Grundlagen der Thermischen Analysetechniken und ihre Anwendungen in der präparativen Chemie

A Physical Organic Approach towards Statistical Modeling of Tetrazole and Azide Decomposition

Nitrogen atom-rich heterocycles and organic azides have found extensive use in many sectors of modern chemistry from drug discovery to energetic materials. The prediction and understanding of their energetic properties are thus key to the safe and effective application of these compounds. In this work, we disclose the use of multivariate linear regression modeling for the prediction of the decomposition temperature and impact sensitivity of structurally diverse tetrazoles and organic azides. We report a data-driven approach for property prediction featuring a collection of quantum mechanical parameters and computational workflows. The statistical models reported herein carry predictive accuracy as well as chemical interpretability. Model validation was successfully accomplished via tetrazole test sets with parameters generated exclusively in silico. Mechanistic analysis of the statistical models indicated distinct divergent pathways of thermal and impact-initiated decomposition.

Trapping of Terminal Platinapolyynes by Copper(I) Catalyzed Click Cycloadditions; Probes of Labile Intermediates in Syntheses of Complexes with Extended sp Carbon Chains, and Crystallographic Studies

The silylated hexatriynyl complex trans-(C₆ F₅ )(p-tol₃ P)₂ Pt(C≡C)₃ SiEt₃ (PtC₆ TES) is converted in situ to PtC₆ H (wet n-Bu₄ N⁺ F^- , THF) and cross coupled with the diyne H(C≡C)₂ SiEt₃ (HC₄ TES; CuCl/TMEDA, O₂ ) to give PtC₁₀ TES (71 %). This sequence is repeated twice to afford PtC₁₄ TES (65 %) and then PtC₁₈ TES (27 %). An analogous series of reactions starting with PtC₈ TES gives PtC₁₂ TES (60 %), then PtC₁₆ TES (43 %), and then PtC₂₀ TES (17 %). Similar cross couplings with H(C≡C)₂ Si(i-Pr)₃ (HC₄ TIPS) give PtC₁₂ TIPS (68 %), PtC₁₄ TIPS (68 %), and PtC₁₆ TIPS (34 %). The trialkylsilyl species (up to PtC₁₈ TES) are converted to 3+2 "click" cycloadducts or 1,4-disubstituted 1,2,3-triazoles trans-(C₆ F₅ )(p-tol₃ P)₂ Pt(C≡C)_n-1 C=CHN(CH₂ C₆ H₅ )N=N (29-92 % after workups). The most general procedure involves generating the terminal polyynes PtC_x H (wet n-Bu₄ N⁺ F^- , THF) in the presence of benzyl azide in DMF and aqueous CuSO₄ /ascorbic acid. All of the preceding complexes are crystallographically characterized and the structural and spectroscopic properties analyzed as a function of chain length. Two pseudopolymorphs of PtC₂₀ TES are obtained, both of which feature molecules with parallel sp carbon chains in a pairwise head/tail packing motif with extensive sp/sp van der Waals contacts.

Syntheses, Structures, Reactivities, and Basicities of Quinolinyl and Isoquinolinyl Complexes of an Electron Rich Chiral Rhenium Fragment and Their Electrophilic Addition Products

