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,η1:1:1:1 -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(η1:1 -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 (En ) ligand complexes was investigated. This leads to the heterobimetallic compounds [(LGa)(µ,η2:1:1 -P4 )(LNi)] (5 a), [(Cp'''Co)(µ,η4:1:1 -E4 )(LGa)] (E=P (6 a), As (6 b), Cp'''=η5 -C5 H2 t Bu3 ) and [(Cp'''Ni)(η3:1:1 -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.

Transformation of the cyclo-P5 Middle Deck in [(Cp*Fe)(Cp'''Co)(µ,η5 :η4 -P5 )] upon Functionalization - A Comprehensive Study of Reactivity.

The heterobimetallic triple-decker complex [(Cp*Fe)(Cp'''Co)(µ,η5 : η4 -P5 )] (1) was functionalized by main group nucleophiles and subsequently electrophilically quenched or oxidized. Reacting 1 with group 14 nucleophiles revealed different organo-substituted P5 R middle-decks depending on the steric and electronic effects of the used alkali metal organyls (2: R=tBu; 3: R=Me). Further, with group 15 nucleophiles, the first structural characterized monosubstituted complexes with phosphanides could be obtained as P5 ligands containing exocyclic {PR2 } units (4: R=Cy, H; 5: R=Ph). These monoanionic complexes 2-5 were isolated and subsequent electrophilic quenching revealed novel types of neutral functionalized polyphosphorus complexes. These complexes bear formal chains of P5 R'R'' (6: R'=tBu, R'=Me) in a 1,3-disubstitution pattern or P6 R'R''R''' units (7: R'=Cy, R''=H, R'''=Me; 8: R'=Me, R''=Ph, R'''=Me) in a 1,1,3-substitution as middle-decks stabilized by one {Cp'''Co} and one {Cp*Fe} fragment. One-electron oxidation of 2, 3 or 5 by AgBF4 gave access to paramagnetic triple-decker complexes bearing P5 R middle-decks in various coordination fashions (R=tBu (10), R=PPh2 (12)). Interestingly, for R=Me (11), a dimerization is observed revealing a diamagnetic tetranuclear cluster containing a unique dihydrofulvalene-type P10 R2 ligand. All complexes were characterized by crystallographic and spectroscopic methods (EPR, multinuclear NMR and mass spectrometry) and their electronic structures were elucidated by DFT calculations.

Halogenation and Nucleophilic Quenching: Two Routes to E-X Bond Formation in Cobalt Triple-Decker Complexes (E=As, P; X=F, Cl, Br, I).

The oxidation of [(Cp'''Co)2 (µ,η2 : η2 -E2 )2 ] (E=As (1), P (2); Cp'''=1,2,4-tri(tert-butyl)cyclopentadienyl) with halogens or halogen sources (I2 , PBr5 , PCl5 ) was investigated. For the arsenic derivative, the ionic compounds [(Cp'''Co)2 (µ,η4 : η4 -As4 X)][Y] (X=I, Y=[As6 I8 ]0.5 (3 a), Y=[Co2 Cl6-n In ]0.5 (n=0, 2, 4; 3 b); X=Br, Y=[Co2 Br6 ]0.5 (4); X=Cl, Y=[Co2 Cl6 ]0.5 (5)) were isolated. The oxidation of the phosphorus analogue 2 with bromine and chlorine sources yielded the ionic complexes [(Cp'''Co)2 (µ-PBr2 )2 (µ-Br)][Co2 Br6 ]0.5 (6 a), [(Cp'''Co)2 (µ-PCl2 )2 (µ-Cl)][Co2 Cl6 ]0.5 (6 b) and the neutral species [(Cp'''Co)2 (µ-PCl2 )(µ-PCl)(µ,η1 : η1 -P2 Cl3 ] (7), respectively. As an alternative approach, quenching of the dications [(Cp'''Co)2 (µ,η4 : η4 -E4 )][TEF]2 (TEF=[Al{OC(CF3 )3 }4 ]- , E=As (8), P (9)) with KI yielded [(Cp'''Co)2 (µ,η4 : η4 -As4 I)][I] (10), representing the homologue of 3, and the neutral complex [(Cp'''Co)(Cp'''CoI2 )(µ,η4 : η1 -P4 )] (11), respectively. The use of [(CH3 )4 N]F instead of KI leads to the formation of [(Cp'''Co)2 (µ-PF2 )(µ,η2 : η1 : η1 -P3 F2 )] (12) and 2, thereby revealing synthetic access to polyphosphorus compounds bearing P-F groups and avoiding the use of very strong fluorinating reagents, such as XeF2 , that are difficult to control.

