The potential of NO+ and O2 +• in switchable reagent ion proton transfer reaction time-of-flight mass spectrometry.

Selected ion flow tube mass spectrometry (SIFT-MS) and proton transfer reaction mass spectrometry with switchable reagent ion capability (PTR+SRI-MS) are analytical techniques for real-time qualification and quantification of compounds in gas samples with trace level concentrations. In the detection process, neutral compounds-mainly volatile organic compounds-are ionized via chemical ionization with ionic reagents or primary ions. The most common reagent ions are H3 O+ , NO+ and O2 +• . While ionization with H3 O+ occurs by means of proton transfer, the ionization via NO+ and O2 +• offers a larger variety on ionization pathways, as charge transfer, hydride abstraction and so on are possible. The distribution of the reactant into various reaction channels depends not only on the usage of either NO+ or O2 +• , but also on the class of analyte compounds. Furthermore, the choice of the reaction conditions as well as the choice of either SIFT-MS or PTR+SRI-MS might have a large impact on the resulting products. Therefore, an overview of both NO+ and O2 +• as reagent ions is given, showing differences between SIFT-MS and PTR+SRI-MS as used analytical methods revealing the potential how the knowledge obtained with H3 O+ for different classes of compounds can be extended with the usage of NO+ and O2 +• .

Three- and Five-Membered Anionic Chains of Pnictogenylboranes.

An unprecedented family of three- and five-membered substituted anionic derivatives of parent pnictogenylboranes is herein reported. Reacting various combinations of the pnictogenylboranes H2 E'-BH2 -NMe3 (E'=P, As) with pnictogen-based nucleophiles MER1R2 (E=P, As; R1=H, R2=t Bu; R1=R2=Ph; M=Na, K) allows for the isolation of the unsymmetrical products [Na(18-crown-6)][H2 E'-BH2 -EHt Bu] (3: E=E'=P; 4: E=E'=As; 5: E=As, E'=P) and [M(C)][H2 E'-BH2 -EPh2 ] (7: E=E'=P, M=Na, C=18-crown-6; 8: E=E'=As; M=K, C=[2.2.2]cryptand; 9: E=P, E'=As, M=Na, C=[2.2.2]cryptand; 10: E=As, E'=P, M=K, C=[2.2.2]cryptand). [Na(18-crown-6)][H2 As-BH2 -t BuPH-BH3 ] (6) is only accessible by a different pathway, using t BuPH2 , BH3 ⋅ SMe2 and NaNH2 as starting materials. Additionally, the synthesis of symmetrical diphenyl-substituted compounds [M(18-crown-6)][Ph2 E-BH2 -EPh2 ] (11: E=P, M=Na; 12: E=As, M=K) is reported which can be regarded as isostructural inorganic, negatively charged analogs of dppm (1,1-bis(diphenylphosphino)methane) and dpam (1,1-bis(diphenylarsino)methane). Furthermore, an elongation of the pnictogen boron backbone in compounds 3, 7 and 9' (similar compound to 9, stabilized however by 18-crown-6), is attainable by reacting them with the pnictogenylboranes H2 E'-BH2 -NMe3 leading to corresponding five-membered chain-like compounds [Na(18-crown-6)][H2 E-BH2 -R1R2P-BH2 -E'H2 ] (E=E'=P, R1=H, R2=t Bu (13); E=E'=P, R1=R2=Ph (14); E=E'=As, R1=R2=Ph (15); E=P, E'=As, R1=R2=Ph (16)). Finally, the thermodynamics of the reaction pathways were evaluated by quantum chemical computations.

Bidentate Phosphanyl- and Arsanylboranes.

A new class of neutral bidentate ligands with pnictogenyl-functional sites has been obtained. The reaction of tmeda⋅(BH2 I)2 (1, tmeda=tetramethylethylendiamine) with different phosphanides yields the corresponding bidentate phosphanylboranes tmeda⋅(BH2 PH2 )2 (2 a), tmeda⋅(BH2 PPh2 )2 (2 b), and tmeda⋅(BH2 tBuPH)2 (2 c). This reaction strategy could be further extended to synthesize the first bidentate arsanylborane tmeda⋅(BH2 AsPh2 )2 (3). Depending on the substituents on the phosphorus, these compounds form different AuI complexes, to build either polymeric tmeda⋅(BH2 PH2 AuCl)2 (4 a), or monomeric tmeda⋅(BH2 PPh2 AuCl)2 (4 b) products. These compounds form also neutral oligomeric group 13/15 chain-like molecules by coordination to a boron moiety such as tmeda⋅(BH2 PH2 BH3 )2 (5 a) and tmeda⋅(BH2 AsPh2 BH3 )2 (5 b). DFT calculations provide insight into the differences between the syntheses of mono- and bidentate pnictogenylboranes.

The Lewis-Base-Stabilized Diphenyl-Substituted Arsanylborane: A Versatile Building Block for Arsanylborane Oligomers.

