Potassium (Diphenylphosphino)-1,3-pentadien-1-yl-5-ylidene Borate

[178327-14-5]  · C17H15BPK  · (300.18)

(triphenylphosphine analog1)

Physical Data: white crystalline solid.

Solubility: not available.

Preparative Methods: 1-diphenylphosphinoboratabenzene is prepared by adding a 0.5 M solution of potassium diphenylphosphide in THF to borabenzene-trimethylphosphine at 20°C.2,3

Purification: recrystallized from THF at (-35°C).

Handling, Storage, and Precautions: air sensitive; all reactions are run in oven dried glassware under either an atmosphere of argon using Schlenk techniques or under an atmosphere of nitrogen inside a dry box.

Zirconium Complex

1-Diphenylphosphinoboratabenzene (DPB) s bonds (h1) to metal centers,4,5 while the rest of the class of boratabenzenes,6 such as 1-methylboratabenzene,7 1-phenylboratabenzene,8 and 1-dimethylaminoboratabenzene,9 act as surrogates of the cyclopentadiene anion by p-bonding (h6) to the metal center.10,11 One exception is a magnesium complex, magnesium (1-dimethylaminoboratabenzene)2, where one ligand participates in h6 bonding while the second h1 bonds.12 The electronic nature of the zirconecene catalyst can be tuned using DPB as a negatively charged analog of triphenylphosphine.13 The X-ray crystal structures of K-DPB·(18-crown-6) and K-1-diphenylaminoboratabenzene·(18-crown-6) provide evidence that the 1-diphenylaminoboratabenzene N-B bond has significant p-bonding, while DPB shows little p-bonding with the boron atom.5 Potassium 1-diphenylphosphinoboratabenzene is added to Cp2ZrHCl (eq 1) to obtain the zirconecene complex in 49% yield.4

Iron Complex

Diphenylphosphide is a unique phosphorus(III) ligand because it has a set of electrons available which increases the electron density on a metal center.4,13g The isoelectronic iron complexes [CpFe(CO)2(PPh3)]+14 and CpFe(CO)2(PPh2)15 allow for a variation of the electronic density on the metal center. DPB adds to CpFe(CO)2I which provides an iron complex where the electron density on the iron atom is greater than the PPh3 complex and less than the PPh2 (eq 2).4

DPB is the only boratabenzene known to h1 bond with iron metal. 1- Dimethylaminoboratabenzene bonds h6 and it has recently found utility in iron complexes.16

Rhodium Complex

Recently, rhodium metal has been found to be extremely useful in organic synthesis. DPB was used to prepare the rhodium complex Rh(PMe3)3(DPB) (eq 3).4,17

Related Reagents.

triphenylphosphine, trimethylphosphine, trimethylphosphite.

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2. Hoic, D. A.; Wolf, J. R.; Davis W. M.; Fu, G. C., Organometallics 1996, 15, 1315.
3. Qiao, S.; Hoic, DA.; Fu, G. C., J. Am. Chem. Soc. 1996, 118, 6329.
4. Hoic, D. A.; Davis, W. M.; Fu, G. C., J. Am. Chem. Soc. 1996, 118, 8176.
5. Hoic, D. A.; DiMare, M.; Fu, G. C., J. Am. Chem. Soc. 1997, 119, 7155.
6. For review on boratabenzene chemistry, see (a) Ashe, A. J.; Al-Ahmad, S.; Fang, XJ., J. Organomet. Chem. 1999, 591, 92. (b) Herberich, G. E. Boratabenzene chemistry revisited. In Advances in Boron Chemistry; Siebert, W., Ed.; The Royal Society of Chemistry: Cambridge, 1997; Special Publication No. 201, p 211.
7. Herberich, G. E.; Englert, E.; Schmitz, A., Organometallics 1997, 16, 3751.
8. Bazan, G. C.; Rodriquez, G.; Ashe, A. J.; Al-Ahmad, S.; Kampf, J. W., Organometallics 1997, 16, 2492.
9. (a) Bazan, G. C.; Rodreguez, G.; Ashe, A. J.; Al-Ahmad, S.; Miller, C., J. Am. Chem. Soc. 1996, 118, 2291. (b) Bazan, G. C.; Rodreguez, G.; Ashe, A. J.; Al-Ahmad, S.; Miller, C., Organometallics 1997, 16, 2492. (c) Ashe, A. J.; Al-Ahmad, S.; Kampf, J. W., Organometallics 1999, 18, 4234. (d) Ashe, A. J.; Al-Ahmad, S., J. Organomet. Chem. 1999, 581, 92.
10. Herberich, G. E.; Ohst, H., Adv. Organomet. Chem. 1986, 25, 199.
11. Herberich, G. E. In Comprehensive Organometallic Chemistry II; Abel, E. W.; Stone, F. G. A.; Wilkinson, G., Eds.; Pergamon: New York, 1995, Vol. 1, Chapt. 5.
12. Zheng, Z.; Englert, U.; Herberich, G. E.; Rosenplänter, J., Inorg. Chem. 2000, 39, 5579.
13. (a) Jordon, R. F.; Bradley, P. K.; Baenziger, N. C.; Lapointe, R. E., J. Am. Chem. Soc. 1990, 112, 1289. (b) Kreutzer, K. A.; Fisher, R. A.; Davis, W. M.; Paltenstein, E.; Buchwald, S. L., Organometallics 1991, 10, 4031. (c) Jordan, R. F.; Taylor, D. F.; Baenziger, N. C., Organometallics 1990, 9, 1546. (d) Jordan, R. F.; Bajgur, C. S.; Dasher, W. E.; Rheingold, A. L., Organometallics 1987, 6, 1041. (e) Alelyunas, Y. W.; Guo, Z.; Lapointe, R. E.; Jordan, R. F., Organometallics 1993, 12, 544. (f) Bazan, G. C.; Cotter, W. D.; Komon, Z. J. A.; Lee, R. A.; Lachicotte, R. J., J. Am. Chem. Soc. 2000, 122, 1371. (g) Bazan, G. C.; Cotter, W. D.; Komon, Z. J. A.; Lee, R. A.; Lachicotte, R. J., J. Am. Chem. Soc. 2000, 122, 1371.
14. (a) Riley, P. E.; Davis, R. E., Organometallics 1983, 2, 286. (b) Davison, A.; Green, M. L. H.; Wilkinson, G. J., J. Chem. Soc. 1961, 3172. (c) Sim, GA.; Woodhouse, D. I.; Knox, G. R. J., Chem. Soc., Dalton Trans. 1979, 629. (d) Janik, T. S.; Krajkowski, L. M.; Churchill, M. R., J. Chem. Cyst. 1995, 25, 751.
15. Burckett-St. Laurent, J. C. T. R.; Haines, R. J.; Nolte, Cr.; Steen, N. D. C. T., Inorg. Chem. 1980, 19, 577.
16. Herberich, G. E.; Englert, E.; Ganter, B.; Pons, M., Eur. J. Inorg. Chem. 2000, 5, 979.
17. Gibson, D. H.; Ong, T. S., Organometallics 1984, 3, 1911.

Larry W. Mann

Wayne State University, Detroit, MI, USA

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