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-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene) donor ligands toward Rh(I)

The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane 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-κ3N,N,S)][BF4] ([3][BF4]). In solution, [2][BF4] exists as a mixture of two isomers, [Rh(CO)2(bdtp-κ2N,N)]+ ([2a]+) and [Rh(CO)2(bdtp-κ3N,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)2][BF4] to give the dinuclear complexes [Rh2(bddf)(COD)2][BF4]2 ([4][BF4]2) and [Rh2(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. Bubbling carbon monoxide into a solution of [4][BF4]2 results in loss of the COD ligand and carbonylation to give [Rh2(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.