Sulfide complexes geometries

The square-planar Ir1 thiolate complex (391) has been prepared by the reaction of Pr(NO)Cl2(PPh3)2] with NaSmes (mes = C6H2Me3-2,4,6).635 reaction of (391) with propylene sulfide affords the Ir111 complex (392), as shown in Reaction Scheme 42. The X-ray structure of (392) confirms the square-pyramidal geometry of the Ir center and the bent nature of the Ir—N=0 linkage. 

There are several possible tests for this assumed tetrahedral geometry. The geometry of ethylene oxide has been determined (71). The observed values of a and f3 of 47.8° and 68.6° compared with the calculated values of 59.2° and 60.4° indicate that the model predicts excessive bending back. In the molecule ethylene sulfide, the ring shape more closely resembles an olefin complex. The observed values of a and /3 of 56.6° and 61.7° (17) are closer to the calculated values of 65.8° and 57.1°, but again the model predicts excessive bending back. 

Soluble mixed-chalcogenido Nb/Se/E complexes (E = S, O) have been reported. The differences in structures and coordination geometries between sulfides and selenides as ligands for Nb have been attributed to their redox properties as well as to size. The presence of terminal Se-H ligands in the metal coordination sphere might be due to the need to avoid accumulation of excessive negative charge around the Nb(Se)3L2 units (L = SH, SeH, OMe). 

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