Robert Wolf

A heterometallic FeGe ₂ cluster that combines germylidyne and metallogermylene sites exhibits flexible Fe–Ge bonding and diverse reactivity, including Lewis-base-triggered isomerization, H ₂ activation, and selective alkene cycloadditions.

Ion pairing, ligand preorganization, and surface interactions between s-block and d-block metal atoms enable concerted bond activation pathways, facilitating catalytic applications such as hydrogenation, cross-coupling, and polymerization.

We report a method for converting white phosphorus (P ₄ ) directly into tetra‐ and pentaphosphanes using N ‐heterocyclic carbene (NHC) copper(I) complexes. The insertion of P ₄ into the metal‐element bonds of the NHC complexes (6Dipp)Cu(Nu) [Nu = O t Bu and N( i Pr) ₂ ] affords [(6Dipp)Cu( κ ² ‐P ₄ O t Bu)] ( 1 ) and [(6Dipp)Cu{ κ ² ‐P ₄ N( i Pr) ₂ }] ( 3 ), which exhibit rotation of the [P ₄ Nu] ⁻ ligand around the copper center in solution. This fluxional process is suppressed at low temperature, as shown by variable‐temperature ³¹ P{ ¹ H} NMR spectroscopy. Treatment of 1 with W(CO) ₅ (thf) resulted in the formation of the bimetallic complex [(6Dipp)Cu(μ, κ ² : κ ¹ ‐P ₄ O t Bu){W(CO) ₅ }] ( 2 ) which does not show fluxional behavior. Reactions of 1 and 3 with p‐block element halides release metal‐free asymmetrically substituted bicyclo[1.1.0]tetraphosphabutane ‘butterfly’ compounds. The polyphosphanes P ₄ (PMes ₂ )(O t Bu) ( 4a ), P ₄ [P{N( i Pr) ₂ } ₂ ](O t Bu) ( 4b ), P ₄ [P{N( i Pr) ₂ } ₂ ]{N( i Pr) ₂ } ( 4c ), and P ₄ (BPh ₂ ){N( i Pr) ₂ } ( 5 ) were isolated as stable compounds. Treatment of 4c with the NHC IMes induces further phosphorus–phosphorus bond cleavage and rearrangement to give NHC‐phosphinidene adduct [ cyclo ‐P ₃ {N( i Pr) ₂ }(P{N( i Pr) ₂ } ₂ )(P═IMes)] ( 6 ). Compound 4c also reacts with W(CO) ₅ (thf) and CuBr·SMe ₂ to give coordination complexes [W(CO) ₅ { κ ¹ ‐P ₄ (P{N( i Pr) ₂ } ₂ )(N{ i Pr} ₂ )}] ( 7 ) and [Cu(Br){ κ ² ‐P ₄ (P{N( i Pr) ₂ } ₂ )(N{ i Pr} ₂ )}] ( 8 ), respectively, demonstrating the ability of 4c to serve as a mono‐ and bidentate ligand for transition metals. All compounds were characterized crystallographically and spectroscopically.

