Ruthenium Complexes with N-Bound 2-Pyridonato Ligand as O-Donors: A New Synthetic Approach and the Effect on Reactivity

In this study, Ru complexes [(η6-p-cymene)RuX(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O))] (3: X=Cl; 4: X=I) were prepared with N-bound 2-pyridonato ligand by thermal base-free MeX elimination from ionic N,N-chelated Ru complexes [(η6-p-cymene)RuX(κ2-L1)](X) (1: X=Cl; 2: X=I; L1={2-[(2,6-iPr2-C6H3)N=CH]-6-(OMe)C5H3N}). The Ru complex 3 was used as O-donor for Lewis (LA) or Brönsted acids. The reactions of 3 with SnCl2, Ph3SnCl, ZnCl2 or HCl provided [(η6-p-cymene)Ru(SnCl3)(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O→SnCl2)] (6), [(η6-p-cymene)RuCl(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O→SnPh3Cl)] (7), and [(η6-p-cymene)RuCl(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O→)]2(μ-ZnCl2) (8) and [(η6-p-cymene)RuCl(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(OH)}](Cl) (9). The easy conversion of the 2-pyridonato ligand in 3 to its 2-hydroxypyridine in 9 evoked testing of 3 and 4 as potential catalysts in base-free transfer-hydrogenation of ketones.

Palladium(II) and Platinum(II) Bis(Stibinidene) Complexes with Intramolecular Hydrogen-Bond Enforced Geometries

The coordination capability of two N,C,N pincer coordinated stibinidenes, i.e. bis(imino)- [2,6-(DippN=CH)2C6H3]Sb (1) or imino-amino- [2-(DippN=CH)-6-(DippNHCH2)C6H3]Sb (2) toward palladium(II) and platinum(II) centers was examined. In the course of this study, seven new square-planar bis(stibinidene) complexes were synthesized and characterized by NMR, IR, Raman, UV-vis spectroscopy and single crystal (sc)-X-ray diffraction analysis. In all cases, both stibinidene ligands 1 or 2 adopt trans positions, but differ significantly in the torsion angle describing mutual orientation of aromatic rings of the stibinidenes along the Sb-Pd/Pt-Sb axes. Furthermore, majority of complexes form isomers in solution most probably due to a hindered rotation around Sb-Pd/Pt bonds caused by bulkiness of 1 and 2. This phenomenon also seems to be influenced by the absence/presence of a pendant -CH2NH- group in 1/2 that is able to form intramolecular hydrogen bonds with the adjacent chlorine atom(s) attached to the metal centers. The whole problem was subjected to a theoretical study focusing a role of hydrogen bonds in structure architecture of the complexes. To describe the UV-vis spectra of these highly coloured complexes, TD-DFT calculations were employed. These outline differences between the stibinidene ligands, the transition metals as well as between the charge of the complexes (neutral or anionic).

B-substituted group 1 phosphides: synthesis and reactivity

1-Boryl-8-phosphinonaphthalenes 1-BCy2-8-PCl2-C10H6 (1) and 1-BCy2-8-PPhCl-C10H6 (2) were prepared and used as starting materials for the synthesis of B-substituted phosphides. The reduction of 1 and 2 by Mg provided neutral compounds [1-BCy-8-PCy-C10H6]2 (3) and [1-BCy2-8-PPh-C10H6]2 (4). Compound 3 represents the dimer of phosphinoborane 1-BCy-8-PCy-C10H6 while complex 4 is a rare example of a discrete B ← P coordinated diphosphine. The reduction of 2 by Na or K in THF yielded B-substituted group 1 phosphides [Na(THF)3]+[1-BCy2-8-PPh-C10H6]- (5) and {[K(THF)2]+[1-BCy2-8-PPh-C10H6]-}∞ (6), which structurally resembled bulky group 1 phosphides. Complex 5 showed easy activation of elemental chalcogens E (E = O, S, Se) to give B-substituted chalcogenophosphinites {[Na(THF)2]+[1-BCy2-8-P(E)Ph-C10H6]}2 (E = O (7), S (8), Se (9)) as the products of chalcogen insertion into the P-Na bond. Importantly no oxidation to dichalcogenophosphinates was observed. Compound 5 is tolerant of the CO polar bonds in organic substrates and the reactions of 5 with 2,3-butanedione or an acyl chloride provided {[Na(THF)2]+[1-BCy2-8-P{CHC(O)C(Me)O}Ph-C10H6]-}2 (10) and [1-BCy2-8-P{C(O)tBu}Ph-C10H6] (11). Finally, B-coordinated phosphatetrylenes [1-BCy2-8-P(SnL)Ph-C10H6] (12) and [1-BCy2-8-P(PbL)Ph-C10H6] (13) (L is {2,6-(Me2NCH2)C6H3}-) were also prepared by substitution reactions of 5.

