Tert-butyl-2,4,6-trimethylphenylphosphine—a chiral secondary phosphine with bulky substituents: synthesis and NMR spectroscopic studies

McFarlane, William; Regius, Christian T.

doi:10.1016/s0277-5387(96)00492-5

Cited by 6 publications

(6 citation statements)

References 14 publications

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“…20 Such an exchange could be rationalized either in terms of a fast rotation [NMR time-scale] of the mesityl group around the PÀC ipso bond or in terms of an inversion of configuration at the phosphorus atom. However, we favor the first exchange pathway (Scheme 2a), considering that the value of the activation barrier of the present process, 11.1 kcal mol À1 , compares well with the value of the rotation barrier of the mesityl group in t-BuMesPH, 13.2 kcal mol À1 , 21 and is considerably lower than the known unimolecular phosphorus inversion barrier for the free secondary phosphine (()-Phi-PrPH, which exceeds 23.3 kcal mol À1 . 22 Yet, it has to be taken into consideration that a possible contribution of the σ-phosphavinyl form Cp-(CO) 2 Mn À ÀC(Me)dP þ HMes to the structure of 3b may significantly lower the inversion barrier at phosphorus, 23 thus preventing totally excluding the latter hypothesis.…”

Section: ' Results and Discussionmentioning

confidence: 85%

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

et al. 2011

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A series of η1-α-phosphinocarbene complexes of manganese, Cp(CO)2MnC(R)PR′R′′ (3; 3a: R = Ph, R′ = H, R′′ = Mes; 3b: R = Me, R′ = H, R′′ = Mes; 3c: R = Ph, R′ = R′′ = Ph; 3d: R = Ph, R′ = R′′ = N(i-Pr)2; 3e: R = Ph, R′ = Me, R′′ = Mes), was generated at low temperature upon nucleophilic addition of the primary phosphine H2PMes and secondary phosphines HPPh2, HP(N(i-Pr)2)2, or (±)-HPMeMes to the cationic carbyne complexes Cp(CO)2Mn+C−R ([1]+; [1a]+: R = Ph; [1b]+: R = Me), followed by deprotonation of the resulting α-phosphoniocarbene intermediates Cp(CO)2MnC(R)P+(H)R′R′′ ([2a−e]+). The η1-α-phosphinocarbene complexes 3c−e derived from secondary phosphines were found to be highly thermolabile, giving upon intramolecular CO insertion the η3-phosphinoketene complexes Cp(CO)Mn(η3-C(O)C(Ph)PR′R′′) (4c: R′ = R′′ = Ph, 4d: i-Pr2N; RR/SS-4e: R′ = Me, R′′ = Mes) in 80−95% yield. The η1-α-phosphinocarbene complexes 3a,b, bearing a mesityl substituent, were isolated in 57−65% yield. The availability of the phosphorus lone pair in such compounds was assessed by their reaction with borane, giving the corresponding adducts Cp(CO)2MnC(R)P(BH3)HMes (5a, R = Ph; 5b, R = Me). Complexes 3a,b slowly rearrange in a nonpolar solvent (benzene) to afford a mixture of the η3-phosphinoketene complexes Cp(CO)Mn(η3-C(O)C(R)PHMes) (4a, R = Ph; 4b, R = Me) and the η1-phosphaalkene complexes Cp(CO)2Mn(η1-P(Mes)C(H)R (6a, R = Ph; 6b, R = Me), and ultimately pure 6a,b as a mixture of E/Z stereoisomers (6a, E/Z 60:40; 6b, E/Z 55:45). By contrast, a stereoselective rearrangement of 3a,b into E-6a,b was observed in a polar solvent (THF), the process being considerably accelerated in the presence of catalytic amounts of base. Deprotonation of 3a by n-BuLi at −80 °C affords the dicarbonyl phosphidocarbene anion [Cp(CO)2MnC(Ph)PMes]Li ([7a]Li), which undergoes an instantaneous CO insertion process upon addition of traces of weak acids (H2O, t-BuOH) to give the cyclic monocarbonylacyl anion [Cp(CO)2 Mn(η2-C(O)C(Ph)PMes]Li ([8a]Li, R = Ph). Besides, deprotonation of 3a,b by t-BuOLi affords directly the cyclic monocarbonylacyl anions [8a,b]Li. The protonation of [8a]Li with various proton sources (HBF4·Et2O, NH4Claq, [Et3NH]Cl) leads to a stereoselective formation of E-6a, illustrating the key role of this anion in the stereoselective 3a → E-6a rearrangement. Alkylation of [8a]Li by MeI resulted in formation of η3-phosphinoketene complex RR/SS-4e as a single pair of diastereomers, whereas its treatment with iodine resulted in thermally unstable η3-phosphinoketene complex Cp(CO)Mn(η3-C(O)C(Ph)PIMes) (11), evolving at room temperature into the η1-phosphaalkene product Cp(CO)2Mn(η1-P(Mes)C(I)Ph) (12) of Z conformation. The solid-state structures of 3b, 4c, 4d, RR/SS-4e, and Z-12 are reported.