Reactions of Li⁺ [(η⁵ -C₅ H₅ )Re(NO)(PPh₃ )]^- with 2- and 4-chloroquinoline or 1-chloroisoquinoline give the corresponding σ quinolinyl and isoquinolinyl complexes 3, 6, and 8. With 3 and 8 there is further protonation to yield HCl adducts, but additions of KH give the free bases. Treatment of 3 with HBF₄ ⋅OEt₂ or H(OEt₂ )₂ ⁺ BAr_f ^- gives the quinolinium salts [(η⁵ -C₅ H₅ )Re(NO)(PPh₃ )(C(NH)C(CH)₄ C(CH)(CH))]⁺ X^- (3-H⁺ X^- ; X^- =BF₄ ^- /BAr_f ^- , 94-98 %). Addition of CF₃ SO₃ CH₃ to 3, 6, or 8 affords the corresponding N-methyl quinolinium salts. In the case of [(η⁵ -C₅ H₅ )Re(NO)(PPh₃ )(C(NCH₃ )C(CH)₄ C(CH)(CH))]⁺ CF₃ SO₃ ^- (3-CH₃ ⁺ CF₃ SO₃ ^- ), addition of CH₃ Li gives the dihydroquinolinium complex (S_Re R_C ,R_Re S_C )-[(η⁵ -C₅ H₅ )Re(NO)(PPh₃ )(C(NCH₃ )C(CH)₄ C(CHCH₃ )(CH₂ ))]⁺ CF₃ SO₃ ^- ((S_Re R_C ,R_Re S_C )-5⁺ CF₃ SO₃ ^- , 76 %) in diastereomerically pure form. Crystal structures of 3-H⁺ BAr_f ^- , 3-CH₃ ⁺ CF₃ SO₃ ^- , (S_Re R_C , R_Re S_C )-5⁺ Cl^- , and 6-CH₃ ⁺ CF₃ SO₃ ^- show that the quinolinium ligands adopt Re⋅⋅⋅C conformations that maximize overlap of their acceptor orbitals with the rhenium fragment HOMO, minimize steric interactions with the bulky PPh₃ ligand, and promote various π interactions. NMR experiments establish the Brønsted basicity order 3>8>6, with K_a (BH⁺ ) values >10 orders of magnitude greater than the parent heterocycles, although they remain less active nucleophilic catalysts in the reactions tested. DFT calculations provide additional insights regarding Re⋅⋅⋅C bonding and conformations, basicities, and the stereochemistry of CH₃ Li addition.

Rendering classical hydrophilic enantiopure Werner salts [M(en)3]n+nX- lipophilic (M/n = Cr/3, Co/3, Rh/3, Ir/3, Pt/4); new chiral hydrogen bond donor catalysts and enantioselectivities as a function of metal and charge

Known hydrophilic halide salts of the title compounds are converted to new lipophilic BArf- (B(3,5-C6H3(CF3)2)4-) salts. These are isolated as hydrates (Λ- or Δ-[M(en)3]n+nBArf-·zH2O; z = 17-9) and characterized by NMR (acetone-d6) and microanalyses. Thermal stabilities are probed by capillary thermolyses and TGA and DSC measurements (onset of dehydration 71-151 °C). In the presence of tertiary amines, they are effective catalysts for enantioselective Michael type carbon-carbon or carbon-nitrogen bond forming additions of 1,3-dicarbonyl compounds (acceptors: trans-β-nitrostyrene, di-tert-butylazodicarboxylate, 2-cyclopenten-1-one; average ee = 33%, 52%, 17%). Effects of the metal and charge upon enantioselectivities are analyzed. A number of properties appear to correlate to the NH Brønsted acidity order ([Pt(en)3]4+ > [Cr(en)3]3+ > [Co(en)3]3+ > [Rh(en)3]3+ > [Ir(en)3]3+).

En route to diplatinum polyynediyl complexes trans,trans-(Ar)(R3P)2Pt(C≡C)nPt(PR3)2(Ar): Untold tales, including end-group strategies

