π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

Abstract

Contents 1. Introduction 3877 2. Bonding 3877 3. Doubly Bonded Compounds 3882 3.1. Compounds of Formula REdER (E ) Group 13 Element) 3882 3.2. Compounds of Formula REdE′R 2 (E Group 13, E′ ) Group 14 Element) and Related Species 3884 3.3. Dianions of Formula [R 2 EdER 2 ] 2-(E ) Group 13 Element) 3884 3.4. Monoanions of Formula [R 2 EdE′R′ 2 ] -(E ) Group 13, E′ ) Group 14 Element) 3885 3.5. Compounds of Formula R 2 E-E ¨′R 2 (E ) Group 13, E′ ) Group 15 Element) and Related Species 3886 3.6. Compounds of Formula R 2 E-E′R and [R 2 E-E′] -(E ) Group 13, E′ ) Group 16 Element) 3888 3.7. Compounds of Formula R 2 EdER 2 , [L:E ¨dE ¨:L] and [RE ¨dE ¨R] 2-(E ) Group 14 Element) 3888 3.8. Compounds of Formula R 2 EdE ¨′R (E ) Group 14, E′ ) Group 15 Element) 3896 3.9. Compounds of Formula [R 2 EdE ¨′R 2 ] + (E ) Group 14, E′ ) Group 15 Element) 3900 3.10. Compounds of Formula R 2 EdE ¨′ (E ) Group 14, E′ ) Group 16 Element) 3901 3.11. Compounds of Formula RE ¨)E ¨R, (E or E′ ) N, P, As, Sb, or Bi) 3902 3.12. Compounds of Formula RE ¨dE′ (E ) Group 15, E′ ) Group 16 Element) 3908 4. Triply Bonded Compounds 3908 4.1. Group 13 Derivatives 3908 4.2. Group 14 Derivatives 3909 4.3. Compounds with Potential Triple Bonding between Group 14 and Group 15 Elements 3912 4.4. Compounds with Potential Triple Bonding between Group 14 and Group 16 Elements 3913 4.5. Compounds with Triple Bonding between Group 15 Elements 3913 5. Conclusions 3914 6. List of Abbreviations 3914 7. Acknowledgments 3915 8. References 3915

Dispersion Forces and Counterintuitive Steric Effects in Main Group Molecules: Heavier Group 14 (Si–Pb) Dichalcogenolate Carbene Analogues with Sub-90° Interligand Bond Angles

“…Melting points were determined on a Meltemp II apparatus using glass capillaries sealed with vacuum grease and are uncorrected. (2). The structure of the potassium salt (29) was also determined from an independently-synthesized sample, as was the structure of the Si(Br)2(SAr Pr i 4 )2 (25), which was a 5 % contaminant.…”

Synthesis and Characterization of N-Heterocyclic Carbene-Coordinated Silicon Compounds Bearing a Fused-Ring Bulky Eind Group

“…We first performed an NMR tube scale reaction of Eind-based 1,2-dibromodisilene, (Eind)BrSi=SiBr(Eind) (1a) [20], in C 6 D 6 with two equivalents of the sterically more bulky NHC, Im-i Pr 2 Me 2 , relative to Im-Me 4 . The progress of the reaction was monitored by 1 H NMR spectroscopy, indicating the selective formation of the mono-NHC adduct of the arylbromosilylene, (Im-i Pr 2 Me 2 )→SiBr(Eind) (2a ), after overnight heating at 70 • C. In the 29 Si NMR spectrum, only one signal was observed at δ = 18.0 ppm, which is comparable to those of (Im-i Pr 2 Me 2 )→SiBr(EMind) (VIb ) (δ = 13.1 ppm) and (Im-Me 4 )→SiBr(Bbt) (VIe) (δ = 10.9 ppm) [22].…”

“…Over many years, a number of unsaturated silicon compounds have been successfully obtained by virtue of the complexation of metal ions and/or coordination of ligands (mainly Lewis bases) in addition to steric protection with bulky substituents [1][2][3][4][5][6][7][8][9][10][11]. Among them, the coordination chemistry of highly-reactive halosilylenes, i.e., halogen-substituted divalent Si(II) species, have attracted a lot of attention as potentially useful precursors for the construction of a wide range of silicon-containing compounds [12][13][14][15][16][17].…”

“…In 2013, Filippou's group reported the unprecedented dicationic NHC complexes of silicon(II) and NHC adducts of iodesilyliumylidene cation SiI + [35]. Subsequently, we reported the reaction of 1,2-dibromodisilenes (1b, 1e, and 1f) having EMind, Bbt, and Tbb groups (Tbb = 2,6-{CH(SiMe 3 ) 2 } 2 -4-t Bu-C 6 H 2 (f)) with NHCs (Im-Me 4 [24]. Recently, Inoue's group reported on the chalcogen-atom transfer and exchange reactions of NHC-bound heavier silaacylium ions, [(Im-Me 4 ) 2 →Si(E)(Ar)] + [Cl − ] (E = S, Se, and Te) [36].…”

Hydride Abstraction and Deprotonation – an Efficient Route to Low Coordinate Phosphorus and Arsenic Species

“…[2][3][4][5][6] Free phosphanylidene-σ 4 -phosphoranes are rather reactive species, with only a handful of published examples where the compound is stabilised by extremely electron withdrawing substituents, [7,8] steric shielding, [9][10][11] or the combination of a rigid backbone and steric shielding. [12] Low co-ordinate arsenic chemistry is significantly less studied than that of phosphorus, with most attention being focused on arsaalkenes (R 2 C=AsR'), diarsenes (RAs=AsR), [13][14][15][16] and phosphine-and carbene-stabilised cationic species. [17][18][19] Until recently, the only semi-isolable arsanylidene-σ 4 -phosphorane to be reported was 2,6-Trip 2 C 6 H 3 As=PMe 3 (Trip = 2,4,6-iPr 3 C 6 H 2 ) [20] which, despite extensive steric shielding, decomposes to the diarsene at room temperature.…”