. Can. J. Chem. 54, 2697Chem. 54, (1976. A series of complexes [LM(C0)3X] (L = +zP(R2pz)3-z, RZPZ = pyrazolyl, or 3,5-dimethylpyrazolyl, x = 0-2; M = Mn, X = C1; M = Re, X = Br) and [(+2P(S)(R2pz))Re(CO), Br] were prepared by the reaction of the appropriate ligand with [M(CO),X] or [M(CO),X],, and were characterized by elemental analysis, solution molecular weight, and infrared, mass, and nmr spectroscopic data. The products are formed via tetracarbonyl intermediates, of which the phosphorus bonded derivative [(+2P(pz))Re(CO),Br] was isolated and characterized. The tricarbonyl complexes [LM(C0)3X] and [(+2P(S)(R2pz))Re(CO)3Br] adopt a cis-octahedral configuration, in which the ligands form four-, five-, or six-membered chelate structures, via (i) the P atom and the 2-N site of the pyrazolyl moiety, with +2P(R2p~)r (ii) the sulphur and 2-N atoms, with +2P(S)(R2pz), (iii) the 2-N atoms of two pyrazolyl rings, with + P ( R ,~Z )~, and (iv) the 2-N atoms of three pyrazolyl rings, resulting in a bicyclic system, with P(R2pz)3.The reactions of [CH3Re(CO)5] with +zP(R2pz)3-z require forcing conditions, resulting in the simultaneous elimination of carbon monoxide and methane, and yielding a variety of products, including tetracarbonyl, tricarbonyl, and ring-metalated species.