Synthesis and characterization of mono and binuclear platinum complexes containing terminal and bridging diynyldiphenylphosphine ligands.

Resumen

A series of mononuclear platinum complexes containing diynyldiphenylphosphine ligands [cis-Pt(C 6F 5) 2(PPh 2C≡CC 6H 4C≡CR)L] n (n = 0, L = tht, R = Ph 2a, Bu t 2b; L = PPh 2C≡CC 6H 4C≡CR, 4a, 4b; n = -1, L = CN -, 3a, 3b) has been synthesized and the X-ray crystal structures of 4a and 4b have been determined. In order to compare the η 2-bonding capability of the inner and outer alkyne units, the reactivity of 2-4 towards [cis-Pt(C 6F 5) 2(thf) 2] or [Pt(η 2-C 2H 4)(PPh 3) 2] has been examined. Complexes 2 coordinate the fragment "cis-Pt(C 6F 5) 2" using the inner alkynyl fragment and the sulfur of the tht ligand giving rise the binuclear derivatives [(C 6F 5) 2Pt(μ-tht)(μ-1κP:2η 2-C α,C β-PPh 2C≡CC 6H 4C≡CR)Pt(C 6F 5) 2] (R = Ph 5a, Bu t 5b). The phenyldiynylphosphine complexes 2a, 3a and 4a react with [Pt(η 2-C 2H 4)(PPh 3) 2] to give the mixed-valence Pt(II)-Pt(0) complexes [{(C 6F 5) 2LPt(μ-1κP:2η 2-C 5,C 6-PPh 2C≡CC 6H 4C≡CPh)}Pt(PPh 3) 2] n (L = tht 6a, CN 8a and PPh 2C≡CC 6H 4C≡CPh 9a) in which the Pt(0) fragment is η 2-complexed by the outer fragment. Complex 6a isomerizes in solution to a final complex [{(C 6F 5) 2(tht)Pt(μ-1κP:2η 2-C αC β-PPh 2C≡CC 6H 4C≡CPh)}Pt(PPh 3) 2] 7a having the Pt(0) fragment coordinated to the inner alkyne function. In contrast, the tert-butyldiynylphosphine complexes 2b and 3b coordinate the Pt(0) unit through the phosphorus substituted inner acetylenic entity yielding 7b and 8b. By using 4a and 2 equiv. of [Pt(η 2-C 2H 4)(PPh 3) 2] as precursors, the synthesis of the trinuclear complex (cis-{(C 6F 5) 2Pt(μ-1κP:2η 2-C 5,C 6-PPh 2C≡CC 6H 4C≡CPh) 2}(Pt(PPh 3) 2) 2] 10a, bearing two Pt(0)(PPh 3) 2 η 2-coordinated to the outer alkyne functions is achieved. The structure of 7a has been confirmed by single-crystal X-ray diffraction.