centres is primarily ionic in nature. Mechanistic studies reveal the intermediacy of a monomeric [CH2CN] -complex, which has been characterised in-situ. Our findings provide an important example in which a bimetallic metal complex achieves a new type of reactivity not previously encountered with monometallic counterparts. The isolation of a [CHCN] 2-dianion through simple deprotonation of CH3CN also offers the possibility of a establishing a broader chemistry of this motif. α-Nitrile anions date back to the late 1800s. The deprotonation of CH3CN, by reaction with Na, was first reported by Holtzwart in 1889. In the 1960s, methods were developed for the isolation of NaCH2CN and LiCH2CN. Tae and co-workers recently reviewed the use of these anions in organic synthesis. Due to the limited delocalisation of the negative charge into the CN π-system, they exhibit strong nucleophilic character and can be used to effect the cyanomethylation of numerous electrophiles. Despite widespread reports of molecular complexes containing the [CH(R)CN] -anion, examples which contain the [CRCN] 2-dianion are incredibly rare. The [CHCN] 2-dianion represents one of the simplest chemical building blocks available, this fragment contains only four atoms and 16 valence electrons. There are unanswered fundamental questions about the electronic structure of [CHCN] 2-and its binding modes to metal centres; theoretically, several structural motifs can be considered (Figure ). These include 1,1-dianion (I), 1,3-dianion (II) and metallocarbene (III) species. To the best of our knowledge, only two structurally characterised compounds have been reported that contain the [CHCN] 2-motif; a diiron complex with connectivity reminiscent of I and tungsten cluster that appears to contain four units of III. A third, closely related species, Li2[(Me3Si)CCN] was reported in the late 1980s, as well as [Mes2Ge(C(Ph)CN)]2 in the 1990s. In the solid-state, Li2[(Me3Si)CCN] forms aggregates which incorporate 1,3-dimetallated dianions (cf. II) with external O or N donors stabilising the Li ions, and [Mes2Ge(C(Ph)CN)]2 is dimeric. In this paper, we report the double deprotonation of CH3CN to form a [CHCN] 2-dianion. This was achieved by reaction of CH3CN with a highly basic Fe-Al bimetallic complex recently developed by our group. The resulting products contain two bimetallic metal fragments bridged by a 1,3-dianion (structure type II). We analyse the electronic structure of the [CHCN] 2-dianion, the nature of its binding to the metals, and its mechanism of formation. Our findings provide new insight into the fundamental chemistry of an uncommon and understudied, yet extremely simple species, [CHCN] 2-. The reaction of 1a with acetonitrile (1 equiv.) in C6D6 at 25 °C proceeded with an immediate colour change from deep red to orange-brown. Over the course of 3 days, 2a crystallised out of the reaction mixture in 33 % yield (Scheme 1). Single crystal X-ray crystallographic analysis revealed that 2a is an unusual metal complex containing two Fe-Al units bridged by a µ2-κC-κN-[CHCN] 2-dianion. Within this structure, the [CHCN] 2-dianion sits across a crystallographic centre of symmetry, meaning that the C, and N-bound bimetallic sites cannot be unambiguously assigned. 2a is also insoluble in common laboratory solvents precluding detailed solution-state characterisation. Preparation of analogue addressed both these issues. Hence, reaction of 1b with CH3CN led to isolation of 2b, a direct analogue of 2a bearing 2,6-xylyl groups in place of mesityl on the ligand periphery. 2b could be unambiguously characterised in both solution and solid state. reported for Li2[(Me3Si)CCN], for which only the SiMe3 carbon resonance was reported. 13 C isotopic labelling of the CH3CN fragment in 2b-[ 13 C] was achieved through reaction of 1b with 13 CH3CN. 2b-[