THE ALPHA-SULFINYL LIGAND-TRANSITION METAL BOND .2. ALPHA-SULFINYL-PALLADIUM(II) COMPLEXES AND THEIR REACTIVITY IN INSERTION REACTIONS

The deprotonation of ArSOCH3 (Ar = C6H5, 1; p-MeC6H4,2) with KH in THF, followed by reaction with cis-[(PPh3)2PdCl2], led to the Pd-C-bonded alpha-sulfinyl complexes trans-[(PPh3)2(Cl)PdCH2SOAr] (Ar = C6H5, 3; Ar = p-MeC6H4, 4). As expected, the ''CH2'' unit appears as an AB part of an ABX2 system (the two heterotopic protons being coupled with both P atoms). The structure of 3 was confirmed by X-ray analysis. The reaction of 3 and 4 with Bu(t)NC afforded complexes [(PPh3)(Bu(t)NC)(Cl)PdC(NBu(t))C(HNBu(t))=CHSOAr] (Ar = C6H5, 5; Ar = p-MeC6H4, 6) via the replacement of PPh3 by Bu(t)NC and insertion of two molecules of the isocyanide into the Pd-C bond. The organic fragment resulting from the insertion of Bu(t)NC was isolated in the beta-enamino sulfoxide form and confirmed by an X-ray analysis on 5. The ionization of the Pd-Cl bond in 3 and 4 in MeCN led to the corresponding solvated cationic forms cis-[(PPh3)2(MeCN)PdCH2SOAr] (Ar = C6H5, 10; Ar = p-MeC6H4, 11). The attempt to dehydrohalogenate 3 with the Wittig reagent Ph3P-CH2 led rather to the isolation of a zwitterionic complex where one of the PPh3 groups had been replaced by Ph3PCH2, [(Cl)(PPh3)(CH2PPh3)(CH2SOPh)Pd], 12, containing two different alpha-functionalized carbanions bonded to Pd(II). Crystallographic details: 3 is triclinic, space group P1BAR, a = 12.517(2) angstrom, b = 16.153(2) angstrom, c = 12.420(2) angstrom, alpha = 104.16(2)degrees, beta = 119.40(2)degrees, gamma = 92.60(2)degrees, Z = 2, and R = 0.046; 5 is monoclinic, space group C2/c, a = 43.577(4) angstrom, b = 9.214(l) angstrom, c = 20.752(2) angstrom, alpha = gamma = 90-degrees, beta = 101.20(l)degrees, Z = 8, and R = 0.037; 10 is triclinic, space group P1BAR, a = 15.111 (1) angstrom, b = 12.873(1) angstrom, c = 12.332(1) angstrom, alpha = 99.89(l)degrees, beta = 101.44(1)degrees, gamma = 98.08(1)degrees, Z = 2, and R = 0.049; 12 is triclinic, space group P1BAR, a = 11.897(1) angstrom, b = 14.891(2) angstrom, c = 11.357(1) angstrom, alpha = 104.24(1)degrees, beta = 98.49(l)degrees, gamma = 96.87(l)degrees, Z = 2, and R = 0.025.