Detailed Density Functional Theory Study of the Cationic Zirconocene Compound [Cp(C₅H₄CMe₂C₆H₄F)ZrMe]⁺

Detailed density functional theory studies at the B3LYP and PBE-D3 levels of theory were performed on the cationic compound [Cp(C5H4CMe2C6H4F)ZrMe]+, with the F atom occupying either the ortho, meta, or para positions of the arene ring. In all cases, the arene ring coordinates with the cationic zirconium metal. The nature of this coordination is such that for the meta- or para-substituted arene ring, it is predominantly the ortho carbon atom of the C–H bond which interacts with the metal, as evident from noncovalent interaction studies. This is further corroborated by the natural bond orbital and quantum theory of atoms in molecular studies. In the case of the F atom being in the ortho position, we obtained clear-cut evidence for a Zr–F coordination

Main Group Multiple C–H/N–H Bond Activation of a Diamine and Isolation of A Molecular Dilithium Zincate Hydride: Experimental and DFT Evidence for Alkali Metal–Zinc Synergistic Effects

The surprising transformation of the saturated diamine (<i>i</i>Pr)NHCH₂CH₂NH(<i>i</i>Pr) to the unsaturated diazaethene [(<i>i</i>Pr)NCHCHN(<i>i</i>Pr)]^2- via the synergic mixture <i>n</i>BuM, (<i>t</i>Bu)₂Zn and TMEDA (where M = Li, Na; TMEDA = <i>N</i>,<i>N</i>,<i>N′</i>,<i>N′</i>-tetramethylethylenediamine) has been investigated by multinuclear NMR spectroscopic studies and DFT calculations. Several pertinent intermediary and related compounds (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂NH(<i>i</i>Pr)]Zn(<i>t</i>Bu)₂ (<b>3</b>), (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu) (<b>5</b>), {(THF)Li[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu)}₂ (<b>6</b>), and {(TMEDA)Na[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu)}₂ (<b>11</b>), characterized by single-crystal X-ray diffraction, are discussed in relation to their role in the formation of (TMEDA)M[(<i>i</i>Pr)NCHCHN(<i>i</i>Pr)]Zn(<i>t</i>Bu) (M = Li, <b>1</b>; Na, <b>10</b>). In addition, the dilithio zincate molecular hydride [(TMEDA)Li]₂[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu)H <b>7</b> has been synthesized from the reaction of (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂NH(<i>i</i>Pr)]Zn(<i>t</i>Bu)₂ <b>3</b> with <i>n</i>BuLi(TMEDA) and also characterized by both X-ray crystallographic and NMR spectroscopic studies. The retention of the Li–H bond of <b>7</b> in solution was confirmed by ⁷Li–¹H HSQC experiments. Also, the ⁷Li NMR spectrum of <b>7</b> in C₆D₆ solution allowed for the rare observation of a scalar ¹<i>J</i>_Li–H coupling constant of 13.3 Hz. Possible mechanisms for the transformation from diamine to diazaethene, a process involving the formal breakage of four bonds, have been determined computationally using density functional theory. The dominant mechanism, starting from (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu) (<b>4</b>), involves the formation of a hydride intermediate and leads directly to the observed diazaethene product. In addition the existence of <b>7</b> in equilibrium with <b>4</b> through the dynamic association and dissociation of a (TMEDA)LiH ligand, also provides a secondary mechanism for the formation of the diazaethene. The two reaction pathways (i.e., starting from <b>4</b> or <b>7</b>) are quite distinct and provide excellent examples in which the two distinct metals in the system are able to interact synergically to catalyze this otherwise challenging transformation

Main Group Multiple C–H/N–H Bond Activation of a Diamine and Isolation of A Molecular Dilithium Zincate Hydride: Experimental and DFT Evidence for Alkali Metal–Zinc Synergistic Effects

