Reaction of the dimetal complexes [MPt{µ-C(OMe)Ph}(CO)₅(PMe₃)₂] with [OMe₃][BF₄] followed by addition of Li[C₆H₄Me-4] or Na[OEt] afforded the compounds [MPt{µ-C(Ph)R}(CO)₅(PMe₃)₂](M = Cr, R = C₆H₄Me-4 or OEt; M = W, R = OEt). Treatment of the compounds [MPt{µ-C(OMe)R}(CO)₄(PMe₃)₃](M = Cr, R = Ph; M = W, R = C₆H₄Me-4) with [OMe₃][BF₄] allowed isolation and characterization of the salts [CrPt(µ-CPh)-(CO)₄(PMe₃)₃][BF₄] and [PtW(µ-CC₆H₄Me-4)(CO)₄(PMe₃)₃][BF₄] respectively. Reaction of [CrPt(µ-CPh)-(CO)₄(PMe₃)₃][BF₄] with Na[OMe] gave the alkylidene-bridged compound [CrPt{µ-C(CO₂Me)Ph}(CO)_4–(PMe₃)₃], the strucure of which was established by X-ray diffraction. Crystals are monoclinic, space group A2/a, Z= 8, in a unit cell with lattice parameters a= 18.27(3), b= 9.84(1), c= 31.93(5)Å, β= 106.2(1)°. The structure has been refined to R 0.12 (R′ 0.12) for 2 292 independent absorption corrected intensities to 2.9 ⩽ 2θ⩽ 50°(Mo-K_αX-radiation) collected at room temperature. The chromium–platinum bond [2.646(7)Å] is bridged by the µ-C(CO₂Me)Ph group [C–Pt 1.98(3), C–Cr 2.27(4)Å]. One of the CO ligands is semi-bridging to the platinum [Cr–C–O 157(3)°]. Related platinum–tungsten compounds [PtW{µ-C(CO₂R)Ph}(CO)₄(PMe₃)₃](R = Me or Et) have also been prepared. The platinum–manganese and –rhenium compounds [MPt(µ-CC₆H₄Me-4)(CO)₂(PR₃)₂(η-C₅H₅)][BF₄](M = Mn, PR₃= PMe₃; M = Re, PR₃= PMe₃ or PMe₂Ph) have been synthesized and an X-ray diffraction study made on the manganese compound which crystallises with a molecule of CH₂Cl₂ per molecule of complex in the asymmetric unit. Crystals are monoclinic, space group P2₁/c, Z= 4, in a unit cell of dimensions a= 10.434(4), b= 19.334(7), c= 14.901(7)Å, and β= 94.42(4)°. The structure has been refined to R 0.044 (R′ 0.046) for 4 223 independent reflections to 2.9 ⩽ 2θ⩽ 55°(Mo-K_αX-radiation) collected at 300 K. In the cation the manganese–platinum bond [2.628(1)Å] is bridged by the CC₆H₄Me-4 group [C–Pt 1.968(8), C–Mn 1.829(8)Å] forming a dimetallacyclopropene ring, the C–Mn separation being indicative of a double bond. The ¹H, ³¹P, and ¹³C (¹H decoupled) n.m.r. spectra of the new compounds are reported and discussed.