The synthesis and properties of the diphenyl-substituted arsanylborane Ph2 AsBH2 SMe2 (1) and Ph2 AsBH2 NMe3 (2) stabilized by a Lewis base (LB) were reported. These compounds were obtained by reaction of KAsPh2 with IBH2 -LB (LB=SMe2 , NMe3 ). Compounds 1 and 2 were used as starting materials for oligomeric/ polymeric arsinoboranes. The neutral species, H3 B-Ph2 AsBH2 NMe3 (3) and Br3 B-Ph2 AsBH2 NMe3 (4), were synthesized by reaction with H3 B and Br3 B, respectively. Upon reaction with IBH2 -LB (LB=SMe2 , NMe3 ), the cationic oligomeric group-13/15-based compounds [(Me3 NBH2 AsPh2 BH2 NMe3 )]I (5) and [H2 B(Ph2 AsBH2 NMe3 )2 ]I (6) were obtained. All compounds were completely characterized. In addition, the oxidation of Ph2 AsBH2 NMe3 with chalcogens was studied. The sulfur Ph2 As(S)BH2 NMe3 (7 b) and selenium Ph2 As(Se)BH2 NMe3 (7 c) oxidation products were both isolated and fully characterized, whereas the bis(trimethylsilyl)peroxide oxidated arsinoborane Ph2 As(O)BH2 NMe3 (7 a) was not stable enough and could only be characterized in solution. DFT computations supported the decomposition pathway of this compound.

Depolymerization of Poly(phosphinoboranes): From Polymers to Lewis Base Stabilized Monomers.

We report on depolymerization reactions of poly(phosphinoboranes). The cleavage of the polymers [H2 PBH2 ]n (2 a), [tBuHPBH2 ]n (2 c), [PhHPBH2 ]n (2 e) and the oligomer [Ph2 PBH2 ]n (2 b), with strong Lewis bases (LBs), in particular with NHCs, leads to the corresponding monomeric phosphanylboranes R1 R2 PBH2 LB. It is observed that the depolymerization depends on the strength and stability of the LBs as well as on the substitution pattern of the poly(phosphinoboranes). The solid state structures of the monomeric phosphinoboranes H2 PBH2 NHCMe (NHC=N-heterocyclic carbene) (4 a), H2 PBH2 NHCdipp (5 a) and tBuHPBH2 NHCMe (4 c) were determined. DFT calculations support the experimentally observed reaction behavior.

A Convenient Route to Mixed Pnictogenylboranes.

We report on the synthesis and characterization of mixed pnictogenylboranes. The substitution of the Lewis base SMe2 in (OC)5 W-PH2 BH2 -SMe2 (2) by different pnictogenylboranes ER2 BH2 -LB (E=P, As, Sb) leads to the Lewis acid/base stabilized butane analogue (OC)5 W-PH2 BH2 ER2 BH2 -LB (3 a, b: E=P; R=H, SiMe3 ; LB=NMe3 ; 4 a, b: E=As; R=H, SiMe3 ; LB=NMe3 ; 5: E=Sb; R=SiMe3 ; LB=NHCMe ). All of these compounds were characterized by single-crystal X-ray structure analysis, mass spectrometry, NMR, and IR spectroscopy. In addition, the very unstable phosphanylborane chain PH2 BH2 PH2 BH2 -NMe3 (1) was synthesized. DFT calculations provide insight into the thermodynamics of these reactions.

Oxidation of Substituted Phosphanylboranes with Chalcogens.

The elemental chalcogens sulfur, selenium, tellurium and bis(trimethylsilyl)peroxide as an oxygen source are applied for the oxidation of the phosphanylboranes Ph2 P-BH2 ⋅NMe3 (1) and tBuHP-BH2 ⋅NMe3 (2). The corresponding monooxidation products Ph2 P(X)-BH2 ⋅NMe3 (X=O-Te, 3 a-d) and tBuHP(X)-BH2 ⋅NMe3 (X=O-Te, 4 a-d) were obtained in good yields and comprehensively characterized by single crystal X-ray structure analysis, NMR, IR spectroscopy and mass spectrometry. The first oxidation step proceeds very selectively for all chalcogenides. For the tBu derivative, a further oxidation can be realised with O2 , S8 and Se yielding tBu(HX)P(X)-BH2 ⋅NMe3 (X=O, S, Se, 5 a-c). The telluride compounds presented herein are the first examples of neutral Te-substituted phosphanylboranes.

Isolation and Characterization of Lewis Base Stabilized Monomeric Parent Stibanylboranes.

The synthesis of the Lewis base stabilized monomeric parent compound of stibanylboranes, "H2 Sb-BH2 ", is reported. Through a salt metathesis route, the silyl-substituted compounds (Me3 Si)2 Sb-BH2 ⋅LB (LB=NMe3 , NHC(Me) ) were synthesized as representatives of derivatives with a Sb-B σ bond. Under very mild conditions, they could be transformed into the target compounds Me3 N⋅H2 B-HSb-BH2 ⋅NMe3 and H2 Sb-BH2 ⋅NHC(Me) , respectively. The products were characterized by X-ray structure analysis, NMR spectroscopy, IR spectroscopy, and mass spectrometry. DFT calculations give further insight into the stability and bonding of these unique compounds.