N-Coordinated tellurenium(II) and telluronium(IV) cations: synthesis, structure and hydrolysis

A set of N-coordinated tellurium(II) compounds containing either C,N-chelating ligands CNR (where CN = 2-(RNCH)C6H4, R = tBu or Dipp; Dipp = 2,6-iPr2C6H3) or N,C,N pincer ligands NCNR (where NCN = 2,6-(RNCH)2C6H4, R = tBu or Dipp) were synthesized. In the case of C,N-chelated compounds, the reaction of CNDippLi with Te(dtc)2 (where dtc = Et2NCS2) in a 1 : 1 molar ratio smoothly provided the carbamate CNDippTe(dtc) which upon treatment with 2 eq. of HCl provided the chloride CNDippTeCl. In contrast, the analogous conversion of NCNRLi with Te(dtc)2 surprisingly furnished ionic bromides [NCNRTe]Br as a result of the exchange of dtc by Br coming from nBuBr present in the reaction mixture. Furthermore, the reaction of CNDippTeCl or [NCNRTe]Br with silver salts AgX (X = OTf or SbF6) provided the expected tellurenium cations [CNDippTe]SbF6 and [NCNRTe]X. To further increase the Lewis acidity of the central atom, the oxidation of selected compounds with 1 eq. of SO2Cl2 was examined yielding stable compounds [CNtBuTeCl2]X and [NCNtBuTeCl2]X. The oxidation of the Dipp substituted compounds proved to be more challenging and an excess of SO2Cl2 was necessary to obtain the oxidized products [CNDippTeCl2]SbF6 and [NCNDippTeCl2]SbF6, which could solely be characterized in solution. Compounds [CNtBuTeCl2]OTf and [NCNtBuTeCl2]OTf were shown to undergo a controlled hydrolysis to the corresponding telluroxanes. All compounds were studied by multinuclear NMR spectroscopy in solution and for selected compounds solid state 125Te NMR spectroscopy and single-crystal X-ray diffraction analysis were performed. The Lewis acidity of the studied cations was examined by the Gutmann-Beckett method using Et3PO as the probing agent. The Te-N chalcogen bonding situation of selected compounds has also been examined computationally by a set of real-space bonding indicators.

Synthesis and reactivity of alkali metal aluminates bearing bis(organoamido)phosphane ligand

In this study, we report a group of alkali metal aluminates bearing bis(organoamido)phosphane ligand. The starting complex {[PhP(NtBu)2]AlMe2}Li·OEt2 (1) was prepared by stepwise deprotonation of the parent PhP(NHtBu)2 by nBuLi and AlMe3. Further derivatization of aluminate 1 was performed by the virtual substitution of lithium -{[PhP(NtBu)2]AlMe2}K (2), methyl substituents - {[PhP(NtBu)2]AlH2}Li·THF (3), modification of steric bulk and induction effects on the phosphorus atom - {[tBuP(N-2,6-iPr2C6H3)2]AlMe2}Li·(OEt2)2 (4), and phosphorus atom oxidation state {[Ph(Y)P(NtBu)2]AlMe2}Li (Y = O (5), S (6), Se (7), Te (8)). The structure causing non-covalent interactions in 1-4 were evaluated with the help of theoretical calculations and topological analysis ranging from π-electron system-metal to agostic interactions of various types. The further reactions of 1 with various nucleophiles were found to be a versatile tool for the preparation of iminophosphonamides via the formation of P-E bond (E = Si, Ge, Sn, Pb, P, and C) and followed by P(III) → P(V) tautomeric shift.

