The reaction of NiCl2(PMe3)2 with Li-t-Bu2As in THF at –78 °C gives [Ni(μ-t-Bu2As)PMe3]2 (1) in 37% yield. 1 reacts with excess p-tolyl isocyanide (CN-p-tol) in hexane at room temperature to give [Ni(µ-t-Bu2As)(CN-p-tol)2]2 (2) in 47% yield. 1 and 2 are the First dinickel diorganoarsenido complexes to be structurally characterized by X-ray diffraction. Crystal data for 1: C22H54As2Ni2P2, Mr = 647.89, monoclinic, I2/a (a nonstandard setting of C2/c, No. 15), a = 16.848 (3) Å, b = 12.069 (1) Å, c = 17.379 (3) Å, β = 114.60 (2)°, U = 3213.2 (5) Å3, Dcalcd = 1.339 g cm–3, Z = 4, λ(Mo Kα) = 0.71069 Å (graphite monochromator), µ(Mo Kα) = 33.24 cm–1, final R = 0.0399 (Rw = 0.0526) from 2245 observed reflections (I > 3σ(I)), 2433 measured. Crystal data for 2: C48H64As2Ni2N4, Mr = 964.34, monoclinic, P21/n (a nonstandard setting of P21/c, No. 14), a = 13.320 (2) Å, b = 12.889 (2) Å, c = 15.042 (3) Å, β = 111.00 (2)°, V = 2410.7 (5) Å3, Dcalcd = 1.328 g cm–3, Z = 2, λ(Mo Kα) = 0.71069 Å (graphite monochromator), μ(Mo Kα) = 21.78 cm–1, final R = 0.0563 (Rw = 0.0657) from 1557 observed reflections (I > 3σ(I)) 1743 measured. 1 contains two 16-electron Ni(I) atoms bridged by two t-Bu2As groups and linked by a single Ni–Ni bond (Ni–Ni = 2.429 (1) Å). A crystallographically imposed twofold axis passes through each As atom, giving a planar symmetrical central Ni2As2 core. Each Ni atom bears a PMe3 group, which is virtually coplanar with the Ni2As2 plane. In 2 the CN-p-tol groups give each Ni atom a pseudotetrahedral geometry. The central Ni2As2 core is again planar by virtue of a crystallographic center of inversion, which lies at the midpoint of the Ni–Ni bond (Ni–Ni = 2.693 (2) Å). Trends in Ni–Ni bond lengths in these and related complexes are correlated with the electron count on the metal centers and the type of bridging atom.