Binding, Release and Functionalization of Intact Pnictogen Tetrahedra Coordinated to Dicopper Complexes.

The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu2 (µ,η1 : η1 -MeCN)][X]2 (X=weakly coordinating anion, NTf2 (1 a), FAl[OC6 F10 (C6 F5 )]3 (1 b), Al[OC(CF3 )3 ]4 (1 c)) was replaced by white phosphorus (P4 ) or yellow arsenic (As4 ) to yield [(DPFN)Cu2 (µ,η2 : η2 -E4 )][X]2 (E=P (2 a-c), As (3 a-c)). The molecular structures in the solid state reveal novel coordination modes for E4 tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E4 tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E4 tetrahedra with release of P4 or As4 and formation of [(DPFN)Cu2 (µ,η1 : η1 -Me NHC)][X]2 (4 a,b) or to an opening of one E-E bond leading to an unusual E4 butterfly structural motif in [(DPFN)Cu2 (µ,η1 : η1 -E4 Dipp NHC)][X]2 (E=P (5 a,b), E=As (6)). With a cyclic alkyl amino carbene (Et CAAC), cleavage of two As-As bonds was observed to give two isomers of [(DPFN)Cu2 (µ,η2 : η2 -As4 Et CAAC)][X]2 (7 a,b) with an unusual As4 -triangle+1 unit.

Conversion of E4 (E4 =P4 , As4 , AsP3 ) by Ni(0) and Ni(I) Synthons - A Comparative Study.

The reactivity of white phosphorus and yellow arsenic towards two different nickel nacnac complexes is investigated. The nickel complexes [(L1 Ni)2 tol] (1, L1 =[{N(C6 H3 i Pr2 -2,6)C(Me)}2 CH]- ) and [K2 ][(L1 Ni)2 (µ,η1 : 1 -N2 )] (6) were reacted with P4 , As4 and the interpnictogen compound AsP3 , respectively, yielding the homobimetallic complexes [(L1 Ni)2 (µ-η2 ,κ1 :η2 ,κ1 -E4 )] (E=P (2 a), As (2 b), AsP3 (2 c)), [(L1 Ni)2 (µ,η3 : 3 -E3 )] (E=P (3 a), As (3 b)) and [K@18-c-6(thf)2 ][L1 Ni(η1 : 1 -E4 )] (E=P (7 a), As (7 b)), respectively. Heating of 2 a, 2 b or 2 c also leads to the formation of 3 a or 3 b. Furthermore, the reactivity of these compounds towards reduction agents was investigated, leading to [K2 ][(L1 Ni)2 (µ,η2 : 2 -P4 )] (4) and [K@18-c-6(thf)3 ][(L1 Ni)2 (µ,η3 : 3 -E3 )] (E=P (5 a), As (5 b)), respectively. Compound 4 shows an unusual planarization of the initial Ni2 P4 -prism. All products were comprehensively characterized by crystallographic and spectroscopic methods.

Redox Chemistry of Heterobimetallic Polypnictogen Triple-Decker Complexes - Rearrangement, Fragmentation and Transfer.

