No abstract

A way into normality: By using [Cp*Ru] complexes with bisphosphite or bisphosphine ligands, selective hydroformylation of propene and 1‐decene to homologated normal aldehydes was accomplished with the highest levels of activity and selectivity ever reported for ruthenium catalyst systems (see scheme). The reaction mechanism was investigated using stoichiometric amounts of [Cp*Ru(Xantphos)H] and [D2]‐1‐decene.

We have studied the formation of several N-acetyl-4-(dimethylamino)pyridine (DMAP) salts (with Cl(-), CH(3)COO(-), and CF(3)COO(-) counterions), which are considered to be the catalytically active species in DMAP-catalyzed acetylation reactions of alcohols. Combined crystal structure analyses, variable temperature matrix IR and NMR spectroscopy as well as computational techniques at the UAHF-PCM-B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level were utilized to examine the structures and dynamics of salt formation. We found clear evidence for the formation of tight ion pairs that are stabilized by dynamic hydrogen-bonding interactions. In nonpolar solvents, the nucleophilicity of acetate in its N-acetyl-DMAP salt only allows a steady-state concentration smaller 1% at room temperature. Thus, we propose additional hydrogen-bonding interactions with alcohols to be the key stabilization factor in subsequent acetylations.

COMMUNICATIONS substrate selectivity of the catalyst A. A further pointer to the high selectivity of the catalyst was obtained with 7 and 8, whose transesterification was not measurably catalyzed by A within 12 h. Addition of 1 and n-hexanol to this mixture again yielded 2 immediately and selectively.

Mono-and bis(guanidine) ligands stabilise bis-μ-oxido dicopper(III) complexes. Here, the formation of these complexes has been investigated in detail by means of lowtemperature stopped-flow techniques for the monoguanidine 2-[3-(dimethylamino)propyl]-1,1,3,3-tetramethylguanidine (TMGdmap) and the related bis(guanidine) 1,3-bis(N,N,N′,N′-tetramethylguanidino)propane (btmgp). Low-temperature IR studies in solution support the formation of bis-μ-oxido complexes. For both systems, no intermediates on the pathways to the bis-μ-oxido complexes could be detected; this has been explained through extensive DFT calculations. In the first step,