Synthesis and reactivity of nickel-stabilised µ2:η2,η2-P2, As2 and PAs units

The reactivity of two paramagnetic nickel(I) compounds, CpNi(NHC) (where Cp = cyclopentadienyl; NHC = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene (IMes) or 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr)), towards [Na(dioxane)x][PnCO] (Pn = P, As) is described. These reactions afford symmetric bimetallic compounds (µ2:η2,η2-Pn2){Ni(NHC)(CO)}2. Several novel intermediates en route to such species are identified and characterised, including a compound containing the PCO- anion in an unprecedented µ2:η2,η2-binding mode. Ultimately, on treatment of the (µ2:η2,η2-Pn2){Ni(NHC)(CO)}2 compounds with carbon monoxide the Pn2 units can be released, affording P4 in the case of the phosphorus-containing species, and elemental arsenic in the case of (µ2:η2,η2-As2){Ni(IMes)(CO)}2

Synthese und Reaktivität von Nickel-stabilisierten μ2:η2,η2-P2-,As2-und PAs-Einheiten

Reaktionen der paramagnetischen Nickel(I)‐Verbindungen CpNi(NHC) (Cp=Cyclopentadienyl; NHC=1,3‐Bis(2,4,6‐trimethylphenyl)imidazol‐2‐yliden (IMes) bzw. 1,3‐Bis(2,6‐diisopropylphenyl)imidazol‐2‐yliden (IPr)) mit [Na(Dioxan)x][PnCO] (Pn=P, As) ergeben symmetrische bimetallische Verbindungen (μ2:η2,η2‐E2){Ni(NHC)(CO)}2. Mehrere Intermediate wurden identifiziert und charakterisiert, unter anderem eine Verbindung mit dem für das PCO−‐Anion zuvor unbekannten μ2:η2,η2‐Koordinationsmodus. Untersuchungen der Folgechemie zeigten, dass bei der Reaktion von (μ2:η2,η2‐Pn2){Ni(IMes)(CO)}2 mit Kohlenstoffmonoxid die Pn2‐Einheit freigesetzt wird. Im Fall der phosphorhaltigen Spezies führt dies zur Bildung von P4 und im Fall von (μ2:η2,η2‐As2){Ni(IMes)(CO)}2 zur Bildung von elementarem Arsen

Synthese und Reaktivität von Nickel-stabilisierten μ2:η2,η2-P2-,As2-und PAs-Einheiten

Reaktionen der paramagnetischen Nickel(I)‐Verbindungen CpNi(NHC) (Cp=Cyclopentadienyl; NHC=1,3‐Bis(2,4,6‐trimethylphenyl)imidazol‐2‐yliden (IMes) bzw. 1,3‐Bis(2,6‐diisopropylphenyl)imidazol‐2‐yliden (IPr)) mit [Na(Dioxan)x][PnCO] (Pn=P, As) ergeben symmetrische bimetallische Verbindungen (μ2:η2,η2‐E2){Ni(NHC)(CO)}2. Mehrere Intermediate wurden identifiziert und charakterisiert, unter anderem eine Verbindung mit dem für das PCO−‐Anion zuvor unbekannten μ2:η2,η2‐Koordinationsmodus. Untersuchungen der Folgechemie zeigten, dass bei der Reaktion von (μ2:η2,η2‐Pn2){Ni(IMes)(CO)}2 mit Kohlenstoffmonoxid die Pn2‐Einheit freigesetzt wird. Im Fall der phosphorhaltigen Spezies führt dies zur Bildung von P4 und im Fall von (μ2:η2,η2‐As2){Ni(IMes)(CO)}2 zur Bildung von elementarem Arsen

Unexpected migratory insertion reactions of M(alkyl)2 (M = Zn, Cd) and diamidocarbenes

The electrophilic character of free diamidocarbenes (DACs) allows them to activate inert bonds in small molecules, such as NH3 and P4. Herein, we report that metal coordinated DACs also exhibit electrophilic reactivity, undergoing attack by Zn and Cd dialkyl precursors to afford the migratory insertion products [(6‐MesDAC‐R)MR] (M=Zn, Cd; R=Et, Me; Mes=mesityl). These species were formed via the spectroscopically characterised intermediates [(6‐MesDAC)MR2], exhibiting barriers to migratory insertion which increase in the order MR2 = ZnEt2 < ZnMe2 < CdMe2. Compound [(6‐MesDAC‐Me)CdMe] showed limited stability, undergoing deposition of Cd metal, by an apparent β‐H elimination pathway. These results raise doubts about the suitability of diamidocarbenes as ligands in catalytic reactions involving metal species bearing nucleophilic ligands (M‐R, M‐H)

Synthesis of a carborane-substituted bis(phosphanido) cobaltate(i), ligand substitution, and unusual P4 fragmentation

Oxidative addition of the P-P single bond of an ortho-carborane-derived 1,2-diphosphetane (1,2-C-2(PMes)(2)B10H10) (Mes = 2,4,6-Me3C6H2) to cobalt(-i) and nickel(0) sources affords the first heteroleptic complexes of a carborane-bridged bis(phosphanido) ligand. The complexes also incorporate labile ligands suitable for further functionalisation. Thus, the cobalt(i) complex [K([18]crown-6)][Co{1,2-(PMes)(2)C2B10H10}(cod)] (cod = 1,5-cyclooctadiene) bearing a labile cyclooctadiene ligand undergoes facile ligand exchange reactions with isonitriles and tert-butyl phosphaalkyne with retention of the bis(phosphanido) ligand. However, in the reaction with one equivalent of P-4, the electron-rich bis(phosphanido) moiety abstracts a single phosphorus atom with formation of a new P-3 chain, while the remaining three P atoms derived from P-4 form an eta(3)-coordinating cyclo-P-3 ligand. In contrast, when the same reaction is performed with two equivalents of the cobalt(i) complex, a dinuclear product is formed which features an unusual P-4 chain in its molecular structure.ISSN:2041-6520ISSN:2041-653

An unusual Ni2Si2P8 cluster formed by complexation and thermolysis

[LSi(eta(2)-P-4)] (L = CH[C(Me)N(Dipp)][C(CH2)N(Dipp)], Dipp = 2,6-diisopropylphenyl) forms well-defined 1 : 1 and 2 : 1 complexes with N-heterocyclic carbene nickel fragments. The cluster compound [(IDipp)Ni2P8(SiL)(2)] (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) is selectively formed by thermolysis of the complex [(IDipp)Ni(mu-eta(2:2)-P-4)SiL]