Two new bimetallic phosphido carbonyl complexes of nickel(0): [Ni-2(CO)(2)(PPh3)(2)(mu-CO)(mu-PPh2)](-) and [Ni-2(CO)(4)(mu-PPh2)(2)](2-)

Toluene solutions of Ni(CO)(2)(PPh3)(2) react with excess potassium metal t o give the [Ni-2(CO)(4)(mu-PPh2)(2)](2-) ion (2) which contains two tetrahe dral Ni centers fused along a common edge. Each Ni achieves an 18 electron configuration without the formation of a Ni-Ni bond (d(Ni-Ni) = 3.397(1) An gstrom) in contrast to the two-electron oxidation product, Ni-2(CO)(4)(mu-P Ph2)(2) (1) (d(Ni-Ni) = 2.510(2) Angstrom). The anion 2 shows a reversible oxidation at -1.5 V and a quasi-reversible oxidation at -1.1 V vs. FeCp2/Fe Cp2+. The negative ion electrospray mass spectrum of 2 shows the one-electr on oxidation product of 2, [Ni-2(CO)(4)(mu-PPh2)(2)](-), along with three d ecarbonylation products [Ni-2(CO)(3)(mu-PPh2)(2)](-), [Ni-2(CO)(2)(mu-PPh2) (2)](-), and [Ni-2(CO)(mu-PPh2)(2)](-) where [Ni-2(CO)(3)(mu-PPh2)(2)](-) i s the base peak. Ethylenediamine solutions of Sn-9(4-) react with Ni(CO)(2) (PPh3)(2) in the presence of 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diaz abicyclo[8.8.8]hexacosane) to reproducibly give [Ni-2(CO)(2)(PPh3)(2)(mu-CO )(mu-PPh2)](-) (3), as one of three products. The anion 3 also has an edge- shared bitetrahedral geometry but, unlike 2, possesses a Ni-Ni bond (d(Ni-N i) = 2.4930(9) Angstrom).