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

Abstract

The synthesis of a series of rhodium and iridium complexes bearing bulky cyclopentadienyl or hydro(trispyrazolyl)borate ligands is described. The rhodium cyclopentadienyl and hydrotris(pyrazolyl)borate diene compounds, [(η 5-C 5Me 4Bu t )Rh(η 4-2,3-MeRC 4H 4] (R = H, 1; Me, 2) and Tp MsRh(η 4-2,3-MeRC 4H 4) (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(C 5Me 4Bu t ) 2 (for 1 and 2), or TlTp Ms (for 3 and 4), as effective C 5Me 4Bu t or Tp Ms transfer reagents. In contrast with these results, attempts to obtain a bis(ethylene) derivative of the Tp tolIr(I) unit (Tp tol stands for hydrotris(3- p-tolylpyrazol-1-yl)borate) have provided instead the Ir(III) complex [(κ 4 - N, N′, N″, C-Tp tol)-Ir(C 2H 5)(C 2H 4)] ( 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 [(κ 5-N , N′, N″, C,C′-Tp tol)-Ir(C 2H 4)] ( 6), which features unusual κ 5-Tp tol coordination. The latter compound reacts with carbon monoxide to yield the corresponding carbonyl, 7.