The tris(2-pyridyl)phosphine complex [P(2-py) 3 W(CO)(NO) 2 ](BF 4 ) 2 acts as a Lewis acid catalyst precursor for the tandem reactions of Friedel–Crafts/aldehyde cyclotrimerization, which lead to the formation of a series of hyper-branched star polymers. ... The organotungsten complex