Synthesis and reactivity of the rhodium monocarbollide complexes [1-NHCMe 2-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10] and [1-NH 3-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10

Abstract

The carborane 7-NHCMe 2- nido-7-CB 10H 12 reacts with [RhCl(PPh 3) 3] in toluene at reflux temperatures to give the charge-compensated 16-electron Rh(III) complex [1-NHCMe 2-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10] ( 1) in good yield. The structure of this product was established by X-ray diffraction (XRD). Upon methanolysis 1 affords [1-NH 3-2-Cl-2-PPh 3- closo-2,1-RhCB 10H 10] ( 2), also a 16-electron charge-compensated Rh(III) complex. Some reactions of 2 were investigated. At room temperature, in the presence of Na 2CO 3, it reacts with acetic, methacrylic, and crotonic anhydrides to give the complexes [1,2-μ-{NHC(R)O}-2-PPh 3- closo-2,1-RhCB 10H 10] [R=Me ( 3), CMeCH 2 ( 4a), and ( E)-CHCHMe ( 4b)], respectively. Benzoyl bromide with 2 and Na 2CO 3 yields [1,2-μ-{NHC(Ph)O}-2-PPh 3- closo-2,1-RhCB 10H 10] ( 5). An XRD study of 4a established that the acyl group is coordinated to the rhodium through the oxygen. In the crystal molecules lie pair-wise linked by a BH⇀Rh bridge so that in one molecule the rhodium atom has a 16-electron valence shell and in the other an 18-electron configuration. However, in solution NMR studies reveal that only monomeric molecules occur. With CNBu t in the presence of Na 2CO 3, compound 2 affords [1-NH 2-2,2-(CNBu t ) 2-2-PPh 3- closo-2,1-RhCB 10H 10] ( 7), the structure of which was determined by XRD. The NMR parameters of the new compounds are reported and discussed.