Table 4. Donor and Acceptor NBOs with an Indication of the Second-Order Interaction Energy E⁽²⁾ in Complexes 1–17^a.

complex	type of interaction	donor	acceptor	E(2)
1	SpB	BD C–C	BD* Hg–C	1.45
	lp–π	LP S	BD* C–C	0.67
2	SpB	LP O	BD* Hg–C	0.74
	HB	LP S	BD* C–H	0.63
3	SpB	LP O	BD* Hg–C	2.28
	HB	LP S	BD* N–H	3.76
4	SpB	LP C	BD* Hg–C	0.89
5	SpB	BD N–C	BD* Hg–C	0.43
6	SpB	LP N	BD* Hg–C	4.88
	HB	LP S	BD* C–H	0.58
7	SpB	LP N	BD* Hg–C	3.47
8	SpB	LP O	BD* Hg–C	0.19
9	SpB	LP O	BD* Hg–C	0.77
10	SpB	BD C–C	BD* Hg–C	0.86
11	SpB	LP N	BD* Hg–C	4.17
12	SpB	LP O	BD* Hg–C	1.37
	HB	LP S	BD* C–H	2.28
13	SpB	LP S	BD* Hg–C	3.57
	HB	LP S	BD* C–H	0.62
14	SpB	BD C–C	BD* Hg–C	1.41
	HB	LP S	BD* N–H	1.11
	CH–π	BD C–C	BD* C–H	0.24
15	SpB	LP F	BD* Hg–C	2.57
	HB	LP F	BD* C–H	0.75
16	SpB	LP Cl	BD* Hg–C	18.30
17	SpB	LP Br	BD* Hg–C	16.90

^aLP, BD, and BD* stand for lone pair, bonding orbital, and antibonding orbital, respectively. Energy values are in kcal/mol.