Selective Photochemistry at Stereogenic Metal and Ligand Centers of cis-[Ru(diphosphine)2(H)2]: Preparative, NMR, solid state, and laser flash studies

TY - JOUR

T1 - Selective Photochemistry at Stereogenic Metal and Ligand Centers of cis-[Ru(diphosphine)2(H)2]

T2 - Preparative, NMR, solid state, and laser flash studies

AU - Câmpian, M.V.

AU - Perutz, R.N.

AU - Procacci, B.

AU - Thatcher, R.J.

AU - Torres, O.

AU - Whitwood, A.C.

PY - 2012/2/22

Y1 - 2012/2/22

N2 - Three ruthenium complexes ∇-[cis-Ru((R,R)-Me-BPE) (H) ] ∇-R,R-Ru1H , Δ-[cis-Ru((S,S)-Me-DuPHOS) (H) ] Δ-S,S-Ru2H , and ∇-[cis-Ru((R,R)-Me-DuPHOS) (H) ] ∇-R,R-Ru2H (1 = (Me-BPE) , 2 = (Me-DuPHOS) ) were characterized by multinuclear NMR and CD spectroscopy in solution and by X-ray crystallography. The chiral ligands allow the full control of stereochemistry and enable mechanistic studies not otherwise available. Oxidative addition of E-H bonds (E = H, B, Si, C) was studied by steady state and laser flash photolysis in the presence of substrates. Steady state photolysis shows formation of single products with one stereoisomer. Solid state structures and circular dichroism spectra reveal a change in configuration at ruthenium for some Δ-S,S-Ru2H /∇-R,R-Ru2H photoproducts from ∇ to Δ (or vice versa) while the configuration for ∇-R,R-Ru1H products remains unchanged as ∇. The X-ray structure of silyl hydride photoproducts suggests a residual H(1)•••Si(1) interaction for Δ-[cis-Ru((R,R)-Me-DuPHOS) (Et SiH)(H)] and Δ-[cis-Ru((R,R)-Me-DuPHOS) (PhSiH )(H)] but not for their Ru(R,R-BPE) analogues. Molecular structures were also determined for ∇-[cis-Ru((R,R)- Me-BPE) (Bpin)(H)], ∇-[Ru((S,S)-Me-DuPHOS) (η -C H )], Δ-[Ru((R,R)-Me-DuPHOS) (η -C H )], and trans-[Ru((R,R)-Me-DuPHOS) (C F )(H)]. In situ laser photolysis in the presence of p-H generates hyperpolarized NMR spectra because of magnetically inequivalent hydrides; these experiments and low temperature photolysis with D reveal that the loss of hydride ligands is concerted. The reaction intermediates [Ru(DuPHOS) ] and [Ru(BPE) ] were detected by laser flash photolysis and have spectra consistent with approximate square-planar Ru(0) structures. The rates of their reactions with H , D , HBpin, and PhSiH were measured by transient kinetics. Rate constants are significantly faster for [Ru(BPE) ] than for [Ru(DuPHOS) ] and follow the substrate order H > D > PhSiH > HBpin.

AB - Three ruthenium complexes ∇-[cis-Ru((R,R)-Me-BPE) (H) ] ∇-R,R-Ru1H , Δ-[cis-Ru((S,S)-Me-DuPHOS) (H) ] Δ-S,S-Ru2H , and ∇-[cis-Ru((R,R)-Me-DuPHOS) (H) ] ∇-R,R-Ru2H (1 = (Me-BPE) , 2 = (Me-DuPHOS) ) were characterized by multinuclear NMR and CD spectroscopy in solution and by X-ray crystallography. The chiral ligands allow the full control of stereochemistry and enable mechanistic studies not otherwise available. Oxidative addition of E-H bonds (E = H, B, Si, C) was studied by steady state and laser flash photolysis in the presence of substrates. Steady state photolysis shows formation of single products with one stereoisomer. Solid state structures and circular dichroism spectra reveal a change in configuration at ruthenium for some Δ-S,S-Ru2H /∇-R,R-Ru2H photoproducts from ∇ to Δ (or vice versa) while the configuration for ∇-R,R-Ru1H products remains unchanged as ∇. The X-ray structure of silyl hydride photoproducts suggests a residual H(1)•••Si(1) interaction for Δ-[cis-Ru((R,R)-Me-DuPHOS) (Et SiH)(H)] and Δ-[cis-Ru((R,R)-Me-DuPHOS) (PhSiH )(H)] but not for their Ru(R,R-BPE) analogues. Molecular structures were also determined for ∇-[cis-Ru((R,R)- Me-BPE) (Bpin)(H)], ∇-[Ru((S,S)-Me-DuPHOS) (η -C H )], Δ-[Ru((R,R)-Me-DuPHOS) (η -C H )], and trans-[Ru((R,R)-Me-DuPHOS) (C F )(H)]. In situ laser photolysis in the presence of p-H generates hyperpolarized NMR spectra because of magnetically inequivalent hydrides; these experiments and low temperature photolysis with D reveal that the loss of hydride ligands is concerted. The reaction intermediates [Ru(DuPHOS) ] and [Ru(BPE) ] were detected by laser flash photolysis and have spectra consistent with approximate square-planar Ru(0) structures. The rates of their reactions with H , D , HBpin, and PhSiH were measured by transient kinetics. Rate constants are significantly faster for [Ru(BPE) ] than for [Ru(DuPHOS) ] and follow the substrate order H > D > PhSiH > HBpin.

UR - http://www.scopus.com/inward/record.url?scp=84857418819&partnerID=8YFLogxK

U2 - 10.1021/ja210568t

DO - 10.1021/ja210568t

M3 - Article

AN - SCOPUS:84857418819

SN - 0002-7863

VL - 134

SP - 3480

EP - 3497

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 7

ER -