Late-Metal Diphosphinosulfinyl S(O)P2 Pincer-type Complexes

The preparation of a new tridentate diphosphinosulfinyl ligand is described as well as the synthesis and properties of some of its Rh, Ir, Ni, Pd, and Pt complexes. The ligand binds in a kappa(3)-PS(O)P fashion in all cases. The M-S lengths in (SOP2)RhCl and (SOP2)IrCl (2.1340(8) and 2.1341(5) angstrom, respectively) are the shortest of all crystallographically characterized Rh- and Ir-S(O)R-2 complexes, which illustrates the significant M-S(O) pi-backbonding for these metals. Akin to Vaska's complex, (SOP2)IrCl binds O-2 to yield a peroxide complex with an O-O length of 1.465(3) angstrom and nu((O-O)) = 847 cm(-1). The C-O stretches of (SOP2)M(CO) (M = Ni, Pd, Pt) are similar to 30-40 cm(-1) higher than those of the analogous (PPh3)(3)M(CO). A number of divalent group 10 complexes of the form [(SOP2)MX](+) for Ni (X = Cl), Pd (X = Cl, Me), and Pt (X = Cl, Me) are reported, as well as the highly electrophilic complex [(SOP2)Pd(NCCH3)](2+). An analysis of the S-O length as a function of the M-S length for all d(8) SOP2 Rh, Ir, Pd, and Pt complexes reveals that the electron-withdrawing capabilities of the sulfinyl group are mediated largely through pi-backbonding for Rh and Ir and mostly through poor sigma-donation for Pd and Pt.