Reactions of {(C6F5)Pt[S(CH2CH2-)2](μ-Cl)}2 and R3P yield the bis(phosphine) species trans-(C6F5)(R3P)2PtCl [R = Et (Pt'Cl), Ph, (p-CF3C6H4)3P; 88-81 %]. Additions of Pt'Cl and H(C≡C)nH (n = 1, 2; HNEt2, 20 mol % CuI) give Pt'C2H (37 %, plus Pt'I, 16 %) and Pt'C4H (88 %). Homocoupling of Pt'C4H under Hay conditions (O2, CuCl, TMEDA, acetone) gives Pt'C8Pt' (85 %), but Pt'C2H affords only traces of Pt'C4Pt'. However, condensation of Pt'C4H and Pt'Cl (HNEt2, 20 mol % CuI) yields Pt'C4Pt' (97 %). Hay heterocouplings of Pt'C4H or trans-(p-tol)(Ph3P)2Pt(C≡C)2H (Pt*C4H) and excess HC≡CSiEt3 give Pt'C6SiEt3 (76 %) or Pt*C6SiEt3 (89 %). The latter and wet n-Bu4N+ F- react to yield labile Pt*C6H (60 %). Hay homocouplings of Pt*C4H and Pt*C6H give Pt*C8Pt* (64 %) and Pt*C12Pt* (64 %). Reaction of trans-(C6F5)(p-tol3P)2PtCl (PtCl) and HC≡CH (HNEt2, 20 mol % CuI) yields only traces of PtC2H. However, an analogous reaction with HC≡CSiMe3 gives PtC2SiMe3 (75 %), which upon treatment with silica yields PtC2H (77 %). An analogous coupling of trans-(C6F5)(Ph3P)2PtCl with H(C≡C)2H gives trans-(C6F5)(Ph3P)2Pt(C≡C)2H (34 %). Advantages and disadvantages of the various trans-(Ar)(R3P)2Pt end-groups are analyzed.

A Synthetic Breakthrough into an Unanticipated Stability Regime: A Series of Isolable Complexes in which C6, C8, C10, C12, C16, C20, C24, and C28 Polyynediyl Chains Span Two Platinum Atoms

The reaction of trans-[PtCl(p-tol){P(p-tol)3}2] (PtCl) and H(C[triple chemical bond]C)2H (cat. CuI, HNEt2) gives PtC4H (82 %), which can be cross-coupled with excess HC[triple chemical bond]CSiEt3 (acetone, O2, CuCl/TMEDA; Hay conditions) to yield PtC6Si (77 %). The addition of nBu4N+F- in wet acetone gives PtC6H (84 %), and further addition of ClSiMe3 (F- scavenger) and excess HC[triple chemical bond]CSiEt3 (Hay conditions) yields PtC(8)Si (23 %). Similar cross-coupling reactions of PtCxH (generated in situ for x>6) and excess H(C[triple chemical bond]C)2SiEt3 give a) x=4, PtC8Si (29 %), PtC12Si (30 %), and PtC16Si (1 %); b) x=6, PtC10Si (59 %) and PtC14Si (7 %); c) x=8, PtC12Si (42 %); and d) x=10, PtC14Si (20 %). Hay homocoupling reactions of PtC4H, PtC6H, PtC8H, and PtC10H give PtC8Pt, PtC12Pt, PtC16Pt, and PtC20Pt (88-70 %), but PtC12H decomposes too rapidly. However, when PtC12Si and PtC14Si are subjected to Hay conditions, protodesilylation occurs in the presence of the oxidizing agent and PtC24Pt (36 %) and PtC28Pt (51 %) are isolated. Reactions of PtC6H and PtC10H with PtCl (CuI, HNEt2) give PtC6Pt (56 %) and PtC10Pt (84 %). The effect of the chain lengths in PtCxPt upon thermal stabilities (>200 degrees C for x< or =20), IR nu(C[triple chemical bond]C) patterns (progressively more bands), colors (yellow to orange to deep red), UV/Vis spectra (progressively red-shifted and more intense bands with epsilon>400,000 M(-1) cm(-1)), redox properties (progressively more difficult oxidations), and NMR spectra (many monotonic trends) are analyzed, including implications for the sp carbon allotrope carbyne. Whereas all other dodecaynes and tetradecaynes rapidly decompose at room temperature, PtC24Pt and PtC28Pt remain stable at >140 degrees C. Crystal structures of PtCxSi (x=6, 8, 10) and PtCxPt (x=6, 8, 10, 12) have been determined.