The redox chemistry of the heterobimetallic triple-decker complexes [(Cp*Fe)(Cp'''Co)(µ,η5 :η4 -E5 )] (E=P (1), As (2), Cp*=1,2,3,4,5-pentamethyl-cyclopentadienyl, Cp'''=1,2,4-tri-tertbutyl-cyclopentadienyl) and [(Cp'''Co)(Cp'''Ni)(µ,η3 :η3 -E3 )] (E=P (10), As (11)) was investigated. Compound 1 and 2 could be oxidized to the monocations 3 and 4 and further to the dications 5 and 6, while the initially folded cyclo-E5 ligand planarizes upon oxidation. The reduction leads to an opposite change in the geometry of the middle deck, which is now folded stronger into the direction of the other metal fragment (formation of monoanions 7 and 8). For the arsenic compound 8, a different behavior is found since a fragmentation into an As6 (9) and As3 ligand complex occurs. The Co and Ni triple-decker complexes 10 and 11 can be oxidized initially to the heterometallic monocations 12 and 13, which are not stable in solution and convert selectively into the homometallic nickel complexes 14 and 15 and the cobalt complexes 16 and 17. This behavior was further proven by the oxidation of [(Cp'''Co)(Cp''Ni)(µ,η3 :η2 -P3 )] (19, Cp''=1,3-di-tertbutyl-cyclopentadienyl) comprising two different Cp ligands. The transfer of {CpR M} fragments can be suppressed when a {W(CO)5 } unit is coordinated to the P3 ligand (20) prior to the oxidation and the mixed cobalt and nickel cation 21 can be isolated. The reduction of 10 and 11 yields the heterometallic monoanions 22 and 23, where no transfer of the {CpR M} fragments is observed.

Reactivity of Cu(I) Nacnac Complexes Toward Polypnictogen Compounds.

The nacnac Cu(I) compound [LCu(MeCN)] (2) (L = [{N(C6H3Me2-2,6)C(Me)}2CH]-) was reacted with complexes containing aromatic cyclo-E5 ([Cp*Fe(η5-E5)], E = P (1a), As (1b), Cp* = η5-C5Me5), cyclo-P4 ([Cp‴Co(η4-P4)] (3), Cp‴ = η5-C5H2tBu3) and cyclo-E3 ligands ([Cp‴Ni(η3-E3)], E = P (4a), As (4b)) yielding the heterometallic complexes [(Cp*Fe)(µ,η5:2-E5)(LCu)] (E = P (5a), As (5b)), [(Cp*Fe)(µ3,η5:2:1-E5)(LCu)2] (E = P (6a), As (6b)), [(Cp‴Co)(µ,η4:2-P4)(LCu)] (7), [(Cp‴Co)(µ3,η4:2:1-P4)(LCu)2] (8), and [(Cp‴Ni)(µ,η3:2-E3)(LCu)] (E = P (9a), As (9b)). These complexes are rare examples of the coordination of a group 11 metal to aromatic cyclo-En (E = P, As; n = 3-5) ligands. All products were comprehensively characterized by crystallographic and spectroscopic methods. Their dynamic behavior in solution was studied by VT (variable-temperature) NMR spectroscopy, and their electronic structures were elucidated by DFT calculations.

Coordination Behavior of [Cp″2Zr(µ1:1-As4)] towards Lewis Acids.

The functionalization of the arsenic transfer reagent [Cp″2Zr(η1:1-As4)] (1) focuses on modifying its properties and enabling a broader scope of reactivity. The coordination behavior of 1 towards different Lewis-acidic transition metal complexes and main group compounds is investigated by experimental and computational studies. Depending on the steric requirements of the Lewis acids and the reaction temperature, a variety of new complexes with different coordination modes and coordination numbers could be synthesized. Depending on the Lewis acid (LA) used, a mono-substitution in [Cp″2Zr(µ,η1:1:1:1-As4)(LA)] (LA = Fe(CO)4 (4); B(C6F5)3 (7)) and [Cp″2Zr(µ,η3:1:1-As4)(Fe(CO)3)] (5) or a di-substitution [Cp″2Zr(µ3,η1:1:1:1-As4)(LA)2] (LA = W(CO)5 (2); CpMn(CO)2 (3); AlR3 (6, R = Me, Et, iBu)) are monitored. In contrast to other coordination products, 5 shows an η3 coordination in which the butterfly As4 ligand is rearranged to a cyclo-As4 ligand. The reported complexes are rationalized in terms of inverse coordination.

