Direct photolytic route to trans-Cr(CO)4(AsPh3)2 and crystal structures of cis-Mo(CO)4(AsPh3)2 and cis-W(CO)4(AsPh3)2

The preparation of trans-Cr(CO)4(AsPh3)2 is accomplished in reasonable yield by the direct photolysis of a solution of Cr(CO)6 and an excess of AsPh3 in heptane. The structures of cis-Mo(CO)4(AsPh3)2 and cis-W(CO)4(AsPh3)2 are reported. These are found to be isostructural and consist of distorted octahedral geometries with AsMAs angles of 102.56(2) and 102.62(2)° for M=Mo and W, respectively. The MoAs distances of 2.6428(9) and 2.6489(9) Å are significantly longer than those in the W analogue at 2.6384(6) and 2.6361(6) Å. On the basis of a comparison to literature data, the AsPh3 ligands in these molecules can be described as extremely compressed.