Equimolar quantities of [MoX(Y)(CO)(NCMe)(η²-RC₂R)₂] and L [= PhP(CH₂CH₂PPh₂)₂] reacted in CH₂Cl₂ at room temperature to give the cationic tridentate linear triphos complexes [MoX(CO)(L-P,P′,P″)(η²-RC₂R)]Y 1–5 (X = Y = Br, R = Me or Ph; X = Cl, Y = I, R = Me or Ph; X = Br, Y = I, R = Me) in high yield. Refluxing the tungsten complexes [WX₂(CO)(L-P,P′)(η²-RC₂R′)] in dry acetonitrile afforded the cationic complexes, [WX(CO)(L-P,P′,P″)(η²-RC₂R′)]X 6–8 (X = Br or I, R = R′ = Me; X = I, R = Me, R′ = Ph), whereas refluxing [WI₂(CO)(L-P,P′)(η²-MeC₂Me)] in slightly wet acetonitrile yielded the unusual crystallographically characterised complex [WI(CO)(L-P,P′,P″)(η²-MeC₂Me)]₂[W₆O₁₉] 9. Silver tetrafluoroborate reacted with an equimolar amount of [MI₂(CO)(L-P,P′)(η²-RC₂R′)] in acetonitrile to give the cationic complexes [MI(CO)(L-P,P′,P″)(η²-RC₂R′)][BF₄] 10–13 (M = Mo, R = R′ = Me or Ph; M = W, R = R′ = Me, R = Me, R′ = Ph). The tetraphenylborate complexes [WI(CO)(L-P,P′,P″)(η²-RC₂R′)][BPh₄] (R = R′ = Me 14, R = Me, R′ = Ph 15) were prepared by an iodide exchange reaction of [WI(CO)(L-P,P′,P″)(η²-RC₂R′)]I with Na[BPh₄] in acetonitrile. The crystal structure for 14 has been determined. The dicationic complexes [W(CO)(NCMe)(L-P,P′,P″)(η²-RC₂R′)][BF₄]₂ 16–18 (R = R′ = Me or Ph; R = Me, R′ = Ph) were prepared by treating [WI₂(CO)(L-P,P′)(η²-RC₂R′)] with 2 equivalents of Ag[BF₄] in acetonitrile. The cationic bromomolybdenum complexes [MoBr(CO)(L-P,P′,P″)(η²-RC₂R)]Br (R = Me or Ph) rearrange in refluxing CHCl₃ in air to give the unusual molybdenum(IV) product [MoBr₂(O){Ph₂P(CH₂)₂PPh(CH₂)₂POPh₂-P,P′,O}] 19, which has been crystallographically characterised.