Yttrium-Catalyzed Amine–Silane Dehydrocoupling: Extended Reaction Scope with a Phosphorus-Based Ligand

Abstract

The scope of the catalytic dehydrocoupling of primary and secondary amines with phenylsilanes has been investigated using [Y{N-(SiMe 3 ) 2 } 3 ] and a four-coordinate analogue bearing a cyclometalated phosphonium methylide ligand. Inclusion of the phosphorus-based ligand on yttrium results in increased substrate scope in comparison to the tris(amide) analogue. While reversible C−H bond activation of the cyclometalated ligand was observed in stoichiometric experiments, Dlabeling experiments and DFT calculations suggest that reversible ligand activation is not involved in silazane formation under catalytic conditions. We suggest that the extended reaction scope with the four-coordinate yttrium phosphonium methylide complex relative to the three-coordinate yttrium (tris)amide complex is a result of differences in the ease of amine inhibition of catalysis.

Tailored Cyclic and Linear Polycarbosilazanes by Barium‐Catalyzed N−H/H−Si Dehydrocoupling Reactions

“…[10] Elsewhere,w ea nd others have shown that oxophilic,d 0 metal complexes provide competent precatalysts to dehydrocouple hydrosilanes and amines. [11][12][13][14] Barium compounds in particular catalyze the coupling of diamines and di(hydrosilanes). [14a,b] We present here an extension of this work to the barium-mediated production of polycarbosilazanes.T he rapid and controlled syntheses of either linear or cyclic polymers by dehydropolymerization of p-xylylenediamine (represented as H 2 N^^NH 2 )a nd diphenylsilane, together with detailed characterizations,a re reported (Scheme 1).…”

“…With 10 % excess,t he polymer P6,w ith am olecular weight of about 4500 gmol À1 ,c orresponding to X n,exp = 28, was obtained (entry 6). [21] Them ain resonances in the 1 H( d = 4.09 and 1.42 ppm), 13 C{ 1 H} (d = 45.79 ppm), and 29 Si{ 1 H} (d = À24.32 ppm) NMR spectra of P5-P7 match those for P2 and P3,t hus confirming the preponderance of regular repetitive units in the polymer backbone ( Figure 4). Thep olycarbosilazane P7,w hich is of comparatively high molecular weight (ca.…”

Catalytic Formation of Silicon–Heteroatom (N, P, O, S) Bonds

“…Limited by a small substrate scope, only nonsterically hindered amines and silanes can be utilized. Subsequently, the Crimmin group has reported dehydrocoupling by incorporating yttrium(III) disilazide and its analogues in the form of a four‐coordinated species bearing a cyclometalated phosphonium methylide ligand . The ligand's presence results in better catalytic activity than that observed for the simple disilazide.…”

Alkali‐Metal‐Catalyzed Cross‐Dehydrogenative Couplings of Hydrosilanes with Amines

“…As a result, significant efforts have been devoted to provide an alternative protocol to create Si−N bonds using N−H/H−Si CDC reactions. Catalyzed reactions have largely involved catalysts based on Ti IV , Al III , Cu I , Rh I ,, Ru 0 , Yb II ,, Y III , Zn II , and U IV , or also metal‐free frustrated Lewis pairs (FLPs) ,. Si−N coupling catalyzed by main‐group metal reagents, chiefly group 2, is particularly effective.…”