Reductive dehalogenation of chloro(alkynyl)phosphines by octacarbonyldicobalt

Abstract Reductive dehalogenation of the (chloro)(phenylethynyl)phosphine (2,4,6- t Bu 3 C 6 H 2 O)(PhCC)PCl, I, by Co 2 (CO) 8 , II, yields the neutral phosphenium ion complex [(R)(R′)]P=Co(CO) 3 , III, (R = 2,4,6- t Bu 3 C 6 H 2 O; R′ = (η 2 -C≡CPh)Co 2 (CO) 6 ), which contains a trigonally planar coordinated phosphorus atom. When NaCo(CO) 4 , V, is used instead of II a dinuclear complex, Co 2 (CO) 6 [μ 2 -P(R)(R′)] 2 , VI, (R = 2,4,6- t Bu 3 C 6 H 2 O; R′ = C≡CPh) is formed in which the phosphido ligands P(R)(R′), bridge in a μ 2 fashion two Co(CO) 3 units. The mechanism of formation of VI, involving a formal dimerization of two [(2,4,6- t Bu 3 C 6 H 2 O)(PhC≡C)]P=Co(CO) 3 fragments, is discussed. However, ( t Bu)(PhC≡C)PCl, VII, reacts with II, to yield the cluster compound VIII, containing the two μ 2 -bridging units ( t Bu)[(η 2 -C≡CPh)Co 2 (CO) 5 ]P and ( t Bu)(PhC≡C)P. Compounds II and VI–VIII were identified from their analytical and spectroscopic (IR, 1 H-, 13 C- and 31 P-NMR) data. The molecular structure of the cluster compound VIII was determined by an X-ray diffraction study.