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Thermolysis of (tBu2PC2H4PtBu2)NiMe2 in benzene or reduction of (tBu2PC2H4PtBu2)NiCl2 with Mg* in THF/benzene affords a solution of mononuclear (tBu2PC2H4PtBu2)Ni(η2-C6H6) (1) and dinuclear {(tBu2PC2H4PtBu2)Ni}2(μ-η2:η2-C6H6) (2) in equilibrium. Complex 2 has been isolated; the X-ray structure analysis reveals an antifacial coordination of the [(tBu2PC2H4PtBu2)Ni0] moieties to adjacent CC bonds of a formal cyclohexatriene ligand. According to solid-state and solution NMR the structure of 2 is static in the solid and fluxional in solution. Displacement of the benzene ligand in 1 or 2 by C6F6 affords mononuclear (tBu2PC2H4PtBu2)Ni(η2-C6F6) (5) for which the molecular structure is also reported.

The complexes (cod)MCl 2 (M ) Pd, Pt; cod ) cis,cis-1,5-cyclooctadiene) react with Li 2 (cot) (cot ) cyclooctatetraene) in a 1,6-diene/diethyl ether mixture (1,6-diene ) hepta-1,6-diene, diallyl ether, dvds (1,3-divinyl-1,1,3,3-tetramethyldisiloxane)) to afford the isolated homoleptic dinuclear Pd 0 and Pt 0 compounds Pd 2 (C 7 H 12 ) 3 (1), Pd 2 (C 6 H 10 O) 3 ‚C 6 H 10 O (2′; 2: Pd 2 (C 6 H 10 O) 3 ), Pd 2 (dvds) 3 (3), and Pt 2 (C 7 H 12 ) 3 (4). When 1-4 are treated with additional 1,6-diene the equally homoleptic but mononuclear derivatives of type M(1,6-diene) 2 (5-8) and with ethene the mixed alkene complexes (C 2 H 4 )M(1,6-diene) (9-12) are obtained in solution.Complexes 1-12 react with donor ligands such as phosphanes, phosphites, or t BuNC to give isolated complexes of types L-M(1,6-diene) (13-41), which have also been prepared by other routes. In all complexes the metal centers are TP-3 coordinated: complexes 1-4 contain chelating and bridging 1,6-diene ligands, whereas the other complexes contain a chelating 1,6-diene ligand and an η 2 -alkene (5-12) or η 1 -donor ligand (13-41). Of the studied 1,6-diene complexes the hepta-1,6-diene derivatives are most reactive, while the diallyl ether complexes are often more convenient to handle. The readily isolable dinuclear hepta-1,6-diene and diallyl ether complexes 1, 2′, and 4, and their mononuclear pure olefin derivatives are among the most reactive sources for naked Pd 0 and Pt 0 . The corresponding L-M(1,6-diene) complexes are equally reactive precursor compounds for the generation of [L-M 0 ] fragments in solution, which for M ) Pd are available otherwise only with difficulty. The results are significant for the operation of naked Pd 0 and L-Pd 0 catalysts in homogeneous catalysis.

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Reaction of (R2PC2H4PR2)Ni(C2H4) with COT gives the mononuclear complexes (R2PC2H4PR2)Ni(η2-C8H8) (R = iPr 1a, tBu 1b). The COT ligand in 1a,b is planar with alternating C−C and CC bonds, corresponding to a formal semiaromatic [C8H8]- ligand. Reactions of 1a with (iPr2PC2H4PiPr2)Ni(η2,η2-C6H10) and of 1b with stoichiometric amounts of {(tBu2PC2H4PtBu2)Ni}2(μ-C6H6) or lithium afford the dinuclear complexes {(iPr2PC2H4PiPr2)Ni}2{μ-η4(1,2,5,6):η4(3,4,7,8)-C8H8} (2a) and {(tBu2PC2H4PtBu2)Ni}2(μ-η2:η2-C8H8) (2b; two isomers). The COT ligand in 2a is tub-shaped and olefinic, whereas in 2b (as in 1a,b) it is planar and semiaromatic. The products are characterized by IR, solution and solid-state NMR spectroscopy, and by X-ray structure analysis.