Syntheses and crystal structures of mononuclear rhodium hydrido complexes from the reactions of [Rh(H)2(PPh3)2(EtOH)2]ClO4 with various nitrogen ligands

Reactions of the Rh hydrido complex [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) with nitrogen ligands such as 2-(4-thiazolyl)benzimidazole (tbz), pyridazine (pdz), imidazole (im) and pyrimidine (pmd) in CH2Cl2 afforded various mononuclear Rh hydrido complexes, [Rh(H)2(PPh3)2(tbz)]ClO4 (2), [Rh(H)2(PPh3)2(pdz)2]ClO4·2CH2Cl2 (3), [Rh(H)Cl(PPh3)2(pdz)2]ClO4·CH2Cl2 (4), [Rh(H)2(PPh3)2(im)2]ClO4·2CH2Cl2 (5), [Rh(H)Cl(PPh3)2(im)2]ClO4·CH2Cl2 (6), [Rh(H)2(PPh3)2(pmd)2]ClO4·CH2Cl2 (7) and the Rh non-hydrido complex [RhCl2(pmd)4]ClO4 (8). The Rh complexes 2, 3, 5 and 6 were crystallographically characterized. The formation process was monitored by 1H NMR and UV–Vis spectra. In all the Rh hydrido complexes, the Rh atom is coordinated by two PPh3 ligands in trans-positions and two nitrogen ligands in the cis-positions. The remaining sites are occupied by one or two hydride atoms to form a saturated 18-electron framework in a slightly distorted octahedral geometry. For complex 2 an appreciable inter-molecular π interaction is observed between planes of tbz and PPh3 ligands, while an intra-molecular hydrogen bonding interaction between C&z.sbnd;H and Cl atoms is found in complex 6. [Copyright &y& Elsevier]