The surprising transformation of the saturated diamine (<i>i</i>Pr)NHCH₂CH₂NH(<i>i</i>Pr) to the unsaturated diazaethene [(<i>i</i>Pr)NCHCHN(<i>i</i>Pr)]^2- via the synergic mixture <i>n</i>BuM, (<i>t</i>Bu)₂Zn and TMEDA (where M = Li, Na; TMEDA = <i>N</i>,<i>N</i>,<i>N′</i>,<i>N′</i>-tetramethylethylenediamine) has been investigated by multinuclear NMR spectroscopic studies and DFT calculations. Several pertinent intermediary and related compounds (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂NH(<i>i</i>Pr)]Zn(<i>t</i>Bu)₂ (<b>3</b>), (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu) (<b>5</b>), {(THF)Li[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu)}₂ (<b>6</b>), and {(TMEDA)Na[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu)}₂ (<b>11</b>), characterized by single-crystal X-ray diffraction, are discussed in relation to their role in the formation of (TMEDA)M[(<i>i</i>Pr)NCHCHN(<i>i</i>Pr)]Zn(<i>t</i>Bu) (M = Li, <b>1</b>; Na, <b>10</b>). In addition, the dilithio zincate molecular hydride [(TMEDA)Li]₂[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu)H <b>7</b> has been synthesized from the reaction of (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂NH(<i>i</i>Pr)]Zn(<i>t</i>Bu)₂ <b>3</b> with <i>n</i>BuLi(TMEDA) and also characterized by both X-ray crystallographic and NMR spectroscopic studies. The retention of the Li–H bond of <b>7</b> in solution was confirmed by ⁷Li–¹H HSQC experiments. Also, the ⁷Li NMR spectrum of <b>7</b> in C₆D₆ solution allowed for the rare observation of a scalar ¹<i>J</i>_Li–H coupling constant of 13.3 Hz. Possible mechanisms for the transformation from diamine to diazaethene, a process involving the formal breakage of four bonds, have been determined computationally using density functional theory. The dominant mechanism, starting from (TMEDA)Li[(<i>i</i>Pr)NCH₂CH₂N(<i>i</i>Pr)]Zn(<i>t</i>Bu) (<b>4</b>), involves the formation of a hydride intermediate and leads directly to the observed diazaethene product. In addition the existence of <b>7</b> in equilibrium with <b>4</b> through the dynamic association and dissociation of a (TMEDA)LiH ligand, also provides a secondary mechanism for the formation of the diazaethene. The two reaction pathways (i.e., starting from <b>4</b> or <b>7</b>) are quite distinct and provide excellent examples in which the two distinct metals in the system are able to interact synergically to catalyze this otherwise challenging transformation

Main group multiple C-H/N-H bond activation of a diamine and isolation of a molecular dilithium zincate hydride : experimental and DFT evidence for Alkali metal-zinc synergistic effects

The surprising transformation of the saturated diamine (iPr)NHCH2CH2NH(iPr) to the unsaturated diazaethene [(iPr)NCH=CHN(iPr)](2-) via the synergic mixture nBuM, (tBu)(2)Zn and TMEDA (where M = Li, Na; TMEDA = N, N,N',N'-tetramethylethylenediamine) has been investigated by multinuclear NMR spectroscopic studies and DFT calculations. Several pertinent intermediary and related compounds (TMEDA)Li[(iPr)NCH2CH2NH(iPr)]Zn(tBu)(2) (3), (TMEDA)Li[(iPr)NCH2CH2N(iPr)]Zn(tBu) (5), {(THF)Li[(iPr)NCH2CH2N(iPr)]Zn(tBu)}(2) (6), and {(TMEDA)Na[(iPr)NCH2CH2N(iPr)]Zn(tBu)}(2) (11), characterized by single-crystal X-ray diffraction, are discussed in relation to their role in the formation of (TMEDA)M[(iPr)NCH=CHN(iPr)]Zn(tBu) (M = Li, 1; Na, 10). In addition, the dilithio zincate molecular hydride [(TMEDA)Li](2)[(iPr)NCH2CH2N(iPr)]Zn(tBu)H 7 has been synthesized from the reaction of (TMEDA)Li[(iPr)NCH2CH2NH(iPr)]Zn(tBu)(2) 3 with nBuLi(TMEDA) and also characterized by both X-ray crystallographic and NMR spectroscopic studies. The retention of the Li-H bond of 7 in solution was confirmed by Li-7-H-1 HSQC experiments. Also, the Li-7 NMR spectrum of 7 in C6D6 solution allowed for the rare observation of a scalar (1)J(Li-H) coupling constant of 13.3 Hz. Possible mechanisms for the transformation from diamine to diazaethene, a process involving the formal breakage of four bonds, have been determined computationally using density functional theory. The dominant mechanism, starting from (TMEDA)Li[(iPr)NCH2CH2N(iPr)]Zn(tBu) (4), involves the formation of a hydride intermediate and leads directly to the observed diazaethene product. In addition the existence of 7 in equilibrium with 4 through the dynamic association and dissociation of a (TMEDA)LiH ligand, also provides a secondary mechanism for the formation of the diazaethene. The two reaction pathways (i.e., starting from 4 or 7) are quite distinct and provide excellent examples in which the two distinct metals in the system are able to interact synergically to catalyze this otherwise challenging transformation