title: "Recapitation" of nido-Metallacarboranes as a Synthetic Tool: Preparation of Apically Substituted CoC(2)B(4) Clusters via Boron Insertion(1).
abstract: Derivatives of CpCo(2,3-Et(2)C(2)B(4)H(4)) containing substituents at the apex boron atom [B(7)], the first examples of apically functionalized small metallacarborane clusters, have been prepared in good yield via boron insertion into the nido-CpCo(2,3-Et(2)C(2)B(3)H(3))(2-) dianion. Reaction of this substrate with BX(3) (X = Cl, Br, I) or PhBCl(2) in toluene at room temperature gave the corresponding CpCo(2,3-Et(2)C(2)B(4)H(3)-7-X) derivatives (2a-c and 3 in which X = Cl, Br, I, and Ph, respectively), all of which were isolated via column chromatography as air-stable yellow solids and characterized via (1)H, (11)B, and (13)C NMR, infrared, UV-visible, and mass spectra. Treatment of the same dianion with 1,4-(Br(2)B)(2)C(6)H(4) afforded air-stable orange crystalline [CpCo(2,3-Et(2)C(2)B(4)H(3)-7)](2)C(6)H(4) (4). The structure of this compound was defined via spectroscopy and X-ray crystallography as a bis(cobaltacarborane) complex linked at the apex borons via a 1,4-phenylene bridge. Crystal data for 4: space group Pbca; a = 15.056(7) Å, b = 21.612 (8) Å, c = 11.641 (3) Å; Z = 4; R = 0.045 for 1582 independent reflections having I > 3sigma(I).
authors.affiliation: Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901.
authors.forename: Michael A.
authors.initials: MA
authors.lastname: Curtis
authors.forename: Michal
authors.initials: M
authors.lastname: Sabat
authors.forename: Russell N.
authors.initials: RN
authors.lastname: Grimes