The cyanide ion plays a key role in a number of industrially relevant chemical processes, such as the extraction of gold and silver from low grade ores. Metal cyanide compounds were arguably some of the earliest coordination complexes studied and can be traced back to the serendipitous discovery of Prussian blue by Diesbach in 1706. By contrast, heavier cyanide analogues, such as the cyaphide ion, CP − , are virtually unexplored despite the enormous potential of such ions as ligands in coordination compounds and extended solids. This is ultimately due to the lack of a suitable synthesis of cyaphide salts. Herein we report the synthesis and isolation of several magnesium−cyaphido complexes by reduction of i Pr 3 SiOCP with a magnesium(I) reagent. By analogy with Grignard reagents, these compounds can be used for the incorporation of the cyaphide ion into the coordination sphere of metals using a simple salt-metathesis protocol.

The synthesis of heterometallic transition metal complexes featuring bridging cyaphide ions (C≡P−) is reported. These are synthesized from reactions of Au(IDipp)(CP) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) with electron‐rich, nucleophilic transition metal reagents, affording Au(IDipp)(μ2−C≡P)Ni(MeIiPr)2 (MeIiPr=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) and Au(IDipp)(μ2−C≡P)Rh(Cp*)(PMe3). These studies reveal that, in contrast to the cyanide ion, bimetallic cyaphido complexes strongly favor a η1 : η2 coordination mode that maximizes the interaction of the second metal (Ni, Rh) with the π‐manifold of the ion (and not the phosphorus atom lone pair). End‐on bridging can be effectively unlocked by blocking the π‐manifold, as demonstrated by reaction of Au(IDipp)(μ2−C≡P)Rh(Cp*)(PMe3) with an electrophilic transition metal reagent, W(CO)5(THF), which affords the heterotrimetallic compound Au(IDipp)(μ3−C≡P)[Rh(Cp*)(PMe3)][W(CO)5].

The systematic assembly of supramolecular arrangements is a persistent challenge in modern coordination chemistry, especially where further aspects of complexity are concerned, as in the case of large molecular mixed‐metal arrangements. One targeted approach to such heterometallic complexes is to engineer metal‐based donor ligands of the correct geometry to build 3D arrangements upon coordination to other metals. This simple idea has, however, only rarely been applied to main group metal‐based ligand systems. Here, we show that the new, bench‐stable tris(3‐pyridyl)stannane ligand PhSn(3‐Py)3 (3‐Py=3‐pyridyl) provides simple access to a range of heterometallic SnIV/transition metal complexes, and that the presence of weakly coordinating counter anions can be used to build discrete molecular arrangements involving anion encapsulation. This work therefore provides a building strategy in this area, which parallels that of supramolecular transition metal chemistry.

The reaction of TaMe 3 Cl 2 with the rigid acridanederived trisamine H 3 NNN yields the tantalum(V) complex [TaCl 2 (NNN cat )]. Subsequent reaction with dioxygen results in the full four-electron reduction of O 2 yielding the oxidobridged bimetallic complex [{TaCl 2 (NNN sq )} 2 O]. This dinuclear complex features an open-shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X-ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O 2 activation was investigated by DFT calculations revealing initial binding of O 2 to the tantalum(V) center followed by complete O 2 scission to produce a terminal oxido-complex.

The synthesis of group 9 pyridine-diimine complexes M(DippPDI)X and [M(DippPDI)L]+ (M = Co, Rh; DippPDI = 1,1’-(pyridine-2,6-diyl)bis(N-(2,6-diisopropylphenyl)ethan-1-imine; X = CP−, CCH−; L = CO, tBuNC) bearing a series of strong-field...

The cyaphide anion, CP−, is shown to undergo three distinct oligomerization reactions in the coordination sphere of metals. Reductive coupling of Au(IDipp)(CP) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) by Sm(Cp*)2(OEt2) (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl), was found to afford a tetra‐metallic complex containing a 2,3‐diphosphabutadiene‐1,1,4,4‐tetraide fragment. By contrast, non‐reductive dimerization of Ni(SIDipp)(Cp)(CP) (SIDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolidin‐2‐ylidene; Cp=cyclopentadienyl), gives rise to an asymmetric bimetallic complex containing a 1,3‐diphosphacyclobutadiene‐2,4‐diide moiety. Spontaneous trimerization of Sc(Cp*)2(CP) results in the formation of a trimetallic complex containing a 1,3,5‐triphosphabenzene‐2,4,6‐triide fragment. These transformations show that while cyaphido transition metal complexes can be readily accessed using metathesis reactions, many such species are unstable to further oligomerization processes.

We review the known chemistry of the cyaphide ion, (C≡P)−. This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini‐review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well‐established salt‐metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation.

Several examples of the cyaphide‐azide 1,3‐dipolar cycloaddition reaction to afford metallo‐triazaphospholes are reported. The gold(I) triazaphospholes Au(IDipp)(CPN3R) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene; R=tBu, Ad, Dipp), magnesium(II) triazaphospholes, {Mg(DippNacNac)(CPN3R)}2 (DippNacNac=CH{C(CH3)N(Dipp)}2, Dipp=2,6‐diisopropylphenyl; R=tBu, Bn), and germanium(II) triazaphosphole Ge(DippNacNac)‐(CPN3tBu) can be prepared straightforwardly, under mild conditions and in good yields, in a manner reminiscent of the classic alkyne‐azide click reaction (albeit without a catalyst). This reactivity can be extended to compounds with two azide functional groups such as 1,3‐diazidobenzene. It is shown that the resulting metallo‐triazaphospholes can be used as precursors to carbon‐functionalized species, including protio‐ and iodo‐triazaphospholes.