Herein, reactivity studies of a cyclic bis‐hydridostannylene (ADC)SnH2 (1‐H2) (ADC=PhC{(NDipp)C}2; Dipp=2,6‐iPr2C6H3) with various unsaturated organic substrates are reported. Reactions of terminal ...alkynes (RC≡CH) with 1‐H2 afford mixed acetylide‐vinyl‐functionalized bis‐stannylenes via dehydrogenation and hydrostannylation. Treatment of 1‐H2 with PhC≡CCH3 gives a unique distannabarrelene via dehydrogenative C(sp3)−H stannylation and hydrostannylation of the C≡CCH3 moiety. 1‐H2 undergoes dehydrogenative 2+2‐cycloaddition reactions with diphenylacetylene, azobenzene, acetone, benzophenone, and benzaldehyde to form the 1,4‐distannabarrelene derivatives. The elimination of H2 in these reactions suggests the masked‐diradical property of 1‐H2. In fact, these 2+2‐cycloaddition products are also accessible on treatments of the Sn(I) diradicaloid (ADC)Sn2 (1) with appropriate reagents. All compounds have been characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction. Moreover, the catalytic activity of 1‐H2 has been shown for the hydroboration of unsaturated substrates.
Reactivity (including catalytic activity) of hydridostannylene (1‐H2) with a variety of unsaturated (alkyne, carbonyl, azo) substrates has been reported. 1‐H2 (e. g.) undergoes dehydrogenative 2+2‐cycloaddition with Ph2CO to form the 1,4‐distannabarrelene 1‐OCPh2, which readily liberates Ph2CO on exposure to H2 and regenerates 1‐H2. Thus, 1‐H2 behaves as a masked Sn‐diradicaloid 1 that also affords 1‐OCPh2 on treatment with Ph2CO.
Mesoionic dithiolates (MIDtAr)Li(LiBr)2(THF)3 (MIDtAr={SC(NDipp)}2CAr; Dipp=2,6‐iPr2C6H3; Ar=Ph 3 a, 3‐MeC6H4 (3‐Tol) 3 b, 4‐Me2NC6H4 (DMP) 3 c) and (MIDtPh)Li(THF)2 (4) are readily accessible (in≥90 ...% yields) as crystalline solids on treatments of anionic dicarbenes Li(ADCAr) (2 a‐c) (ADCAr={C(NDipp)2}2CAr) with elemental sulfur. 3 a‐c and 4 are monoanionic ditopic ligands with both the sulfur atoms formally negatively charged, while the 1,3‐imidazole unit bears a formal positive charge. Treatment of 4 with (L)GeCl2 (L=1,4‐dioxane) affords the germylene (MIDtPh)GeCl (5) featuring a three‐coordinated Ge atom. 5 reacts with (L)GeCl2 to give the Ge−Ge catenation product (MIDtPh)GeGeCl3 (6). KC8 reduction of 5 yields the homoleptic germylene (MIDtPh)2Ge (7). Compounds 3 a‐c and 4–7 have been characterized by spectroscopic studies and single‐crystal X‐ray diffraction. The electronic structures of 4–7 have been analyzed by DFT calculations.
Mesoionic dithiolates Li(MIDts) as well as heteroleptic (MIDt)GeCl and homoleptic (MIDt)2Ge germylenes are reported as crystalline solids. The germylene (MIDt)2Ge features the highest‐lying HOMO (−4.37 eV) and has the smallest HOMO‐LUMO energy gap (2.82 eV) among the hitherto known germylenes. Insertion of GeCl2 into the Ge−Cl bond of (MIDt)GeCl affords the Ge−Ge catenation product (MIDt)GeGeCl3, a mixed‐valence Ge(+1)/Ge(+3) compound.
The first C5‐protonated abnormal N‐heterocyclic carbene (aNHC), PhC{N(2,6‐iPr2C6H3)}2CHC: (4) is readily accessible by C4‐deprotonation of ArC{N(2,6‐iPr2C6H3)}2CHCHX (3 a‐X) (Ar=Ph, X=Br or I) with a ...base. The aNHC 4 is stable at 298 K in D8THF solution and has been spectroscopically characterized. The facile availability of 4 enables the synthesis of a series of main‐group compounds as well as transition‐metal complexes featuring a new phosphorus‐aNHC hybrid ligand. Double deprotonation of ArC{N(2,6‐iPr2C6H3)}2CHCHX (Ar=Ph, 3 a‐X (X=Br or I); 4‐Tol, 3 b‐Br; 4‐DMP, 3 c‐Br; Tol=MeC6H4, DMP=Me2NC6H4) with nBuLi yields the C4,C5‐ditopic carbanionic aNHCs, ArC{N(2,6‐iPr2C6H3)}2(C:)2Li(THF)n (Ar=Ph, 13 a; 4‐Tol, 13 b; 4‐DMP, 13 c), which on treatment with Ph2PCl affords cationic vicinal bisphosphine derivatives ArC{N(2,6‐iPr2C6H3)}2{C(PPh2}2X (Ar=Ph, 14 a‐X, X=Br or I; 4‐Tol, 14 b‐Br; 4‐DMP, 14 c‐Br).
Happy with “H”: Deprotonation of the C2‐arylated 1,3‐imidazolium salt 3‐X affords the C5‐protonated aNHC, (aIPrPh) 4. Double deprotonation of 3‐X yields C4,C5‐ditopic carbanionic aNHC, 13. The facile accessibility of 4 and 13 not only enables easy access to challenging aNHC compounds and phosphorus ligands but also provides a unique platform for the design of new hybrid ligands and heterobimetallic complexes.
