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1. Reductive cleavage of N , N ′-di- tert -butylcarbodiimide generates tert -butylcyanamide ligands, (Me ₃ CNCN) ⁻ , that bind potassium both end-on and side-on in the same single crystal

   https://doi.org/10.1107/S205698902000732X  

   Chung, Amanda B.; Ziller, Joseph W.; Evans, William J. (July 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   N , N ′-Di- tert -butylcarbodiimide, Me 3 CN=C=NCMe 3 , undergoes reductive cleavage in the presence of the Gd II complex, [K(18-crown-6) 2 ][Gd II (N R 2 ) 3 ] ( R = SiMe 3 ), to form a new type of ligand, the tert -butylcyanamide anion, (Me 3 CNCN) − . This new ligand can bind metals with one or two donor atoms as demonstrated by the isolation of a single crystal containing potassium salts of both end-on and side-on bound tert -butylcyanamide anions, (Me 3 CNCN) − . The crystal contains [K(18-crown-6)(H 2 O)][NCNCMe 3 - kN ], in which one ( t BuNCN) − anion is coordinated end-on to potassium ligated by 18-crown-6 and water, as well as [K(18-crown-6)][η 2 -NCNCMe 3 ], in which an 18-crown-6 potassium is coordinated side-on to the terminal N—C linkage. This single crystal also contains one equivalent of 1,3-di- tert -butyl urea, (C 9 H 20 N 2 O), which is involved in hydrogen bonding that may stabilize the whole assembly, namely, aqua( tert -butylcyanamidato)(1,4,7,10,13,16-hexaoxacyclooctadecane)potassium(I)–( tert -butylcyanamidato)(1,4,7,10,13,16-hexaoxacyclooctadecane)potassium(I)– N , N ′-di- tert -butylcarbodiimide (1/1/1) [K(C 5 H 9 N 2 )(C 12 H 24 O 6 )]·[K(C 5 H 9 N 2 )(C 12 H 24 O 6 )(H 2 O)]·C 9 H 20 N 2 . 

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2. Oxygen uptake in complexes related to [NiFeS]- and [NiFeSe]-hydrogenase active sites

   https://doi.org/10.1039/C8SC04436H  

   Yang, Xuemei; Elrod, Lindy C.; Reibenspies, Joseph H.; Hall, Michael B.; Darensbourg, Marcetta Y. (January 2019, Chemical Science)

   A biomimetic study for S/Se oxygenation in Ni(μ-EPh)(μ-SN 2 )Fe, (E = S or Se; SN 2 = Me-diazacycloheptane-CH 2 CH 2 S); Fe = (η 5 -C 5 H 5 )Fe II (CO) complexes related to the oxygen-damaged active sites of [NiFeS]/[NiFeSe]-H 2 ases is described. Mono- and di-oxygenates (major and minor species, respectively) of the chalcogens result from exposure of the heterobimetallics to O 2 ; one was isolated and structurally characterized to have Ni–O–Se Ph –Fe–S connectivity within a 5-membered ring. A compositionally analogous mono-oxy species was implicated by ν (CO) IR spectroscopy to be the corresponding Ni–O–S Ph –Fe–S complex; treatment with O-abstraction agents such as P( o -tolyl) 3 or PMe 3 remediated the O damage. Computational studies (DFT) found that the lowest energy isomers of mono-oxygen derivatives of Ni(μ-EPh)(μ-SN 2 )Fe complexes were those with O attachment to Ni rather than Fe, a result consonant with experimental findings, but at odds with oxygenates found in oxygen-damaged [NiFeS]/[NiFeSe]-H 2 ase structures. A computer-generated model based on substituting − SMe for the N-CH 2 CH 2 S − sulfur donor of the N 2 S suggested that constraint within the chelate hindered O-atom uptake at that sulfur site. 

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3. Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-dithione and isoindoline-1,3-dithione ligands

   https://doi.org/10.1107/S2056989020009676  

   Wheaton, Amelia M.; Guzei, Ilia A.; Berry, John F. (August 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-dithione (SNS), isoindoline-1,3-dithione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis[(acetonitrile-κ N )(6-sulfanylidenepiperidin-2-one-κ S )copper(I)], [Cu 2 I 2 (CH 3 CN) 2 (C 5 H 7 NOS) 2 ] ( I ), bis(acetonitrile-κ N )tetra-μ 3 -iodido-bis(6-sulfanylidenepiperidin-2-one-κ S )- tetrahedro -tetracopper(I), [Cu 4 I 4 (CH 3 CN) 4 (C 5 H 7 NOS) 4 ] ( II ), catena -poly[[(μ-6-sulfanylidenepiperidin-2-one-κ 2 O : S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NOS)] n ( III ), poly[[(piperidine-2,6-dithione-κ S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NS 2 )] n ( IV ), and poly[[(μ-isoindoline-1,3-dithione-κ 2 S : S )copper(I)]-μ 3 -iodido], [CuI(C 8 H 5 NS 2 )] n ( V ). Compounds I and II crystallize as discrete dimeric and tetrameric complexes, whereas III , IV , and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexagonal [Cu 3 I 3 ] structure that is not supported by bridging ligands. Structures I , II , and IV display weak to moderately strong Cu...Cu cuprophilic interactions [Cu...Cu internuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding interactions between the N—H of the ligand and the μ 2 and μ 3 -I − atoms. Structure III contains classical N–H...O interactions between the SNO ligands that connect the molecules in a three-dimensional framework. Complex V features π–π stacking interactions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV , there were three partially occupied solvent molecules of dichloromethane and one partially occupied molecule of acetonitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015). Acta Cryst . C 71 , 9–18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent molecules. The given chemical formula and other crystal data do not take into account the solvent molecules. 

