Camphor-derived β-ketophosphonate complexes of molybdenum (VI) and titanium (IV); crystal and molecular structure of dichloro [(1R)-endo-(+)-3-(diethoxyphosphoryl)camphor]dioxomolybdenum(VI)

Abstract

Reaction of (1R)-endo-(+)-3-(diethoxyphosphoryl)camphor (L) with MoO₂Cl₂ gives [MoO₂Cl₂L] with cis oxygen and trans chloro ligands if the stoicheiometry is 1 : 1 whilst 2 equivalents of L give [MoO₂Cl₂L₂]. On reaction with 1 equivalent of L, TiCl₄ gives [TiCl₄L]. The complexes were characterised by i.r., ¹H, and ³¹P n.m.r. spectroscopy, and shown to contain bidentate binding (through the phosphoryl and carbonyl oxygen atoms) except for [MoO₂Cl₂L₂], where binding is only through the phosphoryl oxygen. The compound [MoO₂Cl₂L] has been characterised crystallographically. Crystals are orthorhombic (space group P2₁2₁2₁) with a= 15.528(2), b= 13.721(2), c= 9.777(1)Å, and Z= 4. The structure was obtained from 1 664 observed intensities measured on a diffractometer and refined to an R value of 0.043. The complex is distorted octahedral about molybdenum with mutually cis oxygen atoms and mutually trans chlorine atoms although the O–Mo–O angle is 102.8 (5)° and the Cl–Mo–Cl angle is only 158.0(1)°. The organic ligand is bound through the phosphoryl and carbonyl oxygen atoms and the geometry of the ligand is little distorted from that of e.g. 3-bromocamphor. The bite angle for the bidentate ligand is 78.6 (3)° and the Mo–O (phosphoryl) bond length [2.183(7)Å] is significantly shorter than to the cabonyl oxygen [2.402(7)Å]. The known absolute configurations of the chiral centres have been confirmed as (1R), (3S), and (4S).