The reaction of Cp*MCl(3) (M = Zr, Hf) with Na-2[Ph(4)P(2)N(4)S(2)] in THF produces the complexes Na[Cp*MCl(2)(Ph(4)P(2)N(4)S(2))] (3a, M = Hf; 3b, M = Zr), which were characterized by Na-23 and P-31 NMR spectroscopy and by the preparation of the protonated derivatives ({Cp*MC12(Ph(4)P(2)N(3)(NH)S-2)}(2) (4a, M = Hf; 4b, M Zr). Complex 4a was shown by X-ray crystallography to be a hydrogen-bonded dimer in which the P2N4S2 ring is bonded to the metal in a tetradentate (eta(4)-N,N’,S,S’) fashion and the proton is attached to nitrogen. The Hf-N bond lengths in 4a are 2.227(10) and 2.241(8) Angstrom and the Hf-S distances are 2.859(3) and 2.911(3) Angstrom. Crystals of 4a are monoclinic, space group P2(1)/n, with a = 11.046(2) a, b = 18.962(4) Angstrom, c 17.548(3) Angstrom, beta 99.55(2)degrees, V = 3624(1) Angstrom(3) and Z = 4. The final R and R(w) values were 0.039 and 0.033, respectively. The methylation of 3a or 3b with methyl triflate or methyl iodide generates the S-methylated derivatives Cp*MCl(2)[Ph(2)P(2)N(4)S(SMe)] (6a, M = Hf; 6b, M = Zr) via the corresponding N-methylated isomers. Complexes 6a and 6b are more conveniently prepared in >90% yields from Cp*MCl(3) and {Li[Ph(4)P(2)N(4)S(SMe)]}(2). An X-ray structural determination shows that the Ph(4)P(2)N(4)S(SMe)- ligand in 6b adopts a tetradentate (eta(4)-N,N’,S,S’) bonding mode. Crystals of 6b are orthorhombic, space group P2(1)2(1)2(1), with a = 19.255(4) Angstrom, b = 22.839(3) Angstrom, c = 8.296(3) Angstrom, V = 3648(1) Angstrom(3), and Z = 4. The final R and R(w) values were 0.071 and 0.072, respectively. The reaction of 6b with an excess of Me(3)P, followed by hydrolysis, yields the open- chain compound [Me(3)PNPPh(2)NS MeNPPh(2)NH(2)]Cl (8) which was characterized by H-1 and P-31 NMR spectroscopy and by X-ray crystallography. Crystals of 8 are triclinic, space group P (1) over bar; with a = 10.551(3) Angstrom, b = 16.572(3) Angstrom, c = 9.878(2) Angstrom, alpha = 99.90(2)degrees, beta = 105.59(2)degrees, gamma = 104.70(2)alpha, V = 1555.0(8) Angstrom(3), and Z = 2. The final R and R(w) values were 0.045 and 0.025, respectively.