Formation of intramolecular rings in ferramonocarbollide complexes

Article abstract of DOI:10.1021/ic800780w

Addition of PPh₂Cl and Tl[PF₆] to CH ₂Cl₂ solutions of [N(PPh₃)₂][6,6,6- (CO)₃-closo-6,1-FeCB₈H₉] (1) affords the isomeric B-substituted species [6,6,6-(CO)₃-n-(PHPh ₂)-closo-6,1-FeCB₈H₈] [n = 7 (2a) or 10 (2b)]. Deprotonation (NaH) of the phosphine ligand in 2a, with subsequent addition of [IrCl(CO)(PPh₃)₂] and TI[PF₆], yields the neutral, zwitterionic complex [6,6,6-(CO)₃-4,7-μ-{Ir(H)(CO) (PPh₃)₂PPh₂}-closo-6,1-FeCB₈H ₇] (3), which contains a B-P-Ir-B ring. Alternatively, deprotonation using NEt₃, followed by addition of HC≡CCH₂Br, affords [6,6,6-(CO)₃-7-(PPh₂C≡CMe)-closo-6,1- FeCB₈H₈] (4). Addition of [Co₂(CO)₈] to CH₂Cl₂ solutions of the latter gives [6,6,6-(CO) ₃-7-(PPh₂-{(μ-η²:η²- C≡CMe)Co₂(CO)₆})-closo-6,1-FeCB₈H ₈] (5), which contains a {C₂Co₂} tetrahedron. In the absence of added substrates, deprotonation of the PHPh₂ group in compounds 2, followed by reaction of the resulting anions with CH ₂Cl₂ solvent, affords [6,6,6-(CO)₃-n-(PPh ₂CH₂Cl)-closo-6,1-FeCB₈H₈] [n = 7 (6a) or 10 (6b)] plus [6,6-(CO)₂-6,7-μ-{PPh₂CH ₂PPh₂}-closo-6,1-FeCB₈H₈] (7, formed from 2a), of which the latter species possesses an intramolecular B-P-C-P-Fe ring. Addition of Me₃NO to CH₂Cl₂ solutions of 2a causes loss of an Fe-bound CO ligand and formation of [6,6-(CO) ₂-6,7-μ-{NMe₂CH₂PPh₂}-closo-6,1- FeCB₈H₈] (8), which incorporates a B-P-C-N-Fe ring. A similar reaction in the presence of ligands L yields [6,6-(CO) ₂-6-L-7-(PPh₂CH₂Cl)-closo-6,1-FeCB ₈H₈] [L = PEt₃ (9) or CNBu^t (10)], in addition to 8.