Lewis pairing and frustration of group 13/15 elements geometrically enforced by (ace)naphthalene, biphenylene and (thio)xanthene backbones

Abstract

The synthesis, structure, and reactivity of mixed group 13/group 15 compounds (E13 = B, Al, Ga, In, Tl; E15 = N, P, Sb, Bi) featuring a rigid (ace)naphthalene, biphenylene or (thio)xanthene backbone are discussed in this review.

A Strained Intramolecular P/Al-FLP and its Reactivity toward Allene

“…The ratio between this distance and the sum of the covalent radii (228 pm) is r = 1.12 indicating a strong interaction. [13] r values in this magnitude are usually observed for element 13 and 15 combinations on the (ace)naphthalene scaffold, [7] e.g. the corresponding acenaphthalene compound Ace(PPh2)(AlCl2) exhibits a P-Al distance of 2.4305(6) Å ( r = 1.07).…”

“…[4,6] Solid state structures of the active FLPs to determine the P•••B distances could not be determined, yet spectroscopic data indicate no interaction between the reactive sites, which is in line with the widely accepted assumption that these backbones prevent an interaction. [7] An analogous chemistry utilizing aluminum as acceptor has not been explored for such a variety of linker scaffolds because of the synthetic difficulties associated with its higher intrinsic Lewis acidity compared to boron. [8] Reported examples feature close arrangements of Lewis acid and base and often an interaction is observed that stabilizes the Lewis acidic alane, thereby rendering the FLP more exothermic and synthetically easier to access.…”

Metal‐Free Phosphorus‐Directed Borylation of C(sp2)−H Bonds

“…Mixed P-B compounds featuring arigid (ace)naphthalene backbone display rich chemistry as ar esult of geometrically enforced P!Bi nteractions. [20] This prompted us to test the direct electrophilic borylation of naphthyl phosphines as an alternative to the previously used ionic coupling approach, starting from peri-halogenated substrates. [21] TheC À Hb orylation of 1 proceeded readily using 3equiv.o fB Br 3 and 1equiv.d i-iso-propylethylamine (DIPEA) in CH 2 Cl 2 .T he reaction is complete within 15 hours at 25 8 8C(Scheme 1).…”

Ring-Opening of THF via an Intramolecular P/Al-Based Frustrated Lewis Pair: Assistance by C6F5 Groups beyond Electronegativity?

“…The reactivity is dependent on the electronic properties of the Lewis sites, which can be tuned by the substituents surrounding them . The first examples were based on Lewis acidic borane and Lewis basic phosphine centers, , a combination that still accounts for the major share of reported FLPs . Systems based on alane moieties as the electrophilic centers remain rare compared to its lighter homologues .…”

“…2 The first examples were based on Lewis acidic borane and Lewis basic phosphine centers, 3,4 a combination that still accounts for the major share of reported FLPs. 5 Systems based on alane moieties as the electrophilic centers remain rare compared to its lighter homologues. 6 This is somewhat surprising, as due to the higher intrinsic Lewis acidity of aluminum(III) it does not even require electron-withdrawing substituents to act in FLPs, achieving reactivities which in some cases surpass the reactivity observed for B-based FLPs.…”