Metal Complexes with Very Large Dipole Moments: the Anionic Carborane Nitriles 12-NC–CB₁₁X₁₁^– (X = H, F, CH₃) as Ligands on Pt(II) and Pd(II)

Abstract

The anionic nitriles 1-R-12-NC-CB11H10(-) (R = H, CH3, I, COOH), 12-NC-1-H-CB11Me10(-), and 12-NC-1-H-CB11F10(-) were prepared, and three of them were examined for complex formation with (Et3P)2Pt(II) and (Et3P)2Pd(II). Several stable internally charge-compensated zwitterionic complexes were obtained and characterized. RI-BP86/SV(P) calculations suggest that their dipole moments exceed 20 D. An attempt to measure the dipole moments in solution failed due to insufficient solubility in solvents of low polarity.

Synthesis, Structural Analysis, and Functional Group Interconversion in the [closo‐B10H8‐1,10‐X2]2– (X = CN, [OCRNMe2]+, OCOR, and [OH2]+) Derivatives

“…For instance, after reaction with LiAlH 4 in boiling THF, 1i[Bu 4 N] was recovered in 63 % from a complex reaction mixture, while in reduction with NaBH 4 –BF 3 · Et 2 O or LiAlH 4 –BF 3 · Et 2 O only inseparable mixtures of products and starting 1i[Bu 4 N] were obtained. The observed resistance to hydrolysis and reduction of the C≡N groups in 1i parallels that reported[15a], for the [ closo ‐1‐CB 11 H 11 ‐12‐CN] – anion and is due to the extensive delocalization of the negative charge from the { closo ‐B 10 } cluster (vide infra).…”

“…The interatomic distances B–C and C≡N in the dinitrile 1i are atypical and the former (avrg 1.566 Å) is longer, while the latter (avrg 1.084 Å) is significantly shorter than those in structurally similar boron cluster nitriles: 1.5420(3) Å and 1.1640(3) in [ closo ‐B 6 H 5 ‐1‐CN] 2– , 1.542(2) Å and 1.157(2) in [ closo ‐B 11 H 10 ‐2‐CN] 2– , and 1.550(3) Å and 1.133(4) in [ closo ‐1‐CB 11 H 11 ‐12‐CN] – . [15a] There is however a report of an unusually short C≡N distance found in [ closo ‐1‐CB 11 HMe 10 ‐12‐CN] – anion (0.99(5) Å) . The B–I distances (avrg 2.178(7) Å) and B–I–C angles (avrg 98.2(3) o ) in 1f are similar to those in other phenyliodonium derivatives of closo ‐boranes .…”

1,12-Diiodo-Ortho-Carborane: A Classic Textbook Example of the Dihalogen Bond

“…In this respect, the synthesis and characterization of the C-halogen derivatives of the carba-closo-dodecaborate anion [1-X-1-CB 11 H 11 ] − (X = F, Cl, Br, I) are described much better [53]. Moreover, the preparation of its 1,12-diiodo derivative [1,12-I 2 -1-CB 11 H 10 ] − , containing iodine atoms in opposite positions of the boron backbone, has recently been described [54]. However, in the case of anionic carboranes, it is rather difficult to find a cation that, on the one hand, will not form additional non-covalent bonds with the anion and, on the other hand, will be small enough not to hinder the formation of intermolecular dihalogen bonds between the anions.…”

Stepwise Introduction of Cyano Groups into nido‐ and closo‐Undecaborate Clusters

“…Boron clusters with cyano groups bonded to one or more B atoms have been described, and different synthetic methods for B cluster −CN‐containing derivatives have been developed . They serve as starting materials for 1) the preparation of boron clusters with other functional groups, 2) cluster Aufbau reactions by insertion of the C atom of the CN group into the boron cage, and 3) as ligands in coordination chemistry . So far, the [3‐NC‐ closo ‐B 11 F 10 ] 2− anion is the only example of a { closo ‐B 11 } cluster with a CN substituent, and { nido ‐B 11 } derivatives are unknown.…”