Cyclopentadienyl Molybdenum(II) Compounds Bearing Ether and Thioether Functions in the Side Chain: Synthesis, Characterization, and Cytotoxic/Cytostatic Studies

A series of molybdenum(II) compounds [(η5 -Cp')Mo(CO)2 (L2 )][BF4 ] (Cp'=C5 H4 (CH2 )2 SPh, C9 H6 (CH2 )2 OMe, L2= N,N-chelating ligand) have been synthesized and characterized by spectroscopic and analytical methods including X-ray crystallography. The in vitro assay on human leukemia cells MOLT-4 has shown that the substitution in the π-ligand in combination with suitable N,N-chelating ligand can lead to species with cytotoxicity considerably higher than reported to cisplatin. Unusually high activity was observed for compounds bearing phenanthroline ligands [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (3,4,7,8-Me4 phen)][BF4 ] (IC50 =0.7±0.3 μM) and [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (4,7-Ph2 phen)][BF4 ] (IC50 values 0.8±0.4 μM).

Stabilization of propene molybdenum and tungsten half-sandwich complexes by intramolecular coordination of a thioether function

This study reports the stabilizing effect of an intramolecularly coordinated thioether function in propene complexes of the general formula [{η⁵:κS-C₅H₄(CH₂)₂SR}M(CO)₂(η²-C₂H₃Me)][BF₄] (M = Mo, W; R = Et, Ph). They are formed by protonation of allyl analogues [{η⁵-C₅H₄(CH₂)₂SR}M(CO)₂(η³-C₃H₅)] by tetrafluoroboric acid in non-coordinating solvents. In contrast to analogues with unsubstituted Cp ligands, these propene complexes are isolable in a pure form and characterized by NMR spectroscopy. The molybdenum compounds are stable at low temperature and the propene ligand can easily be exchanged by thioethers or acetonitrile. Several representatives of the reaction products were characterized by X-ray structure analysis. The stabilization effect in tungsten complexes [{η⁵:κS-C₅H₄(CH₂)₂SR}W(CO)₂(η²-C₂H₃Me)][BF₄] (R = Et, Ph) was unusually high. The compounds are long-term stable at room temperature and do not undergo ligand exchange reactions even with strong chelators such as 1,10-phenanthroline. The molecular structure of the tungsten propene complex was confirmed by X-ray diffraction analysis on a single crystal.

Tin(II) cations stabilized by non-symmetric N,N',O-chelating ligands: synthesis and stability

A series of novel non-symmetric neutral N,N',O-chelating ligands derived from the α-iminopyridine 2-(C(R¹)N(C₆H₃-2,6-iPr₂))-6-(R²R³PO)C₅H₃N (L1: R¹ = H, R² = R³ = Ph; L2: R¹ = Me, R² = R³ = Ph; L3: R¹ = H; R² = Ph, R³ = EtO; L4: R¹ = Me, R² = Ph, R³ = EtO; L5: R¹ = H, R² = R³ = iPrO; L6: R1 = Me, R² = R³ = iPrO) were synthesized. Ligands L1-6 were reacted with SnCl₂ and Sn(OTf)₂ with the aim of studying the influence of different R²R³PO functional groups on the Lewis base mediated ionization of SnCl₂ and Sn(OTf)₂. While all ligands L1-6 provided the corresponding ionic tin(II) complexes [L1-6 → SnCl]⁺[SnCl₃]^- (1-6), only ligands L1, L4 and L6 were able to stabilize tin(II) dications [L1,4,6 → Sn(H₂O)][OTf]₂ (7-9). The auto-ionized compounds [L3-6 → SnCl]⁺[SnCl₃]^- possessing ethylphenyl phosphinate and diisopropylphosphite substituents undergo elimination of EtCl and iPrCl, respectively, yielding compounds 10-13. These can either be interpreted as neutral tin(II)phosphinate chloride (10, 11) and tin(II)phosphonate chloride (12, 13), respectively, containing Sn-O and Sn-Cl bonds, and a PO → SnCl₂ interaction, or as zwitterionic compounds, where the positive charge of the central tin atom is compensated by an [OSnCl₂]^- anion. Finally, DFT studies were performed to better understand the steric and electronic properties of the ligands L1-6 as well as the nature of the bonds in the resulting products, with a particular focus on complexes 10-13.