Synthesis and Multiple Subsequent Reactivity of Anionic cyclo-E3 Ligand Complexes (E=P, As).

A synthetic pathway for the synthesis of novel anionic sandwich complexes with a cyclo-E3 (E=P, As) ligand as an end deck was developed giving [Cp'''Co(η3 -E3 )]- (Cp'''=1,2,4-tri-tert-butylcyclopentadienyl, E=P ([5]), As ([6])) in good yields suitable for further reactivity studies. In the reaction with the chlorophosphanes R2 PCl (R=Ph, Cy, t Bu), neutral complexes with a disubstituted cyclo-E3 P (E=P, As) ligand in [Cp'''Co(η3 -E3 PR2 )] (E=P (7 a-c), As (9 a-c)) were obtained. These compounds can be partially or completely converted into complexes with a cyclo-E3 (E=P, As) ligand with an exocyclic {PR2 } unit in [Cp'''Co(η2 :η1 -E3 PR2 )] (E=P (8 a-c), As (10 a-c)). Additionally, the insertion of the chlorosilylene [LSiCl] (L=(t BuN)2 CPh) into the cyclo-E3 ligand of [5] and [6] was achieved and the novel heteroatomic complexes [Cp'''Co(η3 -E3 SiL)] (E=P (11), As (12)) could be isolated. The reaction pathway was elucidated by DFT calculations.

A General Pathway to Heterobimetallic Triple-Decker Complexes.

A systematic study on the reactivity of the triple-decker complex [(Cp'''Co)2 (µ,η4 :η4 -C7 H8 )] (A) (Cp'''=1,2,4-tritertbutyl-cyclopentadienyl) towards sandwich complexes containing cyclo-P3 , cyclo-P4 , and cyclo-P5 ligands under mild conditions is presented. The heterobimetallic triple-decker sandwich complexes [(Cp*Fe)(Cp'''Co)(µ,η5 :η4 -P5 )] (1) and [(Cp'''Co)(Cp'''Ni)(µ,η3 :η3 -P3 )] (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)(µ3 ,η5 :η4 :η1 -P5 ){W(CO)5 }] (2 a), [(Cp*Fe)(Cp'''Co)(µ4 ,η5 :η4 :η1 :η1 -P5 ){(W(CO)5 )2 }] (2 b), and [(Cp'''Co)(Cp'''Ni)(µ3 ,η3 :η2 :η1 -P3 ){W(CO)5 }] (4), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp'''Ni)2 (µ,η2 :η2 -P2 )] (5). All compounds were fully characterized using single-crystal X-ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis.

Element-Element Bond Formation upon Oxidation and Reduction.

The redox chemistry of [(Cp'''Co)2 (µ,η2 :η2 -E2 )2 ] (E=P (1), As (2); Cp'''=1,2,4-tri(tert-butyl)cyclopentadienyl) was investigated. Both compounds can be oxidized and reduced twice. That way, the monocations [(Cp'''Co)2 (µ,η4 :η4 -E4 )][X] (E=P, X=BF4 (3 a), [FAl] (3 b); E=As, X=BF4 (4 a), [FAl] (4 b)), the dications [(Cp'''Co)2 (µ,η4 :η4 -E4 )][TEF]2 (E=P (5), As (6)), and the monoanions [K(18-c-6)(dme)2 ][(Cp'''Co)2 (µ,η4 :η4 -E4 )] (E=P (7), As (8)) were isolated. Further reduction of 7 leads to the dianionic complex [K(18-c-6)(dme)2 ][K(18-c-6)][(Cp'''Co)2 (µ,η3 :η3 -P4 )] (9), in which the cyclo-P4 ligand has rearranged to a chain-like P4 ligand. Further reduction of 8 can be achieved with an excess of potassium under the formation of [K(dme)4 ][(Cp'''Co)2 (µ,η3 :η3 -As3 )] (10) and the elimination of an As1 unit. Compound 10 represents the first example of an allylic As3 ligand incorporated into a triple-decker complex.

