A Convenient Route to Monoalkyl-Substituted Phosphanylboranes (HRP–BH2–NMe3): Prospective Precursors to Poly[(alkylphosphino)boranes]

A simple method to access borylphosphonium iodides [RH2P-BH2 center dot NMe3]I (1a: R = Me; 1b: R = Et; 1c: R = nPr) by the addition of iodoalkanes to PH2-BH2 center dot NMe3 was developed. Complexes 1a-c were characterized by multinuclear NMR spectroscopy, and 1a and 1b additionally by single-crystal X-ray diffraction. It was possible to synthesize the Lewis-base-stabilized organosubstituted phosphanylborane MePH-BH2 center dot NMe3 (2) from [MePH2-BH2 center dot NMe3] I (1a). Thermolysis of 2 generated a soluble, low-molecular-mass poly(alkylphosphinoborane)consisting of at least 40 repeat units, as identified by ESI-MS. These results are promising for the future preparation of a wide range of Lewis-base-stabilized phosphanylboranes, which are of interest as precursors to poly[(alkylphosphino)boranes] and are otherwise difficult to access by conventional metal-catalyzed methods

Isolation of elusive HAsAsH in a crystalline diuranium(IV) complex

The HAsAsH molecule has hitherto only been proposed tentatively as a short-lived species generated in electrochemical or microwave-plasma experiments. After two centuries of inconclusive or disproven claims of HAsAsH formation in the condensed phase, we report the isolation and structural authentication of HAsAsH in the diuranium(IV) complex [{U(TrenTIPS)}2(μ-η2:η2-As2H2)] (3, TrenTIPS=N(CH2CH2NSiPri3)3; Pri=CH(CH3)2). Complex 3 was prepared by deprotonation and oxidative homocoupling of an arsenide precursor. Characterization and computational data are consistent with back-bonding-type interactions from uranium to the HAsAsH π*-orbital. This experimentally confirms the theoretically predicted excellent π-acceptor character of HAsAsH, and is tantamount to full reduction to the diarsane-1,2-diide form

A General Pathway to Heterobimetallic Triple‐Decker Complexes

A systematic study on the reactivity of the triple-decker complex [(Cp'''Co)(2)(mu,eta(4):eta(4)-C7H8)] (A) (Cp'''=1,2,4-tritertbutyl-cyclopentadienyl) towards sandwich complexes containing cyclo-P-3, cyclo-P-4, and cyclo-P-5 ligands under mild conditions is presented. The heterobimetallic triple-decker sandwich complexes [(Cp*Fe)(Cp'''Co)(mu,eta(5):eta(4)-P-5)] (1) and [(Cp'''Co)(Cp'''Ni)(mu,eta(3):eta(3)-P-3)] (3) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) were synthesized and fully characterized. In solution, these complexes exhibit a unique fluxional behavior, which was investigated by variable temperature NMR spectroscopy. The dynamic processes can be blocked by coordination to {W(CO)(5)} fragments, leading to the complexes [(Cp*Fe)(Cp'''Co)(mu(3),eta(5):eta(4):eta(1)-P-5){W(CO)(5)}] (2 a), [(Cp*Fe)(Cp'''Co)(mu(4),eta(5):eta(4):eta(1):eta(1)-P-5){(W(CO)(5))(2)}] (2 b), and [(Cp'''Co)(Cp'''Ni)(mu(3),eta(3):eta(2):eta(1)-P-3){W(CO)(5)}] (4), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp'''Ni)(2)(mu,eta(2):eta(2)-P-2)] (5). All compounds were fully characterized using single-crystal X-ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis

The Parent Diarsene HAs=AsH as side-on bound ligand in an Iron Carbonyl Complex

The terminal diarsene HAs=AsH ligand attracts special interest concerning its bonding relation in comparison to its isolable relative, ethene. Herein, by the methanolysis of [{Fe(CO)4}As(SiMe3)3] (1) the synthesis of [{Fe(CO)4}(η2‐As2H2)] (2) is reported, containing a parent diarsene as unprecedented side‐on coordinated ligand. Following this synthetic route, also the D‐labeled complex [{Fe(CO)4}(η2‐As2D2)] (2D) could be isolated. The electronic structure and bonding situation of 2 was elucidated by DFT calculations revealing that 2 is best described as an olefin‐like complex. Moreover, the reactivity of 2 towards the Lewis acids [{M(CO)5}(thf)] (M=Cr, W) was investigated, leading to the complexes [Fe(CO)4AsHW(CO)5]2 (3) and [{Fe(CO)4}2AsH{Cr(CO)5}] (4), respectively

Coordination Behavior of a P4-Butterfly Complex towards Transition Metal Lewis Acids – Preservation versus Rearrangement

