TETRAKIS(DIMETHYLPHOSPHONIUMDIMETHYLIDO)DICHROMIUM AND DIMOLYBDENUM .1. CRYSTAL AND MOLECULAR-STRUCTURES

The title compounds, [(CH3)2P(CH2)2]4Cr2 (1) and [(CH3)2P(CH2)2]4Mo2 (2), have been investigated crystallographically, shown to be isomorphous, and shown to have extremely short bonds between the metal atoms. Compound 1 crystallized in space group Pccn with a=13.036 (5) υ, b=13.037 (5) υ, c=13.096 (5) υ, and Z=4. The structure consists of discrete molecules residing on crystallographic inversion centers but having effectively C4h symmetry. The Cr-Cr distance is 1.895 (3) υ. Average values of some other molecular dimensions are as follows: Cr-C, 2.22 (1) υ; P-C, 1.80 (3) υ; ZCr-Cr-C, 103.3 (4)°; zC-Cr-C, 87.0 (6)°. Compound 2 also crystallizes in space group Pccn with a=13.122 (3) υ, b=13.238 (2) υ, c=13.244 (2) υ, and Z=4. The Mo-Mo distance is 2.082 (2) υ, and the average values of the other molecular dimensions are as follows: Mo-C, 2.31 (2) υ; P-C, 1.78 (2) υ; /Mo-Mo-C, 101.5 (8)°; ZC-Mo-C, 88 (1)°. © 1979, American Chemical Society. All rights reserved.