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

Synthesis and Characterization of a Terminal Iron(II)-PH2 Complex and a Series of Iron(II)-PH3 Complexes

Reported is the reaction of a series of iron(II) bisphosphine complexes with PH3 in the presence of NaBArF4 [where BArF4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate]. The iron(II) bisphosphine reagents bear two chlorides or a hydride and a chloride motif. We have isolated six different cationic terminal-bound PH3 complexes and undertaken rigorous characterization by NMR spectroscopy, single crystal X-ray diffraction, and mass spectrometry, where the PH3 often remains intact during the ionization process. Unusual bis- and tris-PH3 complexes are among the compounds isolated. Changing the monophosphine from PH3 to PMe3 results in the formation of an unusual Fe7 cluster, but with no PMe3 being ligated. Finally, by using an iron(0) source, we have provided a rare example of a terminally bound iron-PH2 complex.

Characterization of the Ligand Properties of Donor-stabilized Pnictogenyltrielanes

A general synthesis and the characterization of novel alkyl-substituted NHC-stabilized pnictogenylboranes NHC ⋅ BH2 ER2 (NHC=N-heterocyclic carbene, E=P, As; R2 =Me2 , Ph2 , t BuH, Cy2 , (SiMe3 )2 ) are reported. These compounds were reacted with Ni(CO)4 to the corresponding complexes of the type [(NHC ⋅ BH2 ER2 )Ni(CO)3 ] to determine their donor strength by Tolman Electronic Parameters (TEPs) and their steric demand as ligands compared to classical phosphines, superbasic phosphines and other commonly applied donor systems. The results show that the NHC-stabilized pnictogenyltrielanes can be considered as being highly basic, while their steric influence depends strongly on the organic residues as well as the donor attached to the {BH2 } moiety. Although weaker than commonly used superbasic phosphines, the donor strength of pnictogenyltrielanes in general can be classified as of similar strength as NHCs. The steric and electronic properties can easily be modified by alkyl substitution as evident from the TEP trends.

Reactivity of E4 (E4 =P4 , As4 , AsP3 ) towards Low-Valent Al(I) and Ga(I) Compounds

The reactivity of yellow arsenic and the interpnictogen compound AsP₃ towards low-valent group 13 compounds was investigated. The reactions of [LAl] (1, L=[{N(C₆ H₃ ⁱ Pr₂ -2,6)C(Me)}₂ CH]^- ) with As₄ and AsP₃ lead to [(LAl)₂ (μ,η^1:1:1:1 -E₄ )] (E₄ =As₄ (3 b), AsP₃ (3 c)) by insertion of two fragments [LAl] into two of the six E-E edges of the E₄ tetrahedra. Furthermore, the reaction of [LGa] (2) with E₄ afforded [LGa(η^1:1 -E₄ )] (E₄ =As₄ (4 b), AsP₃ (4 c)). In these compounds, only one E-E bond of the E₄ tetrahedra was cleaved. These compounds represent the first examples of the conversion of yellow arsenic and AsP₃ , 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 -P₄ )(LNi)] (5 a), [(Cp'''Co)(μ,η^4:1:1 -E₄ )(LGa)] (E=P (6 a), As (6 b), Cp'''=η⁵ -C₅ H₂ ^t Bu₃ ) and [(Cp'''Ni)(η^3:1:1 -E₃ )(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.

Selective 1,2 addition of polar X-H bonds to the Ga-P double bond of gallaphosphene L(Cl)GaPGaL

Gallaphosphene L(Cl)GaPGaL 1 (L = HC[C(Me)N(2,6-i-Pr₂-C₆H₃)]₂) reacts at ambient temperature with a series of polar X-H bonds, i.e. ammonia, primary amines, water, phenol, thiophenol, and selenophenol, selectively with 1,2 addition at the polar Ga-P double bond. The gallium atom serves as electrophile and the phosphorous atom is protonated in all reactions. The resulting complexes L(Cl)GaP(H)Ga(X)L (X = NH₂2, NHi-Pr 3, NHPh 4, OH 5, OXyl 6, SPh 7, SePh 8) were characterized by IR and heteronuclear (¹H, ¹³C{¹H}, ³¹P{¹H}) NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction.