Oxidations of N-coordinated Arsinidene and Stibinidene by Substituted Quinones: A Remarkable Follow-Up Reactivity

The reactivity of pnictinidenes [2-(DippN=CH)-6-(DippNHCH₂ )C₆ H₃ ]E (where E=As (1) or Sb (2)) toward substituted ortho- and para-quinones is reported. The central pnictogen atom is easily oxidized by ortho-quinones closing five-membered EO₂ C₂ ring. The oxidized antimony derivatives are stable species, while in the case of arsenic compounds the hydrogen of the pendant amino NHCH₂ group cleaves one newly formed As-O bonds leading to the closure of a new azaarsole ring. Furthermore, a heating of these arsenic heterocycles resulted in a C-H bond activation at the NCH₂ group involved in this heterocycle followed by a reductive elimination of corresponding catechols and arsinidene [2,6-(DippN=CH)C₆ H₃ ]As. Using of para-quinones, resulted in the oxidation of the central atom with a concomitant hydrogen migration from NHCH₂ group even in the case of the antimony derivatives. The reductive elimination of hydroquinones is in this case feasible for all compounds. Studied compounds were characterized by multi-nuclear NMR, IR and Raman spectroscopy and single-crystal X-ray diffraction analysis. The theoretical study focusing the key compounds and reactions is also included.

Beyond simple hetero Diels-Alder Cycloadditions. A New Type of Element-Ligand Cooperativity at N,C,N-coordinated Arsinidene and Stibinidene Centres in the Reaction with an Electron Deficient Alkyne

The reactivity of two types of organopnictogen(I) N,C,N-pincer ligand coordinated compounds, i.e. [2,6-(DippN=CH)2C6H3]E (1-E, where E = As, Sb, Bi; Dipp = 2,6-iPrC6H3) and [2-(DippN=CH)-6-(DippNHCH2)C6H3]E (6-E, where E = As...

The Reactivity of Antimony and Bismuth N,C,N-Pincer Compounds toward K[BEt3H] – the Formation of Heterocyclic Compounds vs. Element-Element Bonds vs. Stable Terminal Sb-H Bonds

The oxidative addition of CF3SO3CH2Si(CH3)3 (NpSiOTf) toward organopnictogen(I) N,C,N-pincer compounds, i.e. [2,6-(DippN=CH)2C6H3]E (1-E, where E = Sb, Bi; Dipp = 2,6-iPr2C6H3) produced compounds [2,6-(DippN=CH)2C6H3]E(NpSi)(OTf) (2-E, where E = Sb, Bi)....

Synthesis and optical properties of N→Ga coordinated gallium boroxines

Reactions of the N,C,N-chelated organogallium amide LGa(NEt₂)₂ (1), where L is {2,6-(Me₂NCH₂)₂C₆H₃}^-, with organoboronic acids RB(OH)₂ yielded molecular gallium boroxines LGa(O₃B₂R₂) (2: R = OH, 3: R = Ph, 4: R = 4-MeO-C₆H₄, 5: R = 4-CHO-C₆H₄, 6: R = Fc), neutral analogues of gallaborates. The molecular structures revealed the presence of a six-membered central GaB₂O₃ ring. The film forming properties of 5 allowed the deposition of transparent thin films by a spin coating method. The thicknesses, refractive index, energy of the optical gap (Eoptg), activation energy of surface electrical conductivity (Esa) and pre-exponential factor (σ₀) of the thin layers of 5 were measured and they are close to those found for related oxygen glass. Finally, GBO 5 was also used as an additive to printing ink and a thin film of 5 was prepared by the gravure printing technique.

