The complex [Rh(CO)₂{HC(pz′)₃}][PF₆], 1⁺[PF₆]⁻ {HC(pz′)₃ = tris(3,5-dimethylpyrazolyl)methane}, prepared by reacting [{Rh(CO)₂(μ-Cl)}₂] with HC(pz′)₃ in the presence of Tl[PF₆], has a distorted square pyramidal structure with a κ³-HC(pz′)₃ ligand. Carbonyl substitution with Lewis bases gives [Rh(CO)L{HC(pz′)₃}][PF₆] {L = PPh₃, 2⁺[PF₆]⁻; L = AsPh₃, 3⁺[PF₆]⁻; L = P(o-tolyl)₃, 4⁺[PF₆]⁻}, which have square planar κ² structures, confirmed by X-ray crystallography for 2⁺[PF₆]⁻. The cations 2⁺ and 3⁺ have the third pyrazolyl ring orientated pseudo-parallel to the square planar metal whereas 4⁺ more likely has the third ring orientated exo to that plane. One-electron oxidation of 2⁺ and 3⁺ gives the Rh(II) dications [Rh(CO)(PPh₃){HC(pz′)₃}]²⁺, 2²⁺, and [Rh(CO)(AsPh₃){HC(pz′)₃}]²⁺, 3²⁺, characterised by ESR spectroscopy. Complex 1⁺[PF₆]⁻reacts with PhCCPh to give [Rh(CO)(η²-PhCCPh){HC(pz′)₃}][PF₆], 5⁺[PF₆]⁻, in which the two-electron donor alkyne occupies an equatorial position in a trigonal bipyramidal κ³ structure. With MeCCR (R = Me or Et), 1⁺[PF₆]⁻ gives the κ² square planar complexes [Rh{η⁴-C₄Me₂R₂C(O)}{HC(pz′)₃}][PF₆] (R = Me, 6⁺[PF₆]⁻; R = Et, 7⁺[PF₆]⁻) in which the cyclopentadienone ligands are coordinated via two Rh–monoalkene bonds; the structurally characterised form of 7⁺ has the two alkyne units linked head-to-head with the CEt termini bound to the ketonic CO group. With HCCPh or HCCH, 1⁺ gives the octahedral, κ³ rhodium(III) metallacyclopentadienes [Rh(CO)(η¹:η¹′-CHCRCHCR){HC(pz′)₃}][PF₆] (R = Ph, 8⁺[PF₆]⁻; R = H, 9⁺[PF₆]⁻) with the two alkynes linked head-to-tail in 8⁺. The reaction of 1⁺ with HCCH also gives the cycloheptatrienone (tropone) derivative [Rh{η⁴-C₆H₆C(O)}{HC(pz′)₃}][PF₆], 10⁺[PF₆]⁻, with a κ³ ligand and the cycloheptatrienone ligand bound to the metal via two Rh–C σ-bonds and one Rh–monoalkene interaction.