Ruthenium and osmium complexes of the general formula MCl 2(PyP)2 (where PyP is the P,N- donor ligand 1-(2-diphenylphosphinoethyl)pyrazole) were synthesized from MCl 2(PPh3)3 (where M = Ru or Os). Three of the five possible stereoisomers of RuCl2(PyP)2 were synthesized and characterized in solution by multinuclear NMR spectroscopy, and the structure of these in the solid state was determined by X-ray crystallography. Two of the analogous Os isomers were also synthesized. It was found that different solvents induced isomerization between these stereoisomers, indicating either lability of the chloride anion or hemilability of the PyP ligand. Bimetallic complexes of the general formula [Ru(μ-Cl)(PyP) 2]2[X]2 were synthesized from chloride abstraction from RuCl2(PyP)2 using either silver (X = OSO2CF3, BF4) or sodium (X = BPh4) salts. The osmium analogue of the Ru bimetallic complexes, [Os(μ-Cl)(PyP) 2]2[BPh4]2, was also synthesized. Solid-state structures were obtained using X-ray crystallography for the osmium bimetallic complex and the ruthenium bimetallic complex where X = OSO 2CF3. The hemilability of PyP was demonstrated through the synthesis of RuCl2(CO)(κ1-P-PyP) (κ2-P,N-PyP), which contains one pendant PyP ligand, bound through the P-donor atom.