The complexes fac-[M(CO) 3 L 3 ] (M=Mo or W, L 3 =MeC(CH 2 SMe) 3 , MeC(CH 2 SeMe) 3 or MeC(CH 2 TeMe) 3 ) have been prepared from [M(CO) 3 (MeCN) 3 ] and characterised by analysis, FAB mass spectrometry, IR, 1 H, 1 3 C{ 1 H}, 7 7 Se, 1 2 5 Te and 9 5 Mo NMR spectroscopies. The complexes are prone to decomposition in solution into tetracarbonyls, and attempts to isolate [Cr(CO) 3 L 3 ] have been unsuccessful. The complexes cis-[Cr(CO) 4 {η 2 -MeC(CH 2 SMe) 3 }], cis-[Mo(CO) 4 (η 2 -MeC(CH 2 SeMe) 3 }] and the robust [M(CO) 4 (S 3 )] (M=Cr, Mo or W, S 3 =1,4,7-trithiacyclononane or 1,4,7-trithiacyclodecane) have been similarly characterised.