Sn,P-coordinated Ru cation: a robust catalyst for aerobic oxidations of benzylamine and benzyl alcohol

A stable ionic κ²Sn,P-coordinated Ru complex shows excellent catalytic activity in aerobic oxidations of benzylamine and benzyl alcohol. This complex is stabilized by a stannylene-phosphine peri-substituted naphthalene ligand, which can act as either a reducing agent for a Ru(III) complex or as a κ²Sn,P-chelating ligand for Ru(II) compounds.

Lewis Superacidic Tellurenyl Cation-Induced Electrophilic Activation of an Inert Carborane

The aryltellurenyl cation [2-(tBuNCH)C6 H4 Te]+ , a Lewis super acid, and the weakly coordinating carborane anion [CB11 H12 ]- , an extremely weak Brønsted acid (pKa =131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C6 H4 Te][CB11 H12 ], in which the Brønsted acidity (pKa 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude. The electrophilic activation of B-H bonds in the carborane moiety gives rise to a proton transfer from boron to nitrogen at slightly elevated temperatures, as rationalized by the isolation of a mixture of the zwitterionic isomers 12- and 7-[2-(tBuN{H}CH)C6 H4 Te(CB11 H11 )] in ratios ranging from 62 : 38 to 80 : 20.

Non-conventional Behavior of a 2,1-Benzazaphosphole: Heterodiene or Hidden Phosphinidene?

The titled 2,1-benzazaphosphole (1) (i. e. ArP, where Ar=2-(DippN=CH)C6 H4 , Dipp=2,6-iPr2 C6 H3 ) showed a spectacular reactivity behaving both as a reactive heterodiene in hetero-Diels-Alder (DA) reactions or as a hidden phosphinidene in the coordination toward selected transition metals (TMs). Thus, 1 reacts with electron-deficient alkynes RC≡CR (R=CO2 Me, C5 F4 N) giving 1-phospha-1,4-dihydro-iminonaphthalenes 2 and 3, that undergo hydrogen migration producing 1-phosphanaphthalenes 4 and 5. Compound 1 is also able to activate the C=C double bond in selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) resulting in the addition products 7-9 with bridged bicyclic [2.2.1] structures. The binding of the maleimides to 1 is semi-reversible upon heating. By contrast, when 1 was treated with selected TM complexes, it serves as a 4e donor bridging two TMs thus producing complexes [μ-ArP(AuCl)2 ] (10), [(μ-ArP)4 Ag4 ][X]4 (X=BF4 (11), OTf (12)) and [μ-ArP(Co2 (CO)6 )] (13). The structure and electron distribution of the starting material 1 as well as of other compounds were also studied from the theoretical point of view.

Non-conventional Behavior of a 2,1-Benzazaphosphole: Heterodiene or Hidden Phosphinidene?

Invited for the cover of this issue are Zoltán Benkő, Libor Dostál and co-workers at the University of Pardubice and the Budapest University of Technology and Economics. The image depicts signs for the two different pathways representing the two differing reaction types which were clearly observed for 2,1-benzazaphosphole. Read the full text of the article at 10.1002/chem.202101686.

Coordination capabilities of bis-(2-pyridyl)amides in the field of divalent germanium, tin and lead compounds

The reactivity of two lithium amides derived from bis-(2-pyridyl)amine (dpa)H or its methyl-substituted congener bis-(6-methyl-2-pyridyl)amine (Me-dpa)H, i.e. (dpa)Li (1) and (Me-dpa)Li (2), toward ECl2 (where E = Ge (dioxane complex) and Sn) is reported. This study produced both heteroleptic complexes (dpa)GeCl (3), [(dpa)SnCl]2 (4), and (Me-dpa)GeCl (5) and homoleptic complexes (dpa)2E (E = Ge (6) or Sn (7)) and (Me-dpa)2E (E = Ge (8) or Sn (9)). The structures of all complexes were established by single-crystal X-ray diffraction analysis showing significant differences depending on the E atom and ligand used. By contrast, in solution, the majority of compounds showed a fluxional behaviour as demonstrated by the NMR study. Finally, it turned out that the Me-dpa ligand, unlike dpa, is able to form ate complexes [(Me-dpa)3E]Li (E = Ge (10), Sn (11) or Pb (12)), whose structures were determined by single-crystal X-ray diffraction analysis. This study revealed the formation of two isomers for Ge and Sn complexes depending on the coordination preference of the lithium atom being coordinated either by nitrogen donors (10-12) or solely by the Ge or Sn electron lone pair (10a and 11a). Furthermore, the NMR experiments proved that the germanium complex 10 exhibits only limited stability in solution and decomposes to germylene 8 and lithium amide 2.

