The reaction of metallophosphanides with MLnX leads to the formation of mixed-metal clusters via complexes that consist of a metallophosphine coordinated through the lone pair on the phosphorus atom to another metal fragment. This synthetic strategy has been employed to initially form trinuclear complexes with the general formula [(Ph2PMLn)( (OC)(2)Co(mu-DMAD) Mo(CO)(2)Cp] (MLn = Mn(CO)(5) 3, WCp(CO)(2) 4, FeCp(CO)(2) 5; DMAD = dimethylacetylenedicarboxylate) from the reaction of the anion [(Ph2P)(OC)(2)Co(mu-DMAD) Mo(CO)(2)Cp](-), 2, with metal halide complexes, MLnX (X = Cl, Br). The complexes 3, 4 and 5 have been characterised spectroscopically, and an X-ray crystal structure of 5 shows that the Ph2PFe(CO)(2)Cp unit has coordinated to the cobalt centre through the lone pair on the phosphorus centre. Subsequent heating of 3 leads to carbonyl loss, and metal - metal bond formation, to yield [(OC)(6)CpCoMnMo(mu-CO)(mu-PPh2)(mu(3)-eta(2)(//)- DMAD)], 6. An X-ray structure determination of 6 confirms that it contains a 'closed' metal triangle. In a related series of reactions the cluster anion [Os-3(CO)(10)(mu-PPh2)](-) was treated with a variety of metal-containing synthons, MLnX. With [FeCp(CO)(2)Cl] the cluster [Os-3(CO)(10)FeCp(CO)(mu-PPh2)( (mu-CO)] 9 was obtained in good yield, and has been shown crystallographically to consist of an osmium triangle 'spiked' by an iron atom, with the Os-Fe bond bridged by the PPh2 group and a carbonyl ligand. With [(Ph3P) MCl] (M = Ag, Au) the tetranuclear 'butterfly' clusters [Os-3(CO)(10)(mu-PPh2)(mu-MPR3)] (10: M = Au, R = Ph; 11: M = Ag, R = Me) are obtained. These two complexes have been characterised spectroscopically and crystallographically.