The weakly coordinated triflate complex [(P^̂P)Pd(OTf)] ⁺(OTf)^- (1) (P^̂P = 1,3-bis(di-tert- butylphosphino)propane) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate. Addition of CH ₃OH or CD₃OD to 1 forms the hydride species [(P ^̂P)PdH(CH₃OH)]⁺(OTf)^- (2-CH₃OH) or the deuteride [(P^̂P)PdD(CD ₃OD)]⁺(OTf)^- (2^D-CD₃OD), respectively. Further reaction with pyridine cleanly affords the stable and isolable hydride [(P^̂P)PdH(pyridine)]⁺(OTf) ^- (2-pyr). This complex yields the hydride fragment free of methanol by abstraction of pyridine with BF₃OEt₂, and thus provides an entry to mechanistic observations including intermediates reactive toward methanol. Exposure of methyl oleate (100 equiv) to 2^D-CD ₃OD resulted in rapid isomerization to the thermodynamic isomer distribution, 94.3% of internal olefins, 5.5% of α,β-unsaturated ester and <0.2% of terminal olefin. Reaction of 2-pyr/BF₃OEt ₂ with a stoichiometric amount of 1-¹³C-labeled 1-octene at -80 °C yields a 50:50 mixture of the linear alkyls [(P ^̂P)Pd¹³CH₂(CH₂) ₆CH₃]⁺ and [(P^̂P)PdCH ₂(CH₂)₆ ¹³CH₃] ⁺ (4a and 4b). Further reaction with ¹³CO yields the linear acyls [(P^̂P)Pd¹³C(=O)^12/13CH ₂(CH₂)₆ ^12/13CH₃(L)] ⁺ (5-L; L = solvent or ¹³CO). Reaction of 2-pyr/BF ₃·OEt₂ with a stoichiometric amount of methyl oleate at -80 °C also resulted in fast isomerization to form a linear alkyl species [(P^̂P)PdCH₂(CH₂) ₁₆C(=O)OCH₃]⁺ (6) and a branched alkyl stabilized by coordination of the ester carbonyl group as a four membered chelate [(P^̂P)PdCH{(CH₂)₁₅CH ₃}C(=O)OCH₃]⁺ (7). Addition of carbon monoxide (2.5 equiv) at -80 °C resulted in insertion to form the linear acyl carbonyl [(P^̂P)PdC(=O)(CH₂)₁₇C(=O)OCH ₃(CO)]⁺ (8-CO) and the five-membered chelate [(P ^̂P)PdC(=O)CH{(CH₂)₁₅CH₃}C(=O) OCH₃]⁺ (9). Exposure of 8-CO and 9 to ¹³CO at -50 °C results in gradual incorporation of the ¹³C label. Reversibility of 7 + CO ⇄ 9 is also evidenced by ΔG = -2.9 kcal mol^-1 and ΔG^† = 12.5 kcal mol^-1 from DFT studies. Addition of methanol at -80 °C results in methanolysis of 8-L (L = solvent) to form the linear diester, 1,19-dimethylnonadecandioate, whereas 9 does not react and no branched diester is observed. DFT yields a barrier for methanolysis of ΔG^† = 29.7 kcal mol ^-1 for the linear (8) vs ΔG^† = 37.7 kcal mol^-1 for the branched species (9).