Syntheses of Lewis-Pairs with “ B→P Donor-Acceptor Interaction” Manuel Kaaz

10th European Workshop on Phosphorus Chemistry Regensburg Syntheses of Lewis-Pairs with “B→P Donor-Acceptor Interaction” Manuel Kaaz Institute of Inorganic Chemistry University of Stuttgart

Introduction ? ? P. Power, Angew. Chem. 1990, 102, 527-538. P. Greiwe. A. Bethäuser, H. Pritzkow, T. Kühler, P. Jutzi, W. Sieber, Eur. J. Inorg. Chem., 2000, 1927-1929. N. Burford, C. Dyker, A. Decken, Angew. Chem. Int. Ed., 2005, 44, 2364-2367.

Introduction Dip = 2,6-Di-iso-propylphenyl Y. Segawa, Y. Suzuki, M. Yamashita, K. Nozaki, J. Am. Chem. Soc, 2008, 130, 16069-16079. L. Weber, Eur. J. Inorg. Chem., 2012, 5595-5609.

Objectives - Synthesis of Lewis-Pairs with „B→P Bond” - Is it really a Donor-Acceptor Interaction?

Synthesis of a 1,3,2-Diazaborolene pros: • acceptable yields (56 %) • works for many substituents • simple work-up cons: • long reaction time (5 d) • only practicable on small scale (<2 g) Y. Segawa, Y. Suzuki, M. Yamashita, K. Nozaki, J. Am. Chem. Soc., 2008, 130, 16069-16079.

Synthesis of a 1,3,2-Diazaborolene pros: • good yields (77 %) • upscalable cons: • two step process • intermediate must be isolated • product must be crystallised • does not work for other substituents Y. Segawa, Y. Suzuki, M. Yamashita, K. Nozaki, J. Am. Chem. Soc., 2008, 130, 16069-16079.

Alternative Synthesis of a 1,3,2-Diazaborolene pros: • one-pot synthesis • short reaction time cons: • product mixture synthesis must be optimised • product must be crystallised

Metalation of a 1,3,2-Diazaborolene Modified reaction conditions: Y. Segawa, Y. Suzuki, M. Yamashita, K. Nozaki, J. Am. Chem. Soc, 2008, 130, 16069-16079.

• B-Si 2.009(1) Å • sum of bond angles at B 358.6(1)° • 11B-NMR δ: 27.0 ppm (s) • water and air stable Synthesis of a N-Heterocyclic Silyl-Boran

Reaction with a 1,3,2-Diazaphospholene

Reaction of a Lithium-Boryls with a Halogeno-Phosphine • P-B 1.930(1) Å • sum of bond angles at B 357.9(1)° • sum of bond angles at P 317.3(2)° • sums of bond angles at N 353.7(3)° / 354.5(3)°

Synthesis of 1,3,2-Diazaphospholenes S. Burck, D. Gudat, M. Nieger, W. Du Mont, J. Am. Chem. Soc., 2006, 128, 3946-3955.

• P-B 1.951(2) Å • sum of bond angles at B 359.1(1)° • sum of bond angles at P 292.05° • sums of bond angles at N 343.1(4)° / 348.1(4)° Reaction of a Lithium-Boryl with a Halogeno-Diazaphospholene

Possible reaction pathway: Reaction of a Lithium-Boryl with Chlorodiphenylphosphine

Alternative Synthesis R. Bartlett, X. Feng, M. Olmstead, P. Power, Phosphorus and Sulfur, 1987, 30, 245,248.

Crystal Structures • P-B-Bond 1.931(1) Å • sum of bond angles at B 359.4(1)° • sum of bond angles at P 298.7(1)° • water and air stable • P-B-Bond 1.946(1) Å • sum of bond angles at B 356.0(1)° • sum of bond angles at P 310.6(1)°

• probably no B→P-donor-acceptor-bond • covalent B-P-bond Comparison of Bond Lengths P. Kolle, H. Noth, R. Paine, Chem. Ber.,1986, 119, 2681. A. Arif, A. Cowley, M. Pakalski, J. Power, Chem. Commun., 1986, 889. B. Riegel, A. Pfitzner, G. Heckmann, H. Binder, E. Fluck, Z. Anorg. Allg. Chem., 1994, 620, 8. X. Feng, M. Olmstead, P. Power, Inorg. Chem., 1986, 25, 4615.

Reaction with BuLi 31P-NMR δ = -131 ppm, 1JPH = 217 Hz 31P-NMR δ = -116 ppm R. Bartlett, X. Feng, M. Olmstead, P. Power, Phosphorus and Sulfur, 1987, 30, 245,248.

Summary and Outlook Summary •successful synthesis of water and air stable N-heterocyclic Silyl-Borans • syntheses of new Boryl-Phosphines with aminophophines and phenylphosphines - planar coordination at B, pyramidal coordination at P - B-P: 1.930(1) – 1.951(2) Å, probably no B→P-bond, covalent bond Outlook • Boryl-Phosphines as ligands for metal-complexes • reactivity of the B-P-bond

Acknowledgments • Prof. Dr. Dietrich Gudat • Dr. Wolfgang Frey • Dr. Daniela Förster and Johannes Bender • AK Gudat • PhoSciNet • University of Stuttgart

Syntheses of Lewis-Pairs with “ B→P Donor-Acceptor Interaction” Manuel Kaaz