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1. Isocyanide Activation by Phosphinimide-Ligated Cr(II) Centers

   https://doi.org/10.1021/acs.organomet.5c00278  

   Rathke, Paul; Rittle, Jonathan (November 2025, Organometallics)

   NA (Ed.)

   This report describes the synthesis and reactivity of the heteroleptic phosphinimide/phosphinimine Cr(II) complex HL′CrAdHMDS, which was obtained by incomplete protonolysis of Cr(HMDS)2(THF)2 in the presence of the bisphosphinimine pro-ligand H2L′Ad. Addition of common ligands such as N-heterocyclic carbenes and isocyanides displaces the remaining HMDS ligand concomitant with complete deprotonation of the phosphinimine pro-ligand furnishing three- and four-coordinated complexes, respectively. The resulting tetrahedral chromium(II) bis(isocyanide) species was found to adopt an unusual S = 1 spin state at room temperature. Under certain reaction conditions, one coordinated isocyanide ligand was found to insert into a chromium-phosphinimide bond. The described compounds are characterized by single-crystal X-ray diffraction and solution-phase spectroscopy, and the mechanism for isocyanide insertion was investigated by DFT calculations. 

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2. Aziridination Reactivity of a Manganese(II) Complex with a Bulky Chelating Bis(Alkoxide) Ligand

   https://doi.org/10.3390/molecules27185751  

   Kurup, Sudheer S.; Woodland, Natalie M.; Lord, Richard L.; Groysman, Stanislav (September 2022, Molecules)

   Treatment of Mn(N(SiMe3)2)2(THF)2 with bulky chelating bis(alkoxide) ligand [1,1′:4′,1′′-terphenyl]-2,2′′-diylbis(diphenylmethanol) (H2[O-terphenyl-O]Ph) formed a seesaw manganese(II) complex Mn[O-terphenyl-O]Ph(THF)2, characterized by structural, spectroscopic, magnetic, and analytical methods. The reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various nitrene precursors was investigated. No reaction was observed between Mn[O-terphenyl-O]Ph(THF)2 and aryl azides. In contrast, the treatment of Mn[O-terphenyl-O]Ph(THF)2 with iminoiodinane PhINTs (Ts = p-toluenesulfonyl) was consistent with the formation of a metal-nitrene complex. In the presence of styrene, the reaction led to the formation of aziridine. Combining varying ratios of styrene and PhINTs in different solvents with 10 mol% of Mn[O-terphenyl-O]Ph(THF)2 at room temperature produced 2-phenylaziridine in up to a 79% yield. Exploration of the reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various olefins revealed (1) moderate aziridination yields for p-substituted styrenes, irrespective of the electronic nature of the substituent; (2) moderate yield for 1,1′-disubstituted α-methylstyrene; (3) no aziridination for aliphatic α-olefins; (4) complex product mixtures for the β-substituted styrenes. DFT calculations suggest that iminoiodinane is oxidatively added upon binding to Mn, and the resulting formal imido intermediate has a high-spin Mn(III) center antiferromagnetically coupled to an imidyl radical. This imidyl radical reacts with styrene to form a sextet intermediate that readily reductively eliminates the formation of a sextet Mn(II) aziridine complex. 

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3. Tying the alkoxides together: an iron complex of a new chelating bulky bis(alkoxide) demonstrates selectivity for coupling of non-bulky aryl nitrenes

   https://doi.org/10.1039/C9CC05319K  

   Kurup, Sudheer S.; Wannipurage, Duleeka; Lord, Richard L.; Groysman, Stanislav (September 2019, Chemical Communications)

   New chelating bis(alkoxide) ligand H 2 [OO] Ph and its iron( ii ) complex Fe[OO] Ph (THF) 2 are described. The coordination of the ligand to the metal center is reminiscent of the coordination of two monodentate alkoxides in previously reported Fe(OR) 2 (THF) 2 species. Fe[OO] Ph (THF) 2 catalyzes selective and efficient dimerization of non-bulky aryl nitrenes to yield the corresponding azoarenes. 

