Icosahedral metallacarborane/carborane species derived from 1,1′-bis(o-carborane)

Abstract

Examples of singly-metallated derivatives of 1,1'-bis(o-carborane) have been prepared and spectroscopically and structurally characterised. Metallation of [7-(1'-1',2'-closo-C2B10H11)-7,8-nido-C2B9H10](2-) with a {Ru(p-cymene)}(2+) fragment affords both the unisomerised species [1-(1'-1',2'-closo-C2B10H11)-3-(p-cymene)-3,1,2-closo-RuC2B9H10] (2) and the isomerised [8-(1'-1',2'-closo-C2B10H11)-2-(p-cymene)-2,1,8-closo-RuC2B9H10] (3), and 2 is easily transformed into 3 with mild heating. Metallation with a preformed {CoCp}(2+) fragment also affords a 3,1,2-MC2B9-1',2'-C2B10 product [1-(1'-1',2'-closo-C2B10H11)-3-Cp-3,1,2-closo-CoC2B9H10] (4), but if CoCl2/NaCp is used followed by oxidation the result is the 2,1,8-CoC2B9-1',2'-C2B10 species [8-(1'-1',2'-closo-C2B10H11)-2-Cp-2,1,8-closo-CoC2B9H10] (5). Compound 4 does not convert into 5 in refluxing toluene, but does do so if it is reduced and then reoxidised, perhaps highlighting the importance of the basicity of the metal fragment in the isomerisation of metallacarboranes. A computational study of 1,1'-bis(o-carborane) is in excellent agreement with a recently-determined precise crystallographic study and establishes that the {1',2'-closo-C2B10H11} fragment is electron-withdrawing compared to H.

Carborane Substituents Promote Direct Electrophilic Insertion over Reduction–Metalation Reactions

“…The isomerization is presumably the result of otherwise untenable steric interaction between the mes and carborane substituents. Strong circumstantial evidence for this conclusion is that in 1 and 2 the arene ring is bent away from the carborane substituent, subtending angles of 10.57(17) and 12.56(11)° respectively with the plane through atoms B5, B9, B12, B13, and B8, and that related sterically driven isomerizations have been noted in 12‐vertex metallacarborane/12‐vertex carborane analogues …”

Exopolyhedral Ligand Orientation Controls Diastereoisomer in Mixed-Metal Bis(Carboranes)

“…Recent years have witnessed a significant amount of interest in the chemistry of bis(carboranes) [1][2][3][4], particularly 1,1 -bis(ortho-carborane), formally [1-(1 -closo-1 ,2 -C 2 B 10 H 11 )-closo-1,2-C 2 B 10 H 11 ] (I), Scheme 1. This species offers a versatile scaffold for derivatisation and, amongst other studies, we have reported the single deboronation/metalation [5], double deboronation/homometalation [6] and stepwise deboronation/metalation-deboronation/heterometalation [7] of I, the latter including the use of {Rh(H)(PPh 3 ) 2 } fragments to afford homogeneous catalyst precursors [8].…”

Large, weakly basic bis(carboranyl)phosphines: an experimental and computational study

“…However, this has now been achieved 3 and consequently a significant amount of new chemistry of 1,1′-bis (o-carborane) has recently appeared. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Several authors have taken advantage of the functionality of its C cage H units to use 1,1′-bis(o-carborane) as a κ 2 ligand, binding transition-metals to the cage through two M-C σ-bonds, with recent studies 7,8,13,19 building on the pioneering work of Hawthorne and co-workers. 21 In marked contrast, very little has been reported concerning main group elements bound to 1,1′-bis(o-carborane).…”