⁹⁵Mo NMR Studies on Cationic Phosphenium Complexes of Molybdenum

Abstract

The 95Mo NMR spectra of cationic molybdenum phosphenium complexes have been measured. Going from fac-[(bpy)(CO)3Mo{PN(Me)CH2CH2NMe(OMe)}] (1a) to fac-[(bpy)(CO)3Mo{PN(Me)CH2CH2NMe}]+ (fac-1b) to mer-[(bpy)(CO)3Mo{PN(Me)CH2CH2NMe}]+ (mer-1b) causes deshielding of the 95Mo doublet resonance (δ −1081 (1a), −1049 (fac-1b), −1015 (mer-1b)), an increase in the Mo−P coupling constant (193 Hz (1a), 264 Hz (fac-1b), 337 Hz (mer-1b)), and an increase in the line width (35 Hz (1a), 90 Hz (fac-1b), 300 Hz (mer-1b)). The conversion of fac-[(bpy)(CO)3Mo{PN(Me)CH2CH2O(OMe)}] (fac-2a) into mer-[(bpy)(CO)3Mo{PN(Me)CH2CH2O}]+ (mer-2b) showed a similar trend in 95Mo NMR data, though fac-[(bpy)(CO)3Mo{PN(Me)CH2CH2O}]+ was not detected in this case. mer-2b exhibits the largest Mo−P coupling constant (343 Hz) among those reported so far. These changes can be reasonably attributed to a dominant contribution from the imbalance of electron density at the Mo in the Ramsey equation due to a significant double-bond character between the molybdenum and the phosphenium phosphorus. Comparison of coupling constants between M and a phosphenium P in [(bpy)(CO)3M{PN(Me)CH2CH2NMe}]+ (M = Mo, W) revealed that the ratio 1 J W - P/1 J Mo - P is 1.67, which is very close to the ratio (1.76) reported for many series of M−phosphine (or phosphite) complexes (M = Mo, W). The 95Mo NMR spectra of cis- and trans-[(bpy)(CO)2Mo{PN(Me)CH2CH2X(OMe)}{PN(Me)CH2CH2X}]+ (X = NMe, cis-1c, trans-1c; X = O, cis-2c, trans-2c) have also been measured; the chemical shifts are understood similarly in terms of the imbalance of electron density at Mo.

Geometrical isomerization of fac/mer-Mo(CO)3(phosphite)3 and cis/trans-Mo(CO)4(phosphite)2 catalyzed by Me3SiOSO2CF3

“…Therefore, the formation of cis-Mo(CO) 4 {P(OMe) 3 }{P(OMe) 2 F} was proposed. The similar OR/F substitution reaction has been reported [6,9,11]. The 31 P NMR spectrum after 24 h, signals due to cis-Mo(CO) 4 -{P(OMe) 3 }{P(OMe) 2 F} increased in intensity and a new singlet at 173.4 ppm attributable to trans-5 was observed.…”

“…(1) [4,5]. This method is applicable for many types of transition 3 {P(NMeCH 2 ) 2 (OR)} [6][7][8][9][10][11][12], M(dppe)(CO) 3 {P(NMeCH 2 ) 2 (OR)} [7], M(bpy)-(CO) 2 {P(NMeCH 2 ) 2 (OR)} 2 [8,11,12], M(CO) 3 {P(NMe-CH 2 ) 2 (OR)} 3 [13], M(CO) 4 {P(NMeCH 2 ) 2 (OR)} 2 [13], CpM(CO) 2 (ER 3 ){P(NMeCH 2 ) 2 (OR)} (M = Cr, Mo, W) [14][15][16][17], and CpM(CO)(ER 3 ){P(NMeCH 2 ) 2 (OR)} (M = Fe, Ru) (ER 3 = CH 3 , SiMe 3 , GeMe 3 , SnMe 3 ) [10,[18][19][20][21][22][23]. Systematic researches for reactions of Mo(bpy)-(CO) 3 {PXY(OR)} with BF 3 Á OEt 2 revealed the effect of the substituents (X, Y) on the stability of cationic phosphenium complexes; the stability increases with increasing the number of amino substituents on the phosphenium phosphorus [9].…”

Anionic phosph(in)ito (“phosphoryl”) ligands: Non-classical “actor” phosphane-type ligands in coordination chemistry

“…BF 3 induces migratory insertion of the CO ligand into the Fe-Me bond followed by an Arbuzov-like dealkylation with F -to give the corresponding  1 -P−phosphonate complex 118 which is converted by PPh 3 addition into 119 incorporating a bond between the phosphonate oxygen and the boron atoms in its structure [220]. The reaction of  1 -P−phosphonate iron complex 120 with the hydroborane 9-BBN proceeds readily and quantitatively at room temperature resulting in the formation of the corresponding formyl complex 121.…”

“…Scheme 39.Reduction of CO ligand of  1 -P−phosphonate iron complexes 117[220] and 120[221] with boron reagents.An halogenation reaction of an amidophosphonato ligand grafted on an iron metallic fragment was reported. Addition of boron trihalides BCl 3 on P-metalated amidophosphonate complex 122 allowed the synthesis of the corresponding halogenated  1 -P−amidophosphonate complexes 123 and 124 which are good precursors for future functionalization on the organophosphorus ligand (Scheme 40,[222]) .Scheme 40.Halogenation reaction of the  1 -P−amidophosphonato ligand in iron complex 122[222].Taking into account the unique properties of O−anionic monodentate and bidentate  1 -P−phosph(in)ito ligands presented in this review, the results recently reported on the O,P-metalated phosphinite trinuclear complex 125 in which the six {Ph 2 P−O} arms bridge the Ti center with the two terminal Pd atoms[223].…”