The reactivity of the P4 butterfly complex [{Cp’’’Fe(CO)2}2(µ,η1:1‐P4)] (1, Cp’’’ = η5‐C5H2tBu3) towards divalent Co, Ni and Zn salts is investigated. The reaction with the bromide salts leads to [{Cp’’’Fe(CO)2}2(µ3,η2:1:1‐P4){MBr2}] (M = Co (2Co), Ni (2Ni), Zn (2Zn)) where the P4 butterfly scaffold is preserved. The use of the weakly ligated Co complex [Co(NCCH3)6][SbF6]2, results in the formation of [{(Cp’’’Fe(CO)2)2(µ3,η4:1:1‐P4)}2Co][SbF6]3 (3), representing the second example of a homoleptic‐like octaphospha‐metalla‐sandwich complex. The formation of the threefold positively charged complex 3 occurs via redox processes, which among others also enables the formation of [{Cp’’’Fe(CO)2}4(µ5,η4:1:1:1:1‐P8){Co(CO)2}][SbF6] (4), bearing a rare octaphosphabicyclo[3.3.0]octane unit as a ligand. On the other hand, the reaction with [Zn(NCCH3)4][PF6]2 yields the spiro complex [{(Cp’’’Fe(CO)2)2(µ3,η2:1:1‐P4)}2Zn][PF6]2 (5) under preservation of the initial structural motif

Cu(I) Complexes Comprising tetrahedral Mo2E2 or Mo2PE units (E=P, As, Sb) as Chelating Ligands

Novel isomorphous tetranuclear complexes, [(dppf)Cu(μ3,η2 : 2 : 2-E2{CpMo(CO)2}2]BF4 [E=P (1), As (4), Sb (5), (dppf=1,1′-bis-(diphenylphosphino)-ferrocene)] and [(dppf)Cu(μ3,η2 : 2 : 2-PE{CpMo(CO)2}2]BF4 [E=As (2), Sb(3)] were synthesized from the reactions between [(dppf)Cu(MeCN)2][BF4] and tetrahedral molybdenum complexes containing unsubstituted homo- and hetero-diatomic group-15 elements [(μ,η2 : 2-E2{CpMo(CO)2}2] [E=P (A), As (D), Sb (E)] and [(μ,η2 : 2-PE{CpMo(CO)2}2] [E=As (B), Sb (C)], respectively. In all these products, the {Mo2E2} or {Mo2PE} moieties coordinate the Cu(I) center via a rare side-on η2-coordination mode. The X-ray structure analyses of [(dppf)Cu(μ3,η2 : 2 : 1-PSb{CpMo(CO)2}2][BF4] demonstrate, for the first time, the utilization of an η1-coordination mode for the ligand complex C to coordinate to the Cu(I) center. All the products were characterized by X-ray crystallography, NMR and IR spectroscopy, mass spectrometry and elemental analysis. Electrochemical studies also revealed the formation of 1–5, and, further, to understand the structure and bonding of the products, theoretical calculations using density functional theory (DFT) were conducted

Monomeric β‐Diketiminato Group 13 Metal Dipnictogenide Complexes with Two Terminal EH2 Groups (E=P, As)

The pnictogenyl Group 13 compounds (Dipp(2)Nacnac)M[E(SiMe3)(2)]Cl and (Dipp(2)Nacnac)M(EH2)(2) (Dipp(2)Nacnac=HC[C(Me)N(Ar)](2), Ar: Dipp=2,6-iPr(2)C(6)H(3); M=Al, Ga, In; E=P, As) were successfully synthesized. The salt metathesis between (Dipp(2)Nacnac)MCl2 and LiE(SiMe3)(2) only led to monosubstituted compounds (Dipp(2)Nacnac)M[E(SiMe3)(2)]Cl [E=P, M=Ga(1), In (2); E=As, M=Ga (3), In (4)], regardless of the stoichiometric ratios used. In contrast to the steric effect of the SiMe3 groups in 1-4, the reactions of the corresponding halides with LiPH2 center dot DME (or KAsH2) facilely yielded the dipnictogenide compounds (Dipp(2)Nacnac)M(EH2)(2) (E=P, M=Al (5), Ga (6), In (7); E=As, M=Al (8), Ga (9)), avoiding the use of flammable and toxic PH3 and AsH3 for their synthesis. The compounds 5-9 are the first examples of monomeric Group 13 diphosphanides and diarsanides in which the metal center is bound to two terminal PH2 and AsH2 groups, respectively. In contrast to the successful synthesis of the indium diphosphanide (Dipp(2)Nacnac)In(PH2)(2), the reaction of (Dipp(2)Nacnac)InCl2 with KAsH2 led to an indium mirror due to the instability of the target product

Potential of Mixed Dipnictogen Molybdenum Complexes in the Self-Assembly of Thallium Coordination Compounds

