Salt metathesis versus protonolysis routes for the synthesis of silylamide Hauser base (R2NMgX; X = halogen) and amido-Grignard (R2NMgR) complexes

摘要

The preparation of silylamide Hauser base (R2NMgX; X = halide) and amido-Grignard (R2NMgR) complexes from simple Grignard reagents using [K{N((SiMe2Bu)-Bu-t)(2)}](n), [K{N((SiMe2Bu)-Bu-t)((SiPr3)-Pr-i)}](n) and[ K{N((SiPr3)-Pr-i)(2)}](n), and their parent silylamines, was explored. Both salt metathesis and protonolysis routes proved ineffective with allylmagnesium chloride as a starting material due to complex Schlenk equilibria, with [Mg(N-RR')(mu-Cl)-(THF)](2) (N-RR' = {N((SiBuMe2)-Bu-t)(2)}(-), 1; {N(S(i)tBuMe(2))((SiPr3)-Pr-i)}(-), 2; {N((SiPr3)-Pr-i)(2)}(-), 3) and [Mg{N((SiPr3)-Pr-i)(2)}(mu-C3H5)](infinity) (4) identified as minor products. In contrast, salt metathesis protocols using potassium silylamides and methylmagnesium iodide gave[ Mg(N-RR')(mu-CH3)](2) (N-RR' = {N((SiBuMe2)-Bu-t)(2)}(-), 7a; {N((SiBuMe2)-Bu-t)((SiPr3)-Pr-i)}(-), 8; {N((SiPr3)-Pr-i)(2)}(-), 9) and[ Mg{N((SiBuMe2)-Bu-t)(2)}(CH3)(DME)] (7b), with[ Mg{N(SitBuMe(2))(2)}(mu-I)(THF)](2) (10) isolated as a side-product during the preparation of 7a. Unusually, methylmagnesium iodide, di-n-butylmagnesium and 7-9 did not react with HNRR' under the conditions we employed. The synthesis of [Na{N((SiBuMe2)-Bu-t)(2)}-(THF)](2) (5a) and [Na{N(SitBuMe(2))(2)}(DME)(2)] (5b) from benzyl sodium and HN((SiBuMe2)-Bu-t)(2), and a solvent-free structure of[ K{N(SitBuMe(2))(2)}] (6), are also reported. Complexes 1, 5b, 7a, 7b, 8, 9 and 10 are fully characterised by single crystal XRD, multinuclear NMR and IR spectroscopy and elemental analysis, whereas complexes 2-4, 5a and 6 were identified by XRD only.