Iodination of cyclo-E5 -Complexes (E=P, As).

In a high-yield one-pot synthesis, the reactions of [Cp*M(η5 -P5 )] (M=Fe (1), Ru (2)) with I2 resulted in the selective formation of [Cp*MP6 I6 ]+ salts (3, 4). The products comprise unprecedented all-cis tripodal triphosphino-cyclotriphosphine ligands. The iodination of [Cp*Fe(η5 -As5 )] (6) gave, in addition to [Fe(CH3 CN)6 ]2+ salts of the rare [As6 I8 ]2- (in 7) and [As4 I14 ]2- (in 8) anions, the first di-cationic Fe-As triple decker complex [(Cp*Fe)2 (µ,η5:5 -As5 )][As6 I8 ] (9). In contrast, the iodination of [Cp*Ru(η5 -As5 )] (10) did not result in the full cleavage of the M-As bonds. Instead, a number of dinuclear complexes were obtained: [(Cp*Ru)2 (µ,η5:5 -As5 )][As6 I8 ]0.5 (11) represents the first Ru-As5 triple decker complex, thus completing the series of monocationic complexes [(CpR M)2 (µ,η5:5 -E5 )]+ (M=Fe, Ru; E=P, As). [(Cp*Ru)2 As8 I6 ] (12) crystallizes as a racemic mixture of both enantiomers, while [(Cp*Ru)2 As4 I4 ] (13) crystallizes as a symmetric and an asymmetric isomer and features a unique tetramer of {AsI} arsinidene units as a middle deck.

Ring Expansions of Nonpolar Polyphosphorus Rings.

The reaction of the phosphinidene complex [Cp*P{W(CO)5 }2 ] (1 a) (Cp*=C5 Me5 ) with the anionic cyclo-Pn ligand complex [(η3 -P3 )Nb(ODipp)3 ]- (2, Dipp=2,6-diisopropylphenyl) resulted in the formation of [{W(CO)5 }2 {µ3 ,η3:1:1 -P4 Cp*}Nb(ODipp)3 ]- (3), which represents an unprecedented example of a ring expansion of a polyphosphorus-ligand complex initiated by a phosphinidene complex. Furthermore, the reaction of the pnictinidene complexes [Cp*E{W(CO)5 }2 ] (E=P: 1 a, As: 1 b) with the neutral complex [Cp'''Co(η4 -P4 )] (Cp'''=1,2,4-tBu3 C5 H2 ) led to a cyclo-P4 E ring (E=P, As) through the insertion of the pentel atom into the cyclo-P4 ligand. Starting from 1 a, the two isomers [Cp'''Co(µ3 ,η4:1:1 -P5 Cp*){W(CO)5 }2 ] (5 a,b), and from 1 b, the three isomers [Cp'''Co(µ3 ,η4:1:1 -AsP4 Cp*){W(CO)5 }2 ] (6 a-c) with unprecedented cyclo-P4 E ligands (E=P, As) were isolated. The complexes 6 a-c represent unique examples of ring expansions which lead to new mixed five-membered cyclo-P4 As ligands. The possible reaction pathways for the formation of 5 a,b and 6 a-c were investigated by a combination of temperature-dependent 31 P{1 H} NMR studies and DFT calculations.

The Triple-Decker Complex [Cp*Fe(µ,η5:η5-P5)Mo(CO)3] as a Building Block in Coordination Chemistry.

