Kinetics and Mechanisms of Ligand Exchange Reactions on (Dihapto-Buckminsterfullerene) Pentacarbonyl Tungsten(0)

Electrochemistry and [60]fullerene displacement reactions of (dihapto-[60]fullerene) pentacarbonyl metal(0) (M = Cr, Mo, W)

“…Buckminsterfullerene ([60]fullerene or C 60 ) reacts with metal carbonyl complexes to form [60]fullerene-metal carbonyl complexes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The dihapto (g 2 ) mode of [60]fullerene-transition metal coordination resembles an olefin-metal bond. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Although all carbons in [60]fullerene are equivalent, the molecule possesses two distinct types of C-C bonds (ring : ring junctions): the C-C bonds between six-membered rings (6 : 6 junction) and the C-C bonds between six-membered and five-membered rings (6 : 5 junctions).…”

A biphasic displacement of [60]fullerene from fac-(dihapto-[60]fullerene)(dihapto-1,10-phenanthroline) tricarbonyl molybdenum (0)

“…The corresponding value for W(CO) 5 (k À1 /k 2 = 1.09(1) at 39°C in CS 2 ), for which no solvent involvement was suggested [1], supports some degree of solvent involvement. In these studies, the observation that the ratio values are nearly independent of L, and independent of the temperature suggested that indeed the transition state (TS 1 ) involves a larger extent of W-C 60 bond-breaking than solvent-W bond-making.…”

“…In fact, due to this high electron affinity, its chemical and physical properties are similar to those of electron-deficient olefins [13,14]. The assertion that [60]fullerene can act as a r-Lewis base is supported by the observation that it can compete with Lewis bases such as triphenylphosphine, tricyclohexylphosphine, and triethyl phosphite for coordination sites in electronically deficient transition metal carbonyl complexes [1][2][3]. The claim that observation that piperidine (pip) displaces dppe from mer-(g 2 -C 60 )(g 2 -dppe)W(CO) 3 to produce mer-(g 2 -C 60 ) (g 1 -pip) 2 W(CO) 3 exclusively [3].…”

“…Table 2 Average values of k obsd and activation parameters for C 60 displacement from fac-(g 2 -C 60 )(g 2 -phen)Mo(CO) 3 This observation is not surprising since [L] ) [C 60 ] (since the source of C 60 in the reacting mixture is fac-(g 2 -C 60 )(g 2 -phen)Mo(CO) 3 . The ratio, k À1 /k 2 , has been used as a criterion to estimate the degree of selectivity of intermediate species [1,2,[27][28][29][30][31].…”

“…Studies of the ligand exchange reactions on the complexes (g 2 -C 60 )W(CO) 5 [1], fac-(g 2 -C 60 )(g 2 -phen)W-(CO) 3 [2], and mer-(g 2 -C 60 )(g 2 -dppe)W(CO) 3 [3], (dppe = 1,2-bis(diphenylphosphino)ethane, phen = 1, 10-phenanthroline) have shown that (i) [60]fullerene is a good p-acceptor and a good r-Lewis base, (ii) the W-C 60 bond enthalpy is in the vicinity of 105-109 kJ/ mol [1,2] and (iii) [60]fullerene can be a labilizing ligand [4,5]. The p-acceptor capacity of [60]fullerene can be explained on the basis that [60]fullerene has a strong tendency to accept electrons [6][7][8][9][10][11][12].…”