Optimized Au–Au distance, R_e, for models 3 and 4 at the different levels. Equilibrium distance R_e in pm; interaction energy V(R_e) in kJ mol⁻¹.

Monomer	Method	Au (basis)	R e	V(Re)
[AuCl(CNCy)]2 (7)	HF	2f	401.1	−27.1
	MP2	2f	349.8	−46.4
	SCS-MP2	2f	358.8	−40.3
	CCSD(T)	2f	360.5	−39.1
	HF	3f2g	399.4	−26.2
	MP2	3f2g	344.6	−49.7
	SCS-MP2	3f2g	354.4	−42.5
	PW91	3f2g	368.3	−26.5
	M06L	3f2g	349.5	−38.4
	PBE-D3	3f2g	347.3	−45.6
	B3LYP-D3	3f2g	345.8	−54.2
	PBEb	3f2g	347.3	−26.9
	B3LYPb	3f2g	345.8	−19.8
[AuCl(CO)]2 (8)	HF	2f	393.1	−12.6
	MP2	2f	352.3	−30.9
	SCS-MP2	2f	362.8	−25.5
	CCSD(T)	2f	363.6	−25.3
	HF	3f2g	394.7	−11.8
	MP2	3f2g	344.2	−33.8
	SCS-MP2	3f2g	356.9	−28.0
	CCSD(T)	3f2g	356.4	−26.9
	PW91	3f2g	361.7	−15.5
	M06L	3f2g	343.9	−24.4
	PBE-D3	3f2g	347.1	−29.2
	B3LYP-D3	3f2g	345.9	−35.8
	PBEb	3f2g	347.1	−14.9
	B3LYPb	3f2g	345.9	−8.4
[AuCl(CNCy)]a	Exp.50		339
			359
[AuCl(CO)]	Exp.52		338

^aCy is cyclohexyl.

^bSingle point at R_e in D3.