Tris(cyclopentadienyl)lanthanide Complexes as Catalysts for Hydroboration Reaction toward Aldehydes and Ketones

Abstract

It was found that homoleptic cyclopentadienyl lanthanide complexes CpLn (Ln = Y (1), Yb (2), Sm (3), Nd (4), La (5), Cp = cyclopentadienyl) can be employed as excellent catalysts for the hydroboration of various aldehydes and ketones toward pinacolborane. These robust lanthanide catalysts exhibited high reactivity with low catalyst loadings (0.01-1 mol %) under mild conditions and good functional group tolerability. These complexes also demonstrated uniquely carbonyl-selective hydroboration in the presence of alkenes and alkynes.

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

“…[4][5][6][7][8] Lanthanide oxophilicity can also enable C-O bond cleavage in ethers or in transesterification reactions; however, reductive catalytic C-O bond cleavage processes are typically inhibited by the stabilization of intermediates containing Ln-O bonds (Ln = lanthanides and group 3). A few examples of hydroboration of ketones and aldehydes, using the homoleptic lanthanum catalysts La{N(SiMe3)2}3 and Cp3La, [9][10][11] or hydroboration and C-O bond cleavage of esters catalyzed by La{C(SiHMe2)3}3 or La{N(SiMe3)2}3, [12][13] suggest strategies for overcoming the Ln-O bond strength to make use of highly electrophilic lanthanide centers. In fact, La{C(SiHMe2)3}3 represents the most active and versatile catalyst for the ringopening hydroboration of epoxides to date.…”

“…Among the analytical techniques capable of probing the grafting process, as well as the structures and dynamics of surface-attached organometallic species, nuclear magnetic resonance (NMR) spectroscopy proved to be particularly powerful. 29,32,[35][36][37][38][39][40][41] Here, definite structural characterizations of the surfacegrafted alkyl lanthanum species were obtained from one-and two-dimensional (1D and 2D) solid-state (SS)NMR measurements on 1 H, 11 B, 13 C and 29 Si nuclei, performed in concert with solution-state NMR, elemental analysis and diffuse reflectance infrared spectroscopy (DRIFTS). Importantly, SSNMR experiments were used to understand and optimize the grafting reactions, to provide spectroscopic signatures of the secondary La↼H-Si interactions in the grafted ligands, and to propose the structures of the active catalytic centers generated by reacting pinacolborane (HBpin) with surface-attached alkyl lanthanum species.…”

Catalytic Hydroboration of Organic Nitriles Promoted by Aluminum Complex

“…[9][10][11][12][13][14] As a result, innumerable procedures have been evolved to accomplish the addition of boranes to nitriles. All these procedures require more or less effective catalysts based on transition-metal complexes such as Co, Fe, Ru, [15][16][17][18][19][20][21][22][23] alkaline earth metal (Mg), [24][25][26][27][28][29][30][31][32][33][34][35] but the processes culminate in frustrated Lewis pairs. [36][37][38] On the other hand, while the reduction of aryl and alkyl nitriles can be achieved using stoichiometric quantities of maingroup reducing agents such as LiAlH 4 and NaBH 4 , [39] the combustible nature of these reagents and large quantities of inorganic waste by-products they generate render the process unattractive, and hence reductive hydroboration is preferable in order to provide further functionality to the resultant amine.…”

La[N(SiMe3)2]3‐Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups

“…For example, some reported catalysts demonstrated high efficiency on aldehydes and ketones but proved to have no catalytic activity on esters at all . Viewing that the ester hydroboration has been reported sparingly, it is rewarding to extend our existed hydroboration work from aldehydes and ketones,[10a‐d] imines and alkynes[10e] as well as carboxylic acids[10f] to esters. Recently, Marks et al .…”