Synthesis and reactions of 4H-1,4-telluraborine.

The B(C6F5)3-catalyzed reaction of the 1,4-telluraborine, Te(PhC[double bond, length as m-dash]C(C6F5))2BOCH2Ph 2 with PhSiH3 gives Te(PhC[double bond, length as m-dash]C(C6F5))2BH 3. Compound 3 acts as a synthetic precursor to Te(PhC[double bond, length as m-dash]C(C6F5))2BCl 4 and Te(PhC[double bond, length as m-dash]C(C6F5))2B(THF)(O3SCF3) 5. In addition, 3 undergoes reactions with alkenes, alkynes, ketones and aldehydes to give a series of hydroboration products, 6-16.

Stoichiometric and catalytic isomerization of alkenylboranes using bulky Lewis bases.

1,1-Carboboration of alkynes with boranes R'B(C6F5)2 (R' = (CH2)3Ph, C6F5) affords mixtures of the E and Z isomers of RCH = CR'B(C6F5)2 (R = (CH2)2Me, (CH2)3Me, (CH2)2Ph, CH2CHMe2, CHMe2, CMe3, CH2OMe, CH2N(CO)2C6H4), treatment of these alkenylboranes with stoichiometric or catalytic amounts of tBu2PH or other donors are shown to induce isomerization. The proposed mechanism involving a zwitterionic borataalkene intermediate is supported by computations.

Facile access to unsymmetrically substituted tellurium-boron based heterocycles.

Reactions of Te-B heterocycles Te((Ph)C[double bond, length as m-dash]C(C6F5))2B(C6F5) 1 with alcohols is shown to afford species of the form Te((Ph)C[double bond, length as m-dash]C(C6F5))2BOR. The subsequent reaction with either 4-Br-C6H4CCH or 3-(C4H3S)CCH proceeds with the liberation of C6F5CCPh to give unsymmetrically substituted Te-B based heterocycles of the form Te((Ph)C[double bond, length as m-dash]C(C6F5))(HC[double bond, length as m-dash]CR)BOCH2Ph.

S(vi) Lewis acids: fluorosulfoxonium cations.

Avenues to S-based Lewis acids were developed via the oxidation of aryl-sulfoxides with XeF2, giving difluorodiarylsulfoxides which react via fluoride abstraction to afford Lewis acidic fluorosulfoxonium cations; this acidity is derived from the S-F σ* orbital and has been probed both experimentally and computationally.

Double FLP-Alkyne Exchange Reactions: A Facile Route to Te/B Heterocycles.

1-Bora-4-tellurocyclohexa-2,5-diene undergoes sequential [4 + 2] cycloadditions/alkyne-elimination reactions to incorporate 2 equiv of terminal alkyne with the loss of diarylalkyne, affording access to a series of 11 new tellurium-boron heterocycles. These alkyne exchange reactions proceed regioselectively and can tolerate a variety of functional groups, thus providing the potential for further derivatization. The mechanism of the exchange reaction is confirmed by a DFT study to involve the interaction of the Te and B with the alkyne in a frustrated Lewis pair fashion in the transition states.

Intramolecular 1,1-carboboration versus intermolecular FLP addition in reactions of boranes and bis(phenylethynyl)telluroether.

Reactions of boranes with Te(CCPh)2 proceed via initial intermolecular 1,1-carboboration followed by either an intramolecular carboboration or an FLP addition to a second molecule of the intermediate, yielding 1-bora-4-tellurocyclohexa-2,5-diene heterocycles or tricylic derivatives of 1,4-ditellurocyclohexa-2,5-diene, respectively. The latter species is also shown to convert to the former upon heating.

1,1-Carboboration to tellurium-boron intramolecular frustrated Lewis pairs.

The tellurium acetylide Ph(CH2)2TeCCPh reacts with boranes via 1,1-carboboration to give a series of borylated vinyl telluroethers. The product Ph(CH2)2TeC(Ph)C(C6F5) B(C6F5)2 reacts with phenylacetylene and iodine to give novel tellurium-boron heterocyclic compounds.

Synthesis and platinum complexes of an alane-appended 1,1'-bis(phosphino)ferrocene ligand.

An aryldimethylalane-appended analogue of 1,1'-bis(diphenylphosphino)ferrocene, FcPPAl, was prepared, and reaction with [Pt(nb)3 ] (nb=norbornene) afforded [Pt(η(2) -nb)(FcPPAl)] (1). Heating a solution of 1 to 80 °C resulted in crystallization of [{Pt(FcPPAl)}2 ] (2), whereas treatment of 1 with C2 H4 , C2 Ph2 , H2 , or CO provided [PtL(FcPPAl)] [L=C2 H4 (3), C2 Ph2 (4)], [PtH2 (FcPPAl)] (5), and [Pt(CO)(FcPPAl)] (6). In all complexes, the FcPPAl ligand is coordinated through both phosphines and the alane. Whereas 2 adopts a T-shaped geometry at platinum, 3-5 are square-pyramidal, and 6 is distorted square-planar. The hydride and carbonyl complexes feature unusual multicenter bonding involving platinum, aluminum, and a hydride or carbonyl ligand.