Abstract
Geometry of neutral [Hn{Co(μ2-CO)(PMe3)2}3] complexes, n = 0→4, in three lowest spin states was optimized at the B3LYP/6-311G* level of theory with GD3 dispersion correction. The most stable quartet spin state was found for [{Co(μ2-CO)(PMe3)2}3] whereas the doublet or triplet spin states are the most stable in the remaining complexes. Hydrogenation of [{Co(μ2-CO)(PMe3)2}3] to the complexes with μ3-H bridges is more advantageous at lower temperatures. Trigonal symmetry is preserved only in [(μ3-H){Co(μ2-CO)(PMe3)2}3]. Neutral H2 units in [(H2){Co(μ2-CO)(PMe3)2}3], [(H2)(μ3-H){Co(μ2-CO)(PMe3)2}3], and [(H2)2{Co(μ2-CO)(PMe3)2}3] are only physisorbed and show vanishing spin density. Spin density is concentrated dominantly at positively charged Co atoms and only the vanishing spin density is located at the negatively charged μ3-H atoms. There are no Co—Co bonds and the Co3 triangles are held together only by μ2-CO and μ3-H bridges.