Table 2.

Ligand effects on the cyclization of (E:Z)-1 with (RPPPR′)Pt²⁺ (see Chart 1)^a

Entry	Ligand	Keq (A:B)b	ΔG (kcal/mol)
1	EtPPPEt	0.68 (14:1)	0.23
2	tBuPPPEt	7.2 (2:1)	−1.2
3	PPPEt	14 (1.2:1)	−1.6
4	EtPPP	1100 (1:10)	−4.1
5	PPP	>4200 (1:>20)	< −4.9

^aReaction conditions: [Pt] = 0.027 M, [Ph₂NH₂][BF₄] = 0.27 M, [1] = 0.27 M, 25(1)°C (see Supplementary Material).

^bRelative concentrations determined by ³¹P NMR. Average of three measurements.