We report a method for converting white phosphorus (P ₄ ) directly into tetra‐ and pentaphosphanes using N ‐heterocyclic carbene (NHC) copper(I) complexes. The insertion of P ₄ into the metal‐element bonds of the NHC complexes (6Dipp)Cu(Nu) [Nu = O t Bu and N( i Pr) ₂ ] affords [(6Dipp)Cu( κ ² ‐P ₄ O t Bu)] ( 1 ) and [(6Dipp)Cu{ κ ² ‐P ₄ N( i Pr) ₂ }] ( 3 ), which exhibit rotation of the [P ₄ Nu] ⁻ ligand around the copper center in solution. This fluxional process is suppressed at low temperature, as shown by variable‐temperature ³¹ P{ ¹ H} NMR spectroscopy. Treatment of 1 with W(CO) ₅ (thf) resulted in the formation of the bimetallic complex [(6Dipp)Cu(μ, κ ² : κ ¹ ‐P ₄ O t Bu){W(CO) ₅ }] ( 2 ) which does not show fluxional behavior. Reactions of 1 and 3 with p‐block element halides release metal‐free asymmetrically substituted bicyclo[1.1.0]tetraphosphabutane ‘butterfly’ compounds. The polyphosphanes P ₄ (PMes ₂ )(O t Bu) ( 4a ), P ₄ [P{N( i Pr) ₂ } ₂ ](O t Bu) ( 4b ), P ₄ [P{N( i Pr) ₂ } ₂ ]{N( i Pr) ₂ } ( 4c ), and P ₄ (BPh ₂ ){N( i Pr) ₂ } ( 5 ) were isolated as stable compounds. Treatment of 4c with the NHC IMes induces further phosphorus–phosphorus bond cleavage and rearrangement to give NHC‐phosphinidene adduct [ cyclo ‐P ₃ {N( i Pr) ₂ }(P{N( i Pr) ₂ } ₂ )(P═IMes)] ( 6 ). Compound 4c also reacts with W(CO) ₅ (thf) and CuBr·SMe ₂ to give coordination complexes [W(CO) ₅ { κ ¹ ‐P ₄ (P{N( i Pr) ₂ } ₂ )(N{ i Pr} ₂ )}] ( 7 ) and [Cu(Br){ κ ² ‐P ₄ (P{N( i Pr) ₂ } ₂ )(N{ i Pr} ₂ )}] ( 8 ), respectively, demonstrating the ability of 4c to serve as a mono‐ and bidentate ligand for transition metals. All compounds were characterized crystallographically and spectroscopically.

Dual nickel photoredox catalysis enables the selective synthesis of arylphosphonium bromides under mild conditions, using commercially available aryl bromides and primary, secondary, and tertiary phosphines.

Heterometallic complexes containing multiple heavier tetrylidyne ligands (RE; E = Si, Ge, Sn, Pb) are promising for cooperative bond activation but are rare because RE units tend to oligomerize. We present the synthesis, electronic structure, and reactivity of an irondigermanium complex, [Fe(GeAr’)2] (1, Ar’ = 2,6-Dipp2-C6H3, Dipp = 2,6-iPr2-C6H3), featuring adjacent Ar’Ge units bonded to Fe through double and single Fe–Ge bonds, respectively. Complex 1 reacts readily with tBuNC, H2, and styrene via coordination, bond activation, and cycloaddition pathways, producing diverse structural outcomes. Coordination of tBuNC to Fe induces a formal reductive elimination of the two Ar’Ge units, forming an iron-digermyne complex (2) with a rare σ,σ-type double-bonding mode. Under mild conditions, H2 is activated, forming a germyl(IV)-iron-germylidyne complex (3). The reaction with styrene involves a [3+2] cycloaddition, yielding a bis(germylene)-iron complex (4). Notably, the reaction with 2,3-dimethyl-1,3-butadiene (DMB) proceeds via an unusual kinetic [3+4] cycloaddition pathway to produce a bis(germylene)-iron species (5), which then irreversibly rearranges into the thermodynamically favored [1+4] product (6). In contrast, the heavier iron-tin analog exhibits distinct reactivity towards these substrates, highlighting fundamental differences between Fe–Ge and Fe–Sn bonding and reactivity.