Reversible and Irreversible [2+2] Cycloaddition Reactions of Heteroallenes to a Gallaphosphene

[2+2] Cycloaddition reactions of gallaphosphene L(Cl)GaPGaL 1 (L=HC[C(Me)N(2,6-i-Pr2 C6 H3 )]2 ) with carbodiimides [C(NR)2 ; R=i-Pr, Cy] and isocyanates [RNCO; R=Et, i-Pr, Cy] yielded four-membered metallaheterocycles LGa(Cl)P[μ-C(X)NR]GaL (X=NR, R=i-Pr 2, Cy 3; X=O, R=Et 4, i-Pr 5, Cy 6). Compounds 4-6 reversibly react with CO2 via [2+2] cycloaddition at ambient temperature to the six-membered metallaheterocycles LGa(Cl)P[μ-C(O)O]-μ-C(O)N(R)GaL (R=Et 7, i-Pr 8, Cy 9). Compounds 2-9 were characterized by IR and heteronuclear (1 H, 13 C{1 H}, 31 P{1 H}) NMR spectroscopy and elemental analysis, while quantum chemical calculations provided a deeper understanding on the energetics of the reactions.

Stibine as a reagent in molecular chemistry - targeted synthesis of primary and secondary stibanyl-gallanes and their lighter homologues

The reactions of SbH₃ with one or two equivalents of (Dipp₂NacNac)Ga (Dipp₂NacNac = HC{C(Me)N(Dipp)}₂; Dipp = 2,6-iPr₂C₆H₃) yield the primary and secondary stibanes (Dipp₂NacNac)GaH(SbH₂) (3) and {(Dipp₂NacNac)GaH}₂(SbH) (5). Their lighter homologs were obtained from the analogous reactions with phosphine and arsine. All compounds were characterized using heteronuclear NMR-spectroscopy, IR-spectroscopy and single-crystal X-ray diffraction.

Multi-Talented Gallaphosphene for Ga-P-Ga Heteroallyl Cation Generation, CO2 Storage, and C(sp3 )-H Bond Activation

Gallaphosphene L(Cl)GaPGaL (2; L=HC[C(Me)N(2,6-i-Pr2 C6 H3 )]2 ), which is synthesized by reaction of LGa(Cl)PCO (1) with LGa, reacts with [Na(OCP)(dioxane)2.5 ] to LGa(OCP)PGaL (3), whereas chloride abstraction with LiBArF 4 yields [LGaPGaL][BArF 4 ] (4; BArF 4 =B(C6 F5 )4 ). 4 represents a heteronuclear analog of the allyl cation according to quantum chemical calculations. Remarkably, 2 reversibly reacts with CO2 to yield L(Cl)Ga-P[μ-C(O)O]2 GaL (5), while reactions with acetophenone and acetone selectively give compounds 6 and 7 by C(sp3 )-H bond activation.

NHC-stabilized Parent Arsanylalanes and -gallanes

The synthesis and characterization of the unprecedented compounds IDipp⋅E'H2 AsH2 (E'=Al, Ga; IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) are reported, the first monomeric, parent representatives of an arsanylalane and arsanylgallane, respectively, stabilized only by a LB (LB=Lewis Base). They are prepared by a salt metathesis reaction of KAsH2 with IDipp⋅E'H2 Cl (E'=Al, Ga). The H2 -elimination pathway through the reaction of AsH3 with IDipp⋅E'H3 (E'=Al, Ga) was found to be a possible synthetic route with some disadvantages compared to the salt metathesis reaction. The corresponding organo-substituted compounds IDipp⋅GaH2 AsPh2 (1) and IDipp⋅AlH2 AsPh2 (2) were obtained by the reaction of KAsPh2 with IDipp⋅E'H2 Cl (E'=Al, Ga). The novel branched parent compounds IDipp⋅E'H(EH2 )2 (E'=Al, Ga; E=P, As) were synthesized by salt metathesis reactions starting from IDipp⋅E'HCl2 (E'=Al, Ga). Supporting DFT computations give insight into the different synthetic pathways and the stability of the products.

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

The pnictogenyl Group 13 compounds (Dipp2 Nacnac)M[E(SiMe3 )2 ]Cl and (Dipp2 Nacnac)M(EH2 )2 (Dipp2 Nacnac=HC[C(Me)N(Ar)]2 , Ar: Dipp=2,6-iPr2 C6 H3 ; M=Al, Ga, In; E=P, As) were successfully synthesized. The salt metathesis between (Dipp2 Nacnac)MCl2 and LiE(SiMe3 )2 only led to monosubstituted compounds (Dipp2 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 ⋅DME (or KAsH2 ) facilely yielded the dipnictogenide compounds (Dipp2 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 (Dipp2 Nacnac)In(PH2 )2 , the reaction of (Dipp2 Nacnac)InCl2 with KAsH2 led to an indium mirror due to the instability of the target product.