A total loss of innocence: double ortho-metallation of bis(triphenylphosphano)iminium cation, [N(PPh3)2]+, by tris(η-naphthalene)tantalate(1−)

Abstract

For the first time [N(PPh(3))(2)](+), or [PPN](+), has been shown to undergo an irreversible reaction with a transition metal complex under ambient conditions and affords a product containing a unique structural motif in which two phenyl groups on one PPh(3) substituent of [PPN](+) are ortho-metallated, while the third phenyl ring is hydrogenated to provide a tantalum bound 1,3-cyclohexadiene group.

The N-atom in [N(PR3)2]+ cations (R = Ph, Me) can act as electron donor for (pseudo) anti-electrostatic interactions

“…The popularity of 1 furthermore derives from its (synthetic) accessibility, its desirable solubility properties (soluble in most organic solvents and in hot water), its fairly hydrophobic character, and because [PPN] + is chemically stable at ambient or slightly forcing conditions (see ref. [8][9][10][11][12][13].…”

“…For example, the bisIJtriphenylphosphane)iminium cation ([PPN] + , 1, Scheme 1) is a popular counter cation ‡ , [8][9][10][11][12][13] to crystallize anionic species; its ability to form π-π stacking networks could be an important factor for the ease with which [PPN] + containing compounds crystallize. 13 Despite the widespread use of 1 as counter ion, surprisingly little information is available concerning the inter-and intramolecular interactions of this ion.…”

“…We choose ijNIJPMe 3 ) 2 ] + as a simplified model compound and calculated its complexation energies with several neutral (2-6) and cationic (7)(8)(9)(10)(11) species at the BP86-D3/def2-TZVP level of theory (see ESI † for details). The results are summarized in Table 1.…”

“…We wondered if perhaps the N-atom is also capable of engaging in intermolecular interactions, to which end we conducted some additional DFT studies and performed a detailed survey of the CSD. We choose ijNIJPMe 3 ) 2 ] + as a simplified model compound and calculated its complexation energies with several neutral (2-6) and cationic (7)(8)(9)(10)(11) species at the BP86-D3/def2-TZVP level of theory (see ESI † for details). The results are summarized in Table 1.…”

Vanadium, niobium and tantalum

“…The chemistry of the naphthalenetantalate was extended upon treatment of [Na(THF) 2 ][Ta(Z 4 -C 10 H 8 ) 3 ] with [PPN]Cl. 51 Although the molecular formula is consistent with the neutral species, Ta(C 10 H 8 )(PPN), unprecedented reactivity is observed. Instead of the expected salt metathesis product, two of the phenyl rings of PPN undergo ortho-metallation; both hydrogen atoms are transferred to the remaining phenyl ring to generate a Z 4 -1,3-cyclohexadiene ligand.…”