Comparisons of Photoinduced Oxidative Addition of B-H, B-B, and Si-H Bonds at Rhodium(5-cyclopentadienyl)phosphine Centers
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- 作者：Marius V. Câ ; mpian ; Jeremy L. Harris ; Naser Jasim ; Robin N. Perutz ; Todd B. Marder ; Adrian C. Whitwood
- 刊名：Organometallics
- 出版年：2006
- 出版时间：October 9, 2006
- 年：2006
- 卷：25
- 期：21
- 页码：5093 - 5104
- 全文大小：206K
- 年卷期：v.25,no.21(October 9, 2006)
- ISSN：1520-6041
文摘
Ultraviolet irradiation of [Rh(
5-C5H5)(PMe3)(C2H4)] (1a), [Rh(5-C5H5)(PPh3)(C2H4)] (1b), and [Rh(5-C5H4CF3)(PMe3)(C2H4)] (1c) (collectively abbreviated as [Rh(Cp')(PR3)(C2H4)]) in the presence ofHBpin (pinacolate = pin = 1,2-O2C2Me4) results in elimination of C2H4 and B-H oxidative addition,leading to the formation of boryl hydride complexes [Rh(Cp')(Bpin)(H)(PR3)]. Complete conversion isachieved in liquid HBpin or by photolysis in hexane at -10 
C. Similarly, photolysis of 1a-c in thepresence of B2pin2 in hexane at -10 C leads to B-B oxidative addition products, [Rh(Cp')(Bpin)2(PR3)]. Irradiation at room temperature leads to formation of [Rh(Cp')(PR3)2] in addition to the desiredproducts. The rhodium boryl products were characterized by multinuclear NMR spectroscopy and, in thecase of [Rh(5-C5H5)(Bpin)(H)(PPh3)], by X-ray crystallography. The structure reveals a Rh-B distanceof 2.0196(15) Å. The H···B separation of 2.09(2) Å together with the bond angles at the metal suggestsome residual H···B interaction. Photolysis of 1a-c in the presence of tertiary and secondary silanes(HSiEt3, HSiiPr3, HSi(OMe)3, HSiMe2Et, HSiMeEt2, and H2SiEt2) results in rhodium silyl hydridecomplexes [Rh(Cp')(SiR'2R' ')(H)(PR3)]. The structure of [Rh(5-C5H5)(SiiPr3)(H)(PMe3)] was determinedby single-crystal X-ray diffraction, yielding a Rh-Si bond length of 2.3617(3) Å and a Rh-H bondlength of 1.508(17) Å. The H···Si distance of 2.278(17) Å and the very unequal H-Rh-P and H-Rh-Si angles suggest some residual H···Si interaction. Competition reactions were performed with 1b dissolvedin hexane in the presence of HBpin and B2pin2 simultaneously. 31P NMR measurements, made afterbrief irradiation, showed a slight preference for B-B oxidative addition over B-H oxidative addition.Similar experiments with three-way competition among HBpin, HSiMe2Et, and HC6F5, analyzed by 1HNMR spectroscopy, showed negligible selectivity among H-B, H-C, and H-Si oxidative addition.Molecular structures were also determined by single-crystal X-ray diffraction for 1b, 1c, [Rh(5-C5H5)(PPh3)2], and [Rh(5-C5H5)Cl2(PPh3)].
5-C5H5)(PMe3)(C2H4)] (1a), [Rh(5-C5H5)(PPh3)(C2H4)] (1b), and [Rh(5-C5H4CF3)(PMe3)(C2H4)] (1c) (collectively abbreviated as [Rh(Cp')(PR3)(C2H4)]) in the presence ofHBpin (pinacolate = pin = 1,2-O2C2Me4) results in elimination of C2H4 and B-H oxidative addition,leading to the formation of boryl hydride complexes [Rh(Cp')(Bpin)(H)(PR3)]. Complete conversion isachieved in liquid HBpin or by photolysis in hexane at -10 C. Similarly, photolysis of 1a-c in thepresence of B2pin2 in hexane at -10 C leads to B-B oxidative addition products, [Rh(Cp')(Bpin)2(PR3)]. Irradiation at room temperature leads to formation of [Rh(Cp')(PR3)2] in addition to the desiredproducts. The rhodium boryl products were characterized by multinuclear NMR spectroscopy and, in thecase of [Rh(5-C5H5)(Bpin)(H)(PPh3)], by X-ray crystallography. The structure reveals a Rh-B distanceof 2.0196(15) Å. The H···B separation of 2.09(2) Å together with the bond angles at the metal suggestsome residual H···B interaction. Photolysis of 1a-c in the presence of tertiary and secondary silanes(HSiEt3, HSiiPr3, HSi(OMe)3, HSiMe2Et, HSiMeEt2, and H2SiEt2) results in rhodium silyl hydridecomplexes [Rh(Cp')(SiR'2R' ')(H)(PR3)]. The structure of [Rh(5-C5H5)(SiiPr3)(H)(PMe3)] was determinedby single-crystal X-ray diffraction, yielding a Rh-Si bond length of 2.3617(3) Å and a Rh-H bondlength of 1.508(17) Å. The H···Si distance of 2.278(17) Å and the very unequal H-Rh-P and H-Rh-Si angles suggest some residual H···Si interaction. Competition reactions were performed with 1b dissolvedin hexane in the presence of HBpin and B2pin2 simultaneously. 31P NMR measurements, made afterbrief irradiation, showed a slight preference for B-B oxidative addition over B-H oxidative addition.Similar experiments with three-way competition among HBpin, HSiMe2Et, and HC6F5, analyzed by 1HNMR spectroscopy, showed negligible selectivity among H-B, H-C, and H-Si oxidative addition.Molecular structures were also determined by single-crystal X-ray diffraction for 1b, 1c, [Rh(5-C5H5)(PPh3)2], and [Rh(5-C5H5)Cl2(PPh3)].