Macropolyhedral boron-containing cluster chemistry. A synthetic approach via the auto-fusion of [6,9-(SMe₂)₂-arachno-B₁₀H₁₂]

Abstract

In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1 in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe2)-nido-B10H12] 2 (30%), but also the two two-cluster species [6,9-(SMe2)2-arachno-B10H11-1-(6-nido-B10H13)] 3 (20%) and [1,6-(nido-B10H13)2] 6 (ca. 0.5%) and the two three-cluster species [6,9-(SMe2)2-arachno-B10H10-1,5-(6-nido-B10H13)2] 4 (5%), characterized crystallographically, and [6,9-(SMe2)2-arachno-B10H10-1,3-(6-nido-B10H13)2] 5 (<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe2)-nido-B10H12] 2 is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe2)2-arachno-B10H12] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre--linked two-cluster compounds as starting substrates, two-cluster [5-(SMe2)-4-(2-nido-B10H13)-nido-B10H11] 7 (0.6%) has been isolated from the reaction of SMe2 with [1,5-(nido-B10H13)2], other identified products being compound 1 (39%) and compound 3 (10.5%).

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

“…However, little is known about the reaction coordinate of this process, beyond that the first step is a dissociation of one ligand residue, to give a 'reactive' {LB 10 H 12 } isomer. 28, 30 The actual alkyne insertion step is not elucidated, although work on other alkynyl group insertions on boron-containing clusters other than ten-vertex {B 10 } species [18][19][20][21][22]31 suggests that models for a continuum of intermediates may be isolatable by choice among appropriate systems. In our present case, we surmised that a competition between the Lewis base [ortho-(HC≡C)-C 5 H 4 N] and its properties as an alkyne ready for insertion into the B 10 H 14 had to exist, and this warranted investigation: part of this further work is described in this present paper.…”

Macropolyhedral boron-containing cluster chemistry: The reaction of syn-B18H22 with SMe2 and I2 in monoglyme: Structure of [7-(SMe2)-syn-B18H20]

“…the characteristically longer nido-decaboranyl 'gunwale' distances, at 1.964(2), and 1.969(2) Å in 2, are present (compare 1.956(3)-2.002(3) Å in 1 [7]). The ligand-substituted subcluster has the ligand at the B(7) position, next to the intercluster B(5/5 0 )-B(6/6 0 ) intercluster fusion; the adjacent gunwale distance B(7)-B(8) is correspondingly shorter, at 1.810(2) Å , similar to the value of 1.830(3) Å for the corresponding distance B(5)-B(10) in its single-cluster model 5-(SMe 2 )B 10 H 12 [4], with the other gunwale remaining 'long' at 2.019(2) Å . The distance involved in the intercluster linkage, B(5/5 0 )-B(6/6 0 ) at 1.788(2) Å , is within normal cluster interboron distance range; that in compound 1 is 1.794(2) Å [7].…”

“…Instead, an oxidizing agent is required to introduce a ligand onto the {B 18 } skeleton: thus deprotonation of syn-B 18 H 22 in monoglyme followed by treatment with I 2 and SMe 2 gives [7-(SMe 2 )-syn-B 18 H 20 ] (41%). qThe development of boron cluster chemistry significantly beyond a cluster size limit of approximately 12-14 boron atoms [1] requires the development of fused-cluster 'macropolyhedral' chemistry [2][3][4]. In many fused cluster species, although the architectures and electronic structures of the individual subclusters are closely related to the architectures and electronic structures of their single-cluster analogues, the reaction chemistry is often quite different to that of their single-cluster analogues [5,6].…”

Boron, aluminium, gallium, indium and thallium

“…The stabilities of the species resulting from these reactions have also been investigated by DFT calculations. 8 An improved synthetic route, via the iodine oxidation of [B 9 H 12 ] À , to the noctadecaborane isomer B 18 H 22 has been published, providing a safe large scale route to this polyborane cluster. 9 In a related study the molecular structure of n-B 18 H 22 and the p-stacked system n-B 18 H 22 Á C 6 H 6 has been determined.…”

“…29 DFT calculations have been used to investigate and compare the bonding and stability in metal pentagonal bipyramidal ( ) containing complexes (M = Al, Ga, In and Tl). 30 Reaction of the closo-carborane anion [CB 7 H 8 ] À with metal carbonyl sources (i.e., Fe 2 (CO) 9 , Ru 3 (CO) 12 , Mn 2 (CO) 10 and Re 2 (CO) 10 ) results in the novel insertion of CO into the cluster framework and formation of a series of {C-OH} substituted (8), or PEt 3 , n = 0; M = Ru or Re L = CO, n = 0; M = Mn, L = CO, n = 1). 31 The arachno-metallacarborane system [4,9-{Fe(CO) 4 }-9,9,9-(CO) 3 -arachno-9,6-FeCB 8 H 11 ][N(PPh 3 ) 2 ](9) has been synthesised from the reaction of [arachno-CB 8 H 14 ] with Fe 3 (CO) 12 .…”