An accessible technique for molecular weight determination by cryoscopy applicable for coordination compounds

Abstract

An improved computerized method is proposed for determination of molecular weights by cryoscopy. The use of a precision digital platinum resistance thermometer greatly simplifies the measurement process in comparison with the classic Beckmann apparatus. All component parts of the device are factory-made (interchangeable) details, which are widely used in laboratory practice. A test report is formed with the aid of a computer using Microsoft Excel software. The use of molecular sieves for drying dimethyl sulfoxide (DMSO), as well as experimental procedures specific to organolithium compounds, make it possible to obtain reproducible measurement results for coordination compounds that are prone to oligomerization in solutions. The molecular structure of the bis(acetylacetonato)di(dimethyl sulfoxide)nickel(II) obtained from dimethyl sulfoxide solutions was determined by single crystal X-ray diffraction. P2₁/c, a = 8.7916(2), b = 12.3061(3), c = 8.7421(2) (Å), β = 99.4460(10)°, Z = 2. The complex [Ni(C₅H₇O₂)₂(C₂H₆OS)₂] is mononuclear with a square-bipyramidal environment of the central atom. The coordination polyhedron of the Ni ion is formed by four oxygen atoms of two chelating acetylacetonate anions in the equatorial position and two atoms of dimethyl sulfoxide molecules in axial positions.

Keywords:

• Cryoscopy
• coordination compounds
• molecular weight
• dimethyl sulfoxide solution
• mononuclear structure

Disclosure statement

No potential conflict of interest was reported by the author(s).