Preparation of metallaphophinoheterocycle complexes and their reactivity attained by cooperative interaction of two metal centers with a substrate

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Metallaphosphaheterocycle is a kind of metalloligand in which a metal-phosphorus covalent bond is incorporated in the ring. The ligand is expected to coordinate to a variety of metal centers through lone pair electrons on the phosphorus center to form heterodinuclear complexes in which two metal centers are located in close proximity.A platinum or palladium fragment was inserted into a phosphorus-carbon bond of phosphorus-bridged [1]ferrocenophane and naphtho[1,8-b,c]phosphete coordinating to a W(CO)_5 fragment. The metallaphosphaheterocycle thus formed was bonded to the W(CO)_5 fragment to form expected heterodinuclear framework. It was found that a ligand located between two metal centers of the dinuclear complex readily dissociates from the platinum or palladium center to form a vacant coordination site.A new phosphaheterocycle in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was prepared and used as a bridging ligand for the preparation of dinuclear group 6 metal complexes (OC)_5M(μ-1)M(CO)_5 (M=W(2a),Mo(2b),Cr(2c)).Photolysis of PPh-bridged [1]ferrocenophane (3)in ether gave PPh-bridged [1.1]ferrocenophane(4). After subsequent sulfurization of the reaction mixture with elemental sulfur, both syn and anti isomers of P(S)Ph-bridged [1.1]ferrocenophane (5)were successfully isolated and characterized by X-ray analysis. Upon heating, anti-3 isomerizes to syn-3, indicating thermodynamic stability of syn-3 over anti-3. A potential utility of syn-3 as a ligand was demonstrated by the formation of [CoCl_2(syn-2)](5)through a reaction of syn-3 with CoCl_2. The X-ray structure of 5 showed a novel chelate framework in which two phosphorus donor atoms are linked doubly with two ferrocene chelates.