LIGAND SUBSTITUTION PROCESSES IN TETRANUCLEAR CARBONYL CLUSTERS .3. MOLECULAR-STRUCTURES OF CO4(CO)8(MU-CO)3[P(C6H5)3] AND CO4(CO)7(MU-CO)3[P(OCH3)3]2
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The structures of Co4(CO)u[P(C6H5)3] (1) and Co4(CO)10[P(OCH3)3]2 (2) have been determined by single-crystal X-ray investigations. These are derived from the C3v structures of the parent Co4(CO)12 species where one and two of the axial carbonyl ligands are replaced by P(C6H5)3 and P(OCH3)3, respectively. Complex 1 crystallizes in the monoclinic space group P2Jn with a = 11.841 (4) , b = 17.045 (5) , c = 15.482 (4) , = 100.55 (2), V = 3072 (1) A3, Z = 4, and p(calcd) = 1.74 g cm3. Diffraction data (29 out to 55) were collected with a four-circle autodiffractometer using Mo Ka radiation. The structure was refined by using the full-matrix least-squares procedure, and the resulting discrepancy indices were R1 = 0.035 and R2 = 0.039 for 4610 independent reflections. Complex 2 also crystallizes in the monoclinic space group P2Jn with a = 14.865 (3) k,b= 11.904 (3) , c = 15.583 (3) , = 90.94 (2), V= 2757 (1) 3, Z = 4, and p(caled) = 1.84 g cm-3. The discrepancy indices were Ri = 0.045 and R2 = 0.059 for 4156 independent reflections. Important bond distance parameters for complexes 1 and 2, respectively, are as follows: Co-Co (basal-apical) = 2.530 and 2.528 A, Co-Co (basal-basal) = 2.482 and 2.454 , Co-C(br)av = 1.937 and 1.929 A, and Co-C(term)av = 1.797 and 1.784 . Two of the bridging CO ligands are asymmetrical in both complexes, with slightly shorter Co-C bond distances to the phosphine- or phosphite-substituted cobalt centers. 1981, American Chemical Society. All rights reserved.
