formed were formed from reaction of Ru₃(μ-H)₂(μ₃-S)(CO)₉ with 1-diphenylphosphino-2-[2-(diphenylphosphino)ethoxy]benzene (POP). Chiral clusters A and B were fully characterized by IR and NMR spectroscopy. Additionally, the molecular structure of A was solved by X-ray crystallography. Chiral cluster A was resolved into its enantiomers by preparative HPLC with a chiral column. The enantiomers were characterized by electronic circular dichroism (ECD) spectroscopy and their absolute stereochemical configuration was determined by X-ray crystallography.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc1538707 |
| Date | 08 1900 |
| Creators | Mayberry, Darrell D. |
| Contributors | Richmond, Michael G., Cundari, Thomas R., Marshall, Paul, 1960-, Chyan, Oliver |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | xii, 110 pages, Text |
| Rights | Public, Mayberry, Darrell D., Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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