This paper reports (i) a rational synthesis of heterometallic sulfide clusters with M-S-M’ (M and M’ = Rh, W, and Cu) groups, (ii) structures and bonding of the M-S-M’ groups determined by X-ray crystallographic analysis and IR spectroscopy, and (iii) reactivity of the M-S-M’ groups unique to higher-nuclearity heterometallic sulfide clusters toward H2O and H2S. A branched-type octanuclear sulfide cluster [{Cp*RhP(OEt)(3)(mu-WS4)(CuCl)Cu}(2)(mu-Cl)(2)] (4, Cp* = eta(5)-C(5)Me(5)) was stepwise prepared from the following sequence : [Cp*RhP(OEt)(3)Cl-2] (1, mononuclear) --> [Cp*RhP(OEt)(3)WS4] (2, dinuclear) --> [Cp*RhP(OEt)(3)(mu-WS4)CuCl] (3, linear-type trinuclear) --> 4 by a systematic building-block method. A bridging sulfide ligand in the W-S-Cu group of 4 reacts with a water-saturated CH2Cl2 solution to convert the terminal O atom of [{CP*RhP(OEt)(3)(mu-WOS3)(CuCl)Cu}(2)(mu-Cl)(2)] (5, linked incomplete cubane-type octanuclear) with a drastic structural change in the cluster framework.The transformation reaction of 4 to 5 includes the first example of the conversion of the bridging S atom in the M-S-M’ group into the terminal O atom without releasing the metal atoms, and this reaction is peculiar to the higher-nuclearity heterometallic sulfide cluster 4. Clusters 4, 5, and 6 ([Cp*RhP(OEt)(3)(mu-WOS3)CuCl], butterfly-type trinuclear) react with H2S in CH2Cl2 giving 3 as a major product. The formation of 3 in these reactions are based on the reactivity of M-S-Cu groups in the sulfide clusters toward H2S: the (mu(3)-S)-Cu bonds are easily broken by H2S, but not the (mu(2)-S)-Cu ones. The crystal data for 1, 2, 3, 4, 5, and 6 confirmed by X-ray analysis are as follows. 1: C16H30Cl2O3PRh, orthorhombic, P2(1)cn, a = 8.988(3) Angstrom, b = 28.591(5) Angstrom, c = 8.276(3) Angstrom, Z = 4. 2: C16H30O3PRhS4W, monoclinic, P2(1)/n, a = 14.633(2) Angstrom, b = 15.191(2) Angstrom, c = 11.490(1) Angstrom, beta = 104.97(1)degrees, Z = 4. 3: C16H30ClCuO3PRhS4W, monoclinic, P2(1)/m, a = 10.221(2) Angstrom, b = 11.943(2) Angstrom, c = 10.809(1) Angstrom, beta = 94.40(1)degrees, Z = 2. 4: C32H60Cl4Cu4O6P2Rh2S8W2, monoclinic, P2(1)/n, a = 10.170(3) Angstrom, b = 14.495(3) Angstrom, c = 19.411(3) Angstrom, beta = 104.42(1)degrees, Z = 2. 5 . 2DMF: C38H74Cl4Cu4N2O10P2Rh2S6W2, monoclinic, P2(1)/c, a = 10.011(3) Angstrom, b = 17.115(3) Angstrom, c = 18.678(3) Angstrom, beta = 95.10(2)degrees, Z = 2. 6: C16H30ClCuO4PRhS3W,orthorhombic, P2(1)nb, a = 14.515(2) Angstrom, b = 17.225(3) Angstrom, c = 10.261(3) Angstrom, Z = 4.