CO-Reduction Chemistry: Reaction of a CO-Derived Formylhydridoborate with Carbon Monoxide, with Carbon Dioxide, and with Dihydrogen.

Treatment of the bulky metallocene hydride Cp*Zr(H)OMes (Cp* = pentamethylcyclopentadienyl, Mes = mesityl) with Piers' borane [HB(CF)] and carbon monoxide (CO) gave the formylhydridoborate complex [Zr]-O═CH-BH(CF) ([Zr] = Cp*Zr-OMes). From the dynamic NMR behavior, its endergonic equilibration with the [Zr]-O-CH-B(CF) isomer was deduced, which showed typical reactions of an oxygen/boron frustrated Lewis pair. It was trapped with CO to give an O-[Zr] bonded borata-β-lactone.

The Chemistry of a Non-Interacting Vicinal Frustrated Phosphane/Borane Lewis Pair.

The dimesitylphosphinocyclopentene/HB(C F ) -derived vicinal trans-1,2-P/B frustrated Lewis pair (FLP) 4 shows no direct phosphane-borane interaction. Toward some reagents it behaves similar to an intermolecular FLP; it cleaves dihydrogen, deprotonates terminal alkynes, and adds to organic carbonyl compounds including CO . It shows typical intramolecular FLP reaction modes (cooperative 1,1-additions) to mesityl azide, to carbon monoxide, and to NO.

A 1,1-Carboboration Route to Bora-Nazarov Systems.

Hydroboration of the conjugated enynes 1 a and 1 b with Piers' borane [HB(C6F5)2] gave the respective dienylboranes trans-2 c and trans-2 d. Their photolysis resulted in the formation of the dihydroborole products 3 c and 3 d. Both were converted to their pyridine adducts 5 c and 5 d, respectively.

Solid-state NMR studies for the determination of 11B electric field-gradient tensor orientations in P/B Frustrated Lewis Pairs and related systems.

A solid state NMR method is described for measuring the angle Θ specifying the orientation of the principal component of the (11)B electric field gradient tensor relative to the (11)B(…31)P internuclear vector of (11)B-(31)P spin pairs. It is based on the anisotropic dephasing of (11)B spins in the dipolar field of (31)P nuclei via (11)B{(31)P} Rotational Echo DOuble Resonance (REDOR) experiments. The method is applied to four solid borane-phosphane compounds related to Frustrated Lewis Pair (FLP) chemistry.