Divergent Reactivity of a Cyclic Bis-Hydridostannylene: A Masked Sn(I) Diradicaloid.

Herein, reactivity studies of a cyclic bis-hydridostannylene [(ADC)SnH]2 (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)Sn]2 (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.

Mesoionic Dithiolates (MIDts) Derived from 1,3-Imidazole-Based Anionic Dicarbenes (ADCs).

Mesoionic dithiolates [(MIDtAr )Li(LiBr)2 (THF)3 ] (MIDtAr ={SC(NDipp)}2 CAr; Dipp=2,6-iPr2 C6 H3 ; Ar=Ph 3 a, 3-MeC6 H4 (3-Tol) 3 b, 4-Me2 NC6 H4 (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 }2 CAr) 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 )2 Ge (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.

Isolation of a Ge(I) Diradicaloid and Dihydrogen Splitting.

The cyclic Ge(I) compound [(ADCPh)Ge]2 (4) (ADCPh = {CN(Dipp)}2CPh, Dipp = 2,6-iPr2C6H3) containing a 6π-electron C4Ge2 framework has been isolated as a red crystalline solid. CASSCF calculations reveal a closed-shell singlet ground state for 4 with a considerable diradical character (y = 34%). Thus, the diradicaloid 4 readily splits dihydrogen at room temperature to yield the elusive bis-hydridogermylene [(ADCPh)GeH]2 (5).

The Viability of C5-Protonated- and C4,C5-Ditopic Carbanionic Abnormal NHCs: A New Dimension in NHC Chemistry.

The first C5-protonated abnormal N-heterocyclic carbene (aNHC), PhC{N(2,6-iPr2 C6 H3 )}2 CHC: (4) is readily accessible by C4-deprotonation of [ArC{N(2,6-iPr2 C6 H3 )}2 CHCH]X (3 a-X) (Ar=Ph, X=Br or I) with a base. The aNHC 4 is stable at 298 K in [D8 ]THF 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-iPr2 C6 H3 )}2 CHCH]X (Ar=Ph, 3 a-X (X=Br or I); 4-Tol, 3 b-Br; 4-DMP, 3 c-Br; Tol=MeC6 H4 , DMP=Me2 NC6 H4 ) with nBuLi yields the C4,C5-ditopic carbanionic aNHCs, [ArC{N(2,6-iPr2 C6 H3 )}2 (C:)2 ]Li(THF)n (Ar=Ph, 13 a; 4-Tol, 13 b; 4-DMP, 13 c), which on treatment with Ph2 PCl affords cationic vicinal bisphosphine derivatives [ArC{N(2,6-iPr2 C6 H3 )}2 {C(PPh2 }2 ]X (Ar=Ph, 14 a-X, X=Br or I; 4-Tol, 14 b-Br; 4-DMP, 14 c-Br).

Isolation of an Anionic Dicarbene Embedded Sn2 P2 Cluster and Reversible CO2 Uptake.

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)SnP]2 as a green crystalline solid. The electronic structure of [(ADC)SnP]2 is analyzed by quantum-chemical calculations. At room temperature, [(ADC)SnP]2 reversibly binds with CO2 and forms [(ADC)2 {SnOC(O)P}SnP]. [(ADC)SnP]2 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 }P]2 , respectively. All compounds are characterized by multinuclear NMR spectroscopy and their solid-state molecular structures are determined by single-crystal X-ray diffraction.