Peter M. Maitlis - publications from PETER M. MAITLIS. 15 January 1933—18 May 2022

Starting life with a dramatic escape from Nazi Germany, Peter Maitlis rose to make important contributions to a variety of areas of organometallic chemistry, many of which have had a continuing influence in both academic and industrial practice. Perhaps his most significant work was his early discovery of pentamethylcyclopentadienyl complexes of rhodium and iridium, compounds that have been eagerly taken up elsewhere for a very wide variety of purposes. His mechanistic work related to the Fischer–Tropsch and Cativa processes had important industrial implications

Terpyridine Ruthenium-Catalyzed One-Pot Conversion of Aldehydes into Amides

TerpyRu(PPh3)Cl2 is an efficient catalyst for rearranging aldoximes to amides without the need for chelating phosphines or additives as in prior examples. The catalyst is also useful in converting aldehydes into amides in a one-pot process using NaHCO3 as an additive. A mechanism involving nucleophilic attack of deprotonated oxime on an adjacent nitrile is suggested

An η¹-Aldehyde Complex and the Role of Hydrogen Bonding in Its Conversion to an η¹-Imine Complex

2-Pyridinecarboxaldehyde displaces Me2CO from [IrH2(Me2CO)2(PPh3)2]+ to give a chelating N,O-bound product containing an η1-O-bound aldehyde group. This is converted to the η1-N-bound imine complex with a variety of substituted amines. When the amine contains a suitably positioned −OH group, intramolecular O−H···H−Ir dihydrogen bonds are detected in the products. This hydrogen bonding influences the relative rates of product formation from 2- and 4-aminophenol (rate ratio 6:1), where only the 2-isomer is capable of forming an intramolecular H-bond

Spectroscopic Detection of a Hydrogen Fluoride Complex of Iridium

Spectroscopic Detection of a Hydrogen Fluoride Complex of Iridiu

Hydrogen Transfer Reduction of Aldehydes with Alkali-Metal Carbonates and Iridium NHC Complexes

Some neopentyl-substituted NHC iridium complexes catalyze the reduction of a variety of aldehydes and even enolizable aldehydes by hydrogen transfer from refluxing 2-propanol with alkali-metal carbonate bases. Imidazole and 1,2,4-triazole complexes had comparable activities. The aldehydes could also be reduced more slowly using a mild carbonate base and no iridium complex

High Turnover Remote Catalytic Oxygenation of Alkyl Groups: How Steric Exclusion of Unbound Substrate Contributes to High Molecular Recognition Selectivity

H-bonding mediated molecular recognition between substrate and ligand −COOH groups orients the substrate so that remote, catalyzed oxygenation of an alkyl C−H bond by a Mn-oxo active site can occur with very high (>98%) regio- and stereoselectivity. This paper identifies steric exclusionexclusion of non H-bonded substrate molecules from the active siteas one requirement for high selectivity, along with the entropic advantage of intramolecularity. If unbound substrate molecules were able to reach the active site, they would react unselectively, degrading the observed selectivity. Both of the faces of the catalyst are blocked by two ligand molecules each with a −COOH group. The acid p-tBuC6H4COOH binds to the ligand −COOH recognition site but is not oxidized and merely blocks approach of the substrate therefore acting as an effective inhibitor for ibuprofen oxidation in both free acid and ibuprofen ester form. Dixon plots show that inhibition is competitive for the free acid ibuprofen substrate, no doubt because this substrate can compete with the inhibitor for binding to the recognition site. In contrast, inhibition is uncompetitive for the ibuprofen-ester substrate, consistent with this ester substrate no longer being able to bind to the recognition site. Inhibition can be reversed with MeCOOH, an acid that can competitively bind to the recognition site but, being sterically small, no longer blocks access to the active site

A Rare η²-Butadienyl Complex from an Alkyne Double Insertion with Double Vinylidene Rearrangement

A rare η2-butadienyl Ir(III) complex with a weak Ir···C bond is formed from 1-alkyne double insertion with the independent double alkyne to vinylidene rearrangement. A reaction intermediate is isolated, and labeling and crossover experiments indicate the intramolecularity of both alkyne to vinylidene rearrangements

A <i>cis</i>-IrL(CO) Group Responds to Increasing Steric Bulk of L by M−L Stretching, Not M−C−O Tilting or Bending

The crystal structures of [Ir(2-R-bq)(PPh3)2(H)(CO)]+ (bq = benzoquinolinato; R = H, i-Pr, t-Bu) show that steric interference caused by contact between the bulky pendant R groups of the bq and the C of the cis-CO is relieved by Ir−N bond stretching in the Irbq system and bending of the trans-Ph3P−Ir−PPh3 groups, rather than by tilting or bending of the CO. Ir−CO is therefore more rigid than the Ir−N and Ir−P bonds. The Ir−N stretching is aided by the presence of a high trans effect H trans to N

Cp* Iridium Complexes Give Catalytic Alkane Hydroxylation with Retention of Stereochemistry

A series of Cp*Ir complexes can catalyze C−H oxidation, with ceric ammonium nitrate as the terminal oxidant and water as the source of oxygen. Remarkably the hydroxylation of cis-decalin and 1,4-dimethylcyclohexane proceeds with retention of stereochemistry. With H2O18, cis-decalin oxidation gave 18O incorporation into the product cis-decalol

Hydrogen Bonding in Anion Recognition: A Family of Versatile, Nonpreorganized Neutral and Acyclic Receptors

The diamides and disulfonamides m-C6H4(CONHAr)2 (Ar = Ph, 1; p-n-BuC6H4, 2, 2,4,6-Me3C6H2, 3), m-C6H4(SO2NHPh)2, 4, and 2,6-C6H3N(CONHPh)2, 5, readily synthesized on a multigram scale, bind strongly to halides and acetate in organic solvents with Ka's as high as 6.1 × 104 (NMR spectroscopy). The binding stoichiometry is 1:1 in solution for all cases except for the 4·F- and 4·OAc- complexes, where both 1:1 and 1:2 binding stoichiometries were found. The association constants in CD2Cl2 (1H NMR) follow the trend Cl- > Br- > I- for all the receptors. F- and OAc- binding may be stronger or weaker than Cl- depending on the nature of the receptor. The presence of the pyridine nitrogen in 5 and of the more rigid amide in 1−3 and 5 vs the less rigid sulfonamide structure in 4 increases selectivity for smaller anions. The enthalpy and entropy of formation for 2·Cl- were ΔH = −31 kJ/mol; ΔS = −23 J/(mol·K) (VT-NMR). The X-ray structure of [PPh4]2[1·Br][Br]·CH2Cl2, shows 1:1 complexation of Br- via two N−H···Br- hydrogen bonds and a syn−syn nonplanar binding conformation for 1. Solution hydrogen bonding was confirmed by FT-IR and NMR spectroscopy. The receptor conformation changes on complexation. Trends in structure/binding relationships show receptor flexibility is an important factor in anion recognition