Microstructure characterization and mechanistic insight into polyether polyols and their associated polyurethanes.

This article reviews the analytical tool chest used for characterizing alkoxylates and their associated copolymer mixtures. Specific emphasis will be placed upon the use of mass spectrometry-based techniques as rapid characterization tools for optimizing reaction processes in an industrial R&D setting. An initial tutorial will cover the use of matrix-assisted laser desorption/ionization-mass spectrometry and tandem mass spectrometry fragmentation for detailed component analysis (e.

Distinct modes of Si-H binding to Rh in complexes of a phosphine-diarylamido-silane (SiNP) pincer ligand.

Syntheses of Rh complexes of the phosphine-amido-silane SiNP ligand are reported. The reaction of the parent (SiNP)H ligand (4) with 0.5 equiv.

Synthesis and characterization of rhodium, iridium, and palladium complexes of a diarylamido-based PNSb pincer ligand.

A new diarylmido-based pincer proto ligand (iPrPNHSbPh) with one -PPri2 and one -SbPh2 side donor has been synthesized. Three complexes of its amido form were prepared using standard metalation techniques: (iPrPNSbPh)PdCl, (iPrPNSbPh)RhCO, and (iPrPNSbPh)Ir(COE), where COE = cis-cyclooctene. These complexes were compared with their previously reported analogs incorporating a -PPh2 side donor in place of -SbPh2.

Dearomatization of the PCP Pincer Ligand in a Re Oxo Complex.

A high-valent, rhenium(V) oxo complex (PCP)ReOCl (1; PCP=bis(2,6-di-tert-butylphosphinomethyl)phenyl) undergoes a deprotonation and "dearomatization" upon treatment with LiN(SiMe ) to give (P*CP)ReOCl (2 a), in which Re is bound to a new dianionic P*CP ligand. Compound 2 a was studied spectroscopically, structurally, and computationally and was determined to have non-negligible Re=C multiple bond character, leading to its formulation as a new pseudo-carbenoid species. Reaction of 2 a or its iodo analogue (P*CP)ReOI (2 b) with CO provided access to (PCP)ReOX(CO ) (X=Cl or I, 3 a/b), the product of 1,3-cycloaddition and C-C bond formation.

Irreversible Hydrolysis of PCP-Supported Rhenium(V) Acetates.

Complexes (PCP)Re(O)(OAc) [R = Pr (4a) and Bu (4b); PCP = κ-P,C,P-2,6-(RPCH)CH] undergo unexpected irreversible hydrolysis to yield (PCP)Re(O)(OAc)(OH) (3a/3b) and free AcOH. 3a and 3b are highly fluxional in solution, possibly via AcOH loss and the intermediacy of (PCP)Re(O), which was isolated for R = Bu (5b).

Structure, Electronics and Reactivity of Ce(PNP) Complexes.

Synthetic methods for the coordination of the monoanionic bis[2-(diisopropylphosphino)-4-methylphenyl]amido (PNP) ligand framework to the cerium(III) cation have been developed and applied for the isolation of a series of {(PNP)Ce} and {(PNP) Ce} type complexes. The structures of the complexes were studied by X-ray diffraction and multinuclear NMR spectroscopy. We found that the cerium(III) ion can induce the elimination of one of the iPr groups at phosphorus to yield a new dianionic PNP tridentate framework (PNP ) featuring a phosphido-donor functionality, which is bound to the cerium ion with the shortest known Ce-P bond of 2.

N-H cleavage as a route to new pincer complexes of high-valent rhenium.

A novel PNN-type pincer ligand has been accessed via imine reduction with LiAlH to provide the phosphine diamino proligand, PNN (1). The ligand, 1, as well as PNP can be metallated directly, via N-H cleavage, with LReOX(OEt) precursors to access six-coordinate (PNP)ReOCl (2) and (PNN)ReOX (3-Cl, X = Cl; 3-Br, X = Br) in good yield. 3-Cl and 3-Br undergo dehydrohalogenation upon treatment with NEt, furnishing the five-coordinate phosphine/diamido PNN-type compounds (PNN)ReOX (4-Cl, X = Cl; 4-Br, X = Br) in excellent yield, presenting as a mixture of rotameric diasteromers.

High-Turnover Aromatic C-H Borylation Catalyzed by POCOP-Type Pincer Complexes of Iridium.

The catalytic C-H borylation of arenes with HBpin (pin = pinacolate) using POCOP-type pincer complexes of Ir has been demonstrated, with turnover numbers exceeding 10 000 in some cases. The selectivity of C-H activation was based on steric preferences and largely mirrored that found in other Ir borylation catalysts. Catalysis in the (POCOP)Ir system depends on the presence of stoichiometric quantities of sacrificial olefin, which is hydrogenated to consume the H2 equivalents generated in the borylation of C-H bonds with HBpin.

Chalcogen extrusion from heteroallenes and carbon monoxide by a three-coordinate rh(i) disilylamide.

We report the reactions of several heteroallenes (carbon disulfide, carbonyl sulfide, and phenyl isocyanate) and carbon monoxide with a three-coordinate, bis(phosphine)-supported Rh(I) disilylamide (1). Carbon disulfide reacts with 1 to afford a silyltrithiocarbonate complex similar to an intermediate previously invoked in the deoxygenation of CO2 by 1, and prolonged heating affords a structurally unusual μ-κ(2)(S,S'):κ(2)(S,S')-trithiocarbonate dimer. Carbonyl sulfide reacts with 1 to afford a structurally unique Rh(SCNCS) metallacycle derived from two insertions of OCS and N-to-O silyl-group migrations.