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Substitution reactions at boron atoms in metallacarboranes

“…of bromine in CCl 4 produces two isomeric monobromides, viz., 3-Br-1-Cp-1,2,4-CoC 2 B 8 H 9 (170) and 6-Br-1-Cp-1,2,4-CoC 2 B 8 H 9 (171), in a ratio of 1 : 10. 143 The reaction of complex 169 with N-bromosuccinimide also gives rise to a mixture of monobromides 170 and 171, but in much lower yields.…”

“…However, the percentage of 173 (according to the 11 B NMR spectroscopic data) was no higher than 10%. 143 Evidently, the introduction of the methyl substituent at the C(4) atom hinders the rearrangement of the substitution product.…”

“…Derivatives containing the bromine atom at position 3 of the cobaltacarborane moiety were not found. 143 The chloromercury derivative 6-HgCl-1-Cp-1,2,4-CoC 2 B 8 H 9 (176) was synthesised by mercuration of complex 169 with mercury trifluoroacetate followed by treatment of the resulting complex with NaCl. The structure of compound 176 was established by X-ray diffraction analysis.…”

“…The reaction of compound 176 with bromine in dichloromethane at room temperature affords monobromide 171. 143…”

New 11-vertex osmacarborane 1,1-(PPh3)2-1-H-3-O(CH2)4-isonido-1,2,4-OsC2B8H9

“…The downfi eld signal at δ = 62.5 belongs to the boron atom possessing a low intercluster coordination number, which is the distinguishing feature of well-known 11-vertex isonidoclusters containing {C 2 B 8 } carborane ligands. [17][18][19][20][21][22][23][24][25] In the 11 В{ 1 H} and 11 B NMR spectra of complex 3, such a signal appears as the singlet, indicating the presence of a substituent at this boron atom, which usually occupies the B(3) position in the {M-C 2 B 8 } metallacarborane moiety. Two slightly broadened singlets at δ = 2.68 and 1.42 with the intensity of 1 H each in the 1 H NMR spectrum of complex 3 correspond to hydrogen atoms of the cluster CH groups.…”