Reactivity of Lanthanocene Amide Complexes toward Ketenes: Unprecedented Organolanthanide-Induced Conjugate Electrophilic Addition of Ketenes to Arenes

Generation and reactivity of neutral 1,3-benzazaphosphole and anionic 1,3-benzazaphospholide ytterbium(iii) complexes

Treatment of Cp3Ln (Ln = Yb, Y) with 5-R3-6-R1-2-R2-1H-1,3-benzazaphosphole (HBp) (HBp1 (1a): R1 = H, R2 = 2,4,6-Me3C6H2, R3 = Me; HBp2(1b): R1 = Me, R2 = C6H5, R3 = H; HBp3(1c): R1 = R3 = H, R2 = C6H5) at room temperature gives the crystalline 1 : 1 Lewis acid-base adducts [(η1(p)-HBp)LnCp3] (2a-d) [Ln = Yb: Bp = Bp1 (2a), Bp2 (2b), Bp3 (2c); Ln = Y: Bp2 (2d)] with Ln-P donor bonds in good yields. Heating 2a-c in toluene leads to the liberation of one molecule of CpH to afford the corresponding N-bonded complexes [Cp2YbBp] (Bp = Bp1 (3a), Bp2 (3b), Bp3 (3c)). Interestingly, the P atom of complexes 3a-c can also be further coordinated to another Lewis acid such as Cp3Yb and B(C6F5)3 to give the adducts [Cp2Yb(μ-η1(N):η2(C,C):η1(P)-Bp)YbCp3] (Bp = Bp1 (4a), Bp2 (4b), Bp3 (4c)) and [Cp2Yb(μ-η1(N):η2(C,C):η1(P)-Bp)B(C6F5)3] (Bp = Bp1 (5a), Bp2 (5b), Bp3 (5c)), respectively. The molecular structures of complexes 2a, 4b-4c and 5c are confirmed by X-ray diffraction analysis.

Isocyanate diinsertion into the N-H bond of the 2-pyridylamino ligand of organolanthanides

[Cp2LnNHPy]2 (Py = 2-pyridyl) (1a-e) react with phenyl isocyanate to form the N-H diinsertion products Cp2Ln[eta2:eta1-PyNCON(Ph)CONHPh](THF) (Ln = Yb (3a), Er (3b), Y (3c), Dy (3d), Gd (3e)). It has been proven that nPr2NH can abstract one PhNCO unit from 3c to form Cp2Y[eta3-OC(NHPh)NPy] (2c) and nPr2NHCONHPh (4), representing a rare example of selective release of a functional group of ligands in organolanthanide chemistry. Hydrolysis of 2c gives the organic nitrogen-containing product PyNHCONHPh (5). Moreover, 3c can also be obtained by the reaction of 2c with PhNCO. These results demonstrate that the diinsertion of PhN=C=O into the N-H bond of coordinated amino ligands might proceed in a stepwise manner. All the compounds were characterized by elemental analysis and spectroscopic properties. The structures of compounds 3a-e and 4 are also determined through X-ray single-crystal diffraction analysis.

Selective Reaction Based on the Linked Diamido Ligands of Dinuclear Lanthanide Complexes

The dinuclear ytterbium pyridyl diamido complexes [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,6)] (1a) and [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,3)] (1b) are easily prepared by protonolysis of Cp(3)Yb with 0.5 equiv of the corresponding diaminopyridine in accepted yields, respectively. Treatment of 1a with 2 equiv of dicyclohexylcarbodiimide (CyN=C=NCy) in THF at low temperature leads to the isolation of the formal double N-H addition product (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyN(CyNH)CN)(2)(C(5)H(3)N-2,6)] (2) in 42% yield. Compound 2 is unstable to heat and slowly isomerized to the mixed neutral/dianionic diguanidinate complex (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyNH)(2)CN(C(5)H(3)N-2,6)NC(NCy)(2)](THF) (3) at room temperature. Similarly, treatment of 1b with 2 equiv of CyN=C=NCy gives the addition/ isomerization product (Cp(2)Yb)(2)[mu-eta(2):eta(2):eta(1)-(CyNH)(2)CN(C(5)H(3)N-2,3)NC(NCy)(2)] (4). Moreover, the reaction of various ytterbium aryl diamido complexes (prepared in situ from [Cp(2)YbMe](2) and aryldiamine, respectively) with CyN=C=NCy affords the corresponding addition products (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,4)] (5), (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,3)](6), and (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(13)H(8)-2,7)] (7), respectively. In contrast to pyridyl-bridged bis(guanidinate monoanion) complexes, aryl-bridged bis(guanidinate monoanion) complexes 5-7 are stable even with prolonged heating at 110 degrees C. All the results not only demonstrate that the presence of the pyridyl bridge can impart the diamido complexes with a unique reactivity and initiate the unexpected reaction sequence but also indicate evidently that the number and distribution of negative charges of the diguanidinate ligand is tunable from double monoanionic units to mixed neutral/dianionic isomers. All the complexes are characterized by elemental analysis and IR spectroscopies. The structures of complexes 1a, 3, 5, 6, and 7 are also determined through X-ray single-crystal diffraction analysis.

Synthesis and structural characterization of lanthanide complexes with the di- or tri-anionic diguanidinate ligand: new insight into the flexibility and distinct reactivity of the linked diguanidinate ligand

Unprecedented disproportionation and deprotonation of the linked diguanidinate ligand have been established, demonstrating, for the first time, that the number and distribution of negative charges on the diguanidinate ligand are tunable, and representing a new and efficient method for synthesis of linked diguanidinate di- and tri-anion complexes.