Unusual Formation and Reactivity of a Diplatinum μ-Phenylethenylidene Complex:  Synthesis and Structures of cis,cis-[(PPh₃)(C₆F₅)₂Pt(μ-η¹:η³-CHPhCCO)Pt(PPh₃)₂] and cis,cis-[(PPh₃)₂Pt{μ-η²(C,S):η¹(C)-C(SPh)(CH₂Ph)}Pt(C₆F₅)₂(CO)] Dinuclear Compounds

Abstract

The µ-phenylethenylidene-bridged diplatinum complex [(OC)(C 6 F 5 ) 2 Pt(µ-CdCHPh)Pt-(PPh 3 ) 2 ], 1, synthesized from the reaction between the mononuclear alkynyl-hydride trans-[Pt(CtCPh)H(PPh 3 ) 2 ] and cis-[Pt(C 6 F 5 ) 2 (CO)(THF)] (THF ) tetrahydrofuran), displays a remarkable reactivity associated with the µ-vinylidene ligand under mild conditions. The reaction of 1 with PPh 3 (molar ratio 1:1) produces an unprecedented reductive coupling of the CO ligand and the vinylidene bridging group to give the compound cis,cis-[(PPh 3 )(C 6 F 5 ) 2 -Pt(µ-η 1 :η 3 -CHPhCCO)Pt(PPh 3 ) 2 ], 2, which contains an expanded, unsaturated benzylideneketene bridging ligand. On the other hand, treatment of 1 with PhSH generates the new diplatinum compound cis,cis-[(PPh 3 ) 2 Pt{µ-η 2 (C,S):η 1 (C)-C(SPh)(CH 2 Ph)}Pt(C 6 F 5 ) 2 (CO)], 3, formed by a formal addition of the PhSH to the carbon-carbon double bond of the vinylidene group in 1. The structures of 2 and 3 have been fully elucidated by X-ray diffraction studies.

Reactivity of [trans-PtH(C⋮CC5H4N-2)(PPh3)2] toward [cis-Pt(C6F5)2(thf)2]. Synthesis of an Unusual Triplatinum Cluster-Substituted Platinum Complex

“…By contrast, the asymmetry caused by coordination of the pyridyl group to the bis(pentafluorophenyl) platinum fragment in complex 4 is more pronounced. Its 19 F NMR spectrum is temperature dependent and similar to that previously observed in other compounds in which the “ cis -Pt(C 6 F 5 ) 2 ” fragment is stabilized by different ligands trans to the C 6 F 5 rings. ,11d, At 223 K 4 displays two different sets of five fluorine signals (4 o -F, 2 p -F, and 4 m -F; AFMRX systems), confirming the presence of two inequivalent and rigid C 6 F 5 groups; but upon heating only the two o -F and two m -F signals of one of them broaden. The m -F resonances coalesce at ca.…”

“…The other set of five signals remains sharp even at high temperature. As has been previously suggested, , this behavior can be explained by assuming that the presence of different ligands trans to the Pt- ipso -C(C 6 F 5 ) bonds (PPh 3 and pyridyl) induces different energy barriers to the rotation of C 6 F 5 groups. In addition, the considerably different sizes of the ligands [PPh 3 and Pt(H)(PPh 3 ) 2 (C⋮CPy)] probably cause different degrees of steric hindrance around the C 6 F 5 rings.…”

“…In this context, we have recently found a simple synthetic route to a related diplatinum complex [ trans -(PPh 3 )(C 6 F 5 )Pt(μ-H)(μ-C⋮CPh)Pt(C 6 F 5 )(PPh 3 )] by treatment of [ trans -PtH(C⋮CPh)(PPh 3 ) 2 ] with the solvated species [ cis -Pt(C 6 F 5 ) 2 (thf) 2 ] (thf = tetrahydrofurane) . Interestingly, if [ trans -PtH(C⋮CPh)(PPh 3 ) 2 ] is treated with [ cis -Pt(C 6 F 5 ) 2 (CO)(thf)], containing only one labile coordination site, the reaction takes quite another course, yielding the unexpected μ-phenylethenylidene bridging complex [ cis , cis -(OC)(C 6 F 5 ) 2 Pt(μ-CCHPh)Pt(PPh 3 ) 2 ] . Lukehart et al4i have also observed that the Pt−H bond of cationic [ trans -PtH(PEt 3 ) 2 (acetone)] + easily adds across the C⋮C triple bond of a terminal alkynyl ligand, yielding analogous complexes containing μ-alkenylidene ligands.…”

Ethynyltolan Platinum Complexes with (Arylalkynyl)phosphane Ligands

“…The approximate calculated activation energy is similar for the ortho-fluorine (∆G ‡ 273K = 50.01 kJ mol -1 ) and for the meta-fluorine atoms (∆G ‡ 268K = 50.63 kJ mol -1 ). The equivalence of the o-F atoms (and the m-F ones as well) at high temperature can be explained either by assuming a rapid rotation of the C 6 F 5 groups around the Pt-C bonds, as previously suggested in other systems with "cis-Pt(C 6 F 5 ) 2 " fragments, [79][80][81][82][83] or by a fast intramolecular exchange of the "cis-Pt(C 6 F 5 ) 2 " unit below and above the platinum coordination plane. This second possibility has been suggested in related derivatives [3,57,84] stabilized by a double alkynyl bridging system and assumes the existence of a formal inversion of the PtC 4 Pt central skeleton, which could take place via intermediate species with one or two µ-η 1 -bonded alkynyl ligands.…”

Chemistry of vinylidene complexes. XXIV. A new μ-vinylidene complex containing RePt core, and platinum-bound carbonyl ligand. Spectroscopic, structural and electrochemical study

“…Moreover, the X-ray structure of only [cis,cis-Pt(C 6 F 5 ) 2 (CO)(μ-C=CHPh)Pt(PPh 3 ) 2 ] was determined [15]. This homometallic PtPt μ-phenylvinylidene complex and its dimeric analog of the type [{cis,cis-(CO)(C 6 F 5 ) 2 PtPt(PPh 3 ) 2 } 2 {μ 4 -1κC α :2κC α :3κC αꞌ :4κC αꞌ -(1,4-C=CH) 2 C 6 H 4 }] were synthesized by reactions of [cis-PtR 2 (CO)(thf)] with corresponding acetylide and diyne complexes [15,16]. Reactions of bimetallic acyl complex [(CO) 3 Fe{μ-Si(OMe) 2 (OMe)}(μ-dppm)Pt{C(O)Me}] with acetylenes led to the series of vinylidene-bridged complexes [(CO) 3 Fe(μ-C=CHR)(μdppm)Pt(CO)] (R = Ph, t-Bu, n-Bu) [17].…”