Abstract Reaction of 8-methoxy-1-naphthyllithium (2) with one equivalent of chlorodiphenylphosphine gives the novel (8-methoxynaphth-1-yl)diphenylphosphine (3) which was oxidised to the corresponding sulfide (4) and selenide (5) by reaction with sulfur and selenium, respectively. The P⋯O peri distance is significantly increased in 4 and 5 at 2.819(3) [2.793(3)] and 2.827(3) [2.806(3)] Ǻ [values in square brackets are for the second independent molecules in each case] relative to the value in 3 of 2.678(2) A. There are short E⋯O interactions ie O(1)⋯S(1) 3.165(3) [3.124(3)], O(1)⋯Se(1) 3.247(3) [3.200(2)] Ǻ and these may be repulsive and responsible for the increased P⋯O separation. The use of the naphthalene backbone in the synthesis of a potential hemilabile ligand is demonstrated by the synthesis and X-ray structure of (8-methoxynaphth-1-yl)diethoxyphosphine ruthenium p-cymene dichloride (6).