4.1. Instrumentation and measurements

NMR spectroscopy: The phosphane ligands and chromium carbonyl derivatives were characterized with ¹H, ¹³C{¹H}, ³¹P{¹H} NMR spectra, but with most of the ligands assistance in the interpretation was required from two-dimensional H,H-correlated COSY-90, H,C-correlated HSQC or C,H-correlated HETCOR, or long-range C,H-correlated COLOC NMR spectra. Most of the spectra were recorded on a Bruker DPX400 spectrometer at room temperature with deuterated chloroform (99.8% D, 0.03% TMS, Aldrich); a few of the ¹H NMR spectra were recorded on a Bruker AM200 spectrometer. The ¹H, ¹³C{¹H} and two-dimensional NMR spectra were referenced to internal tetramethylsilane (TMS) and ³¹P{¹H} NMR spectra to external 85% H₃PO₄. Exceptionally, (2,5-dimethyl­phenyl)bis(3-pyridyl)­phosphane and the chromium complex of (p-thio­methylphenyl)­bis(2-pyridyl)­phosphane were measured with deuterated acetone (99.9% D, Aldrich) because of solubility problems. The ¹H shifts were referenced to the residual signal of protons of partly deuterated acetone (2.05 ppm) and the ¹³C shifts to the shift of deuterated acetone (30.5 ppm).

Mass spectrometry: Accurate masses were recorded with a Micromass LCT spectrometer using ESI+ method and a TOF mass analyzer.

X-ray crystallography: The X-ray measurements were performed with a Nonius KappaCCD diffractometer at the University of Joensuu. Further details of the measurements can be found in the original papers [I], [II], [V].

Quantum mechanical calculations: Geometrical arrangement and steric size of the free ligands were studied theoretically at the University of Joensuu by ab initio Hartree-Fock method using the 3-21G* basis set. The steric size of the free phosphane ligands was estimated by Tolman’s cone angle method [16]. Further details of the modeling work can be found in the original papers [I]–[V].