Decarbonylation of a cyclic bis‐phosphaethynolatostannylene (ADC)Sn(PCO)2 based on an anionic dicarbene framework (ADC = PhC{N(Dipp)C}2; Dipp = 2,6‐iPr2C6H3) under UV light results in the formation ...of a Sn2P2 cluster compound (ADC)SnP2 as a green crystalline solid. The electronic structure of (ADC)SnP2 is analyzed by quantum‐chemical calculations. At room temperature, (ADC)SnP2 reversibly binds with CO2 and forms (ADC)2{SnOC(O)P}SnP. (ADC)SnP2 enables catalytic hydroboration of CO2 and reacts with elemental selenium and Fe2(CO)9 to afford (ADC)2{Sn(Se)P2}SnSe and (ADC)Sn{Fe(CO)4}P2, respectively. All compounds are characterized by multinuclear NMR spectroscopy and their solid‐state molecular structures are determined by single‐crystal X‐ray diffraction.
The Sn2P2 cluster compound (ADC)SnP2 based on an anionic dicarbene (ADC) is isolated as a green crystalline solid. (ADC)SnP2 reversibly binds with CO2 at room temperature to form (ADC)2{SnOC(O)P}SnP and enables catalytic hydroboration of CO2.
•Important recent development in synthesis of multiple bonded pnictogens (P, As, Sb, Bi).•Structure and bonding of dipnictenes.•Heavy main-group element based functionalities.•Electrochemical ...behavior and synthetic accessibility of stable radicals.•Coordination chemistry of dipnictenes.
Dipnictenes are molecules comprising a double bond between two Group 15 elements (referred as pnictogens (Pn) = P, As, Sb, Bi). Over the last decades, the chemistry of dipnictenes has undergone a remarkable advance. This is largely because of the advancement of new ligand sets with distinct stereoelectronic properties. In general, classical dipnictenes are kinetically stabilized by the use of extremely bulky aryl or alkyl substituents. In recent years, numerous ligand frameworks featuring non-carbon donor substituents have also been introduced in dipnictenes chemistry. Now a plethora of dipnictenes with divergent electronic structure, reactivity, and physical properties are known. Among carbon-donor substituents, stable N-heterocyclic carbenes (NHCs) and other singlet carbenes have also been used as potent Lewis bases to derive related unsaturated species. A comprehensive understanding of the structure, bonding, and reactivity of a whole series of dipnictenes (RPn=PnR) (R = a substituent) as well as the influence of substituents on the nature of these species will be instrumental for the advancement of the field, in particular to unveil the relevance of these molecules in materials science. The aim of this review is to outline recent advances in dipnictene chemistry with a special focus on their reactivity. The outcomes show that dipnictenes have emerged from simple laboratory curiosities to versatile and useful synthons in modern main-group chemistry, which is expected to evolve further.
The cyclic Ge(I) compound (ADC
)Ge
(
) (ADC
= {CN(Dipp)}
CPh, Dipp = 2,6-
Pr
C
H
) containing a 6π-electron C
Ge
framework has been isolated as a red crystalline solid. CASSCF calculations reveal a ...closed-shell singlet ground state for
with a considerable diradical character (
= 34%). Thus, the diradicaloid
readily splits dihydrogen at room temperature to yield the elusive bis-hydridogermylene (ADC
)GeH
(
).
Decarbonylation of a cyclic bis-phosphaethynolatostannylene (ADC)Sn(PCO)2 based on an anionic dicarbene framework (ADC = PhC{N(Dipp)C}2 ; Dipp = 2,6-iPr2 C6 H3 ) under UV light results in the ...formation of a Sn2 P2 cluster compound (ADC)SnP2 as a green crystalline solid. The electronic structure of (ADC)SnP2 is analyzed by quantum-chemical calculations. At room temperature, (ADC)SnP2 reversibly binds with CO2 and forms (ADC)2 {SnOC(O)P}SnP. (ADC)SnP2 enables catalytic hydroboration of CO2 and reacts with elemental selenium and Fe2 (CO)9 to afford (ADC)2 {Sn(Se)P2 }SnSe and (ADC)Sn{Fe(CO)4 }P2 , respectively. All compounds are characterized by multinuclear NMR spectroscopy and their solid-state molecular structures are determined by single-crystal X-ray diffraction.
Decarbonylation of a cyclic bis-phosphaethynolatostannylene (ADC)Sn(PCO)
based on an anionic dicarbene framework (ADC = PhC{N(Dipp)C}
; Dipp = 2,6-iPr
C
H
) under UV light results in the formation of ...a Sn
P
cluster compound (ADC)SnP
as a green crystalline solid. The electronic structure of (ADC)SnP
is analyzed by quantum-chemical calculations. At room temperature, (ADC)SnP
reversibly binds with CO
and forms (ADC)
{SnOC(O)P}SnP. (ADC)SnP
enables catalytic hydroboration of CO
and reacts with elemental selenium and Fe
(CO)
to afford (ADC)
{Sn(Se)P
}SnSe and (ADC)Sn{Fe(CO)
}P
, respectively. All compounds are characterized by multinuclear NMR spectroscopy and their solid-state molecular structures are determined by single-crystal X-ray diffraction.
