RESUMO
An unexpected route to hitherto unknown amidine-functionalized phosphinines has been developed that is rapid and simple. Starting from primary amines and CF3-substituted λ3,σ2-phosphinines, a cascade of dehydrofluorination reactions leads selectively to ortho-amidinephosphinines. DFT calculations reveal that this unusual transformation can take place via a series of nucleophilic attacks at the electrophilic, low-coordinate phosphorus atom.
Assuntos
Fósforo , Teoria da Densidade FuncionalRESUMO
An iridium dihydride pincer complex [IrH2 (POCOP)] is immobilized in a hydroxy-functionalized microporous polymer network using the concepts of surface organometallic chemistry. The introduction of this novel, truly innocent support with remote OH-groups enables the formation of isolated active metal sites embedded in a chemically robust and highly inert environment. The catalyst maintained high porosity and without prior activation exhibited efficacy in the gas phase hydrogenation of ethene and propene at room temperature and low pressure. The catalyst can be recycled for at least four times.
RESUMO
A series of substituted phosphinines, 1-phosphabarrelenes and 5-phosphasemibullvalenes were synthesized and evaluated for their potential application as ligands in homogeneous catalytic reactions. While their buried volume (%Vbur ) was calculated to get insight into the steric properties, [LNi(CO)3 ] complexes were prepared in order to determine the corresponding Tolman electronic parameter. ETS-NOCV (extended-transition-state natural orbital for chemical valence) calculations on [LAuCl] complexes further allowed an estimation of the σ- and π-contributions to the L-M interaction. AuI coordination compounds of selected examples were prepared and characterized by single crystal X-ray diffraction. Finally, the three classes of PIII compounds were successfully used in the AuI -catalyzed cycloisomerization of N-2-propyn-1-ylbenzamide, showing very good activities and selectivities, which are comparable with the reported data of cationic phosphorus-based gold catalysts.
RESUMO
Reaction of the trivalent uranium complex [((Ad,Me ArO)3 N)U(DME)] with one molar equiv [Na(OCAs)(dioxane)3 ], in the presence of 2.2.2-crypt, yields [Na(2.2.2-crypt)][{((Ad,Me ArO)3 N)UIV (THF)}(µ-O){((Ad,Me ArO)3 N)UIV (CAs)}] (1), the first example of a coordinated η1 -cyaarside ligand (CAs- ). Formation of the terminal CAs- is promoted by the highly reducing, oxophilic UIII precursor [((Ad,Me ArO)3 N)U(DME)] and proceeds through reductive C-O bond cleavage of the bound arsaethynolate anion, OCAs- . If two equiv of OCAs- react with the UIII precursor, the binuclear, µ-oxo-bridged U2 IV/IV complex [Na(2.2.2-crypt)]2 [{((Ad,Me ArO)3 N)UIV }2 (µ-O)(µ-AsCAs)] (2), comprising the hitherto unknown µ:η1 ,η1 -coordinated (AsCAs)2- ligand, is isolated. The mechanistic pathway to 2 involves the decarbonylation of a dimeric intermediate formed in the reaction of 1 with OCAs- . An alternative pathway to complex 2 is by conversion of 1 via addition of one further equiv of OCAs- .
RESUMO
Gold(i) complexes based on a 2,4,6-triarylphosphinine and a mesoionic carbene derivative have been prepared and characterized crystallographically. Although structurally related, both heterocycles differ significantly in their donor/acceptor properties. These opposed electronic characteristics have been exploited in Au(i)-catalyzed cycloisomerization reactions. For the conversion of the standard substrate dimethyl 2-(3-methylbut-2-enyl)-2-(prop-2-ynyl)malonate the results obtained for both Au-catalysts were found to be very similar and comparable to the ones reported in the literature for other carbene- or phosphorus(iii)-based Au(i)-complexes. In contrast, a clear difference between the catalytic systems was found for the cycloisomerization of the more challenging substrate N-2-propyn-1-ylbenzamide. A combination of the phosphinine-based complex and [AgSbF6] or [Cu(OTf)2] leads to a catalytic species, which is more active than the mesoionic carbene-based coordination compound. We attribute these differences to the stronger π-accepting ability of phosphinines in comparison to mesoionic carbenes. The here presented results show for the first time that phosphinines can be used efficiently as π-accepting ligands in Au(i)-catalyzed cycloisomerization reactions.
RESUMO
We could access for the first time a 5-phosphasemibullvalene derivative via quantitative and selective photochemical di-π-methane rearrangement from the corresponding phosphabarrelene. Due to the striking analogy between phosphorus and carbon, this hitherto unknown transformation of vinyl-phosphorus species provides the possibility to prepare novel, chiral and conformationally rigid organophosphorus cage compounds in a straightforward manner.
