Cationic Two-Coordinate Complexes of Pd(I) and Pt(I) Have Longer Metal-Ligand Bonds Than Their Neutral Counterparts

Abstract

Ozerov and colleagues describe the synthesis and characterization of linear, twocoordinate, cationic phosphine complexes of monovalent Pd and Pt. Comparison of the structures of these complexes to the neutral, zero-valent analogs revealed significant elongation of the M-P bond upon oxidation. Computational studies offer an explanation for the observed phenomenon, showing that molecularorbital-based arguments alone cannot provide a satisfactory rationalization. HIGHLIGHTS Two-coordinate, cationic complexes of monovalent Pd and Pt are synthesized The monovalent cations possess longer, stronger M-L bonds than their zero-valent analogs Theoretical consideration of electrostatic and Pauli effects offers an explanation MacInnis et al., Chem 1, 902-920 December 8, 2016 ª 2016 Elsevier Inc. http://dx.SUMMARY One-electron oxidation of known ( t Bu 3 P) 2 M (1, M = Pd; 2, M = Pt) with [Ph 3 C] [HCB 11 Cl 11 ] leads to two-coordinate, monovalent cations of the formula [( t Bu 3 P) 2 M][HCB 11 Cl 11 ] (3, M = Pd; 4, M = Pt), which also possess linear geometry but with elongated M-P bonds. Spectroscopic and computational studies consistently show that the unpaired electron of the d 9 configuration of 3 and 4 belongs to largely non-bonding orbitals: the s/d z2 hybrid for Pd and the degenerate d x2-y2 /d xy pair for Pt. We show that molecular-orbital-based arguments alone are incapable of predicting or rationalizing the observed M-P bond lengthening on oxidation; correct prediction and rationalization are achieved only by inclusion of electrostatic and Pauli effects. This emphasizes the dangers of interpreting any perturbative changes in bond metrics solely on the basis of energies and occupancies of molecular orbitals; the inclusion of electrostatic and Pauli components is essential to providing a more complete picture. 7 8 9 10 Scheme 1. Synthesis and Reactivity of Pd(I) and Pt(I) Complexes

Isolated Cationic Organometallic Nickel(I) Arene Complexes

“…Since the interaction to cod is markedly stronger than to the arene, the (partial) arene desolvation/slippage appears more likely. Such EPR interfering solvent interactions were already reported for Pd I , Pt I[22] and postulated for Ni I phosphine complexes …”

Synthesis, Characterisation and Reactions of Truly Cationic NiI–Phosphine Complexes

“…This can be explained as follows: according to reports of Ozerov et al. on the similar complex [Pd(P t Bu 3 ) 2 ] + , such a linear, two‐coordinate species would feature an almost axial anisotropy with the principle g values g ∥ =1.971 and g ⊥ =2.338 . This would be in accord with our own calculations (Figure S13) on the two‐coordinate [Ni(P t Bu 3 ) 2 ] + and its g tensor showing one smaller ( g 1 =2.062) and two larger components ( g 2 =2.319, g 3 =2.385) .…”

Synthesis and Characterization of a Linear, Two-Coordinate Pt(II) Ketimide Complex

“…Consequently, these materials are of interest for catalysis, small molecule activation, and as precursors to nanomaterials. [2][3][4][5][6] These properties are perhaps best exemplified by the M(N{SiMe3}2)2-type complexes (M = Mn, Fe, Co). 1 For example, Fe(N{SiMe3}2)2 was found to be an effective pre-catalyst for both alkene hydrogenation and carbonyl hydrosilylation.…”