16:00- - 2 2 Access to a Stable 2 2 4-Membered ing with on-kekulé nglet Biradical haracter from a Disilyne Dr. Katsuhiko Takeuchi 2007 3 2009 3 2012 3 2012 4 2012 4 (JSPS ) 2013 8
eaxys Prize lub Symposium in Japan, March 28, 2014 Profile 01 2007 3 2009 3 2012 3 2012 4 2013 7 JSPS Stephan 2013 8 1
esearch 02 disilyne + Bulky Lewis Base Bulky Lewis Acid Frustrated Lewis Pair Mes* P P Mes* t Bu t Bu P P Mes* esearch 03 2 2 = 3,5-Me 2 6 H 3 2 2 4-membered ring biradicaloid 2
Introduction: Disilyne 04 the first isolable = double bonded compound disilene West (1981) obert. West University of Wisconsin Madison Me 3 Me 3 Me 3 Me 3 Br Br Br Br Me 3 Me 3 Me 3 Me 3 4 K 8 THF Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 the first isolable disilyne 1 Sekiguchi (2004) Introduction: Disilyne 05 Isolable Disilynes t Bu Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Sekiguchi (2004) Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Me 3 Tokitoh (2008) the first aryl substituted disilyne Sekiguchi (2010) unsymmetrically substituted disilyne Me 3 t Bu Me 3 Me 3 Iwamoto, Ishida (2013) the first alkyl substituted disilyne t Bu Me 3 3
Introduction: Disilyne 06 1 2 1 2 137.44(4)º 2.3698(6) Å 2.0622(9) Å cf. Typical Bond Lengths 2.34 ~ 2.37 Å = 2.14 ~ 2.29 Å Introduction: Disilyne 07 160 140 p-orbital r max (pm) 120 100 80 s-orbital 60 Ge Sn Pb Orbital radius of group 14 elements 4
Introduction: Disilyne 08 HF/6-31G(d) E (ev) 5.92 1.88 LUMO+1 1.03 0 6.69 LUMO 7.10 10.89 HOMO H H HOMO 1 Introduction: Disilyne 1) 09 2,3) or 2 H stereo specific 1) Ph H 2 BH 2,4) disilyne 1 Me 3 t Bu Me 3 Me 3 5) i PrDsi 2 6) Dsi 2 i Pr Dsi 2 i Pr i PrDsi 2 1). Kinjo, M. Ichinohe, A. Sekiguchi,. Takagi, M. Sumimoto, and S. agase, J. Am. hem. Soc., 129, 7766 (2007). 2) K. Takeuchi, M. Ikoshi, M. Ichinohe, and A. Sekiguchi, J. Am. hem. Soc., 132, 930 (2010). 3) K. Takeuchi, M. Ikoshi, M. Ichinohe, and A. Sekiguchi, J. Organomet. hem., 696, 1156 (2011). 4) K. Takeuchi, M. Ichinohe, and A. Sekiguchi, Organometallics, 30, 2044 (2011). 5) K. Takeuchi, M. Ichinohe, and A. Sekiguchi, J. Am. hem. Soc., 130, 16848 (2008). Dsi = H(Me 3 ) 2 6) K. Takeuchi, M. Ichinohe, and A. Sekiguchi, J. Am. hem. Soc., 134, 2954 (2012). 5
Introduction: Biradicaloid 10 Biradicals pair of doublet monoradicals triplet biradical singlet biradical biradicaloid yclicbiradicaloids iecke (1995) Bertrand (2002) Power (2004) Lappert (2004) Mes* = 1,3,5- t Bu 3 6 H 2 * = 6 H 3-2,6-( 6 H 3-2,6- i Pr 2 ) 2 eaction with Azobenzenes 11 = 3,5-Me 2 6 H 3 THF r.t. / in dark 1 day disilyne 1 THF r.t. / in dark <5 min 2 2 4-membered ring biradicaloid 2 purple crystals (y. = 58%) cf. Power s Work 1) hexane E = Ge, Sn * = 6 H 3-2,6-( 6 H 3-2,6- i Pr 2 ) 2 1). ui, M. M. Olmsted, J.. Fettinger, G. H. Spikes, and P. P. Power, J. Am. hem. Soc., 127, 17530 (2005). 6
Possible eaction Mechanism 12 i PrDsi 2 π* LUMO cleavage Dsi 2 i Pr Dsi i 2 Pr i PrDsi 2 = cleavage cf. eaction with 2-Butene 1) or 1 day 30 min disilyne 1 hexane 1). Kinjo, M. Ichinohe, A. Sekiguchi,. Takagi, M. Sumimoto, and S. agase, J. Am. hem. Soc., 129, 7766 (2007). Possible eaction Mechanism 12 i PrDsi 2 π* LUMO cleavage Dsi 2 i Pr Dsi i 2 Pr i PrDsi 2 = cleavage B3LYP/6-31G(d) 2' cyclobutene-2' butadiene-2' 0.0 kcal/mol +43.6 kcal/mol +29.9 kcal/mol bis(silylene)-2' not found 7
