Square-Planar Pt(II) and Ir(I) Complexes as the Lewis Bases: Donor–Acceptor Adducts with Group 13 Trihalides and Trihydrides

Abstract

The stability and properties of donor−acceptor adducts of square-planar Pt(II) and Ir(I) complexes (designated as PtX, IrX, or generally MX complexes) with trihydrides and trihalides of group 13 elements of general formula YZ 3 (Y = B, Al, Ga; Z = H, F, Cl, Br) were studied theoretically using DFT methodology in the gas phase. MX complexes were represented by wide range of the ligand environment which included model complexes [Ir(NH 3 ) 3 X] 0 and cis-[Pt(NH 3 ) 2 X 2 ] 0 (X = H, CH 3 , F, Cl, Br) and isoelectronic complexes [Ir(NNN)(CH 3 )] 0 and [Pt(NCN)(CH 3 )] 0 with tridentate NNN and NCN pincer ligands. MX complexes acted as the Lewis bases donating electron density from the doubly occupied 5d z 2 atomic orbital of the metal M atom to the empty valence p z orbital of Y whose evidence was clearly provided by the natural atomic orbital (NAO) analysis. This charge transfer led to the formation of pentacoordinated square pyramidal MX•(YZ 3 ) adducts with M•Y dative bond. Binding energies were −44.7 and −75.2 kcal/mol for interaction of GaF 3 as the strongest acid with PtNCN and IrNNN pincer ligands complexes. Only M•B bonds had covalent character although MX•BZ 3 adducts were the least stable due to large values of Pauli repulsion and deformation energies. The highest degree of covalent character was found for adducts of BH 3 in all series of structures studied. Al and Ga adducts showed remarkably similar behavior with respect to geometry and binding energies.

Tuning the Reactivity and Bonding Properties of Metal Square-Planar Complexes by the Substitution(s) on the Trans-Coordinated Pyridine Ring

“…Differences in Δ E orb contributions to Δ E bind pyrX were in the order of units of kcal/mol when systems with different X’s were compared while differences in Δ E elst could be by up to one order of magnitude higher (see Table and Table S1). However, 2p x (N pyrX ) NAO energy is still a good predictor of the Pt–pyrX bond strength because prevailing Δ E elst is linearly correlated with Δ E orb (see below and Figure S8), as it was already shown in our previous studies on similar systems. , Polarization and charge transfer effects as parts of Δ E orb are strongly influenced by Δ E elst .…”

Hydrogen bonding to metals as a probe for an inverted ligand field

“…33 The range of Lewis acids has been recently expanded to incorporate EX3 neutral molecules of Group 13 elements (E = B, Al, Ga; X = H, F, Cl, Br). 34 In the same way, the HOMO of 7-Cs with main 5dz² contribution is most suited to establish an axial Pt⋯HO interaction, 35 as experimentally observed in compounds 1 and 2. This Pt⋯HO interaction can be considered as an incipient stage in proton transfer from oxygen to metal.…”

Tuning the Reactivity and Bonding Properties of the Pt(II) Complexes by the Substitution(s) on the Trans‐Coordinated Non‐Aromatic Amine Ligand

“…The nonspecific variability of the X … cis-NH 3 interaction could also be the reason why the orbital energies were not mutually dependent with the electrostatic ones for all PtÀ ligand bonds (cf. our previous studies [29,30,32] ) except for the PtÀ w bond in the X-P structures (Figure S2).…”