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4. Crystallographic characterization of rare-earth cyanotriphenylborate complexes and the cyanoborates [NCBPh ₃ ] ¹⁻ , [NCBPh ₂ Me] ¹⁻ , and [NCBPh ₂ (μ-O)BPh ₂ ] ¹⁻

   https://doi.org/10.1107/S2056989021006861  

   Dumas, Megan T.; White, Jessica R.; Ziller, Joseph W.; Evans, William J. (August 2021, Acta Crystallographica Section E Crystallographic Communications)

   The investigation of the coordination chemistry of rare-earth metal complexes with cyanide ligands led to the isolation and crystallographic characterization of the Ln III cyanotriphenylborate complexes dichlorido(cyanotriphenylborato-κ N )tetrakis(tetrahydrofuran-κ O )lanthanide(III), [ Ln Cl 2 (C 19 H 15 BN)(C 4 H 8 O) 4 ] [lanthanide ( Ln ) = dysprosium (Dy) and yttrium Y)] from reactions of LnCl 3 , KCN, and NaBPh 4 . Attempts to independently synthesize the tetraethylammonium salt of (NCBPh 3 ) − from BPh 3 and [NEt 4 ][CN] in THF yielded crystals of the phenyl-substituted cyclic borate, tetraethylazanium 2,2,4,6-tetraphenyl-1,3,5,2λ 4 ,4,6-trioxatriborinan-2-ide, C 8 H 20 N + ·C 24 H 20 B 3 O 3 − or [NEt 4 ][B 3 (μ-O) 3 (C 6 H 5 ) 4 ]. The mechanochemical reaction of BPh 3 and [NEt 4 ][CN] without solvent produced crystals of tetraethylazanium cyanodiphenyl-λ 4 -boranyl diphenylborinate, C 8 H 20 N + ·C 25 H 20 B 2 NO − or [NEt 4 ][NCBPh 2 (μ-O)BPh 2 ]. Reaction of BPh 3 and KCN in THF in the presence of 2.2.2-cryptand (crypt) led to a crystal of bis[(2.2.2-cryptand)potassium] 2,2,4,6-tetraphenyl-1,3,5,2λ 4 ,4,6-trioxatriborinan-2-ide cyanomethyldiphenylborate tetrahydrofuran disolvate, 2C 18 H 36 KN 2 O 6 + ·C 24 H 20 B 3 O 3 − ·C 14 H 13 BN − ·2C 4 H 8 O or [K(crypt)] 2 [B 3 (μ-O) 3 (C 6 H 5 ) 4 ][NCBPh 2 Me]·2THF. The [NCBPh 2 (μ-O)BPh 2 ] 1− and (NCBPh 2 Me) 1− anions have not been structurally characterized previously. The structure of 1-Y was refined as a two-component twin with occupancy factors 0.513 (1) and 0.487 (1). In 4 , one solvent molecule was disordered and included using multiple components with partial site-occupancy factors. 

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5. Higher spin states in some low-energy bis(tetramethyl-1,2-diaza-3,5-diborolyl) sandwich compounds of the first row transition metals: boraza analogues of the metallocenes

   https://doi.org/10.1039/C8NJ05517C  

   Chen, Jianlin; Feng, Hao; Xie, Yaoming; King, R. Bruce; Schaefer, Henry F. (March 2019, New Journal of Chemistry)

   The known sandwich compound [η 5 -(CH 2 ) 3 N 2 (BPh) 2 CMe] 2 Fe in which adjacent C 2 units are replaced by isoelectronic BN units can be considered as a boraza analogues of ferrocene similar to borazine, B 3 N 3 H 6 , considered as a boraza analogue of benzene. In this connection, the related bis(1,2,3,5-tetramethyl-1,2-diaza-3,5-diborolyl) derivatives (Me 4 B 2 N 2 CH) 2 M (M = Ti, V, Cr, Mn, Fe, Co, Ni) for all of the first row transition metals have been optimized using density functional theory for comparison with the isoelectronic tetramethylcyclopentadienyl derivatives (Me 4 C 5 H) 2 M. Low-energy sandwich structures having parallel B 2 N 2 C rings in a trans orientation are found for all seven metals. The 1,2-diaza-3,5-diborolyl ligand appears to be a weaker field ligand than the isoelectronic cyclopentadienyl ligand as indicated by higher spin ground states for some (η 5 -Me 4 B 2 N 2 CH) 2 M sandwich compounds relative to the corresponding metallocenes (η 5 -Me 4 C 5 H) 2 M. Thus (η 5 -Me 4 B 2 N 2 CH) 2 Cr has a quintet ground state in contrast to the triplet ground state of (η 5 -Me 4 C 5 H) 2 Cr. Similarly, the sextet ground state of (η 5 -Me 4 B 2 N 2 CH) 2 Mn lies ∼18 kcal mol −1 below the quartet state in contrast to the doublet ground state of the isoelectronic (Me 4 C 5 H) 2 Mn. These sandwich compounds are potentially accessible by reaction of 1,2-diaza-3,5-diborolide anions with metal halides analogous to the synthesis of [η 5 -(CH 2 ) 3 N 2 (BPh) 2 CMe] 2 Fe. 

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