Photochemical synthesis, spectroscopic properties and barriers to alkene rotation in the novel bis(alkene)tetracarbonyl complexes of tungsten

Stereochemical Nonrigidity of Organometallic Complexes

“…A more recent study 86 of series of W(CO) 4 (ene) 2 complexes by 13 C NMR showed that from the highest barrier, for l-pentene rotation ( G ‡ = 45.8 kJ mol −1 ), to the lowest barrier, for cyclohexenone ( G ‡ = 38.8 kJ mol −1 ), there was only a difference of ∼7 kJ mol −1 . It appears that the different steric effects of the alkenes in these complexes have little effect on the barrier to rotation.…”

An investigation of ethylene rotational barriers for 5-coordinate d 8 metal bis-ethylene complexes

“…The majority of measured rotational barriers lie between 10 and 16 kcal mol À1 [7,8]; this narrow range mostly reflects the range of convenient dynamic NMR measurements. Ligand-dependence studies have been reported for (acac 0 )Rh(C 2 H 4 ) 2 (range: 11.7-19.2 kcal mol À1 ) [9], (Tp)Re(L)(CO)(C 2 H 4 ) (range: 8-12.7 kcal mol À1 ) [10], trans-(alkene) 2 W(CO) 4 (range: 9.3-11.6 kcal mol À1 ) [11], and (R 3 P) Pt(C 2 H 4 ) 2 (range: 10.2-13.0 kcal mol À1 , Me x Ph 3Àx P (x = 0, 1, 2, 3)) [12]. A number of bis-ethylene systems that are rigid on the NMR timescale have also been reported, including the Ir(I) compounds (R 3 Sb) 2 IrCl(C 2 H 4 ) 2 [13], (Me 2 PhP) 3 Ir(C 2 H 4 ) 2 + [14], (Et 3 P) 2 IrCl(C 2 H 4 ) 2 [15], Cp⁄Ir(C 2 H 4 ) 2 [16], and the Os(0) complex (Me 3 P) 2 Os(CO)(C 2 H 4 ) 2 [17].…”

Carbonyltungsten(0) complexes of acryloylferrocene: Synthesis and characterization

“…Olefin-substituted Group 6 metal carbonyls are conveniently accessible from the parent M(CO) 6 complexes (M = Cr, Mo, W) by means of photolytic CO displacement in the presence of olefins: ethene and linear alkenes [15][16][17][18][19], cycloalkenes [19][20][21], a,b-unsaturated esters [22] and tetracyanoethene [23]. A recent kinetic study [24] on the photochemical conversion of W(CO) 6 into a trans-W(CO) 4 (g 2 -olefin) 2 complex using E-cyclooctene as a model olefin owing to its extraordinary coordination properties [25] showed that the photolysis of M(CO) 6 in the presence of an olefin is expected to yield the stable final product trans-M(CO) 4 (g 2 -olefin) 2 through the intermediate M(CO) 5 (g 2 -olefin) and cis-M(CO) 4 (g 2 -olefin) 2 complexes.…”