Borane reaction chemistry. Alkyne insertion reactions into boron-containing clusters. Products from the thermolysis of [6,9-(2-HCC–C5H4N)2-arachno-B10H12]

Abstract

The stirring of [ortho-(HC[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] in benzene affords [6,9-{ortho-(HC[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 1 in 93% yield. In the solid state, 1 has an extended complex three-dimensional structure involving intramolecular dihydrogen bonding, which accounts for its low solubility. Thermolysis of 1 gives the known [1-(ortho-C(5)H(4)N)-1,2-closo-C(2)B(10)H(11)] 2 (13%), together with new [micro-5(N),6(C)-(NC(5)H(4)-ortho-CH(2))-nido-6-CB(9)H(10)] 3 (0.4%), [micro-7(C),8(N)-(NC(5)H(4)-ortho-CH(2))-nido-7-CB(10)H(11)] (0.4%) , 4 binuclear [endo-6'-(closo-1,2-C(2)B(10)H(10))-micro-(1(C),exo-6'(N))-(ortho-C(5)H(4)N)-micro-(exo-8'(C),exo-9'(N))-(ortho-(CH(2)CH(2))-C(5)H(4)N)-arachno-B(10)H(10)] (0.5%) 5, and [exo-6(C)-endo-6(N)-(ortho-(CH[double bond]CH)-C(5)H(4)N)-exo-9(N)-(ortho-(HC[triple bond]C)-C(5)H(4)N)-arachno-B(10)H(11)] 6. An improved solvent-free route to 2 is also presented. This set of compounds features an increasing cluster incorporation of the ethynyl moiety, initially by an effective internal hydroboration, affording an arachno to nido and then a nido to arachno:closo sequence of cluster geometry. An alternative low-temperature route to internal hydroboration is demonstrated in the room temperature reaction of [closo-B(11)H(11)][N(n)Bu(4)](2) with CF(3)COOH and [ortho-(HC[triple bond]C)-C(5)H(4)N], which gives [micro-1(C),2(B)-[ortho-C(5)H(4)N-CH(2)]-closo-1-CB(11)H(10)] 7 (40%) in which one carbon atom is incorporated into the cluster; a similar reaction with [ortho-(N[triple bond]C)-C(5)H(4)N] affords [N(n)Bu(4)][7-(ortho-N[triple bond]C-C(5)H(4)N)-nido-B(11)H(12)], 8 (68%) and stirring [ortho-(N[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] quantitatively affords the cyano analogue of 1, [6,9-{ortho-(N[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 9. All compounds were characterised by single-crystal X-ray diffraction analysis and NMR spectroscopy.

Reversible Small‐Molecule Interactions with Coordinatively Unsaturated Metal Centers Held in Metallathiaborane Clusters

“…An additional distance is shorter than the sum of the van der Waals radii of two hydrogen atoms (2.4 Å), that is, the para ‐phenyl hydrogen atom of P(2) and the hydrogen atom of B(6) have a normalized distance of 2.23 Å. This value is similar to that seen previously in [6,9‐{ ortho ‐(HC≡C)–C 5 H 4 N} 2 ‐ arachno ‐B 10 H 12 ], which also exhibits an insolubility ascribed to the enhanced intermolecular attractions through CH ··· HB dihydrogen bonding . The conglomerate of chains is bound and isolated from each other by the PhMe 2 groups of P(1), for which there are no significantly short interatomic contacts.…”

“…This value is similar to that seen previously in [6,9-{ortho-(HC≡C)-C 5 H 4 N} 2 -arachno-B 10 H 12 ], which also exhibits an insolubility ascribed to the enhanced intermolecular attractions through CH···HB dihydrogen bonding. [30] The conglomerate of chains is bound and isolated from each other by the PhMe 2 groups of P(1), for which there are no significantly short interatomic contacts. There is a further close contact between B(3)-H and a methyl hydrogen atom of P(2) with a normalized distance of 2.02 Å, and this value as well as the B-H-H and C-H-H angles of 131.4 and 161.5°are similar to those above.…”

Small‐Molecule Kinase‐Inhibitors‐Loaded Boron Cluster as Hybrid Agents for Glioma‐Cell‐Targeting Therapy

“…The direct reaction between ethynyl/erlotinib and decaborane via decaborane/acetonitrile adduct formation followed by alkyne insertion was first attempted. However, the coordination capability of the nitrogen from the quinazoline produced a complex mixture, but not the desired compounds, as has been previously reported for the synthesis of 1‐(C 5 H 4 N)‐1,2‐ closo ‐C 2 B 10 H 11 . Consequently, the ethynyl moiety was used as connector to design several families with a linker between TKR‐interacting group and the icosahedral boron cluster.…”

High Yielding Synthesis of Carboranes Under Mild Reaction Conditions Using a Homogeneous Silver(I) Catalyst: Direct Evidence of a Bimetallic Intermediate

“…Several attempts have been made to optimize the yield, which is typically 30 %, of 1‐(2′‐pyridyl)‐1,2‐dicarba‐ closo ‐dodecaborane 9. One method produced the product in 45 % yield but required the use of a solvent‐free thermolysis procedure at 100 °C in a sealed tube 10. At 40 °C and room temperature in the presence of 1 b the desired product 6 was isolated in 88 and 63 % yield, respectively (Scheme ).…”

“…[9] One method produced the product in 45 % yield but required the use of a solvent-free thermolysis procedure at 100 8C in a sealed tube. [10] At 40 8C and room temperature in the presence of 1 b the desired product 6 was isolated in 88 and 63 % yield, respectively (Scheme 3). By using a lower reaction 4,7,10,13,16,19,22,25,28-nonaoxahentriacont-30-yn-1-oate.…”