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Unusual reactivity of a sterically hindered diphosphazane ligand, $EtN\{P(OR)_2\}_2$, $(R = C_6H_3(Pr^i)_2-2,6)$ towards $(\eta^3$-allyl)palladium precursors

Krishna, Heera and Krishnamurthy, Setharampattu S and Nethaji, Munirathinam and Murugavel, Ramaswamy and Prabusankar, Ganesan (2007) Unusual reactivity of a sterically hindered diphosphazane ligand, $EtN\{P(OR)_2\}_2$, $(R = C_6H_3(Pr^i)_2-2,6)$ towards $(\eta^3$-allyl)palladium precursors. In: Dalton Transactions (27). pp. 2908-2914.

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Abstract

The reactivity of $(\eta^3$-allyl)palladium chloro dimers $[(1-R-\eta^3-C_3H_4)PdCl]_2$ (R = H or Me) towards a sterically hindered diphosphazane ligand $[EtN\{P(OR)_2\}_2]$ $(R = C_6H_3(Pr^i)_2-2,6)$, has been investigated under different reaction conditions. When the reaction is carried out using $NH_4PF_6$ as the halide scavenger, the cationic complex $[(1-R-\eta^3-C_3H_4)Pd\{EtN(P(OR)_2)_2\}]PF_6$ (R = H or Me) is formed as the sole product. In the absence of $NH_4PF_6$, the initially formed cationic complex, $[(\eta^3-C_3H_5)Pd\{EtN(P(OR)_2)_2\}]Cl$, is transformed into a mixture of chloro bridged complexes over a period of 4 days. The dinuclear complexes, $[(\eta^3-C_3H_5)Pd_2(\mu-Cl)_2\{P(O)(OR)_2\}\{P(OR)\2(NHEt)\}]$ and $[Pd(\mu-Cl)\{P(O)(OR)_2\}\{P(OR)_2(NHEt)\}]_2$ are formed by $P-N$ bond hydrolysis, whereas the octa-palladium complex $[(\eta^3-C_3H_5)(2-Cl-\eta^3-C_3H_4)Pd_4(\mu-Cl)_4(\mu-EtN\{P(OR)_2\}_2)]_2$, is formed as a result of nucleophilic substitution by a chloride ligand at the central carbon of an allyl fragment. The reaction of $[EtN\{P(OR)_2\}_2]$ with $[(\eta^3-C_3H_5)PdCl]_2$ in the presence of $K_2CO_3$ yields a stable dinuclear ($\eta^3$-allyl)palladium(I) diphosphazane complex, $[(\eta^3-C_3H_5)[\mu-EtN\{P(OR)_2\}_2Pd_2Cl]$ which contains a coordinatively unsaturated T-shaped palladium center. This complex exhibits high catalytic activity and high TON’s in the catalytic hydrophenylation of norbornene.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to The Royal Society of Chemistry.
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 10 Jun 2008
Last Modified: 19 Sep 2010 04:45
URI: http://eprints.iisc.ernet.in/id/eprint/14252

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