Synthesis and characterization of mixed-ligand oxorhenium complexes with the SNN type of ligand. Isolation of a novel ReO[SN][S][S] complex

A new series of mixed-ligand oxorhenium complexes 4-9, with ligands 1-3 (L1 H(2)) containing the SNN donor set and monodentate thiols as coligands (L2H ), is reported. All complexes were synthesized using ReOCl3(PPh3)(2) as pre cursor. They were isolated as crystalline products and characterized by ele mental analysis and IR and NMR spectroscopy. The ligands 1 and 2 (general f ormula RCH2CH2NHCH2CH2SH, where R = N(C2H5)(2) in 1 and pyrrolidin-1-yl in 2) act as tridentate SNN chelates to the ReO3+ core, leaving one open coord ination site cis to the oxo group. The fourth coordination site is occupied by a monodentate aromatic thiol which acts as a coligand. Thus, three new "3+1" [SNN][S] oxorhenium complexes 4-6 (general formula ReO[RCH2CH2NCH2CH2 S][SX], where R = N(C2H5)(2) and X = phenyl in 4, R = N(C2H5)(2) and X = p- methylphenyl in 5, and R = pyrrolidinlyl and X = p-methylphenyl in 6) were prepared in high yield. Complex 4 adopts an almost perfect square pyramidal geometry (tau = 0.07), while 6 forms a distorted square pyramidal geometry (tau = 0.24). In both complexes 4 and 6, the basal plane is formed by the SNN donor set of the tridentate ligand and the S of the monodentate thiol. On the other hand, the ligand 3, [(CH3)(2)CH](2)NCH2CH2NHCH2CH2SH, acts as a bidentate ligand, probably due to steric hindrance, and it coordinates to the ReO3+ core through the SN atoms, leaving two open coordination sites c is to the oxo group. These two vacant positions are occupied by two molecul es of the monodentate thiol coligand, producing a novel type of "2+1+1" [SN ][S][S] oxorhenium mixed-ligand complexes 7-9 (general formula ReO[[(CH3)(2 )CH](2)NCH2CH2NHCH2CH2S][SX][SX], where X = phenyl in 7, p-methylphenyl in 8, and benzyl in 9). The coordination sphere about rhenium in 7 and 8 consi sts of the SN donor set of ligand 3, two sulfurs of the two monodentate thi ols, and the doubly bonded oxygen atom in a trigonally distorted square pyr amidal geometry (tau = 0.44 and 0.45 for 7 and 8, respectively). Detailed N MR assignments were determined for complexes 5 and 8.