We report the synthesis of hexafluorophosphate (PF6–) salts directly from white phosphorus (P4) and simple fluorides MF (M = Li, Na, K, Cs, NMe4) in a single step. The utilization of p-quinones, such as 2,3-dichloro-4,5-dicyano-1,4-benzoquinone (DDQ) offers a selective fluorination pathway, which affords MPF6 salts in up to 95% yield in acetonitrile (MeCN). NMR investigations of the DDQ-mediated P4 fluorination reaction revealed the formation of PF3 and PF5·MeCN as key reaction intermediates. Donor–acceptor interactions between DDQ and fluoride are critical, effectively increasing the fluoride concentration and enabling efficient fluorination to PF6–. Tetraethylene glycol (TEG) selectively stops the reaction at the adduct K[PF5·TEG]. In contrast, noncoordinating dichloromethane (DCM) favors PF3 formation by suppressing EDA interactions through low fluoride solubility, possibly via the tris(hydroquinonyl)phosphite P(DDQH)3, underscoring the critical role of fluoride solubility. This work demonstrates that quinone–fluoride interactions can be exploited for oxidative fluorination chemistry, establishing a new conceptual framework for P4 fluorination.

Heterometallic complexes containing multiple heavier tetrylidyne ligands (RE; E = Si, Ge, Sn, Pb) are promising for cooperative bond activation but are rare because RE units tend to oligomerize. We present the synthesis, electronic structure, and reactivity of an irondigermanium complex, [Fe(GeAr’)2] (1, Ar’ = 2,6-Dipp2-C6H3, Dipp = 2,6-iPr2-C6H3), featuring adjacent Ar’Ge units bonded to Fe through double and single Fe–Ge bonds, respectively. Complex 1 reacts readily with tBuNC, H2, and styrene via coordination, bond activation, and cycloaddition pathways, producing diverse structural outcomes. Coordination of tBuNC to Fe induces a formal reductive elimination of the two Ar’Ge units, forming an iron-digermyne complex (2) with a rare σ,σ-type double-bonding mode. Under mild conditions, H2 is activated, forming a germyl(IV)-iron-germylidyne complex (3). The reaction with styrene involves a [3+2] cycloaddition, yielding a bis(germylene)-iron complex (4). Notably, the reaction with 2,3-dimethyl-1,3-butadiene (DMB) proceeds via an unusual kinetic [3+4] cycloaddition pathway to produce a bis(germylene)-iron species (5), which then irreversibly rearranges into the thermodynamically favored [1+4] product (6). In contrast, the heavier iron-tin analog exhibits distinct reactivity towards these substrates, highlighting fundamental differences between Fe–Ge and Fe–Sn bonding and reactivity.

Organophosphorus compounds are synthesized directly from white phosphorus using Bu ₃ SnCl, NaBH ₄ and organic electrophiles (E ⁺ ). Recycling of the tin reagent is demonstrated in the synthesis of tetrakis(hydroxymethyl)phosphonium chloride (THPC).

Heterometallic complexes containing multiple heavier tetrylidyne ligands (RE; E = Si, Ge, Sn, Pb) are promising for cooperative bond activation but are rare because RE units tend to oligomerize. We present the synthesis, electronic structure, and reactivity of an irondigermanium complex, [Fe(GeAr’)2] (1, Ar’ = 2,6-Dipp2-C6H3, Dipp = 2,6-iPr2-C6H3), featuring adjacent Ar’Ge units bonded to Fe through double and single Fe–Ge bonds, respectively. Complex 1 reacts readily with tBuNC, H2, and styrene via coordination, bond activation, and cycloaddition pathways, producing diverse structural outcomes. Coordination of tBuNC to Fe induces a formal reductive elimination of the two Ar’Ge units, forming an iron-digermyne complex (2) with a rare σ,σ-type double-bonding mode. Under mild conditions, H2 is activated, forming a germyl(IV)-iron-germylidyne complex (3). The reaction with styrene involves a [3+2] cycloaddition, yielding a bis(germylene)-iron complex (4). Notably, the reaction with 2,3-dimethyl-1,3-butadiene (DMB) proceeds via an unusual kinetic [3+4] cycloaddition pathway to produce a bis(germylene)-iron species (5), which then irreversibly rearranges into the thermodynamically favored [1+4] product (6). In contrast, the heavier iron-tin analog exhibits distinct reactivity towards these substrates, highlighting fundamental differences between Fe–Ge and Fe–Sn bonding and reactivity.