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Section: ' Results and Discussionmentioning

confidence: 85%

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

et al. 2011

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“…These in turn clearly depend on steric effects, with bonds to smaller phosphido ligands being thermodynamically favored. Relevant cone angles reported by Tolman 24 and others include those for PH 2 Ph (101°), PH 2 Mes (110°), 7 PH 2 -Mes* (132°), 25 PH 2 Cy (115°), 26 PHPh 2 (128°), PHCy 2 (143°), 27 and PHMes 2 (170°). 27 For primary arylphosphido complexes, the Pt-P bond strengths follow the order Pt-PHPh > Pt-PHMes > Pt-PHMes*; a similar steric trend is seen for diarylphosphides (Pt-PPh 2 > Pt-PMes 2 ).…”

Section: Introductionmentioning

confidence: 98%

“…Relevant cone angles reported by Tolman 24 and others include those for PH 2 Ph (101°), PH 2 Mes (110°), 7 PH 2 -Mes* (132°), 25 PH 2 Cy (115°), 26 PHPh 2 (128°), PHCy 2 (143°), 27 and PHMes 2 (170°). 27 For primary arylphosphido complexes, the Pt-P bond strengths follow the order Pt-PHPh > Pt-PHMes > Pt-PHMes*; a similar steric trend is seen for diarylphosphides (Pt-PPh 2 > Pt-PMes 2 ). In these cases, the predicted decrease in P-H bond energies with increasing substitution on the aryl group(s) is apparently outweighed by effects on the Pt-P bonds.…”

Section: Introductionmentioning

confidence: 98%

Terminal Platinum(II) Phosphido Complexes: Synthesis, Structure, and Thermochemistry

Wicht¹,

Paisner²,

Lew³

et al. 1998

Organometallics

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A series of terminal Pt(II) phosphido complexes Pt(dppe)(Me)(PRR‘) (R = H; R‘ = Mes* (1), R‘ = Mes (2), R‘ = Ph (3), R‘ = Cy (4); R = R‘ = Mes (5); R = R‘ = Ph (6); R = R‘ = Cy (7); R = R‘ = Et (8); R = Ph, R‘ = i-Bu (9)) has been prepared by proton transfer from the appropriate phosphine to the methoxide ligand of Pt(dppe)(Me)(OMe) (10) (dppe = Ph2PCH2CH2PPh2; Mes* = 2,4,6-(t-Bu)3C6H2; Mes = 2,4,6-Me3C6H2; Cy = cyclo-C6H11). Complexes 1 and 2 were also made by deprotonation of the cations [Pt(dppe)(Me)(PH2Ar)][BF4] (Ar = Mes* (13); Ar = Mes (14)). For comparison to 1, the arylthiolate and aryloxide complexes Pt(dppe)(Me)(EMes*) (E = S (11); E = O (12)) were also prepared from 10. NMR studies of the proton-transfer equilibria between Pt(dppe)(Me)(X), Pt(dppe)(Me)(Y), and the acids HY and HX (see Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw, J. E. J. Am. Chem. Soc. 1987, 109, 1444−1456 and Bryndza, H. E.; Domaille, P. J.; Tam, W.; Fong, L. K.; Paciello, R. A.; Bercaw, J. E. Polyhedron 1988, 7, 1441−1452) provide an approximate partial ranking of Pt−P bond strengths in this series: Pt−PHPh > Pt−PHMes > Pt−PHMes*; Pt−PPh2 > Pt−PMes2. Complementary solution calorimetry investigations probe the role of entropic effects on the equilibria. Both steric and electronic factors appear to be important in controlling relative Pt−P bond strengths. The Pt−S bonds in 11 and Pt(dppe)(Me)(SPh) are stronger than the analogous Pt−P bonds in 1 and 3. Complexes 1 and 5·THF were structurally characterized by X-ray crystallography.

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“…All phosphines were purchased from Aldrich or Strem and used as received unless otherwise noted. Mes 2 PH 22 and tBu(Mes)PH 23 were prepared as reported in the literature. Paratone-N oil was purchased from Hampton Research.…”

Section: Introductionmentioning

confidence: 99%

Reactions of phosphines with electron deficient boranes

et al. 2009

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A series of classical B(C(6)F(5))(3)-phosphine adducts are shown to be reactive molecules. Reaction of (THF)B(C(6)F(5))(3) with phosphines are shown to effect ring-opening of THF affording the zwitterionic phosphonium-borate species of the form R(2)PH(C(4)H(8)O)B(C(6)F(5))(3) and R(3)P(C(4)H(8)O)B(C(6)F(5))(3). Alternatively, treatment of (THF)B(C(6)F(5))(3) with a lithium phosphide (R(2)PLi, R = tBu, Ph Mes) affords species of the form [Li(THF)(x)][R(2)P(C(4)H(8)O)B(C(6)F(5))(3)]. Additionally, double THF ring-opening is also demonstrated to give species of the form [Li(THF)(x)][R(2)P(C(4)H(8)OB(C(6)F(5))(3))(2)]. In addition a series of classical borane-phosphine adducts are also shown to undergo thermal rearrangement reactions to give the zwitterionic products of aromatic substitution R(2)PH(C(6)F(4))BF(C(6)F(5))(2) and R(3)P(C(6)F(4))BF(C(6)F(5))(2). The mechanism of these substitutions is considered. A series of crystallographic studies of phosphine-borane adducts, THF ring-opened zwitterions and para-attack zwitterionic phosphonium borates are reported and discussed.

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Tert-butyl-2,4,6-trimethylphenylphosphine—a chiral secondary phosphine with bulky substituents: synthesis and NMR spectroscopic studies

Cited by 6 publications

References 14 publications

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Terminal Platinum(II) Phosphido Complexes: Synthesis, Structure, and Thermochemistry

Reactions of phosphines with electron deficient boranes

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Tert-butyl-2,4,6-trimethylphenylphosphine—a chiral secondary phosphine with bulky substituents: synthesis and NMR spectroscopic studies

Cited by 6 publications

References 14 publications

Synthesis of η1-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Synthesis of η1-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Terminal Platinum(II) Phosphido Complexes: Synthesis, Structure, and Thermochemistry

Reactions of phosphines with electron deficient boranes

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Product

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About

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations