A series of classical B(C(6)F(5))(3)-phosphine adducts are shown to be reactive molecules. Reaction of (THF)B(C(6)F(5))(3) with phosphines are shown to effect ring-opening of THF affording the zwitterionic phosphonium-borate species of the form R(2)PH(C(4)H(8)O)B(C(6)F(5))(3) and R(3)P(C(4)H(8)O)B(C(6)F(5))(3). Alternatively, treatment of (THF)B(C(6)F(5))(3) with a lithium phosphide (R(2)PLi, R = tBu, Ph Mes) affords species of the form [Li(THF)(x)][R(2)P(C(4)H(8)O)B(C(6)F(5))(3)]. Additionally, double THF ring-opening is also demonstrated to give species of the form [Li(THF)(x)][R(2)P(C(4)H(8)OB(C(6)F(5))(3))(2)]. In addition a series of classical borane-phosphine adducts are also shown to undergo thermal rearrangement reactions to give the zwitterionic products of aromatic substitution R(2)PH(C(6)F(4))BF(C(6)F(5))(2) and R(3)P(C(6)F(4))BF(C(6)F(5))(2). The mechanism of these substitutions is considered. A series of crystallographic studies of phosphine-borane adducts, THF ring-opened zwitterions and para-attack zwitterionic phosphonium borates are reported and discussed.

Treatment of aminoalkynes (ynamines), Me3Si-CC-NR2 [NR2 = N(CH2CH2)2NMe, N(CHMe-CH2)2CH2], with dialkylaluminum hydrides, H-AlR′2 (R′ = CH2 tBu, iBu, tBu), afforded by hydroalumination the corresponding alkenyl derivatives R′2Al-(Me3Si)CC(H)-NR2 (3 to 6) in which the opposite Lewis functionalities adopted a cis-arrangement with the aluminum and nitrogen atoms on the same side of the resulting CC double bonds. Intramolecular Al–N interactions gave four-membered AlC2N heterocycles, but ring strain may cause relatively long Al–N distances of 2.07 to 2.15 Å. These compounds represent a new type of Lewis acid–base pairs, and we observed C–H bond activation by opening of the Al–N bond upon treatment with H-CC-C6H5. Compound 7 was isolated, which had the proton attached to nitrogen and the anionic ethynyl group bonded to aluminum. The formation of 7 is reversible in solution with an increasing dissociation into the starting compounds at elevated temperatures. Two different structural motifs were obtained upon reaction of the Lewis acid–base pairs with dicyclohexylcarbodiimide, which inserted selectively into the bond between the aluminum and the vinylic carbon atom. In the first compound (8) an amidinato ligand was formed, which coordinated the metal atom by both nitrogen atoms to give an AlCN2 heterocycle. A six-membered heterocycle (9) resulted from the insertion of only one CN double bond of the carbodiimide into the Al–C(vinyl) bond. 9 had an unchanged interaction of the metal atom with the α-nitrogen atom of the former ynamine. The latter compound may be considered an intermediate, and rearrangement to yield an amidinato compound analogous to 8 was indeed observed with extended reaction time.

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A detailed study of structure, bonding and reactivity of new 1-zirconacyclobuta-2,3-dienes is presented in comparison to a lighter Ti analog. We found a unique C–H activation at the widely used rac-(ebthi) ligand for that only occurs for Zr.

The vicinal frustrated P/B Lewis pair (FLP) Mes(2)PCH(2)CH(2)B(C(6)F(5))(2) reacts with 9-borabicyclo[3.3.1]nonane (9-BBN) by C(6)F(5)vs. H exchange at boron to give the new [B]-H functionalized FLP Mes(2)PCH(2)CH(2)B(H)(C(6)F(5)) (4) and 9-C(6)F(5)-BBN. The latter was characterized as an isonitrile adduct by X-ray diffraction. The new FLP 4 forms an adduct with pyridine and it undergoes clean hydroboration reactions with 1-pentyne or added styrene or dimesitylvinylphosphane. The products formed stable adducts with pyridine; two such examples were also characterized by X-ray crystal structure analysis. A similar alkyl vs. hydrogen exchange was observed upon treatment of an Al/N based Lewis pair, iBu(2)Al-(Me(3)Si)C=C(H)-N(CH(2)CH(2))(2)NMe (14), with 9-BBN.