d10-ML2 Complexes: Structure, Bonding, and Catalytic Activity

Abstract

Our goal in this chapter is to show how one can obtain a better understanding of the decisive factors for the selectivity and efficiency of catalytically active metal complexes. This ongoing research project has been designated the 'Fragment-oriented Design of Catalysts' and aims at providing design principles for a more rational development of catalysts. To this end, we have performed a series of studies in which we systematically investigate the effect of a specific variation on the reactivity of the catalyst. Thus, we will summarize previous results on not only how the reaction barrier varies when different bonds are activated by palladium, different ligands are attached to palladium but also how different metal centers perform compared to palladium. In a final section, we present a case study on newly obtained results about the effect of adding substituents with different electronegativity to the phosphine ligands at the metal center. A red thread throughout the chapter, and our methodology in general, is the application of the activation strain model of chemical reactivity. This is a predictive model that provides a quantitative relationship between trends in barrier heights and variation of geometric and electronic properties of the reactants.

The activation strain model and molecular orbital theory

“…Yet, one may wonder why bending Ni(PH 3 ) 2 is more feasible than bending, for example, Pd(PH 3 ) 2 . This issue has been addressed in a study on a large set of d 10 ‐ML 2 catalyst complexes . The systematic approach taken revealed a number of interesting trends, which we will address using two representative series, namely Rh(PH 3 ) 2 − , Pd(PH 3 ) 2 , Ag(PH 3 ) 2 + in which the metal center is varied, and Pd(NH 3 ) 2 , Pd(PH 3 ) 2 , Pd(CO) 2 in which the ligand is varied.…”

“…This issue has been addressed in a study on a large set of d 10 -ML 2 catalyst complexes. 46,87 The systematic approach taken revealed a number of interesting trends, which we will address using two representative series, namely Rh(PH 3 ) 2 − , Pd(PH 3 ) 2 , Ag(PH 3 ) 2 + in which the metal center is varied, and Pd(NH 3 ) 2 , Pd(PH 3 ) 2 , Pd(CO) 2 in which the ligand is varied. It is found that the bite angle becomes less flexible when the metal center is varied from Ag + to Rh − , and increasingly flexible from Pd(NH 3 ) 2 to Pd(CO) 2 .…”

“…Conveniently, there is no special computer code required to perform activation strain analyses: all necessary quantities can be computed using any of the regular quantum‐chemical software packages available. As a result, the activation strain model has been applied by various research groups, on a range of chemical processes, such as nucleophilic substitution, cycloaddition, oxidative addition, isomerization, and many other processes from organic and organometallic chemistry.…”

“…9 Conveniently, there is no special computer code required to perform activation strain analyses: all necessary quantities can be computed using any of the regular quantum-chemical software packages available. As a result, the activation strain model has been applied by various research groups, on a range of chemical processes, such as nucleophilic substitution, 1,[10][11][12][13][14][15][16][17][18][19] cycloaddition, [20][21][22][23][24][25][26][27][28][29][30][31][32][33] oxidative addition, [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] isomerization, [50][51][52][53][54][55] and many other processes from organic…”

Complexes of Copper(I) Thiocyanate with Monodentate Phosphine and Pyridine Ligands and the P(,N)‐Donor Diphenyl(2‐pyridyl)phosphine

“…The past few decades have witnessed an increasing interest in the chemistry of d 10 metal systems because of their rich photochemical properties, [1] catalytic applications [2] PPh 2 py/2-methylpyridine (mpy) and P(4-FPh) 3 /mpy complexes, wherein centrosymmetric dimers with eight-membered central rings are obtained: [(R 3 P)(mpy)Cu(NCS) 2 -Cu(PR 3 )(mpy)], as is also the case in the parent 1:2 CuNCS/ PPh 2 py adduct [(pyPh 2 P) 2 Cu(NCS) 2 Cu(PPh 2 py) 2 ]. For the 1:1:1 CuNCS/P(4-FPh) 3 /py and PPh 3 /Brmpy (Brmpy = 3bromo-4-methylpyridine) adducts, and, likely, CuNCS/ PPh 2 py/py (1:1:1), single-stranded polymers of the form [···Cu(NCS)(PR 3 )(py-base) (Cu)···] (ϱ|ϱ) with linearly bridging NCS ligands were obtained.…”