A new cluster benzyl, Re₃Cl₃(CH₂Ph)₆, and tertiary phosphine (L) adducts of the corresponding cyclohexyl, Re₃Cl₃(C₆H₁₁)₆L₃, and of the permethyl, Re₃Me₃L_2,3, have been prepared. The structure of the diethylphenylphosphine derivative Re₃Me₉(PEt₂Ph)₂ has been confirmed by a single-crystal X-ray structure determination. Crystals are monoclinic, space group C2/c, with dimensions a= 27.220(4), b= 9.817(1), c= 26.051(5)Å, and β= 102.65(2)° and the structure was solved by direct methods and refined by least squares to an R of 0.043 using 4 982 unique observed intensities. The Re₃Me₉ unit present in the trinuclear molecule is considerably distorted as a result of steric compression from the two strongly bound phosphines. The trinuclear rhenium(III) phosphine adducts undergo cleavage reactions to give dimeric compounds of rhenium(III) or rhenium(II), examples being Re₂Me₆(PMe₂Ph)₂ and Re₂Cl₂(CH₂SiMe₃)₂(PMe₃)₄. The reactions of the blue trimethylsilylmethyl cluster Re₃Cl₃(CH₂SiMe₃)₆ with CO, NO, and HCl are described. Nitric oxide is shown to give an insertion product with an N-(trimethylsilylmethyl)-N-nitrosohydroxylaminato-chelate ring, of formula Re₃Cl₃(CH₂SiMe₃)₅{ON(CH₂SiMe₃)-NO} whose structure has also been confirmed by X-ray structure determination. Crystals are monoclinic, space group P2₁/a, with a= 33.33(4), b= 11.733(5), c= 11.947(6)Å, and β= 92.93(4)°. The structure was solved by direct methods and refined by least squares to an R of 0.067 using 4 360 observed data. The nitrosohydroxylaminato-ligand chelates symmetrically (Re-O 2.10 Å× 2) to one of the metal atoms, using one out-of-plane and the in-plane terminal sites.