Although the triple-decker complex [Cp*Fe(µ,η5:η5-P5)Mo(CO)3] (2) was first reported 26 years ago, its reactivity has not yet been explored. Herein, we report a new high-yielding synthesis of 2 and the isolation of its new polymorph (2'). In addition, we study its reactivity towards AgI and CuI ions. The reaction of 2 with Ag[BF4] selectively produces the coordination compound [Ag{Cp*Fe(µ,η5:η5-P5)Mo(CO)3}2][BF4] (3). Its reaction with Ag[TEF] and Cu[TEF] ([TEF]- = [Al{OC(CF3)3}4]-) leads to the selective formation of the complexes [Ag{Cp*Fe(µ,η5:η5-P5)Mo(CO)3}2][TEF] (4) and [Cu{Cp*Fe(µ,η5:η5-P5)Mo(CO)3}2][TEF] (5), respectively. The X-ray structures of compounds 3⁻5 each show an MI ion (MI = AgI, CuI) bridged by two P atoms from two triple-decker complexes (2). Additionally, four short MI···CO distances (two to each triple-decker complex 2) participate in stabilizing the coordination sphere of the MI ion. Evidently, the X-ray structure for compound 3 shows a weak interaction of the AgI ion with one fluorine atom of the counterion [BF4]-. Such an Ag···F interaction does not exist for compound 4. These findings demonstrate the possibility of using triple-decker complex 2 as a ligand in coordination chemistry and opening a new perspective in the field of supramolecular chemistry of transition metal compounds with phosphorus-rich complexes.

Ring Contraction by NHC-Induced Pnictogen Abstraction.

The reaction of [Cp'''Co(η4 -P4 )] (1) (Cp'''=1,2,4-tBu3 C5 H2 ) with Me NHC (Me NHC=1,3,4,5-tetramethylimidazol-2-ylidene) leads through NHC-induced phosphorus cation abstraction to the ring contraction product [(Me NHC)2 P][Cp'''Co(η3 -P3 )] (2), which represents the first example of an anionic CoP3 complex. Such NHC-induced ring contraction reactions are also applicable for triple-decker sandwich complexes. The complexes [(Cp*Mo)2 (µ,η6:6 -E6 )] (3 a, 3 b) (Cp*=C5 Me5 ; E=P, As) can be transformed to the complexes [(Me NHC)2 E][(Cp*M)2 (µ,η3:3 -E3 )(µ,η2:2 -E2 )] (4 a, 4 b), with 4 b representing the first structurally characterized example of an NHC-substituted AsI cation. Further, the reaction of the vanadium complex [(Cp*V)2 (µ,η6:6 -P6 )] (5) with Me NHC results in the formation of the unprecedented complexes [(Me NHC)2 P][(Cp*V)2 (µ,η6:6 -P6 )] (6), [(Me NHC)2 P][(Cp*V)2 (µ,η5:5 -P5 )] (7) and [(Cp*V)2 (µ,η3:3 -P3 )(µ,η1:1 -P{Me NHC})] (8).

Open Chain Polyarsenides of the Lanthanides.

The reaction of [(Cp'''Co)2 (µ,η2:2 -As2 )2 ] with the decamethylsamarocenes [Cp*2 Sm(THF)2 ] or [Cp*2 Sm], or the bis(tetramethyl-n-propyl)samarocene [(C5 Me4 (n-propyl))2 Sm] resulted in the mixed d/f polyarsenides [(Cp'''Co)2 As4 Sm(η5 -C5 Me4 R)2 ] (R=Me, n-propyl). They are the first structural representatives of open chain-like polyarsenides as ligands in the coordination sphere of lanthanides. Their formation can be explained by an intramolecular As-As coupling within the cobalt polyarsenide complex after reduction by the divalent samarium complex. Density functional theory calculations give insight into the structural change of the (As2 )2 unit in [{Cp'''Co(µ,η2:2 -As2 )}2 ] upon reduction.

The Cobalt cyclo-P4 Sandwich Complex and Its Role in the Formation of Polyphosphorus Compounds.

