Stable η¹-Alkynyl−μ,η¹:η²-Alkenyl Complexes from the Reaction of Terminal Alkynes with Encumbered Dinuclear Platinum Compounds and Their Formyl, Methoxycarbonyl, and Hydride Derivatives

Abstract

The stepwise reaction of terminal alkynes with [(OC)Pt(μ-PBut 2)2Pt(H)(PBut 2H)]OTf yields intermediate η1-alkynyl−hydride-bridged complexes, and then stable η1-alkynyl/alkenyl-bridged derivatives containing an electrophilic carbonyl ligand. The latter is attacked by nucleophiles (H- and MeO-) to give a rare platinum formyl species, which is slowly converted into a stable hydride or a stable methoxycarbonyl complex.

Rearrangement or C−H Activation Processes Promoted by Reaction with the Solvate [cis-Pt(C6F5)2(thf)2]

“…As far as we know, this structural feature has no precedent in the literature, the most similar examples being a (μ-hydroxy)(μ-alkyne) bridging system in a pentanuclear ruthenium cluster and a (μ-hydroxy)(μ-allenylidene) trinuclear osmium cluster . Notwithstanding, a good number of vinyl groups acting as bridging ligands between two transition metals have been reported, − although the examples containing platinum are really scarce, − in particular, those referring to homopolynuclear derivatives. ,, It should be noted that recently a (μ-hydride)(μ-vinyl) dinuclear intermediate species has been proposed in the formation of the (μ-alkylidene) complex [Pt 2 (dppm) 2 (μ-H)(μ-CHCH 2 Ph)](BF 4 ) 5 ORTEP view of [ cis,cis -(PPh 3 ) 2 Pt{μ-1κ C α :η 2 -CHCHC(OH)Ph 2 }(μ-OH)Pt(C 6 F 5 ) 2 ] ( 5f ).…”

“…The use of transition metal complexes to activate carbon−hydrogen bonds has become one of the most pursued goals of organometallic chemistry. − Nowadays, the activation of C−H bonds in alkynes is one of the most active fields of research in this area, mainly due to their implications in the alkyne/vinylidene tautomerization, as well as in some catalytic processes. − In this context, we have recently reported that [ cis -Pt(C 6 F 5 ) 2 (thf) 2 ] reacts with the alkyne platinum(0) derivative [Pt(η 2 -HC⋮CPh)(PPh 3 ) 2 ] to yield, through an unexpectedly easy C−H activation, the (μ-hydride)(μ-alkynyl) diplatinum complex [ cis , cis -(PPh 3 ) 2 Pt(μ-H)(μ-1κ C α :η 2 -C⋮CPh)Pt(C 6 F 5 ) 2 ], while the reaction of the same solvate substrate [ cis -Pt(C 6 F 5 ) 2 (thf) 2 ] with the hydride−alkynyl platinum(II) complex [ trans -PtH(C⋮CPh)(PPh 3 ) 2 ] leads, also under very mild reaction conditions, to the (μ-hydride)(μ-alkynyl) diplatinum isomer [ trans -(PPh 3 )(C 6 F 5 )Pt(μ-H)(μ-1κ C α :η 2 -C⋮CPh)Pt(C 6 F 5 )(PPh 3 )]. , Although many different structural types of dimeric hydride-bridged platinum complexes have been reported, − these two acetylide-bridged diplatinum isomers belong to a rare class of these compounds, which contains mixed bridging systems consisting of a hydride and a hydrocarbon ligand. In fact, as far as we are aware, the only other reported examples are the analogous cationic (μ-alkylidene)(μ-hydride) complexes [Pt 2 (L−L) 2 (μ-CHCH 2 Ar)(μ-H)] + − and the cationic (μ-hydride)(μ-carbonyl) or (μ-hydride)(μ-isocyanide) derivatives [Pt 2 (L−L) 2 (μ-CX)(μ-H)] + (X = O , or NR 33 ), which are formally diplatinum(I) species.…”

Bridging and Terminal (Phosphanido)platinum Complexes

“…Complex [(C 6 F 5 ) 2 Pt(μ‐PPh 2 )(μ‐H)Pt(PHPh 2 )(PPh 3 )] (Pt–Pt) ( 63 ) is obtained from reactions of cis ‐[Pt(C 6 F 5 ) 2 (PHPh 2 ) 2 ] with [Pt(norbornene) 3 ] and PPh 3 45. The alkynyl complex [(PH t Bu 2 )(PhC 2 )Pt(μ‐P t Bu 2 )(μ‐H)Pt(PH t Bu 2 )(CO)] + (Pt–Pt) ( 64 ) is produced by the reaction of 53b with phenylacetylene 60. Bridging hydrides resulting from protonation of the Pt I –Pt I bond are obtained upon treatment of 53a with triflic acid {complex [(PH t Bu 2 )(CO)Pt(μ‐P t Bu 2 )(μ‐H)Pt(PH t Bu 2 )] 2+ (Pt–Pt) ( 65 )}51 or by action of 2 equiv.…”

C–H and P–C(Ph) activation competitive processes caused by interaction with the solvate [cis-Pt(C6F5)2(thf)2]

“…[1][2][3][4][5][6] Of particular importance is the C-H bond activation of terminal alkynes due to their involvement in alkyne/vinylidene tautomerization, as well as in some catalytic processes. [7][8][9][10][11][12][13][14][15][16] In this field, our group has recently reported an easy C-H bond activation of a terminal alkyne at platinum(0) derivatives [Pt(g 2 -HC≡CR)(PPh 3 ) 2 ], (R = Ph, (4-CH 3 )C 6 H 4 , (4-CN)C 6 H 4 , CMe=CH 2 , C(OH)Me 2 and C(OH)-EtMe), in very mild conditions, by reaction with the platinum(II) species [cis-Pt(C 6 F 5 ) 2 (thf) 2 ], to yield the (l-hydride)(l-acetylide) diplatinum complexes [cis,cis-(PPh 3 ) 2 Pt(l-H)(l-1jC a :g 2 -C≡CR)-Pt(C 6 F 5 ) 2 ] (Chart 1, i). 17, 18 Interestingly, the reaction, in very mild conditions, of the same solvate [cis-Pt(C 6 F 5 ) 2 (thf) 2 ] with the isomeric Pt(II) substrates [trans-PtH(C≡CR)(PPh 3 ) 2 ], leads to the corresponding (l-hydride)(l-acetylide) diplatinum isomers [trans-(PPh 3 )(C 6 F 5 )Pt(l-H)(l-1jC a :g 2 -C≡CR)Pt(C 6 F 5 )(PPh 3 )] (Chart 1, ii).…”