Overall rate constants k_NMR^a for the addition of methanol to 1-phenylpropyne catalysed by [(PPh₃)AuX] gold(i) determined from NMR experiments and rate constants k_MS^b of degradation of diaurated intermediate B ([Au₂(PPh₃)₂(PhCCCH₃,CH₃O)]⁺) determined by ESI-MS experiments.

X	TsOHc equiv.e	iPr-BU*H2SO4d equiv.e	k NMR [dm3 mol−1 min−1]	k MS [min−1]
SbF6	—	—	0.12	0.12 ± 0.03
SbF6	0.5	—	—	0.20 ± 0.06
SbF6	1	—	0.39	0.19 ± 0.05
SbF6	2	—	0.62	0.30 ± 0.02
SbF6	4	—	0.80	0.48 ± 0.09
SbF6	—	0.5	0.28	0.33 ± 0.13
SbF6	—	1	0.40	0.38 ± 0.16
SbF6	—	2	0.40	0.42 ± 0.10
SbF6	—	4	0.39	—
OTf	—	—	0.19	0.13 ± 0.02
PF6	—	—	0.16	0.14 ± 0.04
OTf	—	1	0.30	0.25 ± 0.03
PF6	—	1	0.26	0.26 ± 0.09

^aThe reaction was performed in CD₃OD (0.6 M 1-phenylpropyne with 1.25 mol% [Au(PPh₃)X]). The rate constants were determined by the kinetic modelling of the decay of the reactant monitored by NMR.

^bThe reaction was performed in CH₃OH (0.06 M 1-phenylpropyne with 1.25 mol% [Au(PPh₃)X]) diluted after the time delay 5 min with CD₃OH. The rate constants were determined by delayed reactant labelling.

^cDifferent mol% of p-toluenesulfonic acid (TsOH) was added to the reaction mixture.

^dDifferent mol% of bambusuril iPr-BU*H₂SO₄ was added to the reaction mixture.

^eEquivalents refer to the concentration of [(PPh₃)Au]⁺. 1 equivalent is 1.25 mol% concentration.