C-C Plasticity in Boron Chemistry: Modulation of the Cc···Cc Distance in Mixed Pyrrolyl/Dicarbollide Complexes
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- 作者：Jordi Llop ; Clara Viñ ; as ; Francesc Teixidor ; Lluí ; s Victori ; Raikko Kivekä ; s ; and Reijo Sillanpä ; ä
- 刊名：Organometallics
- 出版年：2001
- 出版时间：September 17, 2001
- 年：2001
- 卷：20
- 期：19
- 页码：4024 - 4030
- 全文大小：144K
- 年卷期：v.20,no.19(September 17, 2001)
- ISSN：1520-6041
文摘
The single, double, and triple bond distances are well defined in conventional organiccompounds. Cluster boron chemistry, in particular the o-carboranes, provides the possibilityto modulate the C-C distance in an almost continuous way within the same family ofcompounds. As an example, mixed pyrrolyl/dicarbollide sandwich cobalt complexes derivedfrom closo-[3-Co(
5-NC4H4)-1,2-C2B9H11] (1) display a continuous range of Cc···Cc distancesbetween 1.640(7) for the parent compound and 1.919(6) for closo-[3-Co(5-NC4H4)-1,2-(SCH3)2-1,2-C2B9H9] (5). Here, Cc represents the cluster carbon atom. The Cc···Cc modulation wasachieved merely by modifying the substituents on the carbon of the cluster compound. Thecomplexes studied were synthesized by reaction of the appropriate closo cluster, e.g., 1,2-(SCH3)2-1,2-C2B10H10 with a suspension of K[NC4H4] and anhydrous CoCl2. The newcompounds are closo-[3-Co(5-NC4H4)-1,2-(SCH3)2-1,2-C2B9H9] (5), closo-[3-Co(5-NC4H4)-1,2-(SC6H5)2-1,2-C2B9H9] (6), and closo-[3-Co(5-NC4H4)-1-C6H5-1,2-C2B9H10] (7). Their crystalstructures were elucidated by single-crystal X-ray diffraction and are compared with thoseof the parent compound closo-[3-Co(5-NC4H4)-1,2-C2B9H11] (1) and earlier preparedcompounds closo-[3-Co(5-NC4H4)-1-CH3-2-C4H9-1,2-C2B9H9] (2) and closo-[3-Co(5-NC4H4)-1-C6H5-2-C3H5-1,2-C2B9H9] (3). Purely alkyl substituents alter the Cc···Cc distance of theparent compound very little, which implies that steric effects, although relevant, are notthe major cause of the lengthening. In contrast, substituents with lone pairs alter the Cc···Ccdistance substantially. Computational methods suggest that the cause of the elongation isthe transfer of electron density from the available lone pairs on the substituents to the 
*orbitals on Cc, producing a decrease in the Cc···Cc bond order and, thereby, an increase inthe Cc···Cc distance.
5-NC4H4)-1,2-C2B9H11] (1) display a continuous range of Cc···Cc distancesbetween 1.640(7) for the parent compound and 1.919(6) for closo-[3-Co(5-NC4H4)-1,2-(SCH3)2-1,2-C2B9H9] (5). Here, Cc represents the cluster carbon atom. The Cc···Cc modulation wasachieved merely by modifying the substituents on the carbon of the cluster compound. Thecomplexes studied were synthesized by reaction of the appropriate closo cluster, e.g., 1,2-(SCH3)2-1,2-C2B10H10 with a suspension of K[NC4H4] and anhydrous CoCl2. The newcompounds are closo-[3-Co(5-NC4H4)-1,2-(SCH3)2-1,2-C2B9H9] (5), closo-[3-Co(5-NC4H4)-1,2-(SC6H5)2-1,2-C2B9H9] (6), and closo-[3-Co(5-NC4H4)-1-C6H5-1,2-C2B9H10] (7). Their crystalstructures were elucidated by single-crystal X-ray diffraction and are compared with thoseof the parent compound closo-[3-Co(5-NC4H4)-1,2-C2B9H11] (1) and earlier preparedcompounds closo-[3-Co(5-NC4H4)-1-CH3-2-C4H9-1,2-C2B9H9] (2) and closo-[3-Co(5-NC4H4)-1-C6H5-2-C3H5-1,2-C2B9H9] (3). Purely alkyl substituents alter the Cc···Cc distance of theparent compound very little, which implies that steric effects, although relevant, are notthe major cause of the lengthening. In contrast, substituents with lone pairs alter the Cc···Ccdistance substantially. Computational methods suggest that the cause of the elongation isthe transfer of electron density from the available lone pairs on the substituents to the *orbitals on Cc, producing a decrease in the Cc···Cc bond order and, thereby, an increase inthe Cc···Cc distance.