Synthesis and activation potential of an open shell diphosphineElectronic supplementary information (ESI) available: X-ray crystallographic data in CIF format (CIF), experimental details (PDF). CCDC 1502928-1502933, 1538644 and 1538645. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7cc02114c

A paramagnetic W III alkyne complex bearing free terminal diphenylphosphino groups at the side-on coordinated alkyne was synthesized using a stepwise template strategy. This moderately stable metal supported open shell diphosphine shows an unprecedented spontaneous splitting of nitric oxide providing a W II -η 2 -C 2 {P(NH 2 )Ph 2 }{P(O)Ph 2 } + complex featuring an amino phosphonium and a phosphine oxide substituent. A cationic bisphosphine assembled by a modular synthetic concept and carrying a paramagnetic S = 1/2 tungsten centre in the backbone shows an unusual spontaneous splitting of nitric oxide assisted by H atom transfer steps.