The reaction of the complexes [Pt(C boolean AND P)(S2C-R)] (C boolean AND P = CH2-C6H4-P(o-tolyl)(2)-kappa C,P,R = NMe2, OEt) with an equimolar amount of HgX2 (X = Cl, Br) gives the tetranuclear derivatives [Pt(C boolean AND P)(S2C-R)HgX(mu-X)](2) [R = NMe2, X = Br (3), I (4); R = OEt, X = Br (5), I (6)] containing Pt-->Hg donor-acceptor bonds. The reaction of [Pd(C boolean AND P)(S2CNMe2)] with HgI2 affords the complex [Pd(C boolean AND P)(S2CNMe2)HgI(mu-I)](2) (9) similar to the complexes 3-6; by contrast the reaction of [Pd(C boolean AND P)(S2C-R)] (R = NMe2, OEt2) with HgBr2 leads to the corresponding dinuclear complexes [PdBr(S2C-R)(mu-C boolean AND P)HgBr] [R = NMe2 (10), OEt (11)] with the didentate C boolean AND P cyclometalating ligand, -CH2-C6H4-P(o-tolyl)(2)-C,P (resulting from the C-H activation of the P(o-tolyl)(3)) acting in an unprecedented bridging mode. Compound 4 (C24H26HgI2NPPtS2) crystallizes in the triclinic system, space group P (1) over bar : a = 9.5755(11) Angstrom, b = 11.1754(12) Angstrom, c = 14.501(2) Angstrom, alpha = 84.826(5)degrees, beta = 81.611(7)degrees, gamma = 68.606(9)degrees, V = 1428.5(3) Angstrom(3), and Z = 1. Compound 11.0.5 HgBr2 . C2H4Cl2 (C24H25Br2HgOPPdS2 . 0.5 HgBr2 . C2H4Cl2) crystallizes in the monoclinic system, space group P2(1)/c : a 15.571(2) Angstrom, b = 10.7425(10) Angstrom, c = 19.655(2) Angstrom, beta = 94.741(12)degrees, V = 3276.5(5) Angstrom(3), and Z = 4.