Synthesis, Structure, and Reactivity of Palladacycles That Contain a Chiral Rhenium Fragment in the Backbone: New Cyclometalation and Catalyst Design Strategies

The bromocyclopentadienyl complex [(eta5-C5H4Br)Re(CO)3] is converted to racemic [(eta5-C5H4Br)Re(NO)(PPh3)(CH2PPh2)] (1 b) similarly to a published sequence for cyclopentadienyl analogues. Treatment of enantiopure (S)-[(eta5-C5H5)Re(NO)(PPh3)(CH3)] with nBuLi and I2 gives (S)-[(eta5-C5H4I)Re(NO)(PPh3)(CH3)] ((S)-6 c; 84 %), which is converted (Ph3C+ PF6 -, PPh2H, tBuOK) to (S)-[(eta5-C5H4I)Re(NO)(PPh3)(CH2PPh2)] ((S)-1 c). Reactions of 1 b and (S)-1 c with Pd[P(tBu)3]2 yield [{(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(mu-X)}2] (10; X = b, Br, rac/meso, 88 %; c, I, S,S, 22 %). Addition of PPh3 to 10 b gives [(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(PPh3)(Br)] (11 b; 92 %). Reaction of (S)-[(eta5-C5H5)Re(NO)(PPh3)(CH2PPh2)] ((S)-2) and Pd(OAc)(2) (1.5 equiv; toluene, RT) affords the novel Pd3(OAc)4-based palladacycle (S,S)-[(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(mu-OAc)2Pd(mu-OAc)2Pd(mu-PPh2CH2)(Ph3P)(ON)Re(eta5-C5H4)] ((S,S)-13; 71-90 %). Addition of LiCl and LiBr yields (S,S)-10 a,b (73 %), and Na(acac-F6) gives (S)-[(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(acac-F6)] ((S)-16, 72 %). Reaction of (S,S)-10 b and pyridine affords (S)-[(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(NC5H5)(Br)] ((S)-17 b, 72 %); other Lewis bases yield similar adducts. Reaction of (S)-2 and Pd(OAc)2 (0.5 equiv; benzene, 80 degrees C) gives the spiropalladacycle trans-(S,S)-[{(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)}2Pd] (39 %). The crystal structures of (S)-6 c, 11 b, (S,S)- and (R,R)-132 C7H8, (S,S)-10 b, and (S)-17 b aid the preceding assignments. Both 10 b (racemic or S,S) and (S)-16 are excellent catalyst precursors for Suzuki and Heck couplings.

“Heavy Fluorous” Cyclopentadienes and Cyclopentadienyl Complexes with Three to Five Ponytails: Facile Syntheses from Polybromocyclopentadienyl Complexes, Phase Properties, and Electronic Effects

The reactions between [(eta5-C5H(5-x)Br(x))M(CO)3] (M = Re, Mn; x = 1, 3, 4, 5) and [IZn[(CH2)(n)R(f8)]] (n = 2, 3; R(f8) = (CF2)7CF3) in the presence of [Cl2PdL2] catalysts give the title complexes [[eta5-C5H(5-x)[(CH2)(n)R(f8)]x]M(CO)3]. In the case of x = 5, the major product is actually [[eta5-C5H[(CH2)(n)R(f8)]4]M(CO)3], in which one of the bromides has been substituted by hydride. Minor amounts of multiple hydride substitution products are formed, all of them readily separable on fluorous silica gel. Irradiation of the manganese complexes in CF3C6H5/MeOH/ether gives uncoordinated cyclopentadienes, which can be deprotonated and reattached to other metals. Partition coefficients have been measured (CF3C6F11/toluene): complexes with three or more ponytails are highly fluorophilic, with values of > 99.8: < 0.2. The IR [symbol: see text]CO bands have been used to probe the inductive effects of the ponytails at the metal centers.

