Carbon−Phosphorus Bond Activation of Tri(2-thienyl)phosphine at Dirhenium and Dimanganese Centers

Reaction of [Re₂(CO)₉(NCMe)] with tri(2-thienyl)phosphine (PTh₃) in refluxing cyclohexane affords three substituted dirhenium complexes: [Re₂(CO)₉(PTh₃)] (1), [Re₂(CO)₈(NCMe)(PTh₃)] (2), and [Re₂(CO)₈(PTh₃)₂] (3). Complex 2 was also obtained from the room-temperature reaction of [Re₂(CO)₈(NCMe)₂] with PTh₃ and is an unusual example in which the acetonitrile and phosphine ligands are coordinated to the same rhenium atom. Thermolysis of 1 and 3 in refluxing xylene affords [Re₂(CO)₈(μ-PTh₂)(μ-η¹:κ¹-C₄H₃S)] (4) and [Re₂(CO)₇(PTh₃)(μ-PTh₂)(μ-H)] (5), respectively, both resulting from carbon−phosphorus bond cleavage of a coordinated PTh₃ ligand. Reaction of [Re₂(CO)₁₀] and PTh₃ in refluxing xylene gives a complex mixture of products. These products include 3−5, two further binuclear products, [Re₂(CO)₇(PTh₃)(μ-PTh₂)(μ-η¹:κ¹-C₄H₃S)] (6) and [Re₂(CO)₇(μ-κ¹:κ²-Th₂PC₄H₂SPTh)(μ-η¹:κ¹-C₄H₃S)] (7), and the mononuclear hydrides [ReH(CO)₄(PTh₃)] (8) and trans-[ReH(CO)₃(PTh₃)₂] (9). Binuclear 6 is structurally similar to 4 and can be obtained from reaction of the latter with 1 equiv of PTh₃. Formation of 7 involves a series of rearrangements resulting in the formation of a unique new diphosphine ligand, Th₂PC₄H₂SPTh. Reaction of [Mn₂(CO)₁₀] with PTh₃ in refluxing toluene affords the phosphine-substituted product [Mn₂(CO)₉(PTh₃)] (10) and two carbon−phosphorus bond cleavage products, [Mn₂(CO)₆(μ-PTh₂)(μ-η¹:η⁵-C₄H₃S)] (11) and [Mn₂(CO)₅(PTh₃)(μ-PTh₂)(μ-η¹:η⁵-C₄H₃S)] (12). Both 11 and 12 contain a bridging thienyl ligand that is bonded to one manganese atom in a η⁵-fashion. The molecular structures of eight of these new complexes were established by single-crystal X-ray diffraction studies, allowing a detailed analysis of the disposition of the coordinated ligands.