The coordination chemistry of the homo- and heterodipnictogen tetrahedrane complexes [{CpMo(CO)2}2(μ,η2:2-EE′)] (E, E′ = P, As, Sb) (A–F) toward Tl[BArF24] ([BArF24]− = [B(3,5-C6H3(CF3)2)4]−) was studied. Controlled by the used tetrahedranes A–F, and thus depending on the respective pnictogen atoms, the monomers [Tl(η2-A)][BArF24] ([A]Tl) and [Tl(η2-B)][BArF24] ([B]Tl), the double substituted [Tl(η1-C)2][BArF24] ([C]2Tl) or the even higher aggregated compounds [Tl2(η2-D)3(μ,η2:1-D)(μ,η1:1-D)][BArF24]2 ([D]5Tl2), [Tl2(η2-E)2(μ,η2:1-E)3] [BArF24]2 ([E]5Tl2) and [Tl2(η2-F)3(μ,η2:1-F)3][BArF24]2 ([F]6Tl2) were obtained. Utilization of [BArF24]− promises additional stabilization of TlI via η6-coordination of two of its aryl rings as found in compounds [A]Tl, [B]Tl and [C]2Tl. Within the series of reactivity of A–F, the heavier congeners D, E and F tend to form larger aggregates in which σ(E–E′) bond contributions to the coordination behavior were observed. Interatomic distances suggest the presence of Tl···Tl interactions in [E]5Tl2 and [F]6Tl2. The features of the respective coordination compounds were studied in the solid-state as well as in solution. For the latter at least a partial dissociation of the assemblies in solution was indicated. The isolated solid-state aggregates are the first examples of heterodipnictogen units as ligands in self-assembled TlI-based coordination compounds

Reactivity of E4_4 (E4_4 =P4_4 , As4_4 , AsP3_3) towards Low‐Valent Al(I) and Ga(I) Compounds

The reactivity of yellow arsenic and the interpnictogen compound AsP$_3$ towards low-valent group 13 compounds was investigated. The reactions of [LAl] (1, L=[{N(C$_6$H$_3$$^i$Pr$_2$-2,6)C(Me)}$_2$CH]−) with As$_4$ and AsP$_3$ lead to [(LAl)$_2$(μ,η$^{1:1:1:1}$-E$_4$)] (E$_4$=As$_4$ (3 b), AsP$_3$ (3 c)) by insertion of two fragments [LAl] into two of the six E−E edges of the E$_4$ tetrahedra. Furthermore, the reaction of [LGa] (2) with E$_4$ afforded [LGa(η$^{1:1}$-E$_4$)] (E$_4$=As$_4$ (4 b), AsP$_3$ (4 c)). In these compounds, only one E−E bond of the E$_4$ tetrahedra was cleaved. These compounds represent the first examples of the conversion of yellow arsenic and AsP$_3$, respectively, with group 13 compounds. Furthermore, the reactivity of the gallium complexes towards unsaturated transition metal units or polypnictogen (E$_n$) ligand complexes was investigated. This leads to the heterobimetallic compounds [(LGa)(μ,η$^{2:1:1}$-P$_4$)(LNi)] (5 a), [(Cp’’’Co)(μ,η$^{4:1:1}$-E$_4$)(LGa)] (E=P (6 a), As (6 b), Cp’’’=η$^5$-C$_5$H$_2$$^t$Bu$_3$) and [(Cp’’’Ni)(η$^{3:1:1}$-E$_3$)(LGa)] (E=P (7 a), As (7 b)), which combine two different ligand systems in one complex (nacnac and Cp) as well as two different types of metals (main group and transition metals). The products were characterized by crystallographic and spectroscopic methods

Synthesis and Redox Chemistry of a Homoleptic Iron Arsenic Prismane Cluster

The redox chemistry of the homoleptic iron prismane cluster [{Cp*Fe}3(μ3,η4:4:4-As6)] (A, Cp*=C5Me5) is investigated both electrochemically and synthetically. While its first oxidation leads to the diamagnetic species [{Cp*Fe}3(μ3,η4:4:4-As6)][X] ([1][TEF], [1][FAl], [TEF]−=[Al{OC(CF3)3}4]−, [FAl]−=[FAl{O(1-C6F5)C6F10}3]−), the second oxidation yields the paramagnetic [{Cp*Fe}3(μ3,η4:4:4-As6)][TEF]2 ([2][TEF]2). The reduction of A leads to the monoanionic compound [K@[2.2.2]-cryptand][{Cp*Fe}3(μ3,η4:4:4-As6)] ([K@crypt][3]), while a second reduction could only be traced spectroscopically. All compounds were comprehensively characterized, revealing the structural changes accompanying the described redox processes. All findings are supported by spectroscopic as well as computational studies