The 7-aza-N-indolyl phosphine ligands PR₂(N₂C₇H₅) (L¹, R = Ph; L², R = NC₄H₄) were prepared in a two-step process involving treatment of 7-azaindole with BuLi, followed by reaction of the lithium salt with PClR₂. L¹ and L² react with [MCl₂(cod)] (M = Pd, Pt) to give [PdCl₂(L-κ²P,N)] (1a, L = L¹; 1b, L = L²) or [PtCl₂(L-κ²P,N)] (2a, L = L¹; 2b, L = L²) and with [Rh(μ-Cl)(cod)]₂ in the presence of CO to give [RhCl(CO)(L-κ²P,N)] (3a, L = L¹; 3b, L = L²). Crystal structures for 1a,b and 3a,b are reported, and structural and spectroscopic evidence confirm that L² is a poorer σ-donor/better π-acceptor than L¹. The complexes [PdClMe(L-κ²P,N)] (4a, L = L¹; 4b, L = L²), prepared from [PdClMe(cod)], react with AgOTf to yield [PdMe(OTf)(L-κ²P,N)] (5a, L = L¹; 5b, L = L²). Complexes 5a,b are active catalysts for the co-polymerisation of CO and ethene, with activities similar to previously reported catalysts containing P,N-donor ligands. From the stepwise insertion reactions of CO and ethene with 5a,b, the acyl complexes [Pd{C(O)Me}(OTf)(L-κ²P,N)] (7a, L = L¹; 7b, L = L²) and alkyl complexes [Pd{CH₂CH₂C(O)Me-κ²C,O}(L-κ²P,N)]OTf (8a, L = L¹; 8b, L = L²) have been isolated and crystallographically characterised, and the acyl complexes [Pd{C(O)CH₂CH₂C(O)Me-κ²C,O}(L-κ²P,N)]OTf (9a, L = L¹; 9b, L = L²) have been spectroscopically characterised. Reactions of 7a and 9a with MeOH gave methyl acetate and methyl 4-ketopentanoate respectively, with formation of palladium metal and conversion of the remaining palladium to [Pd(L¹-κ²P,N)₂](OTf)₂10 which has been crystallographically characterised.