Synthesis and Reactivity of a Cationic Platinum(II) Alkylidene Complex

Reactivity of Cationic Agostic and Carbene Structures Derived from Platinum(II) Metallacycles

“…As reported in preliminaryf orm, [10] the hydrogenolysis of the cationic alkylidene 8 (see below) yieldedt he agosticm etallacycle 4a that existed in equilibrium with ah ydride complex 6 featuring also a d-agostic structure. Naturally,t he same equilibrium mixture (ca.…”

“…[32][33][34] In accordance with this premise, the low-temperature addition of [H(OEt 2 ) 2 ][BAr F ]t os olutionso f1a and 1b (À30 8C, Et 2 Os olvent) led to the formation of the expectedp latinacycles, 4a and 4b,r espectively.C omplex 4a had been reported recently in preliminary form as resulting from the hydrogenation of the cationic alkylidene 8 (see below). [10] The new compounds were characterised by microanalysis, NMR spectroscopy and X-ray crystallography.T he trans species 4a gives rise to two 31 P{ 1 H} doubletsw ith d = 82.5 and 63.8 ppm, with a 2 J PP coupling constant of 314 Hz and 1 J PPt values of 2780 and 2678 Hz, respectively.I ts PtÀCH 2 and Pt···H 3 CÀ protons resonate with chemical shifts of d = 4.15 and 2.48 ppm and present 1 H-195 Pt coupling constantsof1 07 and 65 Hz, respectively.…”

“…[9] For platinum, the bulky phosphine PiPr 2 Xyl permitted the synthesis of the bis(metallacyclic) derivative[ Pt(C^P) 2 ]a nd allowed for the investigation of an uncommon electrophilic alkylidene unit bound to ac ationic Pt II centre. [10] Prompted by these results, we set out to study the formation of platinacycles derived from phosphines bearing xylyl substituents. [2, 5a, 6, 7] BeyondP i Pr 2 Xyl (structure I), the bis(xylyl) phosphine PMeXyl 2 wasa lso chosen (structure II).…”

“…Part of the results concerning Pt II complexes of ligand I (PiPr 2 Xyl) (Xyl = 2,6-dimethylphenyl) were communicated recently. [10] Specifically,t he neutralb is(metallacycle) 1a,i ts cationic derivative 4a and the alkylidene 8 were reported in preliminary form, along with some derivatives of the latter species (compounds 6, 9·dmap,a nd 10). [10] Results and Discussion Mono-and bis-platinacycles from phosphines I-III…”

“…[35] PtÀCH 2 and Pt···CH 3 distances in complexes 4 have values of 2.090(4) and 2.429(4) in4a,and of 2.180(3) and 2.340(3) in4b (an incorrect 2.30 v alue was earlier given for the agostici nteraction in 4a). [10] The d-agostic bond in 4b is unusually short in comparison with other long-range (from g to z)p latinum agostic interactions, [7c, 29-31] andi ti so nly slightly longert han the 2.309(5) value found in some of Spencer's b-agostic Pt II compounds. [28b] In fact, it stands in the middle part of the range found for PtÀ Cd istances in h 1 -a nd h 2 -arenes coordinated to d 8 -ML 3 fragments (2.…”