N-(N',N',N'',N''-tetramethyl)guanidine-substituted phosphines as monodentate, bidentate or tridentate ligands in transition metal chemistry

Article abstract of DOI:10.1016/S0022-328X(96)06444-3

The diorganophosphinous-N-(N',N',N'',N''-tetramethyl)guanidinides 1a and 1b and the organophosphorous-bis-N-(N',N',N'',N''-tetramethyl)guanidines 2 and 3 are used as ligands towards carbonyls of xerovalent transition metals.In most cases coordination via phosphorous is observed. 1b and 2 act as PN-donors towards the (tetracarbonyl)molibdenum fragment, forming chelate complexes involving one five-membered ring. 3 acts as a PNN'-donor towards molibdenum carbonyls, forming a bicyclic chelate complex.X-ray structure determinations were performed for the octacarbonyldimanganese compound 7, the tricarbonnylnickel complex 8 and the tetracarbonyliron derivative 10.The dimangenese compound 7 was found to be diaxially substituted with short MnC bonds but standard MnP bond lengths.The nickel compound 8 exhibited short PNi bonds, long NiC bonds and short CO bonds, consistent with enhanced ?-back donation from metal to phosphorous.The coordination geometry at the iron atom in 10 was found to be trigonal bipyramidal with phosphorous in the axial position, strongly distorted towards square pyramydal. - Keywords: Carbonyls; Transition metal chemistry; Coordination geometry