10.1021/jp405228f.s001 Dorian S. N. Parker Dorian S. N. Parker Nadia Balucani Nadia Balucani Domenico Stranges Domenico Stranges Ralf I. Kaiser Ralf I. Kaiser Alexander Mebel Alexander Mebel A Crossed Beam and ab Initio Investigation on the Formation of Boronyldiacetylene (HCCCC<sup>11</sup>BO; <i>X</i><sup>1</sup>Σ<sup>+</sup>) via the Reaction of the Boron Monoxide Radical (<sup>11</sup>BO; <i>X</i><sup>2</sup>Σ<sup>+</sup>) with Diacetylene (C<sub>4</sub>H<sub>2</sub>; <i>X</i><sup>1</sup>Σ<sub>g</sub><sup>+</sup>) American Chemical Society 2013 BO C 1 carbon atom gas phase reaction boron monoxide hydrogen atom emission exit transition state HCCCC terminal carbon atoms ab Initio Investigation CN boronyldiacetylene molecule RRKM C 4H X 1Σg kJ C 4H X 1Σg reaction dynamics 11BO 2013-08-29 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/A_Crossed_Beam_and_ab_Initio_Investigation_on_the_Formation_of_Boronyldiacetylene_HCCCC_sup_11_sup_BO_i_X_i_sup_1_sup_sup_sup_via_the_Reaction_of_the_Boron_Monoxide_Radical_sup_11_sup_BO_i_X_i_sup_2_sup_sup_sup_with_Diacetylene_C_sub_4_sub_H_sub_2_sub_i_X/2559355 The reaction dynamics of the boron monoxide radical (<sup>11</sup>BO; <i>X</i><sup>2</sup>Σ<sup>+</sup>) with diacetylene (C<sub>4</sub>H<sub>2</sub>; <i>X</i><sup>1</sup>Σ<sub>g</sub><sup>+</sup>) were investigated at a nominal collision energy of 17.5 kJ mol<sup>–1</sup> employing the crossed molecular beam technique and supported by <i>ab initio</i> and statistical (RRKM) calculations. The reaction is governed by indirect (complex forming) scattering dynamics with the boron monoxide radical adding with its boron atom to the carbon–carbon triple bond of the diacetylene molecule at one of the terminal carbon atoms without entrance barrier. This leads to a doublet radical intermediate (C<sub>4</sub>H<sub>2</sub><sup>11</sup>BO), which undergoes unimolecular decomposition through hydrogen atom emission from the C1 carbon atom via a tight exit transition state located about 18 kJ mol<sup>–1</sup> above the separated products. This process forms the hitherto elusive boronyldiacetylene molecule (HCCCC<sup>11</sup>BO; <i>X</i><sup>1</sup>Σ<sup>+</sup>) in a bimolecular gas phase reaction under single collision conditions. The overall reaction was determined to be exoergic by 62 kJ mol<sup>–1</sup>. The reaction dynamics are compared to the isoelectronic diacetylene (C<sub>4</sub>H<sub>2</sub>; <i>X</i><sup>1</sup>Σ<sub>g</sub><sup>+</sup>)–cyano radical (CN; <i>X</i><sup>2</sup>Σ<sup>+</sup>) system studied previously in our group. The characteristics of boronyl-diacetylene and the boronyldiacetylene molecule (HCCCC<sup>11</sup>BO; <i>X</i><sup>1</sup>Σ<sup>+</sup>) as well as numerous intermediates are reported for the first time.