Cyclopentadienyl-Based Anticancer Drugs: Improvement of Cytotoxic Activity through Functionalisation of the π Ligand

Cytotoxic complexes containing molybdenum are widely studied as a potential substitution for commercially used drugs that often suffer from pronounced side effects and cellular resistance. Compounds of the type [(η⁵ -Cp')Mo(CO)₂ (^N,N L)][BF₄ ], where Cp is cyclopentadienyl and ^N,N L is a bidentate ligand, are well known for their strong anticancer activity. It is a generally accepted paradigm that the nature of the coordinated ^N,N L ligand has a major impact on the cytotoxicity. In this study, a series of new functionalised Cp complexes of molybdenum was synthesised from derivatised fulvenes as π-ligand precursors. Indeed, the coordination sphere's modulation by various N,N-chelating ligands afforded species active toward leukemic cell line MOLT-4 with IC₅₀ values depending on the character of the N,N-chelator used. However, following study clearly showed that functionalisation of the Cp ring with an amine moiety considerably improved cytotoxicity. These results are of crucial importance for the future design of highly active cytotoxic drugs, as modification of cyclopentadienyl is believed to have a minor effect on biological activity.

Synthesis and properties of 1,2,3-diazapnictol-5-yl substituted ferrocenes

A series of new ferrocene derivatives bearing 1,2,3-diazapnictolyl substituents were synthesised and their spectroscopic and electrochemical properties were studied.

(N),C,N-Coordinated Heavier Group 13-15 Compounds: Synthesis, Structure and Applications

The aim of this review is to summarize recent achievements in the field of (N),C,N-coordinated group 13-15 compounds not only regarding their synthesis and structure, but mainly focusing on their potential applications. Relevant compounds contain various types of N-coordinating ligands built up on an ortho-(di)substituted phenyl platform. Thus, group 13 and 14 derivatives were used as single-source precursors for the deposition of semiconducting thin films, as building blocks for the preparation of high-molecular polymers with remarkable optical and chemical properties or as compounds with interesting reactivity in hydrometallation processes. Group 15 derivatives function as catalysts in the Mannich reaction, in the allylation of aldehydes or activation of CO₂ . They were used as transmetallation reagents in transition metal catalysed coupling reactions. The univalent species serve as ligands for transition metals, activate alkynes or alkenes and are utilized as catalysts in the transfer hydrogenation of azo-compounds.

Organogermanium(II) Hydrides as a Source of Highly Soluble LiH

The reactions of monomeric C,N-chelated organogermanium(II) hydride L(H)Ge⋅BH₃ with organolithium salts RLi yielded lithium hydrogermanatoborates (Li(THF)₂ {BH₃ [L(H)GeR]})₂ . Compound (Li(THF)₂ {BH₃ [L(H)GePh]})₂ was used as a source of LiH for the reduction of organic C=O or C=N bonds in nonpolar solvents accompanied by the elimination of a neutral complex L(Ph)Ge⋅BH₃ . The interaction of (Li(THF)₂ {BH₃ [L(H)GePh]})₂ with the polar C=O bond was further investigated by computational studies revealing a plausible geometry of a pre-reactive intermediate. The experimental and theoretical studies suggest that, although the Li atom of (Li(THF)₂ {BH₃ [L(H)GePh]})₂ coordinates the C=O bond, the GeH fragment is the active species in the reduction reaction. Finally, benzaldehyde was reduced by a mixture of L(H)Ge⋅BH₃ with PhLi in nonpolar solvents.

