The synthesis and reactivity of the tert‐butyl‐substituted arsanylborane tBuAsHBH2 ⋅ NMe3 (1) stabilized by a Lewis base (LB) are reported. Compound 1 is obtained by the reaction of in situ generated NatBuAsH with IBH2 ⋅ NMe3. By the reaction of 1 with Lewis acids the neutral compounds BBr3 ⋅ tBuAsHBH2 ⋅ NMe3 (2) and BH3 ⋅ tBuAsHBH2 ⋅ NMe3 (3) as well as coordination products towards Group 6 metal complexes [M(CO)4(tBuAsHBH2 ⋅ NMe3)2] (M=Cr, Mo, W; 4 a–c) are obtained. Upon reaction with IBH2 ⋅ LB (LB=SMe2, NMe3), the cationic oligomeric arsanylboranes [(Me3N ⋅ BH2tBuAsHBH2 ⋅ NMe3)]I (5) and [H2B(tBuAsHBH2 ⋅ NMe3)2]I (6) were isolated. Compound 1 was also used as starting material for the synthesis of the first oligomeric arsanylboranes obtained by thermal oligomerization under different conditions. DFT computations support the experimental observations.
The coordination behavior of different pnictogenylboranes towards group 6 metal Lewis acids is investigated. The resulting complexes with phosphanylboranes [(CO)4M(PH2BH2 ⋅ NMe3)2] (M=Cr, Mo, W; 1–3), arsanylboranes ([(CO)4M(AsH2BH2 ⋅ NMe3)2] (M=Cr, Mo, W; 4–6) and tBu‐substituted phosphanylboranes [(CO)4M(tBuPHBH2 ⋅ NMe3)2] (M=Cr, W; 7–8) are fully characterized by multinuclear NMR spectroscopy, single crystal X‐ray diffraction and IR spectroscopy. The systematic nature of the approach of the synthesis and the high purity of the compounds enable a comparative investigation of the coordination behavior of pnictogenylboranes. The influences of the metal center, the pnictogen atom and the substituent at the pnictogen atom on the coordination behavior of pnictogenylboranes are compared.
The reactivity of the organic‐substituted arsanylborane tBuAsHBH2NMe3 (1) towards different elemental chalcogenes as well as organic oxidants such as O‐NMe3, Me3Si−O−O‐SiMe3, MesCNO and cyclohexenesulfide is reported. By the reaction of 1 with grey selenium, the selenium oxidation product tBuAs(Se)HBH2NMe3 (2) was obtained. For the oxidation with sulfur, the two products tBuAs(S)HBH2NMe3 (3 a) and tBuAs(S)SHBH2NMe3 (3 b) could be isolated as oils. The structural characterization of As(tBuAs(S)SHBH2NMe3)3 (4) as well as corresponding DFT computations allow insights into the decomposition behavior of 3 a and 3 b in solution. For the reaction of MesCNO with 1, the formation of an unusual As−H activation product Mes‐C(NOH)‐AstBu‐BH2NMe3 (5) is observed. In the reaction with Me3N−O, the first isolatable oxo‐arsanylboranes tBuAs(O)HBH2NMe3 (6 a) and tBuAs(O)OHBH2NMe3 (6 b) are obtained, with 6 b also being accessible via the controlled reaction of 1 with air.
The reaction of the Lewis base‐stabilized phosphinoborane monomer tBuHPBH2NMe3 (2a) with catalytic amounts of bis(η5:η1‐adamantylidenepentafulvene)titanium (1) provides a convenient new route to the polyphosphinoborane [tBuPH‐BH2]n (3a). This method offers access to high molar mass materials under mild conditions and with short reaction times (20 °C, 1 h in toluene). It represents an unprecedented example of a transition metal‐mediated polymerization of a Lewis base‐stabilized Group 13/15 compound. Preliminary studies of the substrate scope and a potential mechanism are reported.
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