Small bite-angle diphosphines--synthesis and structure of low-valent complexes of bis

• Published in: Canadian journal of chemistry Vol. 84; no. 2; pp. 319 - 329
• Main Authors: Filby, Maria, Deeming, Antony J, Hogarth, Graeme
• Format: Journal Article
• Language: English
• Published: NRC Research Press 01.02.2006
• Subjects: Chelates; Chemical properties; Ligands; Canada
• ISSN: 0008-4042; 1480-3291

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)4([η.sup.2]-dotpm)] (M = Cr, Mo, W; 1-3), [CpRuCl([η.sup.2]-dotpm)] (4), and cis-[M[X.sub.2]([η.sup.2]-dotpm)] (M = Pt, X = Cl, Br, I; 5a-5c, M = Pd, X = CI; 6). The backbone protons are relatively acidic and can be deprotonated using n-BuLi or LiN[(Si[Me.sub.3]).sub.2]. Subsequent alkylation by RX (X = halogen; R = Me, Et, C[H.sub.2]Ph) affords cis-[[M(CO).sub.4]([η.sup.2]-Rdotpm)] (M = Cr, Mo, W, R = Me; 79, M = Mo, W, R = Et, C[H.sub.2]Ph; 12-15), [CpRuCl([η.sup.2]-Medotpm)] (10), and cis-[Pt[I.sub.2]( [η.sup.2]-Medotpm)] (11). Thermolysis of cis-[Mo[(CO).sub.4]([η.sup.2]-Medotpm)] (8) yields what is believed to be the coordinately and electronically unsaturated complex [Mo[(CO).sub.3]( [η.sup.2]-Medotpm)] (16), suggesting that derivatives of dotpm (cone angle 194??) are bulky enough to stabilize a 16-electron complex. Crystal structures of 2, 3, 7-9, 13, and 14 have been determined (diphosphine bite angles ranging from 66.58(3)?? to 70.96(5)??.