Rhodium and iridium olefin complexes with bulky cyclopentadienyl and hydrotris(pyrazolyl)borate ligands

The synthesis of a series of rhodium and iridium complexes bearing bulky cyclopentadienyl or hydro(tri-spyrazolyl) borate ligands is described. The rhodium cyclopentadienyl and hydrotris(pyrazolyl) borate diene compounds, [(eta(5)-C5Me4But)Rh(eta(4)-2,3-MeRC4H4] (R = H, 1; Me, 2) and Tp(Ms)Rh(eta(4)-2,3-MeRC4H4) (R = H, 3; Me, 4; Tp(Ms) is hydrotris(3-mesitylpyrazol-1-yl) borate), respectively, have been prepared from the corresponding Rh(I) diene precursors and Zn(C5Me4But)(2) (for 1 and 2), or TlTp(Ms) (for 3 and 4), as effective C5Me4But or Tp(Ms) transfer reagents. In contrast with these results, attempts to obtain a bis(ethylene) derivative of the Tp(tol)Ir(I) unit (Tp(tol) stands for hydrotris(3-p-tolylpyrazol-1-yl) borate) have provided instead the Ir(III) complex [(kappa(4)-N,N',N '',C-Tp(to)l)-Ir(C2H5)(C2H4)] (5), whose formation requires C-H bond activation of a molecule of ethylene and of one of the Tp(tol) p-tolyl substituents. In refluxing toluene 5 experiences metalation of a second p-tolyl substituent to give [(kappa(5)-N,N',N '',C,C ''-Tp(tol))-Ir(C2H4)] (6), which features unusual kappa(5)-Tp(tol) coordination. The latter compound reacts with carbon monoxide to yield the corresponding carbonyl, 7. (C) 2009 Elsevier B. V. All rights reserved.