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Article: Accurate molecular structures of 16-electron rhodium hydrido boryl complexes: Low-temperature single-crystal X-ray and neutron diffraction and computational studies of [(PR3)2RhHCl(boryl)] (boryl = Bpin, Bcat)

TitleAccurate molecular structures of 16-electron rhodium hydrido boryl complexes: Low-temperature single-crystal X-ray and neutron diffraction and computational studies of [(PR3)2RhHCl(boryl)] (boryl = Bpin, Bcat)
Authors
Issue Date2003
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/organometallics
Citation
Organometallics, 2003, v. 22 n. 22, p. 4557-4568 How to Cite?
AbstractRhodium hydrido boryl complexes of the form [(PR3)2RhHCl{B(OR′)2}] are key first intermediates in several Rh-catalyzed borylation processes. Previous theoretical studies have examined model compounds, e.g with PH3 and BH2 or B(OH)2 groups, and there were little structural data available for this class of compounds to compare with the calculated structures. This paper reports the results of single-crystal X-ray (at 120 K) and neutron (at 20 K) diffraction studies on two such complexes, namely [(PiPr3)2RhHCl(Bpin)] (3Bpin) and [(PiPr3)2RhHCl(Bcat)] (3Bcat) (pin = OCMe2CMe2O; cat = 1,2-O2C6H4), providing the first accurate location of the hydride ligands in a hydrido boryl complex. The orientations of the boryl ligands with respect to the equatorial plane of a distorted-trigonal-bipyramidal (DTBP) structure differs for the two compounds (Bpin lies nearly perpendicular to this plane, whereas Bcat is roughly coplanar with it), and the Cl-Rh-B angles are also very different, being 117.73(4) and 137.87(5)° (X-ray data), respectively, for 3Bpin and 3Bcat. The Rh-H distances are 1.571(5) and 1.531(11) Å, and the B-Rh-H angles are only 67.8(2) and 68.5(4)°, leading to B⋯H separations of 2.013(5) and 2.004(10) Å (neutron data) in the two compounds. Thus, these are best described as RhIII hydrido boryl rather than RhI σ-borane (σ-HB(OR)2) complexes, although there is a modest residual B⋯H interaction in both compounds. DFT calculations on model compounds employing PH3 and PMe3, as well as on 3Bpin and 3Bcat, incorporating the actual PiPr3, Bpin, and Bcat ligands allowed a detailed examination of the factors influencing structure and bonding in these compounds as well as a direct comparison of theory and experiment. The perpendicular arrangement of the boryl ligand is calculated to be favored for all cases except for 3Bcat (i.e. PiPr3; Bcat), for which steric constraints appear to be responsible for a small preference for the coplanar form. This and the calculated geometric parameters are in good agreement with the experimental structures. The theoretical study confirms the residual B⋯H interaction in both 3Bpin and 3Bcat, indicating that B-H interaction can occur through both the "empty" BO2 p(π*) and BO2 σ* orbitals, which are mutually perpendicular. The latter interaction has not been addressed in previous studies. The degree of oxidative addition of the B-H bond depends on the electron-donating properties of the phosphine ligand and also on the nature and orientation of the boryl ligand. Thus, the balance of factors involved in the determination of the structure of these species is quite subtle, and care needs to be taken in using models in the analysis of these systems.
