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1. Small Molecule Activation with Intramolecular “Inverse” Frustrated Lewis Pairs

   https://doi.org/10.1002/chem.202005143  

   Manankandayalage, Chamila ; Unruh, Daniel K. ; Krempner, Clemens ( March 2021 , Chemistry – A European Journal)

   The intramolecular “inverse” frustrated Lewis pairs (FLPs) of general formula 1‐BR₂‐2‐[(Me₂N)₂C=N]‐C₆H₄(3–6) [BR₂=BMes₂(3), BC₁₂H₈, (4), BBN (5), BBNO (6)] were synthesized and structurally characterized by multinuclear NMR spectroscopy and X‐ray analysis. These novel types of pre‐organized FLPs, featuring strongly basic guanidino units rigidly linked to weakly Lewis acidic boryl moieties via anortho‐phenylene linker, are capable of activating H−H, C−H, N−H, O−H, Si−H, B−H and C=O bonds.4and5deprotonated terminal alkynes and acetylene to form the zwitterionic borates 1‐(RC≡C‐BR₂)‐2‐[(Me₂N)₂C=NH]‐C₆H₄(R=Ph, H) and reacted with ammonia, BnNH₂and pyrrolidine, to generate the FLP adducts 1‐(R₂HN→BR₂)‐2‐[(Me₂N)₂C=NH]‐C₆H₄, where the N‐H functionality is activated by intramolecular H‐bond interactions. In addition,5was found to rapidly add across the double bond of H₂CO, PhCHO and PhNCO to form cyclic zwitterionic guanidinium borates in excellent yields. Likewise,5is capable of cleaving H₂, HBPin and PhSiH₃to form various amino boranes. Collectively, the results demonstrate that these new types of intramolecular FLPs featuring weakly Lewis acidic boryl and strongly basic guanidino moieties are as potent as conventional intramolecular FLPs with strongly Lewis acidic units in activating small molecules.

    

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2. Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

   https://doi.org/10.3762/bjoc.14.211  

   Fiedler, Tobias ; Barbasiewicz, Michał ; Stollenz, Michael ; Gladysz, John A ( January 2018 , Beilstein Journal of Organic Chemistry)

   Two routes to the title compounds are evaluated. First, a ca. 0.01 M CH 2 Cl 2 solution of H 3 B·P((CH 2 ) 6 CH=CH 2 ) 3 ( 1 ·BH 3 ) is treated with 5 mol % of Grubbs' first generation catalyst (0 °C to reflux), followed by H 2 (5 bar) and Wilkinson's catalyst (55 °C). Column chromatography affords H 3 B·P( n- C 8 H 17 ) 3 (1%), H 3 B· P ((CH 2 ) 13 C H 2 )( n -C 8 H 17 ) (8%; see text for tie bars that indicate additional phosphorus–carbon linkages, which are coded in the abstract with italics), H 3 B· P ((CH 2 ) 13 C H 2 )((CH 2 ) 14 ) P ((CH 2 ) 13 C H 2 )·BH 3 ( 6 ·2BH 3 , 10%), in,out -H 3 B·P((CH 2 ) 14 ) 3 P·BH 3 ( in,out - 2 ·2BH 3 , 4%) and the stereoisomer ( in,in / out,out )- 2 ·2BH 3 (2%). Four of these structures are verified by independent syntheses. Second, 1,14-tetradecanedioic acid is converted (reduction, bromination, Arbuzov reaction, LiAlH 4 ) to H 2 P((CH 2 ) 14 )PH 2 ( 10 ; 76% overall yield). The reaction with H 3 B·SMe 2 gives 10 ·2BH 3 , which is treated with n -BuLi (4.4 equiv) and Br(CH 2 ) 6 CH=CH 2 (4.0 equiv) to afford the tetraalkenyl precursor (H 2 C=CH(CH 2 ) 6 ) 2 (H 3 B)P((CH 2 ) 14 )P(BH 3 )((CH 2 ) 6 CH=CH 2 ) 2 ( 11 ·2BH 3 ; 18%). Alternative approaches to 11 ·2BH 3 (e.g., via 11 ) were unsuccessful. An analogous metathesis/hydrogenation/chromatography sequence with 11 ·2BH 3 (0.0010 M in CH 2 Cl 2 ) gives 6 ·2BH 3 (5%), in,out - 2 ·2BH 3 (6%), and ( in,in / out,out )- 2 ·2BH 3 (7%). Despite the doubled yield of 2 ·2BH 3 , the longer synthesis of 11 ·2BH 3 vs 1 ·BH 3 renders the two routes a toss-up; neither compares favorably with precious metal templated syntheses. 

