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The bis(imido) complexes (BDI)Nb(N t Bu)2 and (BDI)Nb(N t Bu)(NAr) (BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate; Ar = 2,6-diisopropylphenyl) were shown to engage in 1,2-addition and [2 + 2] cycloaddition reactions with a wide variety of substrates. Reaction of the bis(imido) complexes with dihydrogen, silanes, and boranes yielded hydrido-amido-imido complexes via 1,2-addition across Nb-imido π-bonds; some of these complexes were shown to further react via insertion of carbon dioxide to give formate-amido-imido products. Similarly, reaction of (BDI)Nb(N t Bu)2 with tert-butylacetylene yielded an acetylide-amido-imido complex. In contrast to these results, many related mono(imido) Nb BDI complexes do not exhibit 1,2-addition reactivity, suggesting that π-loading plays an important role in activating the Nb-N π-bonds toward addition. The same bis(imido) complexes were also shown to engage in [2 + 2] cycloaddition reactions with oxygen- and sulfur-containing heteroallenes to give carbamate- and thiocarbamate-imido complexes: some of these complexes readily dimerized to give bis-μ-sulfido, bis-μ-iminodicarboxylate, and bis-μ-carbonate complexes. The mononuclear carbamate imido complex (BDI)Nb(NAr)(N( t Bu)CO2) (12) could be induced to eject tert-butylisocyanate to generate a four-coordinate terminal oxo imido intermediate, which could be trapped as the five-coordinate pyridine or DMAP adduct. The DMAP adducted oxo imido complex (BDI)NbO(NAr)(DMAP) (16) was shown to engage in 1,2-addition of silanes across the Nb-oxo π-bond; this represents a new reaction pathway in group 5 chemistry.

The nitrido‐ate complex [(PN)2Ti(N){μ2‐K(OEt2)}]2 (1) (PN−=(N‐(2‐PiPr2‐4‐methylphenyl)‐2,4,6‐Me3C6H2) reductively couples CO and isocyanides in the presence of DME or cryptand (Kryptofix222), to form rare, five‐coordinate TiII complexes having a linear cumulene motif, [K(L)][(PN)2Ti(NCE)] (E=O, L=Kryptofix222, (2); E=NAd, L=3 DME, (3); E=NtBu, L=3 DME, (4); E=NAd, L=Kryptofix222, (5)). Oxidation of 2–5 with [Fc][OTf] afforded an isostructural TiIII center containing a neutral cumulene, [(PN)2Ti(NCE)] (E=O, (6); E=NAd (7), NtBu (8)) and characterization by CW X‐band EPR spectroscopy, revealed unpaired electron to be metal centric. Moreover, 1e− reduction of 6 and 7 in the presence of Kryptofix222cleanly reformed corresponding discrete TiII complexes 2 and 5, which were further characterized by solution magnetization measurements and high‐frequency and ‐field EPR (HFEPR) spectroscopy. Furthermore, oxidation of 7 with [Fc*][B(C6F5)4] resulted in a ligand disproportionated TiIV complex having transoid carbodiimides, [(PN)2Ti(NCNAd)2] (9). Comparison of spectroscopic, structural, and computational data for the divalent, trivalent, and tetravalent systems, including their 15N enriched isotopomers demonstrate these cumulenes to decrease in order of backbonding as TiII→TiIII→TiIV and increasing order of π‐donation as TiII→TiIII→TiIV, thus displaying more covalency in TiIII species. Lastly, we show a synthetic cycle whereby complex 1 can deliver an N‐atom to CO and CNAd. [ABSTRACT FROM AUTHOR]

Abstract: The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc−OCP precursor. Upon reduction with KC8, isolation of the dinuclear complex, namely [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4−, stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X‐ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc−OCPPCO−Sc skeleton but also to compare to the linear mode observed in the precursor. [ABSTRACT FROM AUTHOR]

Abstract: The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc−OCP precursor. Upon reduction with KC8, isolation of the dinuclear complex, namely [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4−, stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X‐ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc−OCPPCO−Sc skeleton but also to compare to the linear mode observed in the precursor. [ABSTRACT FROM AUTHOR]

Abstract: The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc−OCP precursor. Upon reduction with KC8, isolation of the dinuclear complex, namely [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4−, stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X‐ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc−OCPPCO−Sc skeleton but also to compare to the linear mode observed in the precursor. [ABSTRACT FROM AUTHOR]

Abstract: The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc−OCP precursor. Upon reduction with KC8, isolation of the dinuclear complex, namely [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4−, stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X‐ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc−OCPPCO−Sc skeleton but also to compare to the linear mode observed in the precursor. [ABSTRACT FROM AUTHOR]

The complex [(nacnac)Ti(OAr)]2(μ2:η2,η2-P2) ( 1) is formed via reductive decarbonylation of the phosphaethynolate ion −[OCP], which serves as a P atom source. Complex 1 is the first structurally characterized Group 4 transition metal P2 complex and its structure reveals the rhombic Ti2P2 core is essentially planar with short bond lengths suggesting some degree of multiple bonding character between the Ti-P and P-P sites. Computational studies of 1 provide an understanding of the Ti2P2 core as well as the origin of the highly downfield 31P NMR spectroscopic signal. [ABSTRACT FROM AUTHOR]

