Small bite-angle diphosphines — Synthesis and structure of low-valent complexes of bis(di-ortho-tolylphosphino)methane (dotpm) and related ligands

Author: Filby Maria   Deeming Antony J   Hogarth Graeme   Lee Mo-yin (Venus)  

Publisher: NRC Research Press

ISSN: 1480-3291

Source: Canadian Journal of Chemistry, Vol.84, Iss.2, 2006-02, pp. : 319-329

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Abstract

The coordination chemistry of bis(di-ortho-tolylphosphino)methane (dotpm) has been studied. It is an excellent chelating ligand and a range of low-valent mononuclear complexes have been prepared; cis-[M(CO)42-dotpm)] (M = Cr, Mo, W; 13), [CpRuCl(η2-dotpm)] (4), and cis-[MX22-dotpm)] (M = Pt, X = Cl, Br, I; 5a5c, M = Pd, X = Cl; 6). The backbone protons are relatively acidic and can be deprotonated using n-BuLi or LiN(SiMe3)2. Subsequent alkylation by RX (X = halogen; R = Me, Et, CH2Ph) affords cis-[M(CO)42-Rdotpm)] (M = Cr, Mo, W, R = Me; 79, M = Mo, W, R = Et, CH2Ph; 1215), [CpRuCl(η2-Medotpm)] (10), and cis-[PtI22-Medotpm)] (11). Thermolysis of cis-[Mo(CO)42-Medotpm)] (8) yields what is believed to be the coordinately and electronically unsaturated complex [Mo(CO)32-Medotpm)] (16), suggesting that derivatives of dotpm (cone angle 194°) are bulky enough to stabilize a 16-electron complex. Crystal structures of 2, 3, 79, 13, and 14 have been determined (diphosphine bite angles ranging from 66.58(3)° to 70.96(5)°.Key words: diphosphine, transition metal, bulky, carbonyl, ortho-tolyl.On a étudié la chimie de coordination du bis(di-ortho-tolylphosphino)méthane (dotpm). C'est un excellent ligand chélatant et on en a préparé un large éventail de complexes mononucléaires de faible valence, dont les cis-[M(CO)42-dotpm)] (M = Cr, Mo, W; 13), [CpRuCl(η2-dotpm)] (4) et cis-[MX22-dotpm)] (M = Pt, X = Cl, Br, I; 5a5c, M = Pd, X = Cl; 6). Les protons du squelette sont relativement acides et peuvent être déprotonés en utilisant du n-BuLi ou du LiN(SiMe3)2. Des alkylations subséquentes par du RX (X = halogène; R = Me, Et, CH2Ph) conduisent à la formation des cis-[M(CO)42-Rdotpm)] (M = Cr, Mo, W, R = Me; 79, M = Mo, W, R = Et, CH2Ph; 1215), [CpRuCl(η2-Medotpm)] (10) et cis-[PtI22-Medotpm)] (11). La thermolyse du cis-[Mo(CO)42-Medotpm)] (8) conduit à la formation d'un composé qu'on croit être le complexe coordonné et électroniquement insaturé [Mo(CO)32-Medotpm)] (16) qui suggère que les dérivés dotpm (angle du cône de 194°) sont suffisamment encombrants pour stabiliser un complexe à 16 électrons. On a déterminé les structures cristallines des composés 2, 3, 79, 13 et 14 dans lesquels l'angle de morsure de la diphosphine varie de 66,58(3)° à 70,96(5)°.Mots clés : diphosphine, métal de transition, encombrant, carbonyle, ortho-tolyle.[Traduit par la Rédaction]

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