Synthesis, structure, and reactivity of fluorous phosphorus/carbon/phosphorus pincer ligands and metal complexes

Reactions of the diphosphine 1,3-C6H4(CH2PH2)2 and fluorous alkenes H2C=CHR(fn)(R(fn)=(CF2)(n-1)CF3; n = 6, 8) at 75 degrees C in the presence of AIBN give the title ligands 1,3-C6H4(CH2P(CH2CH2R(fn))2)2(3-R(fn)) and byproducts 1,3-C6H4(CH3)(CH2P(CH2CH2R(fn))2)(4-R(fn)) in 1 : 3 to 1 : 5 ratios. Workups give -R(fn) in 4--17% yields. Similar results are obtained photochemically. Reaction of 1,3-C6H4(CH2Br)2 and HP(CH2CH2R(f8))2 (5) at 80 degrees C (neat, 1 : 2 mol ratio) gives instead of simple substitution the metacyclophane [1,3-C6H4(CH2P(CH2CH2R(f8))2 CH2-1,3-C(6)H(4)CH(2)P[lower bond 1 end](CH2CH2R(f8))2C[upper bond 1 end]H2](2+)2Br-, which upon treatment with LiAlH(4) yields 3-R(f8)(20%), 4-R(f8), and other products. Efforts to better access 3-R(f8), either by altering stoichiometry or using various combinations of the phosphine borane (H3B)PH(CH2CH2R(f8))2 and base, are unsuccessful. Reactions of 3-R(fn) with Pd(O2CCF3)2 and [IrCl(COE)2]2(COE=cyclooctene) give the palladium and iridium pincer complexes (2,6,1-C6H3(CH2 P(CH2CH2R(fn))(2)(2)Pd(O2CCF3)(10-R(fn); 80-90%) and (2,6,1-C6H3(CH2P(CH2CH2R(f8))2)2)Ir(Cl)(H)(11-R(f8); 29%), which exhibit CF3C6F(11)/toluene partition coefficients of >96 : <4. The crystal structure of 10-R(f8) shows CH2CH2R(f8) groups with all-anti conformations that extend in parallel above and below the palladium square plane to create fluorous lattice domains. NMR monitoring shows a precursor to 11-R(f8) that is believed to be a COE adduct.

Syntheses and reactivities of disubstituted and trisubstituted fluorous pyridines with high fluorous phase affinities: solid state, liquid crystal, and ionic liquid-phase properties

Reactions of 2,6-dibromo-, 3,5-dibromo-, and 2,4,6-tribromopyridine with IZnCH(2)CH(2)R(f8) (R(f8) = (CF(2))(7)CF(3)) in THF at 65 degrees C in the presence of trans-Cl(2)Pd(PPh(3))(2) (5 mol %) gave the fluorous pyridines 2,6- and 3,5-NC(5)H(3)(CH(2)CH(2)R(f8))(2) (1 and 2; 85%, 31%) and 2,4,6-NC(5)H(2)(CH(2)CH(2)R(f8))(3) (3, 61%). Reaction of 2,6-pyridinedicarboxaldehyde with [Ph(3)PCH(2)CH(2)R(f8)](+)I(-)/K(2)CO(3) (p-dioxane/H(2)O, 95 degrees C) gave 2,6-NC(5)H(3)(CH[double bond]CHCH(2)R(f8))(2) (95%; 70:30 ZZ/ZE), which was treated with H(2) (1 atm, 12 h) and 10% Pd/C to yield 2,6-NC(5)H(3)(CH(2)CH(2)CH(2)R(f8))(2) (5, 95%), a higher homologue of 1. Longer reaction times afforded piperidine cis-2,6-HNC(5)H(8)(CH(2)CH(2)CH(2)R(f8))(2) (6, 98%). The stereochemistry was established by NMR analysis of the N-benzylpiperidine. Pyridines 1-3 and 5 are low-melting white solids with CF(3)C(6)F(11)/toluene partition coefficients (24 degrees C) of 93.8:6.2, 93.9:6.1, >99.7:<0.3, and 90.4:9.6, respectively (6, 93.6:6.4). Reaction of 1 and CF(3)SO(3)H gave a pyridinium salt, and Cl(2)Pd(NCCH(3))(2) (0.5 equiv) yielded trans-Cl(2)Pd(1)(2). The crystal structure of the former, which also exhibited liquid crystalline and ionic liquid phases, was determined.