Coordination properties of N2S (1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N2S2 (1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane or 1,2-bis[3-(3,5-dirnethy1-1-pyrazolyl)-2-thiapropyl]benzene) donor ligands toward Rh(I)

The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapeiitane ligand (bdtp) reacts with [Rh(COD)(THF)(2)][BF4] to give [Rh(COD)(bdtp)]-[BF4] ([1][BF4]), which is fluxional in solution on the NMR time scale. Its further treatment with carbon monoxide leads to a displacement of the 1,5-cyclooctadiene ligand, generating a mixture of two complexes, namely, [Rh(CO)(2)(bdtp)][BF4] ([2][BF4]) and [Rh(CO)(bdtp-kappa(3)N,N,S)][BF4] ([3][BF4]). In solution, [2][BF4] exists as a mixture of two isomers, [Rh(CO)(2)(bdtp-kappa(2)N,N)](+) ([2a](+)) and [Rh(CO)(2)(bdtp-kappa(3)N,N,S)](+) ([2b](+); major isomer rapidly interconverting on the NMR time scale. At room temperature, [2][BF4] easily loses one molecule of carbon monoxide to give [3][BF4]. The latter is prone to react with carbon monoxide to partially regenerate [2][BF4]. The ligands 1,2-bis [3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl] benzene (bddf) and 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) are seen to react with two equivalents of [Rh(COD)(THF)21[BF4] to give the dinuclear complexes [Rh-2(bddf)(COD)(2)][BF4](2) ([4][BF4](2)) and [Rh-2(bddo)(COD)(2)][BF4](2) ([5][BF4](2)), respectively. In such complexes, the ligand acts as a double pincer holding two rhodium atoms through a chelation involving S and N donor atoms. Babbling carbon monoxide into a solution of [4][BF4](2) results in loss of the COD ligand and carbonylation to give [Rh-2(bddf)(CO)(4)][BF4](2) ([6][BF4](2)). The single-crystal X-ray structures of [3][CF3SO3], [5][BF4](2) and [6][BF4](2) are reported. (C) 2004 Elsevier B.V. All rights reserved.