Reactivity of boraguanidinato germylenes toward carbonyl compounds and isocyanides: C-O, C-F and C-N bond activation

The reactions of two equivalents of germylene [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge (1) with carbonyl compounds RC(O)R' resulted in carbonyl functionality activation and the formation of 4-(R,R')-1,2-digerma-3-oxa-cyclobutanes (R/R' = Ph/CF₃ (2) or C₆F₅/H (3)). Surprisingly, the analogous reaction of 1 with C₆F₅C(O)Me led to the insertion of the germanium atom into the C-F bond of the perfluorophenyl group, thus producing a spiro compound (4) with a germanium atom sharing 1,2-digerma-3,5-diaza-4-bora-cyclopentane and 1-germa-2,4-diaza-3-boracyclobutane rings. Furthermore, the reaction of 1 with 2e^- donors was investigated. In the case of 4-dimethylaminopyridine (DMAP), an expected complex [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge(DMAP) (5) was isolated, but using t-BuNC resulted in the formation of germanium(iv) cyanide [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge(CN)(t-Bu) (6) as a result of C-N bond activation in the starting isocyanide. In contrast, mixing other isocyanides RNC (R = Cy or Ad) with 1 in solution led only to an equilibrium between the starting compounds and most probably the corresponding complexes [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge(CNR) (R = Cy (7a) or Ad (8a)) based on NMR studies. From these equilibrium mixtures, fortuitously, single crystals of digerma-spiro-complexes (7 and 8) containing two germanium atoms (one of them coordinated to a particular isocyanide) were obtained and structurally authenticated by the X-ray diffraction technique.

Antimony(i) → Pd(ii) complexes with the (μ-Sb)Pd2 coordination framework

The reaction of the antimony(i) compound ArSb (1) (where Ar = C₆H₃-2,6-(CH[double bond, length as m-dash]NtBu)₂) with various dimeric allyl palladium(ii) complexes [Pd(η³-allyl)(μ-X)]₂ (where allyl = C₃H₅ or C₃H₄Me; X = Cl or CF₃CO₂) in a 1 : 1 stoichiometric ratio gave unique complexes with the μ-ArSb moiety bridging two palladium fragments, i.e. [{Pd(η³-C₃H₅)Cl}₂(μ-ArSb)] (2), [{Pd(η³-C₃H₄Me)Cl}₂(μ-ArSb)] (3) and [{Pd(η³-C₃H₅)(CF₃CO₂)}₂(μ-ArSb)] (4). Compound 1 serves formally as a 4e donor in 2-4. The treatment of 2 with another equivalent of ArSb led to the formation of the [Pd(η³-C₃H₅)(Cl)(μ-ArSb)] complex (5), proving that 1 is able to function as a 2e donor in target complexes as well. The structures of 2-5 were described in detail both in solution (NMR and mass spectrometry) and in the solid state (single crystal X-ray diffraction analysis). DFT methods were used to compare bonding in the 1 : 1 (5) and 1 : 2 (2) complexes. Furthermore, a comprehensive ¹²¹Sb Mössbauer spectroscopic investigation of complexes 2 and 5 along with parent ArSbCl₂ (6) and 1 was performed. For comparison, complexes [Fe(CO)₄(ArSb)] (7) and [Mo(CO)₅(ArSb)] (8) were also included in this study.

Synthesis and coordination properties of new σ2,λ3-P/N switchable chelators based on [1,2,3]-diazaphosphole

New ligands with σ²,λ³-P/N switching ability were synthesised and their coordination properties toward transition metals were studied.

Enhanced cytotoxicity of indenyl molybdenum(ii) compounds bearing a thiophene function

New indenyl molybdenum(ii) compounds with improved cytotoxic properties were synthesized and evaluated in lung cancer cells A549.

Propene complexes of molybdenum and tungsten stabilized by intramolecular coordination of the 1-(quinol-8-yl)indenyl ligand

Synthesis, reactivity and properties of unusually stable propene complexes of molybdenum and tungsten are reported.