Coordination properties of N 2S (1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N 2S 2 (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)

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The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane ligand ( bdtp) reacts with [Rh(COD)(THF) 2][BF 4] to give [Rh(COD)( bdtp)][BF 4] ([ 1][BF 4]), 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)][BF 4] ([ 2][BF 4]) and [Rh(CO)( bdtp-κ 3 N, N, S)][BF 4] ([ 3][BF 4]). In solution, [ 2][BF 4] exists as a mixture of two isomers, [Rh(CO) 2( bdtp-κ 2 N, N)] + ([ 2a] +) and [Rh(CO) 2( bdtp-κ 3 N, N, S)] + ([ 2b] +; major isomer) rapidly interconverting on the NMR time scale. At room temperature, [ 2][BF 4] easily loses one molecule of carbon monoxide to give [ 3][BF 4]. The latter is prone to react with carbon monoxide to partially regenerate [ 2][BF 4]. 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][BF 4] to give the dinuclear complexes [Rh 2( bddf)(COD) 2][BF 4] 2 ([ 4][BF 4] 2) and [Rh 2( bddo)(COD) 2][BF 4] 2 ([ 5][BF 4] 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][BF 4] 2 results in loss of the COD ligand and carbonylation to give [Rh 2( bddf)(CO) 4][BF 4] 2 ([ 6][BF 4] 2). The single-crystal X-ray structures of [ 3][CF 3SO 3], [ 5][BF 4] 2 and [ 6][BF 4] 2 are reported.