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4. Synthesis, characterization, and alkoxide transfer reactivity of dimeric Tl ₂ (OR) ₂ complexes

   https://doi.org/10.1039/d0dt03917a  

   Grass, Amanda; Kulathungage, Lakshani Wathsala; Wannipurage, Duleeka; Yousif, Maryam; Ward, Cassandra L.; Groysman, Stanislav (February 2021, Dalton Transactions)

   null (Ed.)

   Reaction of LiOC t Bu 2 Ph with TlPF 6 forms the dimeric Tl 2 (OC t Bu 2 Ph) 2 complex, a rare example of a homoleptic thallium alkoxide complex demonstrating formally two-coordinate metal centers. Characterization of Tl 2 (OC t Bu 2 Ph) 2 by 1 H and 13 C NMR spectroscopy and X-ray crystallography reveals the presence of two isomers differing by the mutual conformation of the alkoxide ligands, and by the planarity of the central Tl–O–Tl–O plane. Tl 2 (OC t Bu 2 Ph) 2 serves as a convenient precursor to the formation of old and new [M(OC t Bu 2 Ph) n ] complexes (M = Cr, Fe, Cu, Zn), including a rare example of T-shaped Zn(OC t Bu 2 Ph) 2 (THF) complex, which could not be previously synthesized using more conventional LiOR/HOR precursors. The reaction of [Ru(cymene)Cl 2 ] 2 with Tl 2 (OC t Bu 2 Ph) 2 results in the formation of a ruthenium( ii ) alkoxide complex. For ruthenium, the initial coordination of the alkoxide triggers C–H activation at the ortho -H of [OC t Bu 2 Ph] which results in its bidentate coordination. In addition to Tl 2 (OC t Bu 2 Ph) 2 , related Tl 2 (OC t Bu 2 (3,5-Me 2 C 6 H 3 )) 2 was also synthesized, characterized, and shown to exhibit similar reactivity with iron and ruthenium precursors. Synthetic, structural, and spectroscopic characterizations are presented. 

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5. Highly covalent metal–ligand π bonding in chelated bis- and tris(iminoxolene) complexes of osmium and ruthenium

   https://doi.org/10.1039/d0dt01287d  

   Gianino, Jacqueline; Brown, Seth N. (June 2020, Dalton Transactions)

   The bis(aminophenol) 2,2′-biphenylbis(3,5-di- tert -butyl-2-hydroxyphenylamine) (ClipH 4 ) forms trans -(Clip)Os(py) 2 upon aerobic reaction of the ligand with {( p -cymene)OsCl 2 } 2 in the presence of pyridine and triethylamine. A more oxidized species, cis -β-(Clip)Os(OCH 2 CH 2 O), is formed from reaction of the ligand with the osmium( vi ) complex OsO(OCH 2 CH 2 O) 2 , and reacts with Me 3 SiCl to give the chloro complex cis -β-(Clip)OsCl 2 . Octahedral osmium and ruthenium tris-iminoxolene complexes are formed from the chelating ligand tris(2-(3′,5′-di- tert -butyl-2′-hydroxyphenyl)amino-4-methylphenyl)amine (MeClampH 6 ) on aerobic reaction with divalent metal precursors. The complexes’ structural and electronic features are well described using a simple bonding model that emphasizes the covalency of the π bonding between the metal and iminoxolene ligands rather than attempting to dissect the parts into discrete oxidation states. Emphasizing the continuity of bonding between disparate complexes, the structural data from a variety of Os and Ru complexes show good correlations to π bond order, and the response of the intraligand bond distances to the bond order can be analyzed to illuminate the polarity of the bonding between metal and the redox-active orbital on the iminoxolenes. The osmium compounds’ π bonding orbitals are about 40% metal-centered and 60% ligand-centered, with the ruthenium compounds’ orbitals about 65% metal-centered and 35% ligand-centered. 

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