Molecular Structure of Biradicaloid 2 13 2 1 1' 1 1 1' 2' a purple crystal from THF 1.758(3) 2.4658(15) 2.618(2) 1.756(3) 1' Monoclinic 2/c Z = 4 1 = 0.0394 [I>2σ(I)] w 2 = 0.1193 [All Data] GOF = 1.032 Figure 1. OTEP drawing and selected structural parameters of 2. Σ(1) = 318º in Å Σ(1) = 360º sum of the internal angles of the ring = 360º cf. elated ompounds 1) 2) Σ(Ge) = 322º Σ(Sn) = 256º = 2.697 Å 3) 1). ui, M. M. Olmsted, and P. P. Power, J. Am. hem. Soc., 126, 6510 (2004). 2) H. ox, P. B. Hitchcock, M. F. Lappert, and L. J.-M. Pierssens, Angew. hem., Int. Ed., 43, 4500 (2004). 3). Wiberg, H. Schuster, A. mon, and K. Peters, Angew. hem., Int. Ed., 25, 79 (1986). AIM Analysis of Biradicaloid 2 14 2' 2 ( = 3,5-Me 2 6 H 3 ) calc (exp) Σ( ring ) Σ( ring ) 1.785 Å 2.651 Å 304º 360º (1.757 Å) (2.618 Å) (318º) (360º) Bond ritical Point Figure 1. Optimized structure and bond paths of the model compound 2'. B3LYP/6-31G(d) 8
M Studies of Biradicaloid 2 15 (Me 3 ) 2 H skeletal δ 19.4 (Me 3 ) 2 H δ 1.0, 0.3 2 ( = 3,5-Me 2 6 H 3 ) Me i Pr (Me 3 ) 2 H Dsi 2i Pr δ 10.4 8 6 4 2 0 [ppm] Figure 1. 1 H M spectrum of 2 in THF-d 8. 50 25 0 25 50 [ppm] Figure 2. 29 M spectrum of 2 in THF-d 8. cf. Theoretical Studies GIAO/B3LYP6-311G(3d)//B3LYP6-31G(d) 2' (singlet) 2' (triplet) planar-2' (TS) 0.0 kcal/mol δ(skeletal ) 14.7 +12.8 kcal/mol +36.8 kcal/mol δ(skeletal ) 52.3 60000 UV-Vis Spectrum of Biradicaloid 2 0.02 [ev] 0.38 2.39 16 LUMO+1 (σ* orbital of 2 2 ring) 40000 [ε] 20000 356 nm [ε = 4300] c 529 nm [ε = 32000] b a [ f ] 0.01 LUMO 4.60 5.33 HOMO 0 200 400 TDDFT alculation [nm] 600 0.00 800 HOMO 1 8.98 transition a: 515 nm (f = 0.0115) transition b: 514 nm (f = 0.0123) transition c: 367 nm (f = 0.0016) HOMO 1 LUMO HOMO LUMO HOMO LUMO+1 6π aromaticity? HOMO 12 2' B3LYP/6-31G(d) Figure 1. UV-Vis spectrum of 2 in hexane superimposed by the calculated band position of 2' (left) and MOs of 2' (right). 9
omaticity of Biradicaloid 2 17 in Å 1.758(3) 2.618(2) 1.7479(14) 2.5889(8) 1.756(3) 1.7536(13) Σ(1) = 318º Σ(1) = 360º sum of the internal angles of the ring = 360º Σ(1) except l1 = 325º Σ(1) = 360º sum of the internal angles of the ring = 360º Figure 1. Selected structural parameters of biradicaloid 2 (left) and l 2 -adduct 4 (right). cf. IS Values of Model ompounds 2' IS(1) = 4.2 4' IS(1) = 2.1 B3LYP/6-31G(d) eactivity of Biradicaloid 2 18 MeOH (excess) THF r.t. / 1 h + cis-3 (y. = 65%) closed-shell reactivity trans-3 2 = 3,5-Me 2 6 H 3 O1 1 1 2 2 Figure 1. OTEP drawing of cis-3. cf. intra- or inter-molecular H + transfer cis- or trans-3 LUMO of 2 10
eactivity of Biradicaloid 2 19 MeOH (excess) THF r.t. / 1 h + cis-3 (y. = 65%) closed-shell reactivity trans-3 2 = 3,5-Me 2 6 H 3 l 4 (excess) THF r.t. / 20 min 1 1 l1 1' 1' l1' 4 (y. = 55%) radical-type reactivity Figure 1. OTEP drawing of 4. cf. eactivity of lyl adical o eaction MeOH l 4 Summary 20 = 3,5-Me 2 6 H 3 disilyne 1 2 2 2 4-membered ring 2 was synthesized by the reaction of disilyne 1 with azobenzen M data of 2 suggest that 2 has a singlet ground state. Theoretical calculations show no bonding interaction between the skeletal atoms of 2. Although 2 has 6π-electrons in the 4-membered ring, the IS value indicates small aromaticity. eactions of 2 with MeOH and l 4 show that 2 has both closed-shell and radical-type reactivity. 11
Acknowledgment University of Tsukuba Prof. Dr. Akira Sekiguchi A/Prof. Dr. Masaaki Ichinohe Dr. Vladimir Ya. Lee Dr. Masaaki akamoto and all members of Sekiguchi, Stephan, and Ozawa groups! 21 University of Toronto Prof. Dr. Doug W. Stephan Kyoto University Prof. Dr. Fumiyuki Ozawa Dr. Masayuki Wakioka 12