The reaction of [Li(Ph4P2N4S2R)THF]2 (R - Me, (t)Bu, Ph, CH2PPh2) with the metallocene dihalides MCp2Cl2 (M = Ti, Zr, Hf) in THF products complexes of the type MCp2Cl(Ph4P2N4S2R) in which the Ph4P2N4S2R- anion is bonded to the metal in an eta2-N,S fashion as demonstrated by an X-ray structural determination of ZrCp2Cl( Ph4P2N4S2tBu) (2a). Crystals of 2a are triclinic, space group P1BAR, with a = 12.439(4) angstrom, b = 18.200(5) angstrom, c = 10.370(2) angstrom, alpha = 100.40(2)-degrees, beta = 106.65(2)-degrees, gamma = 72.53(2)-degrees, V = 2136(1) angstrom3, and Z = 2. The final R and R(W) values were 0.054 and 0.061, respectively. The dimensions of the three-membered ZrNS ring are d(Zr-S) = 2.634(2) angstrom, d(Zr-N) = 2.206(5) angstrom, and d(S-N) = 1.697(6) angstrom. The treatment of 2a with electrophiles results in the regiospecific functionalization of the P2N4S2 ring. The reactions of 2a with methyl iodide or bromide produce the unsymmetrical S,S’-diorgano derivative Ph4P2N4(S(t)Bu)(SMe) and the S-bromo derivative Ph4P2N4(StBu)(SBr), respectively. By contrast, the reaction of 2a with 2 molar equiv of HCl gas generates [Ph4P2N4S2tBuH2]Cl (4) in which the two nitrogen atoms, separated by the two-coordinate sulfur in the Ph4P2N4S2tBu- anion have been protonated. Compound 4 was characterized by P-31 and H-1-N-15 HMQC NMR spectra and by X-ray crystallography which revealed that 4 exists as a hydrogen-bonded dimer in the solid state. Crystals of 4 are triclinic, space group P1BAR with a = 12.797(4) angstrom, b = 14.618(3) angstrom, c = 8.276(5) angstrom, alpha = 90.48(3)-degrees, beta = 105.59(3)-degrees, gamma = 81.24(2)-degrees, V = 1473(1) angstrom3, and Z = 2. The final R and R(W) values were 0.045 and 0.033, respectively. An X-ray structural determination of Ph4P2N4(SPh)(SBr) (5b), prepared by bromination of [Li(Ph4P2N4S2Ph)THF]2 Or [ZrCp2Cl(Ph4P2N4S2Ph)], gave an S-Br distance of 2.573(5) angstrom. Crystals of 5b are orthorhombic, space group P2(1)2(1)2(1) with a = 14.534(7) angstrom, b = 17.647(5) angstrom, c = 11.523(5) angstrom, V = 2955(1) angstrom3, and Z = 4. The final R and R(W) values were 0.063 and 0.042, respectively. Surprisingly, the complex 2a does not react with strong nucleophiles such as Li[Et3BH] or methyllithium.