A synthetic approach to the sandwich complex [Cp'''Co(η4 -P4 )] (2) containing a cyclo-P4 ligand as an end-deck was developed. Complex 2 is the missing homologue in the series of first-row cyclo-Pn sandwich complexes, and shows a unique tendency to dimerize in solution to form two isomeric P8 complexes [(Cp'''Co)2 (µ,η4 :η2 :η1 -P8 )] (3 and 4). Reactivity studies indicate that 2 and 3 react with further [Cp'''Co] fragments to give [(Cp'''Co)2 (µ,η2 :η2 -P2 )2 ] (5) and [(Cp'''Co)3 P8 ] (6), respectively. Furthermore, complexes 2, 3, and 4 thermally decompose forming 5, 6, and the P12 complex [(Cp'''Co)3 P12 ] (7). DFT calculations on the P4 activation process suggest a η3 -P4 Co complex as the key intermediate in the synthesis of 2 as well as in the formation of larger polyphosphorus complexes via a unique oligomerization pathway.

Homo- and heterobimetallic transition metal cluster derived from [Cp*Fe(η5-E5)] (E = P, As) - unprecedented structural motifs of the resulting polypnictogen ligands.

A general synthetic procedure to neutral homo- and heterobimetallic cage compounds exhibiting various structural motifs of the polypnictogen ligands starting from [Cp*Fe(η5-E5)] (E = P (1), As (2); Cp* = C5Me5) is reported. The impact of the implemented transition metal precursors {Cp'''M} (M = Cr, Mn, Fe, Ni; Cp''' = 1,2,4-tBu3C5H2) emphasises the variability of the isolated complexes exhibiting a broad variety of structural motifs of the pnictogen ligands. Spectroscopic, crystallographic, and theoretical investigations provide insight into the structure of the partially unprecedented polypnictogen ligands.

Controlled introduction of functional groups at one P atom in [Cp*Fe(η5-P5)] and release of functionalised phosphines.

By salt metathesis reactions of the anionic complexes of the type [Cp*Fe(η4-P5R)]- (R = tBu (1a), Me (1b), -C[triple bond, length as m-dash]CPh (1c); Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) with organic electrophiles (XRFG; X = halogen; RFG = (CH2)3Br, (CH2)4Br, Me) a variety of organo-substituted polyphosphorus ligand complexes of the type [Cp*Fe(η4-P5RRFG)] (2) are obtained. Thereby, organic substituents with different functional groups (FG), such as halogens or nitriles, are introduced. In [Cp*Fe(η4-P5RR')] (2a: R = tBu, R' = (CH2)3Br), the bromine substituent can be easily substituted, leading to functionalized complexes [{Cp*Fe(η4-P5tBu)}(CH2)3{Cp*Fe(η4-P5Me)}] (4) and [Cp*Fe(η4-P5RR')] (5) (R = tBu, R' = (CH2)3PPh2) or by abstraction of a phosphine to the asymmetric substituted phosphine tBu(Bn)P(CH2)3Bn (6). The reaction of the dianionic species [K(dme)2]2[Cp*Fe(η4-P5)] (I') with bromo-nitriles leads to [Cp*Fe{η4-P5((CH2)3CN)2}] (7), allowing the introduction of two functional groups attached to one phosphorus atom. 7 reacts with ZnBr2 in a self-assembly reaction to form the supramolecular compound [Cp*Fe{η4-P5((CH2)3CN)2}ZnBr2]n (8).

Pentaphosphaferrocene-mediated synthesis of asymmetric organo-phosphines starting from white phosphorus.

The synthesis of phosphines is based on white phosphorus, which is usually converted to PCl3, to be afterwards substituted step by step in a non-atomic efficient manner. Herein, we describe an alternative efficient transition metal-mediated process to form asymmetrically substituted phosphines directly from white phosphorus (P4). Thereby, P4 is converted to [Cp*Fe(η5-P5)] (1) (Cp* = η5-C5(CH3)5) in which one of the phosphorus atoms is selectively functionalized to the 1,1-diorgano-substituted complex [Cp*Fe(η4-P5R'R″)] (3). In a subsequent step, the phosphine PR'R″R‴ (R' ≠ R″ ≠ R‴ = alky, aryl) (4) is released by reacting it with a nucleophile R‴M (M = alkali metal) as racemates. The starting material 1 can be regenerated with P4 and can be reused in multiple reaction cycles without isolation of the intermediates, and only the phosphine is distilled off.