DFT calculations on IrH(PH₃)₃(SH)⁺

Geometry Optimization.

The geometry of IrH(PH₃)₃(SH)⁺ complex was optimised with and without the PF₆^- counter-ion. The results are dramatically different. For the isolated complex the result is similar to the IrH(PH₃)₃(OH)⁺ analogue, with the H (O-H) bending towards the hydride (Ir-H). With the introduction of the counter-ion the experimental geometry is roughly reproduced. In Figure 3 both optimised geometries are shown. Table 5 compares optimised and experimental structures for [IrH(PH₃)₃(SH)⁺] [PF₆^-].

Figure 3: Comparison of the molecular structures of optimized IrH(PH₃)₃(SH)⁺ and [IrH(PH₃)₃(SH)⁺][PF₆^-].

Table 5: Structural Parameters for the optimized and experimental [IrH(PMe₃)₃(OH)⁺][PF₆^-].

	Optimized (Å)	Experimental (Å)		Ptimized (°)	Real (°)
Ir - H2	1.651	1.642	H12 - S - Ir	104.6	110.6
Ir - S	2.467	2.437	S - Ir - H2	79.7	76.5
Ir - P3	2.378	2.299	H - Ir - P3	77.6	82.7
Ir - P7	2.509	2.378	P3 - Ir - P7	89.8	82.7
Ir - P13	2.381	2.354	P13 - Ir - P17	178.9	164.3
Ir - P17	2.381	2.343	-	-	-

The influence of the counter-ion is clearly shown from these calculations.

Mulliken Charge Analysis.

The results of the Mulliken charge analysis for the optimized structure are shown in Table 6.

Table 6: Mulliken Charges for the optimized [IrH(PH₃)₃(SH)⁺] [PF₆^-]

Ir	0.0437
H2	-0.0235
S	-0.3595
H12	0.2353
F	-0.8140

These results reinforce the knowledge of the influence of the counter-ion in determining the molecular structure of [IrH(PH₃)₃(SH)⁺]. It is basically an electrostatic interaction that distorts the S-H group towards the PF₆^- anion.

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