Synthesis and reactivity of metallacyclic manganese .alpha.-hydroxyalkyl complexes containing aliphatic bridges and phosphorus and nitrogen donor atoms; first carbonylation of an isolable .alpha.-hydroxyalkyl complex

Vaughn, George D.; Gladysz, J. A.

doi:10.1021/ja00267a017

Cited by 28 publications

(18 citation statements)

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“…60 In contrast with (39), Mn(H)(CO) 4 [PPh 2 CH 2 CH 2 CHO] did not cyclize, and attempts to prepare the cyclized material via indirect routes led only to the acyclic aldehyde. 61 Preparation of (41), however, was readily accomplished (Equation (13)), so the factors that control the equilibrium between the open chain hydride-aldehyde and the a-hydroxyalkyl complex are subtle. 61 In related chemistry, Mn(TMS)(CO) 5 was reported to effect conversion of methyl ketals to methyl enol ethers, as shown in Equation (14), with more than 1 0 examples being provided.…”

Section: Addition Of Manganese Hydrides To Organic Unsaturationmentioning

confidence: 99%

“…61 Preparation of (41), however, was readily accomplished (Equation (13)), so the factors that control the equilibrium between the open chain hydride-aldehyde and the a-hydroxyalkyl complex are subtle. 61 In related chemistry, Mn(TMS)(CO) 5 was reported to effect conversion of methyl ketals to methyl enol ethers, as shown in Equation (14), with more than 1 0 examples being provided. Under 1400 kPa of CO, species of the type Mn(CO) 5 [C(O)CR 1 (OMe)CH 2 R 2 ], inferred to be CO-insertion-trapped a-methoxyalkyl intermediates, were isolated f r o m two of these reactions.…”

Section: Addition Of Manganese Hydrides To Organic Unsaturationmentioning

confidence: 99%

“…On this basis, it was suggested that the 16-fold greater rate when R = H over when R = TMS might be due in part to electrophilic assistance by intramolecular hydrogen bonding to the developing acyl group. 61 Enough thermodynamic driving force for the insertion of CO is apparently generated by the strong Si-0 bond in (58) to form its threemembered ring, as shown in Equation (21). 83 Subsequent removal of the silyl group by chromatography on wet silica gel reveals that the equilibrium between (59) and (60) lies towards the open-chain acyl.…”

Section: Omementioning

confidence: 99%

“…Insertion of CO 2 into the Mn-C bond of a strained four-membered ring compound produced (61) in 40% yield (Equation (22)), but no insertion into the corresponding five-membered manganacycle was detected. …”

Section: Omementioning

confidence: 99%

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Manganese Alkyls and Hydrides

Flood

1995

Comprehensive Organometallic Chemistry II

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Section: Addition Of Manganese Hydrides To Organic Unsaturationmentioning

confidence: 99%

Section: Addition Of Manganese Hydrides To Organic Unsaturationmentioning

confidence: 99%

Section: Omementioning

confidence: 99%

Section: Omementioning

confidence: 99%

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Manganese Alkyls and Hydrides

Flood

1995

Comprehensive Organometallic Chemistry II

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“…The formation of hydroxyalkyl complexes similar to complex 48 have been reported by Vaughn (Scheme 34) and Garralda (Scheme 35), wherein the insertion of an aldehyde into a metal-hydride bond was observed. 6,96,97 In these investigations, it was proposed that the character of the hydride ligand was relatively acidic, which enabled its addition to the carbonyl. 96,97 Scheme 34…”

Section: Hydroxyalkyl Complexesmentioning

confidence: 99%

Coordination Chemistry of Phosphinocarbonyls with Platinum

Koedyk¹

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<p>This thesis reports the coordination chemistry of phosphinocarbonyl ligands with platinum and describes the influence of phosphine substituents on the mechanism of chelation and the coordination mode of the carbonyl moiety. The ligands synthesised were 2-diphenylphosphinobenzaldehyde (1), 2-diphenylphosphinoacetophenone (2), 2-bis(pentafluorophenyl)phosphinobenzaldehyde (3), and 2-di-tert-butylphosphinobenzaldehyde (4). Compounds 1, 3, and 4 were selected on the basis of their steric bulk and extent to which they donate electron density to the metal. Compound 2 contained the same phosphine substituents to 1, but is the methyl ketone analogue and therefore does not contain the CHO moiety. The cone angle and electronic parameter of compounds 1–4 were compared to the reported values of PPh3, PPh(C6F5)2, and PPhtBu2. Compounds 3 and 4 were similarly bulky, and had larger cone angles than 1. The electron donating capacity of compound 4 was greater than that of 1, and compound 3 was the least electron donating. A new synthetic method for the preparation of 4 is also reported. The coordination chemistry of ligands 1–4 was investigated with platinum(II) and platinum(0) starting materials to assess the influence of the steric and electronic parameters of the phosphine on the chelation of the ligand through the carbonyl to platinum. Coordination of the ligand went through the initial coordination of the phosphine and, depending on the identity of that phosphine, may be followed by chelation of the carbonyl moiety to form a P,C chelate. However, the site of the platinum–carbon bond in the P,C metallacycle depends on the ligand employed. Coordination of the phosphinoaldehyde ligands 1, 3, and 4 produced Pt-C bonds via the C-H activation of the aldehyde CHO group whereas for ketophosphine 2, C-H activation occurred at the α-methyl group. The rate at which C-H activation occurred increased with increasing electron donation from the phosphorus to platinum. Compound 4 chelates to platinum more rapidly than compound 1, while 3 did not undergo chelation at room temperature. Although chelation was only observed to occur via C-H activation, the final products of the coordination reactions of 1–4 with platinum starting materials differed depending on the identity of the ligand. The C-H activation of two molecules of 1 with platinum(II) or platinum(0) produced a platina-β-diketone, cis-[Pt(P,C-2-PPh2C6H4CO)2] (21), which is capable of coordinating to H+, Li+, BF2 +, and [Rh(1,5-cyclooctadiene)]+ between the mutually cis carbonyl groups. One carbonyl moiety of 21 can also undergo condensation with primary amines and ammonia to produce platina-β-ketoimine complexes. The ketone moiety of ligand 2 reacted with platinum(II) starting materials through C-H activation of the terminal methyl group to form the six-membered bis-chelate complex analogous to complex 21. The reaction of 2 with platinum(0) starting materials resulted in the formation of a platinum hydride intermediate which mediated chelation through the partial reduction of the ketone group of one ligand, to form the product, [Pt(P,C-2-PPh2C6H4COCH2)(P,C-2-PPh2C6H4C(OH)CH3)] (48) . The reaction of 3 with [PtMe2(1,5-hexadiene)] at elevated temperatures resulted in the formation of [Pt(P,C-2-PPh2C6H4)(P,C-2-PPh2C6H4CO)] (54) – a decarbonylated and ortho-metallated complex containing a four-membered metallacycle. The platinum-phosphorus bond in the four-membered ring of 54 has a bond distance of 2.385(2) Å – the longest Pt–P bond reported to date. Ligand 4 reacted rapidly with platinum(II) starting materials and produced numerous chelation products. Complexes of ligand 4 were only observed to contain mutually trans phosphines, likely due to the steric bulk of the tert-butyl substituents. Comparison of the coordination chemistry of ligands 1–4 suggests that the propensity toward C-H activation of the ligands is predominantly determined by the electronic character of the phosphine (although steric effects cannot be disregarded), and the more electron-rich the phosphine, the more rapidly chelation occurs.</p>

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