We have performed new electronic structure calculations for the five lowest 1A′ states of ozone using the multi-reference configuration interaction method with an augmented triple zeta valence atomic basis set. Several avoided crossings, which are important for interpreting the Huggins–Hartley band system, are identified and two-dimensional diabatic potential energy surfaces are constructed. It is argued that the Huggins and the Hartley band systems are due to excitation of the same electronic state.
We have calculated one-dimensional potential cuts of twenty-five singlet/triplet A′/A″ states of ozone. The calculations are performed at the multi-reference configuration interaction level of electronic structure theory with the aug-cc-pVTZ set of atomic basis functions. It is found that many triplet potentials cross the 31A′(1B2) potential, on which the fragmentation after excitation in the Huggins–Hartley band system primarily proceeds. These crossings allow the population of the three spin-forbidden product channels O(3P)+O2(a1Δg), O(3P)+O2(b1Σg+) and O(1D)+O2(X3Σg−). Possible consequences of singlet–triplet crossings for the Wulf band are also briefly discussed.
MP(tBu)2 (M=Li, Na, K), KH and KN(SiMe3 )2 are shown to activate HD reversibly. In the case of MP(tBu)2 this leads to isotopic scrambling and the formation of H2 , D2 , H(D)P(tBu)2 and MH(D) in C6 D6 . In toluene, KP(tBu)2 reacts with H2 but also leads to isotopic scrambling into the methyl groups of the solvent toluene. DFT calculations reveal that these systems effect H2 activation via cooperative interactions with the Lewis acidic alkali metal and the basic phosphorus, carbanion, or hydride centres, mimicking frustrated Lewis pair (FLP) behaviour.
DOI : 10.1002/anie.201806849 Anahtar Kelimeler :
H2 activation, alkali metals, amides, frustrated Lewis pairs, phosphides
Abstract Extensive DFT calculations provide deep mechanistic insights into the acylation reactions of tert‐butyl dibenzo‐7‐phosphanobornadiene with PhCOX (X=Cl, Br, I, OTf) in CH2Cl2 solution. Such reactions are initialized by the nucleophilic P⋅⋅⋅C attack to the carbonyl group to form the acylphosphonium intermediate A+ together with X− anion, followed either by nucleophilic X−⋅⋅⋅P attack (X=Cl, Br, and I) toward A+ to eliminate anthracene or by slow rearrangement or decomposition of A+ (X=OTf). In contrast to the first case (X=Cl) that is rate‐limited by the initial P⋅⋅⋅C attack, other reactions are rate‐limited by the second X−⋅⋅⋅P attack for X=Br and I and even thermodynamically prevented for X=OTf, leading to isolable phosphonium salts. The rearrangement of phosphonium A+ is initiated by a P‐C bond cleavage, followed either by sequential proton‐shifts to form anthracenyl acylphosphonium or by deprotonation with additional base Et3N to form neutral anthracenyl acylphosphine. Our DFT results strongly support the separated acylphosphonium A+ as the key reaction intermediate that may be useful for the transfer of acylphosphenium in general.
The stoichiometric reactions of the alkylfluorides 1-fluoroadamantane (Ad-F), fluorocyclohexane (Cy-F), 1-fluoropentane (Pent-F) and benzyl fluorides with secondary boranes pinacolborane (HBpin), catecholborane (HBcat), 9-borabicyclo(3.3.1)nonane (9-BBN) and Piers borane (HB(C6 F5 )2 ) are described. While HBcat, 9-BBN and HB(C6 F5 )2 reduce Ad-F to Ad-H, the latter borane was shown to react with secondary and primary fluoroalkanes, affording C-F borylation, while benzyl fluorides undergo Friedel-Crafts chemistry.