We report the synthesis and photo-reactivity of d0 niobium imido azido complexes supported by β-diketiminate ligands, which leads to the unprecedented formation of nitrides through a photo-assisted intramolecular rearrangement. This provides a new entry to metal nitrides that does not require low-valent metal centers and is a rare example in which the metal-imido moiety in group 5 complexes participates in reactivity. [ABSTRACT FROM AUTHOR]

The nitrido-ate complex [(PN) 2 Ti(N){μ 2 -K(OEt 2 )}] 2 (1) (PN - =(N-(2-P i Pr 2 -4-methylphenyl)-2,4,6-Me 3 C 6 H 2 ) reductively couples CO and isocyanides in the presence of DME or cryptand (Kryptofix222), to form rare, five-coordinate Ti II complexes having a linear cumulene motif, [K(L)][(PN) 2 Ti(NCE)] (E=O, L=Kryptofix222, (2); E=NAd, L=3 DME, (3); E=N t Bu, L=3 DME, (4); E=NAd, L=Kryptofix222, (5)). Oxidation of 2-5 with [Fc][OTf] afforded an isostructural Ti III center containing a neutral cumulene, [(PN) 2 Ti(NCE)] (E=O, (6); E=NAd (7), N t Bu (8)) and characterization by CW X-band EPR spectroscopy, revealed unpaired electron to be metal centric. Moreover, 1e - reduction of 6 and 7 in the presence of Kryptofix222cleanly reformed corresponding discrete Ti II complexes 2 and 5, which were further characterized by solution magnetization measurements and high-frequency and -field EPR (HFEPR) spectroscopy. Furthermore, oxidation of 7 with [Fc*][B(C 6 F 5 ) 4 ] resulted in a ligand disproportionated Ti IV complex having transoid carbodiimides, [(PN) 2 Ti(NCNAd) 2 ] (9). Comparison of spectroscopic, structural, and computational data for the divalent, trivalent, and tetravalent systems, including their 15 N enriched isotopomers demonstrate these cumulenes to decrease in order of backbonding as Ti II →Ti III →Ti IV and increasing order of π-donation as Ti II →Ti III →Ti IV , thus displaying more covalency in Ti III species. Lastly, we show a synthetic cycle whereby complex 1 can deliver an N-atom to CO and CNAd., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A dinuclear hafnium complex containing the parent imido ligand [(PN)(PNC)Hf=NH{μ 2 -K}] 2 (2) (PN - =(N-(2-P i Pr 2 -4-methylphenyl)-2,4,6-Me 3 C 6 H 2 ; PNC 2- =(N-(2-P i Pr 2 -4-methylphenyl)-2,4,6-CH 2 Me 2 C 6 H 2 ), was prepared by reduction of the bisazide trans-[(PN) 2 Hf(N 3 ) 2 ] (1) with two equiv of KC 8 . Encapsulation of K + in 2 with crown-ether or cryptand affords the first discrete salt [K(encap)][(PN)(PNC)Hf≡NH] (encap=18-crown-6(THF) 2 , 3; 2,2,2-Kryptofix, 4), featuring a terminal parent imide and possessing some of the shortest Hf-N bond lengths known to date. DFT calculations revealed formation of 2 to proceed via an extremely basic monomeric nitrido, [(PN) 2 Hf≡N] - (A), having a computed pK BH+ of ∼57 followed by heterolytic splitting of an inert 1,2-CH bond of a benzylic methyl group across the Hf≡N triple bond in A. An electronic structure analysis reveals A to possess a covalent Hf≡N triple bond and of super-basic character. We also showcase reactivity of the Hf≡NH bond with various electrophiles., (© 2022 Wiley-VCH GmbH.)

In the last seven years, chemistry of the phosphaethynolate reagent, Na(OCP)(1,4-dioxane) 2.5 , has seen a surge in organic and inorganic chemistry-A renaissance to cyanate chemistry in a new guise. Whereas there have been many reports of main group reactivity with [OCP] - , largely from group 14, in more recent times the use of electropositive metals has garnered significant interest given their ability to disguise in various oxidation states. Herein, we report and discuss advances in such studies of [OCP] - with early transition metal and f-block metal scaffolds., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc-OCP precursor. Upon reduction with KC 8 , isolation of the dinuclear complex, namely [K(OEt 2 )] 2 [(nacnac)Sc(OAr)] 2 (OCPPCO), is observed, leading to a unique motif [OCPPCO] 4- , stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X-ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc-OCPPCO-Sc skeleton but also to compare to the linear mode observed in the precursor., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The complex [(nacnac)Ti(OAr)] 2 (μ 2 :η 2 ,η 2 -P 2 ) (1) is formed via reductive decarbonylation of the phosphaethynolate ion - [OCP], which serves as a P atom source. Complex 1 is the first structurally characterized Group 4 transition metal P 2 complex and its structure reveals the rhombic Ti 2 P 2 core is essentially planar with short bond lengths suggesting some degree of multiple bonding character between the Ti-P and P-P sites. Computational studies of 1 provide an understanding of the Ti 2 P 2 core as well as the origin of the highly downfield 31 P NMR spectroscopic signal., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)