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3. Effects of Chain Ends on Thermal and Mechanical Properties and Recyclability of Poly( γ ‐butyrolactone)

   https://doi.org/10.1002/pola.29180  

   Tang, Jing ; Chen, Eugene Y. ‐X. ( September 2018 , Journal of Polymer Science Part A: Polymer Chemistry)

   This work investigates effects of poly(γ‐butyrolactone) (PγBL) with different initiation and termination chain ends on five types of materials properties, including thermal stability, thermal transitions, thermal recyclability, hydrolytic degradation, and dynamic mechanical behavior. Four different chain‐end‐capped polymers with similar molecular weights, BnO‐[C(=O)(CH₂)₃O]_n‐R, R = C(=O)Me, C(=O)CH=CH₂, C(=O)Ph, and SiMe₂CMe₃, along with a series of uncapped polymers R′O‐[C(=O)(CH₂)₃O]_n‐H (R′ = Bn, Ph₂CHCH₂) withM_nranging from low (4.95 kg mol⁻¹) to high (83.2 kg mol⁻¹), have been synthesized. The termination chain end R showed a large effect on polymer decomposition temperature and hydrolytic degradation, relative to H. Overall, for those properties sensitive to the chain ends, chain‐end capping renders R‐protected linear PγBL behaving much like cyclic PγBL. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2018,56, 2271–2279

    

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4. Macrocyclic Complexes Derived from Four cis ‐L 2 Pt Corners and Four Butadiynediyl Linkers; Syntheses, Electronic Structures, and Square versus Skew Rhombus Geometries

   https://doi.org/10.1002/chem.202100305  

   Collins, Brenna K. ; Clough Mastry, Melissa ; Ehnbom, Andreas ; Bhuvanesh, Nattamai ; Hall, Michael B. ; Gladysz, John A. ( June 2021 , Chemistry – A European Journal)

   The dialkyl malonate derived 1,3‐diphosphines R₂C(CH₂PPh₂)₂(R=a, Me;b, Et;c,n‐Bu;d,n‐Dec;e, Bn;f,p‐tolCH₂) are combined with (p‐tol₃P)₂PtCl₂ortrans‐(p‐tol₃P)₂Pt((C≡C)₂H)₂to give the chelatescis‐(R₂C(CH₂PPh₂)₂)PtCl₂(2 a–f, 94–69 %) orcis‐(R₂C(CH₂PPh₂)₂)Pt((C≡C)₂H)₂(3 a–f, 97–54 %). Complexes3 a–dare also available from2 a–dand excess 1,3‐butadiyne in the presence of CuI (cat.) and excess HNEt₂(87–65 %). Under similar conditions,2and3react to give the title compounds [(R₂C(CH₂PPh₂)₂)[Pt(C≡C)₂]₄(4 a–f; 89–14 % (64 % avg)), from which ammonium salts such as the co‐product [H₂NEt₂]⁺Cl⁻are challenging to remove. Crystal structures of4 a,bshow skew rhombus as opposed to square Pt₄geometries. The NMR and IR properties of4 a–fare similar to those of mono‐ or diplatinum model compounds. However, cyclic voltammetry gives only irreversible oxidations. As compared to mono‐platinum or Pt(C≡C)₂Pt species, the UV‐visible spectra show much more intense and red‐shifted bands. Time dependent DFT calculations define the transitions and principal orbitals involved. Electrostatic potential surface maps reveal strongly negative Pt₄C₁₆cores that likely facilitate ammonium cation binding. Analogous electronic properties of Pt₃C₁₂and Pt₅C₂₀homologs and selected equilibria are explored computationally.

    

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5. Organo‐Functionalized Lacunary Double Cubane‐Type Oxometallates: Synthesis, Structure, and Properties of [(M II Cl) 2 (V IV O) 2 {((HOCH 2 CH 2 )(H)N(CH 2 CH 2 O))(HN(CH 2 CH 2 O) 2 )} 2 ] (M=Co, Zn)

   https://doi.org/10.1002/chem.202301389  

   Shuaib, Damola T. ; Swenson, LaSalle ; Kaduk, James A. ; Chang, Tieyan ; Chen, Yu‐Sheng ; McNeely, James ; Khan, M. Ishaque ( October 2023 , Chemistry – A European Journal)

   Organofunctionalized tetranuclear clusters [(M^IICl)₂(V^IVO)₂{((HOCH₂CH₂)(H)N(CH₂CH₂O))(HN(CH₂CH₂O)₂)}₂] (1, M=Co,2: M=Zn) containing an unprecedented oxometallacyclic {M₂V₂Cl₂N₄O₈} (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO₅N} and trigonal bipyramidal {MO₃NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1and2in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1and2are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [J_iso(V^IV−V^IV)=−5.4(1); −3.9(2) cm⁻¹], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [J_iso(V^IV−Co^II)=−12.6 and −7.5 cm⁻¹] contained in1.

    

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