Persistent Identifierhttp://hdl.handle.net/10722/167853
ISSN
2015 Impact Factor: 4.186
2015 SCImago Journal Rankings: 2.043
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorLam, WHen_US
dc.contributor.authorShimada, Sen_US
dc.contributor.authorBatsanov, ASen_US
dc.contributor.authorLin, Zen_US
dc.contributor.authorMarder, TBen_US
dc.contributor.authorCowan, JAen_US
dc.contributor.authorHoward, JAKen_US
dc.contributor.authorMason, SAen_US
dc.contributor.authorMcintyre, GJen_US
dc.date.accessioned2012-10-08T03:12:14Z-
dc.date.available2012-10-08T03:12:14Z-
dc.date.issued2003en_US
dc.identifier.citationOrganometallics, 2003, v. 22 n. 22, p. 4557-4568en_US
dc.identifier.issn0276-7333en_US
dc.identifier.urihttp://hdl.handle.net/10722/167853-
dc.description.abstractRhodium hydrido boryl complexes of the form [(PR3)2RhHCl{B(OR′)2}] are key first intermediates in several Rh-catalyzed borylation processes. Previous theoretical studies have examined model compounds, e.g with PH3 and BH2 or B(OH)2 groups, and there were little structural data available for this class of compounds to compare with the calculated structures. This paper reports the results of single-crystal X-ray (at 120 K) and neutron (at 20 K) diffraction studies on two such complexes, namely [(PiPr3)2RhHCl(Bpin)] (3Bpin) and [(PiPr3)2RhHCl(Bcat)] (3Bcat) (pin = OCMe2CMe2O; cat = 1,2-O2C6H4), providing the first accurate location of the hydride ligands in a hydrido boryl complex. The orientations of the boryl ligands with respect to the equatorial plane of a distorted-trigonal-bipyramidal (DTBP) structure differs for the two compounds (Bpin lies nearly perpendicular to this plane, whereas Bcat is roughly coplanar with it), and the Cl-Rh-B angles are also very different, being 117.73(4) and 137.87(5)° (X-ray data), respectively, for 3Bpin and 3Bcat. The Rh-H distances are 1.571(5) and 1.531(11) Å, and the B-Rh-H angles are only 67.8(2) and 68.5(4)°, leading to B⋯H separations of 2.013(5) and 2.004(10) Å (neutron data) in the two compounds. Thus, these are best described as RhIII hydrido boryl rather than RhI σ-borane (σ-HB(OR)2) complexes, although there is a modest residual B⋯H interaction in both compounds. DFT calculations on model compounds employing PH3 and PMe3, as well as on 3Bpin and 3Bcat, incorporating the actual PiPr3, Bpin, and Bcat ligands allowed a detailed examination of the factors influencing structure and bonding in these compounds as well as a direct comparison of theory and experiment. The perpendicular arrangement of the boryl ligand is calculated to be favored for all cases except for 3Bcat (i.e. PiPr3; Bcat), for which steric constraints appear to be responsible for a small preference for the coplanar form. This and the calculated geometric parameters are in good agreement with the experimental structures. The theoretical study confirms the residual B⋯H interaction in both 3Bpin and 3Bcat, indicating that B-H interaction can occur through both the "empty" BO2 p(π*) and BO2 σ* orbitals, which are mutually perpendicular. The latter interaction has not been addressed in previous studies. The degree of oxidative addition of the B-H bond depends on the electron-donating properties of the phosphine ligand and also on the nature and orientation of the boryl ligand. Thus, the balance of factors involved in the determination of the structure of these species is quite subtle, and care needs to be taken in using models in the analysis of these systems.en_US
dc.languageengen_US
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/organometallicsen_US
dc.relation.ispartofOrganometallicsen_US
dc.titleAccurate molecular structures of 16-electron rhodium hydrido boryl complexes: Low-temperature single-crystal X-ray and neutron diffraction and computational studies of [(PR3)2RhHCl(boryl)] (boryl = Bpin, Bcat)en_US
dc.typeArticleen_US
dc.identifier.emailLam, WH:chsue@hku.hken_US
dc.identifier.authorityLam, WH=rp00719en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1021/om030434den_US
dc.identifier.scopuseid_2-s2.0-0345356309en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0345356309&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume22en_US
dc.identifier.issue22en_US
dc.identifier.spage4557en_US
dc.identifier.epage4568en_US
dc.identifier.isiWOS:000186106500032-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridLam, WH=26642862800en_US
dc.identifier.scopusauthoridShimada, S=7402762440en_US
dc.identifier.scopusauthoridBatsanov, AS=35448086200en_US
dc.identifier.scopusauthoridLin, Z=7404230177en_US
dc.identifier.scopusauthoridMarder, TB=7006433068en_US
dc.identifier.scopusauthoridCowan, JA=36545968800en_US
dc.identifier.scopusauthoridHoward, JAK=35444331700en_US
dc.identifier.scopusauthoridMason, SA=7202152393en_US
dc.identifier.scopusauthoridMcIntyre, GJ=7102465973en_US

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