Tuning the Porphyrin Building Block in Self‐Assembled Cages for Branched‐Selective Hydroformylation of Propene

Abstract

Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination‐driven self‐assembly of tris(meta‐pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand‐template approach, in which the ligand acts as a template for cage formation. Previously, first‐generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported. Binding studies demonstrate that the association constant for the formation of second‐generation cage L2 is nearly an order of magnitude higher than that of L1. This strengthened binding allows cage L2 to remain intact in polar and industrially relevant solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be maintained in polar and coordinating solvents by using the second‐generation assembly.

A Tris(3‐pyridyl)stannane as a Building Block for Heterobimetallic Coordination Polymers and Supramolecular Cages

“…However, the corresponding tris(3‐pyridyl) ligands, especially those featuring main group bridgehead atoms (limited to Si, P and Bi), have seen only limited use in the literature. Notably, Reek has employed P(3‐Py) 3 as a ligand template to construct well‐defined catalytic cavities for regioselective hydroformylation . Boomishankar has also used the silyl ligand MeSi(3‐Py) 3 and its 3‐quinolyl analogue MeSi(3‐Qy) 3 to obtain a series of 2D metal‐organic frameworks (MOFs) and one example of a discrete molecular cage (e.g., Figure b) .…”

“…Notably,R eek has employed P(3-Py) 3 as al igand template to construct well-definedc atalytic cavities for regioselective hydroformylation. [17,18] Boomishankar has also used the silyl ligand MeSi(3-Py) 3 and its 3-quinolyl analogue MeSi(3-Qy) 3 to obtain as eries of 2D metal-organic frameworks (MOFs) [19] and one example of ad iscrete molecular cage (e.g.,F igure 1b). [20] It can be noted, however, that although obtained in high yields thesep reviously investigated P-and MeSi-bridgehead tris(3-pyridyl) ligands are either air sensitivea nd/orr equire chromatographic purification, making them time-consumingo rd ifficult to prepare and handle.…”

Metal-organic frameworks as kinetic modulators for branched selectivity in hydroformylation

“…At present, the branched-selective hydroformylation of olefins without directing groups is still challenging and can be achieved only by complex Rh catalysts with a selectivity for 2-methylhexanale from 1hexene up to 75% 23,24 and up to 86% for 2-methylbutanale from 1-butene 25 . Supramolecular chemistry has also been used to tune regioselectivity in Rh-catalysed hydroformylation [26][27][28] . The chemistry of Co-catalysed "branched-selective" hydroformylation is rare and yields at best moderate selectivity of acetal-protected products 29 .…”

Self‐Assembled Cofacial Zinc–Porphyrin Supramolecular Nanocapsules as Tuneable 1O2 Photosensitizers

“…Furthermore, the well-defined cavity found in these systemsh as also been used as as caffold for the isolation of metallocatalysts for use in confined-spacec atalysis. [19][20][21] Porphyrina nd Zn-porphyrin moieties are commonly considered to be inert building blocks for theses upramolecular architectures,and few precautions are usuallytaken regardingtheir exposure to natural light. However,p orphyrins and metalloporphyrins are well-knownp hotosensitizers and the production of reactive 1 O 2 might impact the way that both host-guest chemistry and catalysis proceeds within these species.…”