Bridging acetylene complexes of nickel and platinum; X-ray crystal structure of [Pt3(Et3P)4(PhC2Ph)2]

Photochemical route to unusual tri-tungsten ferrocenylacetylene cluster [W3{μ-η2,η2- (H)CCFc}2(CO)12] and a dimetallacyclodecatetraene [W2{μ-η2,η2,η2,η2- (Fc)CC(H)C(H)C(Fc)C(Fc)C(H)C(H)C(Fc)}(CO)6]

“…One carbonyl on each of the end tungsten pentacarbonyl units shows semi-bridging character (W(1)-C(5)-O(5) = 165.3(6)°), consistent with the presence of donor-acceptor metal-metal bonds (vide infra). Two ferrocenylacetylene molecules straddle the W-W bonds by means of g 2 ,g 2 bonding in a similar fashion to that observed in [Pt 3 (l 2 -g 2 -PhC 2 Ph) 2 (Et 3 P) 4 ] [10]. The average W-W bond distance (3.1 Å ) is longer than that of W-W bond in [W 2 (OPr i ) 6 (py)(l-C 2 H 2 )] (2.567(1) Å ) [11], [W 2 (g-C 5 H 4 Pr i ) 2 Cl 2 (l-NPh)(l-C 2 Et 2 )] (2.5923(5) Å ) [12], [W 2 (g-C 5 H 4 Pr i ) 2 Cl 3 (PMe 3 )(l-Cl)(l-C 2 Et 2 )] (2.814 (2) Å ) [12], [W 2 (l-PhC 2 AuPPh 3 )(CO) 4 (g-C 5 H 5 ) 2 ] (2.958 (1) Å ) [13] and [Cp * W 2 Fe 2 (CO) 6 (O) 2 (l-O)(l 3 -S) 2 (g 2 -CC(Me)C@CH 2 )] (2.8535(7) Å ) [14], but comparable to that in complex [Cp 2 W 2 Os(CO) 7 (C 2 Tol 2 )] (3.087 Å (av)) [15].…”

Metallomimetic Chemistry of Boron

“…As described earlier, alkynes and olefins readily interact with both the empty and the filled orbitals of many transition-metal centers, forming side-on complexes that are well described by the Dewar–Chatt–Duncanson model (Figure ). , We also discussed the formation of metallacyclohexadienes from the reaction of TM complexes with alkynes . It is this second binding motif which was found by Timms to be dominant in the reactivity of fluoroborylene [FB:] 37 the first reported transient boryleneand its derivative chloroborylene [ClB:] with acetylenes. , Indeed, when generated in the gas phase and exposed to acetylene, both of these hypovalent boron halides afforded, among other products, cyclic C 4 H 4 B 2 X 2 compounds (Figure A).…”

“…225,226 The formation of dimetallacyclohexadienes from alkynes is also a staple of TM chemistry. 227 Relatedly, the first examples of Diels−Alder reactions of dienes with diborenes have been very recently reported. 228…”

“…8,9 We have also discussed the formation of metallacyclohexadienes from the reaction of TM complexes with alkynes. 214 It is this second binding motif which was found by Timms to be dominant in the reactivity of fluoroborylene [FB:] 37 -the first reported transient borylene -and its derivative chloroborylene [ClB:] with acetylenes. 240,241 Indeed, when generated in the gas phase and exposed to acetylene, both of these hypovalent boron halides afforded, among other products, cyclic C4H4B2X2 compounds (Figure 21, A).…”

“…Such a process is somewhat metallomimetic in nature because it involves the interaction of the alkyne HOMO with a boron-centered orbital and the backdonation of a B–B orbital into the C–C π* orbital. However, the resulting diboracyclobutene 30 is unstable and can undergo a second [2 + 2] cycloaddition with acetylene or a rearrangement to the thermodynamically stable 1,3-isomer. , The formation of dimetallacyclohexadienes from alkynes is also a staple of TM chemistry . Relatedly, the first examples of Diels–Alder reactions of dienes with diborenes have been very recently reported …”