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Tetradecaisopropoxydihydridotetratungsten, W4(Mu-H)2 (OPr(i))14, has been isolated from the reaction between W2(NMe2)6 (M identical M) and excess isopropanol and has been characterized by ir, nmr, mass spectroscopy and a single crystal X-ray study. The latter reveals a centrosymmetric molecule, (W2(Mu-H)(OPr(i))7)2, having a chain of four tungsten atoms with two short, 2.446(1) angstroms, and one long, 3.407(1) angstroms, tungsten-to-tungsten distances. Each tungsten atom is coordinated to five oxygen atoms and a bridging hydride in a distorted octahedral geometry.

M2(NMe2)6 compounds (M = Mo,W) react with Me3SiCl (2 equiv) in hydrocarbon solvents to give M2Cl2(NMe2)4 and Me3SiNMe2. An amine catalyzed reaction sequence is proposed: (1) HNMe2 + Me3SiCl yields Me3SiNMe2 + HCl (ii) M-NMe2 + HCl yields M-Cl + HNMe2. This sequence is supported by the observations that W2(NMe2)6 does not react with Me3SiCl in the absence of amine and that W2Cl2(NMe2))4 reacts rapidly with HN(CD3)2 to give W2(NMe2)6 with complete scrambling of dimethylamine. In solution W2Cl2(NMe2)6 and W2(NMe2)6 exist in equilibrium with W2Cl(NMe2)5 (K approx. 1 at 30 C). The compounds M2Cl2(NMe2)4 have been characterized by variable temperature nmr studies, infrared and mass spectroscopy and single crystal X-ray crystallography., Prepared in cooperation with Texas A and M Univ., College Station. Dept. of Chemistry.

The great majority of compounds containing metal-metal triple bonds of the x3mmx3 type where X is a monodentate ligand (including some where the ligand atmos are not all the same) have perfectly, or almost perfectly, staggered ethane-like rotational conformations. The great majority of compounds containing metal-metal quadruple bonds are of the type X4MMX4 ( again including those where more than one type of ligand is present) and have essentially eclipsed rotational conformations. The relatively few exceptions to each of these generalizations are of interest because they provide further insight into the nature of metal-metal multiple bonds.

The dinuclear alkoxides, Mo2 (OR) 6, which contain metal-to-metal triple bonds, react with carbon monoxide at room temperature and 1 Atmos. A reversible reaction has been established for R=Bu: Mo2 (OBut) 6+ CO Mo2 (OBut) 6 CO. The compound Mo2(OBut) 6 CO has been structurally characterized and shown to contain a carbonyl-bridged metal-to-metal double bond. The Mo-to-Mo distance is 2.489(1)A. In the presence of an excess of CO, Mo(CO) 6 is ultimately formed along with other as yet, uncharacterized molybdenum containing compounds. (Author), Prepared in cooperation with Texas A and M Univ., College Station.

The compounds Mo2(OPr(i))6(NO)2, I, and Mo2(OPr(i)8, II have been structurally characterized. Each compound has rigorous inversion symmetry and virtual C2v symmetry and in each there is essentially trigonal bipyramidal coordination about each molybdenum atom., Prepared in cooperation with Texas A and M Univ., College Station.

The occurrence of transition metal complexes containing metal-to-metal multiple bonds is now well documented. Scores of such compounds have been structurally characterized and several have been subjected to detailed spectroscopic examination. Recently X sub X-SW calculations have been carried out on compounds containing M-M bounds and the results have been correlated with the observed spectroscopic data. Despite the emergence of a basic understanding of the electronic structure of these compounds little is known about (i) the mechanisms of their formation and (ii) the relationships that exist between the formation/existence of dinuclear compounds with M-M multiple bonds and cluster or polynuclear compounds of the same empirical formula. We have sought to gain insight into some of these mystiques by looking for the formation of heterodinuclear compounds containing M-M multiple bonds. We report here some findings relating to compounds containing triple bonds between molybdenum and tungsten atoms. (Author)

The occurrence of compounds containing metal-to-metal multiple bonds is now a well documented facet of transition metal chemistry. In this series we are studying the reactions of such compounds with regard to their ability (1) to undergo reactions of the type well documented in mononuclear chemistry and (2) to act as building blocks for the systematic synthesis of new cluster (polynuclear) compounds. Both have important catalytic implications., Prepared in cooperation with Texas A and M Univ., College Station.

The existence of an extensive chemistry centering around the triplybonded Mo-Mo and W-W units is now well established and has recently been reviewed. A firm structural base for interpreting this chemistry has been provided by more than a score of x-ray crystallographic structure determinations. Among these, however, there have been only a few pairs of molybdenum and tungsten compounds with the same or very similar sets of ligands. The comparisons afforded by such pairs are valuable in developing the comparative chemistry of the M-M multiple bonds in the 2nd and 3rd transition series. (Author), Prepared in cooperation with Texas A and M Univ., College Station. Dept. of Chemistry.

Prepared in cooperation with Texas A and M Univ., College Station.

From the reaction between Cr(NEt)4 and CO2 (4 equiv) two crystalline compounds have been isolated and structurally characterized: I, Cr2(O2CNEt2)4(Mu-NEt2)2 and II, Cr2(O2CNEt2)42HNEt2. Compound I is the major product when CO2 is allowed to react slowly with Cr(NEt2)4; compound II predominates when CO2(4 equiv) is added rapidly. These results are compared with previous studies of CO2 insertion reactions involving early transition metal dialkylamides and with the known reactions of Cr(NEt2)4. A reaction pathway leading from Cr(NEt2)4 to I and II is proposed to involve beta-hydrogen elimination from a (CR(IV) -NEt2) moiety followed by reductive elimination of ET2NH and the generation of Cr(II). I crystallizes in space group Pbcn with a = 19.122(8), b = 11.024(2), c = 18.114(6)A, V = 3818(3)A(3), and Z = 4. II crystalizes in the space group Pl with a = 10.936(2), b = 11.170(2), c = 8.871(2)A, alpha = 99.46(1), beta = 98.56(1), gamma = 108.58(1), V = 989.4(6)A(3), and Z = 2., See also AD-A053 493.

Prepared in cooperation with Texas A and M Univ., College Station, TX. See also report dated 4 Oct 77, AD-A045 818.